I'm sorry but I don't want to be an Emperor -- that's not my business -- I don't want to rule or conquer anyone. I should like to help everyone if possible, Jew, gentile, black man, white. We all want to help one another, human beings are like that.
We all want to live by each other's happiness, not by each other's misery. We don't want to hate and despise one another. In this world there is room for everyone and the earth is rich and can provide for everyone.
The way of life can be free and beautiful.
But we have lost the way.
Greed has poisoned men's souls -- has barricaded the world with hate; has goose-stepped us into misery and bloodshed.
We have developed speed but we have shut ourselves in: machinery that gives abundance has left us in want. Our knowledge has made us cynical, our cleverness hard and unkind. We think too much and feel too little: More than machinery we need humanity; More than cleverness we need kindness and gentleness. Without these qualities, life will be violent and all will be lost.
The aeroplane and the radio have brought us closer together. The very nature of these inventions cries out for the goodness in men, cries out for universal brotherhood for the unity of us all. Even now my voice is reaching millions throughout the world, millions of despairing men, women and little children, victims of a system that makes men torture and imprison innocent people. To those who can hear me I say "Do not despair".
The misery that is now upon us is but the passing of greed, the bitterness of men who fear the way of human progress: the hate of men will pass and dictators die and the power they took from the people, will return to the people and so long as men die [now] liberty will never perish...
Soldiers -- don't give yourselves to brutes, men who despise you and enslave you -- who regiment your lives, tell you what to do, what to think and what to feel, who drill you, diet you, treat you as cattle, as cannon fodder.
Don't give yourselves to these unnatural men, machine men, with machine minds and machine hearts. You are not machines. You are not cattle. You are men. You have the love of humanity in your hearts. You don't hate -- only the unloved hate. Only the unloved and the unnatural. Soldiers -- don't fight for slavery, fight for liberty.
In the seventeenth chapter of Saint Luke it is written " the kingdom of God is within man " -- not one man, nor a group of men -- but in all men -- in you, the people.
You the people have the power, the power to create machines, the power to create happiness. You the people have the power to make life free and beautiful, to make this life a wonderful adventure. Then in the name of democracy let's use that power -- let us all unite. Let us fight for a new world, a decent world that will give men a chance to work, that will give you the future and old age and security. By the promise of these things, brutes have risen to power, but they lie. They do not fulfil their promise, they never will. Dictators free themselves but they enslave the people. Now let us fight to fulfil that promise. Let us fight to free the world, to do away with national barriers, do away with greed, with hate and intolerance. Let us fight for a world of reason, a world where science and progress will lead to all men's happiness.
Soldiers -- in the name of democracy, let us all unite!
https://www.youtube.com/watch?v=phc8joTm_1M
Friday, October 14, 2011
Eisenhower Farewell Speech
Good evening, my fellow Americans.
First, I should like to express my gratitude to the radio and television networks for the opportunities they have given me over the years to bring reports and messages to our nation. My special thanks go to them for the opportunity of addressing you this evening.
Three days from now, after a half century in the service of our country, I shall lay down the responsibilities of office as, in traditional and solemn ceremony, the authority of the Presidency is vested in my successor.
This evening I come to you with a message of leave-taking and farewell, and to share a few final thoughts with you, my countrymen. Like every other citizen, I wish the new President, and all who will labor with him, Godspeed. I pray that the coming years will be blessed with peace and prosperity for all.
Our people expect their President and the Congress to find essential agreement on issues of great moment, the wise resolution of which will better shape the future of the nation. My own relations with the Congress, which began on a remote and tenuous basis when, long ago, a member of the Senate appointed me to West Point, have since ranged to the intimate during the war and immediate post-war period, and finally to the mutually interdependent during these past eight years. In this final relationship, the Congress and the Administration have, on most vital issues, cooperated well, to serve the nation good, rather than mere partisanship, and so have assured that the business of the nation should go forward. So, my official relationship with Congress ends in a feeling -- on my part -- of gratitude that we have been able to do so much together.
We now stand ten years past the midpoint of a century that has witnessed four major wars among great nations. Three of these involved our own country. Despite these holocausts, America is today the strongest, the most influential, and most productive nation in the world. Understandably proud of this pre-eminence, we yet realize that America's leadership and prestige depend, not merely upon our unmatched material progress, riches and military strength, but on how we use our power in the interests of world peace and human betterment.
Throughout America's adventure in free government, our basic purposes have been to keep the peace, to foster progress in human achievement, and to enhance liberty, dignity and integrity among peoples and among nations. To strive for less would be unworthy of a free and religious people. Any failure traceable to arrogance or our lack of comprehension or readiness to sacrifice would inflict upon us grievous hurt, both at home and abroad.
Progress toward these noble goals is persistently threatened by the conflict now engulfing the world. It commands our whole attention, absorbs our very beings. We face a hostile ideology global in scope, atheistic in character, ruthless in purpose, and insidious in method. Unhappily, the danger it poses promises to be of indefinite duration. To meet it successfully, there is called for, not so much the emotional and transitory sacrifices of crisis, but rather those which enable us to carry forward steadily, surely, and without complaint the burdens of a prolonged and complex struggle with liberty the stake. Only thus shall we remain, despite every provocation, on our charted course toward permanent peace and human betterment.
Crises there will continue to be. In meeting them, whether foreign or domestic, great or small, there is a recurring temptation to feel that some spectacular and costly action could become the miraculous solution to all current difficulties. A huge increase in newer elements of our defenses; development of unrealistic programs to cure every ill in agriculture; a dramatic expansion in basic and applied research -- these and many other possibilities, each possibly promising in itself, may be suggested as the only way to the road we wish to travel.
But each proposal must be weighed in the light of a broader consideration: the need to maintain balance in and among national programs, balance between the private and the public economy, balance between the cost and hoped for advantages, balance between the clearly necessary and the comfortably desirable, balance between our essential requirements as a nation and the duties imposed by the nation upon the individual, balance between actions of the moment and the national welfare of the future. Good judgment seeks balance and progress. Lack of it eventually finds imbalance and frustration. The record of many decades stands as proof that our people and their Government have, in the main, understood these truths and have responded to them well, in the face of threat and stress.
But threats, new in kind or degree, constantly arise. Of these, I mention two only.
A vital element in keeping the peace is our military establishment. Our arms must be mighty, ready for instant action, so that no potential aggressor may be tempted to risk his own destruction. Our military organization today bears little relation to that known by any of my predecessors in peacetime, or, indeed, by the fighting men of World War II or Korea.
Until the latest of our world conflicts, the United States had no armaments industry. American makers of plowshares could, with time and as required, make swords as well. But now we can no longer risk emergency improvisation of national defense. We have been compelled to create a permanent armaments industry of vast proportions. Added to this, three and a half million men and women are directly engaged in the defense establishment. We annually spend on military security alone more than the net income of all United States corporations.
Now this conjunction of an immense military establishment and a large arms industry is new in the American experience. The total influence -- economic, political, even spiritual --is felt in every city, every Statehouse, every office of the Federal government. We recognize the imperative need for this development. Yet we must not fail to comprehend its grave implications. Our toil, resources, and livelihood are all involved. So is the very structure of our society.
In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military-industrial complex. The potential for the disastrous rise of misplaced power exists and will persist. We must never let the weight of this combination endanger our liberties or democratic processes. We should take nothing for granted. Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals, so that security and liberty may prosper together.
Akin to, and largely responsible for the sweeping changes in our industrial-military posture, has been the technological revolution during recent decades. In this revolution, research has become central, it also becomes more formalized, complex, and costly. A steadily increasing share is conducted for, by, or at the direction of, the Federal government.
Today, the solitary inventor, tinkering in his shop, has been overshadowed by task forces of scientists in laboratories and testing fields. In the same fashion, the free university, historically the fountainhead of free ideas and scientific discovery, has experienced a revolution in the conduct of research. Partly because of the huge costs involved, a government contract becomes virtually a substitute for intellectual curiosity. For every old blackboard there are now hundreds of new electronic computers. The prospect of domination of the nation's scholars by Federal employment, project allocations, and the power of money is ever present -- and is gravely to be regarded.
Yet, in holding scientific research and discovery in respect, as we should, we must also be alert to the equal and opposite danger that public policy could itself become the captive of a scientific-technological elite.
It is the task of statesmanship to mold, to balance, and to integrate these and other forces, new and old, within the principles of our democratic system – ever aiming toward the supreme goals of our free society.
Another factor in maintaining balance involves the element of time. As we peer into society's future, we -- you and I, and our government -- must avoid the impulse to live only for today, plundering for our own ease and convenience the precious resources of tomorrow. We cannot mortgage the material assets of our grandchildren without risking the loss also of their political and spiritual heritage. We want democracy to survive for all generations to come, not to become the insolvent phantom of tomorrow.
During the long lane of the history yet to be written, America knows that this world of ours, ever growing smaller, must avoid becoming a community of dreadful fear and hate, and be, instead, a proud confederation of mutual trust and respect. Such a confederation must be one of equals. The weakest must come to the conference table with the same confidence as do we, protected as we are by our moral, economic, and military strength. That table, though scarred by many past frustrations, cannot be abandoned for the certain agony of the battlefield.
Disarmament, with mutual honor and confidence, is a continuing imperative. Together we must learn how to compose differences, not with arms, but with intellect and decent purpose. Because this need is so sharp and apparent, I confess that I lay down my official responsibilities in this field with a definite sense of disappointment. As one who has witnessed the horror and the lingering sadness of war, as one who knows that another war could utterly destroy this civilization which has been so slowly and painfully built over thousands of years, I wish I could say tonight that a lasting peace is in sight.
Happily, I can say that war has been avoided. Steady progress toward our ultimate goal has been made. But so much remains to be done. As a private citizen, I shall never cease to do what little I can to help the world advance along that road.
So, in this my last good night to you as your President, I thank you for the many opportunities you have given me for public service in war and in peace. I trust that in that service you find some things worthy. As for the rest of it, I know you will find ways to improve performance in the future.
You and I, my fellow citizens, need to be strong in our faith that all nations, under God, will reach the goal of peace with justice. May we be ever unswerving in devotion to principle, confident but humble with power, diligent in pursuit of the Nations' great goals.
To all the peoples of the world, I once more give expression to America's prayerful and continuing aspiration: We pray that peoples of all faiths, all races, all nations, may have their great human needs satisfied; that those now denied opportunity shall come to enjoy it to the full; that all who yearn for freedom may experience its spiritual blessings. Those who have freedom will understand, also, its heavy responsibilities; that all who are insensitive to the needs of others will learn charity; and that the scourges of poverty, disease and ignorance will be made to disappear from the earth; and that, in the goodness of time, all peoples will come to live together in a peace guaranteed by the binding force of mutual respect and love.
Now, on Friday noon, I am to become a private citizen. I am proud to do so. I look forward to it.
Thank you, and good night.
First, I should like to express my gratitude to the radio and television networks for the opportunities they have given me over the years to bring reports and messages to our nation. My special thanks go to them for the opportunity of addressing you this evening.
Three days from now, after a half century in the service of our country, I shall lay down the responsibilities of office as, in traditional and solemn ceremony, the authority of the Presidency is vested in my successor.
This evening I come to you with a message of leave-taking and farewell, and to share a few final thoughts with you, my countrymen. Like every other citizen, I wish the new President, and all who will labor with him, Godspeed. I pray that the coming years will be blessed with peace and prosperity for all.
Our people expect their President and the Congress to find essential agreement on issues of great moment, the wise resolution of which will better shape the future of the nation. My own relations with the Congress, which began on a remote and tenuous basis when, long ago, a member of the Senate appointed me to West Point, have since ranged to the intimate during the war and immediate post-war period, and finally to the mutually interdependent during these past eight years. In this final relationship, the Congress and the Administration have, on most vital issues, cooperated well, to serve the nation good, rather than mere partisanship, and so have assured that the business of the nation should go forward. So, my official relationship with Congress ends in a feeling -- on my part -- of gratitude that we have been able to do so much together.
We now stand ten years past the midpoint of a century that has witnessed four major wars among great nations. Three of these involved our own country. Despite these holocausts, America is today the strongest, the most influential, and most productive nation in the world. Understandably proud of this pre-eminence, we yet realize that America's leadership and prestige depend, not merely upon our unmatched material progress, riches and military strength, but on how we use our power in the interests of world peace and human betterment.
Throughout America's adventure in free government, our basic purposes have been to keep the peace, to foster progress in human achievement, and to enhance liberty, dignity and integrity among peoples and among nations. To strive for less would be unworthy of a free and religious people. Any failure traceable to arrogance or our lack of comprehension or readiness to sacrifice would inflict upon us grievous hurt, both at home and abroad.
Progress toward these noble goals is persistently threatened by the conflict now engulfing the world. It commands our whole attention, absorbs our very beings. We face a hostile ideology global in scope, atheistic in character, ruthless in purpose, and insidious in method. Unhappily, the danger it poses promises to be of indefinite duration. To meet it successfully, there is called for, not so much the emotional and transitory sacrifices of crisis, but rather those which enable us to carry forward steadily, surely, and without complaint the burdens of a prolonged and complex struggle with liberty the stake. Only thus shall we remain, despite every provocation, on our charted course toward permanent peace and human betterment.
Crises there will continue to be. In meeting them, whether foreign or domestic, great or small, there is a recurring temptation to feel that some spectacular and costly action could become the miraculous solution to all current difficulties. A huge increase in newer elements of our defenses; development of unrealistic programs to cure every ill in agriculture; a dramatic expansion in basic and applied research -- these and many other possibilities, each possibly promising in itself, may be suggested as the only way to the road we wish to travel.
But each proposal must be weighed in the light of a broader consideration: the need to maintain balance in and among national programs, balance between the private and the public economy, balance between the cost and hoped for advantages, balance between the clearly necessary and the comfortably desirable, balance between our essential requirements as a nation and the duties imposed by the nation upon the individual, balance between actions of the moment and the national welfare of the future. Good judgment seeks balance and progress. Lack of it eventually finds imbalance and frustration. The record of many decades stands as proof that our people and their Government have, in the main, understood these truths and have responded to them well, in the face of threat and stress.
But threats, new in kind or degree, constantly arise. Of these, I mention two only.
A vital element in keeping the peace is our military establishment. Our arms must be mighty, ready for instant action, so that no potential aggressor may be tempted to risk his own destruction. Our military organization today bears little relation to that known by any of my predecessors in peacetime, or, indeed, by the fighting men of World War II or Korea.
Until the latest of our world conflicts, the United States had no armaments industry. American makers of plowshares could, with time and as required, make swords as well. But now we can no longer risk emergency improvisation of national defense. We have been compelled to create a permanent armaments industry of vast proportions. Added to this, three and a half million men and women are directly engaged in the defense establishment. We annually spend on military security alone more than the net income of all United States corporations.
Now this conjunction of an immense military establishment and a large arms industry is new in the American experience. The total influence -- economic, political, even spiritual --is felt in every city, every Statehouse, every office of the Federal government. We recognize the imperative need for this development. Yet we must not fail to comprehend its grave implications. Our toil, resources, and livelihood are all involved. So is the very structure of our society.
In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military-industrial complex. The potential for the disastrous rise of misplaced power exists and will persist. We must never let the weight of this combination endanger our liberties or democratic processes. We should take nothing for granted. Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals, so that security and liberty may prosper together.
Akin to, and largely responsible for the sweeping changes in our industrial-military posture, has been the technological revolution during recent decades. In this revolution, research has become central, it also becomes more formalized, complex, and costly. A steadily increasing share is conducted for, by, or at the direction of, the Federal government.
Today, the solitary inventor, tinkering in his shop, has been overshadowed by task forces of scientists in laboratories and testing fields. In the same fashion, the free university, historically the fountainhead of free ideas and scientific discovery, has experienced a revolution in the conduct of research. Partly because of the huge costs involved, a government contract becomes virtually a substitute for intellectual curiosity. For every old blackboard there are now hundreds of new electronic computers. The prospect of domination of the nation's scholars by Federal employment, project allocations, and the power of money is ever present -- and is gravely to be regarded.
Yet, in holding scientific research and discovery in respect, as we should, we must also be alert to the equal and opposite danger that public policy could itself become the captive of a scientific-technological elite.
It is the task of statesmanship to mold, to balance, and to integrate these and other forces, new and old, within the principles of our democratic system – ever aiming toward the supreme goals of our free society.
Another factor in maintaining balance involves the element of time. As we peer into society's future, we -- you and I, and our government -- must avoid the impulse to live only for today, plundering for our own ease and convenience the precious resources of tomorrow. We cannot mortgage the material assets of our grandchildren without risking the loss also of their political and spiritual heritage. We want democracy to survive for all generations to come, not to become the insolvent phantom of tomorrow.
During the long lane of the history yet to be written, America knows that this world of ours, ever growing smaller, must avoid becoming a community of dreadful fear and hate, and be, instead, a proud confederation of mutual trust and respect. Such a confederation must be one of equals. The weakest must come to the conference table with the same confidence as do we, protected as we are by our moral, economic, and military strength. That table, though scarred by many past frustrations, cannot be abandoned for the certain agony of the battlefield.
Disarmament, with mutual honor and confidence, is a continuing imperative. Together we must learn how to compose differences, not with arms, but with intellect and decent purpose. Because this need is so sharp and apparent, I confess that I lay down my official responsibilities in this field with a definite sense of disappointment. As one who has witnessed the horror and the lingering sadness of war, as one who knows that another war could utterly destroy this civilization which has been so slowly and painfully built over thousands of years, I wish I could say tonight that a lasting peace is in sight.
Happily, I can say that war has been avoided. Steady progress toward our ultimate goal has been made. But so much remains to be done. As a private citizen, I shall never cease to do what little I can to help the world advance along that road.
So, in this my last good night to you as your President, I thank you for the many opportunities you have given me for public service in war and in peace. I trust that in that service you find some things worthy. As for the rest of it, I know you will find ways to improve performance in the future.
You and I, my fellow citizens, need to be strong in our faith that all nations, under God, will reach the goal of peace with justice. May we be ever unswerving in devotion to principle, confident but humble with power, diligent in pursuit of the Nations' great goals.
To all the peoples of the world, I once more give expression to America's prayerful and continuing aspiration: We pray that peoples of all faiths, all races, all nations, may have their great human needs satisfied; that those now denied opportunity shall come to enjoy it to the full; that all who yearn for freedom may experience its spiritual blessings. Those who have freedom will understand, also, its heavy responsibilities; that all who are insensitive to the needs of others will learn charity; and that the scourges of poverty, disease and ignorance will be made to disappear from the earth; and that, in the goodness of time, all peoples will come to live together in a peace guaranteed by the binding force of mutual respect and love.
Now, on Friday noon, I am to become a private citizen. I am proud to do so. I look forward to it.
Thank you, and good night.
Thursday, July 28, 2011
Determinism and Free Will
On Determinism and Free Will - Erwin Schrödinger's mystical epilogue to What Is Life?
As a reward for the serious trouble I have taken to expound the purely scientific aspects of our problem sine ira et, studio, I beg leave to add my own, necessarily subjective, view of the philosophical implications.
According to the evidence put forward in the preceding pages the space-time events in the body of a living being which correspond to the activity of its mind, to its self-conscious or any other actions, are (considering also their complex structure and the accepted statistical explanation of physico-chemistry) if not strictly deterministic at any rate statistico-deterministic. To the physicist I wish to emphasize that in my opinion, and contrary to the opinion upheld in some quarters, quantum indeterminacy plays no biologically relevant role in them, except perhaps by enhancing their purely accidental character in such events as meiosis, natural and X-ray-induced mutation and so on — and this is in any case obvious and well recognized.
For the sake of argument, let me regard this as a fact, as I believe every unbiased biologist would, if there were not the well-known, unpleasant feeling about 'declaring oneself to be a pure mechanism'. For it is deemed to contradict Free Will as warranted by direct introspection. But immediate experiences in themselves, however various and disparate they be, are logically incapable of contradicting each other. So let us see whether we cannot draw the correct, non-contradictory conclusion from the following two premises:
(i) My body functions as a pure mechanism according to the Laws of Nature.
(ii) Yet I know, by incontrovertible direct experience, that I am directing its motions, of which I foresee the effects, that may be fateful and all-important, in which case I feel and take full responsibility for them.
The only possible inference from these two facts is, I think, that I — I in the widest meaning of the word, that is to say, every conscious mind that has ever said or felt 'I' — am the person, if any, who controls the 'motion of the atoms' according to the Laws of Nature. Within a cultural milieu (Kulturkreis) where certain conceptions (which once had or still have a wider meaning amongst other peoples) have been limited and specialized, it is daring to give to this conclusion the simple wording that it requires. In Christian terminology to say: 'Hence I am God Almighty' sounds both blasphemous and lunatic. But please disregard these connotations for the moment and consider whether the above inference is not the closest a biologist can get to proving God and immortality at one stroke.
In itself, the insight is not new. The earliest records to my knowledge date back some 2,500 years or more. From the early great Upanishads the recognition ATHMAN = BRAHMAN (the personal self equals the omnipresent, all-comprehending eternal self) was in Indian thought considered, far from being blasphemous, to represent the quintessence of deepest insight into the happenings of the world. The striving of all the scholars of Vedanta was, after having learnt to pronounce with their lips, really to assimilate in their minds this grandest of all thoughts. Again, the mystics of many centuries, independently, yet in perfect harmony with each other (somewhat like the particles in an ideal gas) have described, each of them, the unique experience of his or her life in terms that can be condensed in the phrase: DEUS FACTUS SUM (I have become God).
To Western ideology the thought has remained a stranger, in spite of Schopenhauer and others who stood for it and in spite of those true lovers who, as they look into each other's eyes, become aware that their thought and their joy are numerically one — not merely similar or identical; but they, as a rule, are emotionally too busy to indulge in clear thinking, in which respect they very much resemble the mystic.
Allow me a few further comments. Consciousness is never experienced in the plural, only in the singular. Even in the pathological cases of split consciousness or double personality the two persons alternate, they are never manifest simultaneously. In a dream we do perform several characters at the same time, but not indiscriminately: we are one of them; in him we act and speak directly, while we often eagerly await the answer or response of another person, unaware of the fact that it is we who control his movements and his speech just as much as our own.
How does the idea of plurality (so emphatically opposed by the Upanishad writers) arise at all? Consciousness finds itself intimately connected with, and dependent on, the physical state of a limited region of matter, the body. (Consider the changes of mind during the development of the body, as puberty, ageing, dotage, etc., or consider the effects of fever, intoxication, narcosis, lesion of the brain and so on.) Now, there is a great plurality of similar bodies. Hence the pluralization of consciousnesses or minds seems a very suggestive hypothesis. Probably all simple, ingenuous people, as well as the great majority of Western philosophers, have accepted it.
It leads almost immediately to the invention of souls, as many as there are bodies, and to the question whether they are mortal as the body is or whether they are immortal and capable of existing by themselves. The former alternative is distasteful, while the latter frankly forgets, ignores or disowns the facts upon which the plurality hypothesis rests. Much sillier questions have been asked: Do animals also have souls? It has even been questioned whether women, or only men, have souls.
Such consequences, even if only tentative, must make us suspicious of the plurality hypothesis, which is common to all official Western creeds. Are we not inclining to much greater nonsense, if in discarding their gross superstitions we retain their naive idea of plurality of souls, but 'remedy' it by declaring the souls to be perishable, to be annihilated with the respective bodies?
The only possible alternative is simply to keep to the immediate experience that consciousness is a singular of which the plural is unknown; that there is only one thing and that what seems to be a plurality is merely a series of different aspects of this one thing, produced by a deception (the Indian MAJA); the same illusion is produced in a gallery of mirrors, and in the same way Gaurisankar and Mt Everest turned out to be the same peak seen from different valleys.
There are, of course, elaborate ghost-stories fixed in our minds to hamper our acceptance of such simple recognition. E.g. it has been said that there is a tree there outside my window but I do not really see the tree. By some cunning device of which only the initial, relatively simple steps are explored, the real tree throws an image of itself into my consciousness, and that is what I perceive. If you stand by my side and look at the same tree, the latter manages to throw an image into your soul as well. I see my tree and you see yours (remarkably like mine), and what the tree in itself is we do not know. For this extravagance Kant is responsible. In the order of ideas which regards consciousness as a singulare tantum it is conveniently replaced by the statement that there is obviously only one tree and all the image business is a ghost-story.
Yet each of us has the indisputable impression that the sum total of his own experience and memory forms a unit, quite distinct from that of any other person. He refers to it as 'I'. What is this 'I?
If you analyse it closely you will, I think, find that it is just a little bit more than a collection of single data (experiences and memories), namely the canvas upon which they are collected. And you will, on close introspection, find that what you really mean by 'I' is that ground-stuff upon which they are collected. You may come to a distant country, lose sight of all your friends, may all but forget them; you acquire new friends, you share life with them as intensely as you ever did with your old ones. Less and less important will become the fact that, while living your new life, you still recollect the old one. 'The youth that was I', you may come to speak of him in the third person, indeed the protagonist of the novel you are reading is probably nearer to your heart, certainly more intensely alive and better known to you. Yet there has been no intermediate break, no death. And even if a skilled hypnotist succeeded in blotting out entirely all your earlier reminiscences, you would not find that he had killed you. In no case is there a loss of personal existence to deplore. Nor will there ever be.
As a reward for the serious trouble I have taken to expound the purely scientific aspects of our problem sine ira et, studio, I beg leave to add my own, necessarily subjective, view of the philosophical implications.
According to the evidence put forward in the preceding pages the space-time events in the body of a living being which correspond to the activity of its mind, to its self-conscious or any other actions, are (considering also their complex structure and the accepted statistical explanation of physico-chemistry) if not strictly deterministic at any rate statistico-deterministic. To the physicist I wish to emphasize that in my opinion, and contrary to the opinion upheld in some quarters, quantum indeterminacy plays no biologically relevant role in them, except perhaps by enhancing their purely accidental character in such events as meiosis, natural and X-ray-induced mutation and so on — and this is in any case obvious and well recognized.
For the sake of argument, let me regard this as a fact, as I believe every unbiased biologist would, if there were not the well-known, unpleasant feeling about 'declaring oneself to be a pure mechanism'. For it is deemed to contradict Free Will as warranted by direct introspection. But immediate experiences in themselves, however various and disparate they be, are logically incapable of contradicting each other. So let us see whether we cannot draw the correct, non-contradictory conclusion from the following two premises:
(i) My body functions as a pure mechanism according to the Laws of Nature.
(ii) Yet I know, by incontrovertible direct experience, that I am directing its motions, of which I foresee the effects, that may be fateful and all-important, in which case I feel and take full responsibility for them.
The only possible inference from these two facts is, I think, that I — I in the widest meaning of the word, that is to say, every conscious mind that has ever said or felt 'I' — am the person, if any, who controls the 'motion of the atoms' according to the Laws of Nature. Within a cultural milieu (Kulturkreis) where certain conceptions (which once had or still have a wider meaning amongst other peoples) have been limited and specialized, it is daring to give to this conclusion the simple wording that it requires. In Christian terminology to say: 'Hence I am God Almighty' sounds both blasphemous and lunatic. But please disregard these connotations for the moment and consider whether the above inference is not the closest a biologist can get to proving God and immortality at one stroke.
In itself, the insight is not new. The earliest records to my knowledge date back some 2,500 years or more. From the early great Upanishads the recognition ATHMAN = BRAHMAN (the personal self equals the omnipresent, all-comprehending eternal self) was in Indian thought considered, far from being blasphemous, to represent the quintessence of deepest insight into the happenings of the world. The striving of all the scholars of Vedanta was, after having learnt to pronounce with their lips, really to assimilate in their minds this grandest of all thoughts. Again, the mystics of many centuries, independently, yet in perfect harmony with each other (somewhat like the particles in an ideal gas) have described, each of them, the unique experience of his or her life in terms that can be condensed in the phrase: DEUS FACTUS SUM (I have become God).
To Western ideology the thought has remained a stranger, in spite of Schopenhauer and others who stood for it and in spite of those true lovers who, as they look into each other's eyes, become aware that their thought and their joy are numerically one — not merely similar or identical; but they, as a rule, are emotionally too busy to indulge in clear thinking, in which respect they very much resemble the mystic.
Allow me a few further comments. Consciousness is never experienced in the plural, only in the singular. Even in the pathological cases of split consciousness or double personality the two persons alternate, they are never manifest simultaneously. In a dream we do perform several characters at the same time, but not indiscriminately: we are one of them; in him we act and speak directly, while we often eagerly await the answer or response of another person, unaware of the fact that it is we who control his movements and his speech just as much as our own.
How does the idea of plurality (so emphatically opposed by the Upanishad writers) arise at all? Consciousness finds itself intimately connected with, and dependent on, the physical state of a limited region of matter, the body. (Consider the changes of mind during the development of the body, as puberty, ageing, dotage, etc., or consider the effects of fever, intoxication, narcosis, lesion of the brain and so on.) Now, there is a great plurality of similar bodies. Hence the pluralization of consciousnesses or minds seems a very suggestive hypothesis. Probably all simple, ingenuous people, as well as the great majority of Western philosophers, have accepted it.
It leads almost immediately to the invention of souls, as many as there are bodies, and to the question whether they are mortal as the body is or whether they are immortal and capable of existing by themselves. The former alternative is distasteful, while the latter frankly forgets, ignores or disowns the facts upon which the plurality hypothesis rests. Much sillier questions have been asked: Do animals also have souls? It has even been questioned whether women, or only men, have souls.
Such consequences, even if only tentative, must make us suspicious of the plurality hypothesis, which is common to all official Western creeds. Are we not inclining to much greater nonsense, if in discarding their gross superstitions we retain their naive idea of plurality of souls, but 'remedy' it by declaring the souls to be perishable, to be annihilated with the respective bodies?
The only possible alternative is simply to keep to the immediate experience that consciousness is a singular of which the plural is unknown; that there is only one thing and that what seems to be a plurality is merely a series of different aspects of this one thing, produced by a deception (the Indian MAJA); the same illusion is produced in a gallery of mirrors, and in the same way Gaurisankar and Mt Everest turned out to be the same peak seen from different valleys.
There are, of course, elaborate ghost-stories fixed in our minds to hamper our acceptance of such simple recognition. E.g. it has been said that there is a tree there outside my window but I do not really see the tree. By some cunning device of which only the initial, relatively simple steps are explored, the real tree throws an image of itself into my consciousness, and that is what I perceive. If you stand by my side and look at the same tree, the latter manages to throw an image into your soul as well. I see my tree and you see yours (remarkably like mine), and what the tree in itself is we do not know. For this extravagance Kant is responsible. In the order of ideas which regards consciousness as a singulare tantum it is conveniently replaced by the statement that there is obviously only one tree and all the image business is a ghost-story.
Yet each of us has the indisputable impression that the sum total of his own experience and memory forms a unit, quite distinct from that of any other person. He refers to it as 'I'. What is this 'I?
If you analyse it closely you will, I think, find that it is just a little bit more than a collection of single data (experiences and memories), namely the canvas upon which they are collected. And you will, on close introspection, find that what you really mean by 'I' is that ground-stuff upon which they are collected. You may come to a distant country, lose sight of all your friends, may all but forget them; you acquire new friends, you share life with them as intensely as you ever did with your old ones. Less and less important will become the fact that, while living your new life, you still recollect the old one. 'The youth that was I', you may come to speak of him in the third person, indeed the protagonist of the novel you are reading is probably nearer to your heart, certainly more intensely alive and better known to you. Yet there has been no intermediate break, no death. And even if a skilled hypnotist succeeded in blotting out entirely all your earlier reminiscences, you would not find that he had killed you. In no case is there a loss of personal existence to deplore. Nor will there ever be.
Thursday, January 21, 2010
Stellar Evolution
Where are Stars Born?
Astronomers believe that molecular clouds, dense clouds of gas located primarily in the spiral arms of galaxies are the birthplace of stars. Dense regions in the clouds collapse and form 'protostars' so a star begins its life as a large and comparatively cool mass of gas. The contraction of this gas and the subsequent rise of temperature continue until the interior temperature of the star reaches a value of about 1,000,000°C (about 1,800,000°F).
At this point a nuclear reaction takes place in which the nuclei of hydrogen atoms combine with heavy hydrogen deuterons (nuclei of so-called heavy hydrogen atoms) to form the nucleus of the inert gas helium. The latter reaction liberates large amounts of nuclear energy, and the further contraction of the star is halted. Once the star has started nuclear fusion, it becomes a 'main sequence' star.
Main Sequence Stars
Main sequence stars are stars, like our Sun, that burn hydrogen to helium in their cores. For a given chemical composition and stellar age, a stars' luminosity, the total energy radiated by the star per unit time, depends only on its mass. Stars that are ten times more massive than the Sun are over a thousand times more luminous than the Sun. However, we should not be too embarrassed by the Sun's low luminosity: it is ten times brighter than a star half its mass. The more massive a main sequence star, the brighter and bluer it is.
For example, Sirius - the dog star, located to the lower left of the constellation Orion, is more massive than the Sun, and is noticeably bluer. On the other hand, Alpha Centauri, our nearest neighbour, is less massive than the Sun, and is thus redder and less luminous.
Since stars have a limited supply of hydrogen in their cores, they have a limited lifetime as main sequence stars. This lifetime is proportional to f M / L, where f is the fraction of the total mass of the star, M, available for nuclear fusion in the core and L is the average luminosity of the star during its main sequence lifetime. Because of the strong dependence of luminosity on mass, stellar lifetimes depend sensitively on mass. Thus, it is fortunate that our Sun is not more massive than it is since high mass stars rapidly exhaust their core hydrogen supply.
Once a star exhausts its core hydrogen supply, the star becomes redder, larger, and more luminous: it becomes a red giant star. This relationship between mass and lifetime enables astronomers to put a lower limit on the age of the universe.
Death of an "Ordinary" Star
After a low mass star like the Sun exhausts the supply of hydrogen in its core, there is no longer any source of heat to support the core against gravity. The core of the star collapse under gravity's pull until it reaches a high enough density to start converting helium to carbon. Meanwhile, the stars' outer envelope expands and the star evolves into a red giant. When the Sun becomes a red giant, its atmosphere will envelope the Earth and our planet will be consumed in a fiery death. The Sun will eventually evolve into a red super-giant as it exhausts the helium in its core. At this stage, it will have an outer envelope extending out towards Jupiter. During this brief phase of its existence, which last only a few tens of thousands of years, the Sun will lose mass in a powerful wind.
Eventually, the Sun will lose all of the mass in its envelope and leave behind a hot core of carbon imbedded in a nebula of expelled gas. Radiation from this hot core will ionize the nebula produces a striking 'planetary nebula', much like the nebulas seen around the remnants of other stars. The carbon core will eventually cool and become a white dwarf, the dense dim remnant of a once bright star. The final fate of low-mass dwarfs is unknown, except that they cease to radiate appreciably. Most likely they become burned-out cinders, or black dwarfs.
Death of a Massive Star
Massive stars burn brighter and perish more dramatically than most. When a star ten times more massive then Sun exhaust the helium in the core, the nuclear fusion cycle continues. The carbon core contracts further and reaches high enough temperature to burn carbon to oxygen, neon, silicon, sulphur and finally to iron.
Iron is the most stable form of nuclear matter and there is no energy to be gained by converting it to any heavier element. Without any source of heat to balance the gravity, the iron core collapses until it reaches nuclear densities. This high density core resists further collapse causing the in-falling matter to 'bounce' off the core.
This sudden core bounce (which includes the release of energetic neutrinos from the core) produces a supernova explosion. For one brilliant month, a single star burns brighter than a whole galaxy of a billion stars. Supernova explosions inject carbon, oxygen, silicon and other heavy elements up to iron into interstellar space. They are also the site where most of the elements heavier than iron are produced.
Future generations of stars formed from this heavy element enriched gas will therefore start life with a richer supply of heavier elements than the earlier generations of stars. Without supernova, the fiery death of massive stars, there would be no carbon, oxygen or other elements that make life possible.
The fate of the hot neutron core depends upon the mass of the progenitor star. If the progenitor mass is around ten times the mass of the Sun, the neutron star core will cool to form a neutron star. Neutron stars are potentially detectable as 'pulsars', powerful beacons of radio emission. A limit exists for the size of neutron stars, however, beyond which such stars are gravitationally bound to keep contracting until they become a black hole, from which light radiation cannot escape.
If the progenitor mass is larger, then the resultant core is so heavy that not even nuclear forces can resist the pull of gravity and the core collapses to form a black hole.
excerpt borrowed from http://www.astronomytoday.com/cosmology/evol.html
Astronomers believe that molecular clouds, dense clouds of gas located primarily in the spiral arms of galaxies are the birthplace of stars. Dense regions in the clouds collapse and form 'protostars' so a star begins its life as a large and comparatively cool mass of gas. The contraction of this gas and the subsequent rise of temperature continue until the interior temperature of the star reaches a value of about 1,000,000°C (about 1,800,000°F).
At this point a nuclear reaction takes place in which the nuclei of hydrogen atoms combine with heavy hydrogen deuterons (nuclei of so-called heavy hydrogen atoms) to form the nucleus of the inert gas helium. The latter reaction liberates large amounts of nuclear energy, and the further contraction of the star is halted. Once the star has started nuclear fusion, it becomes a 'main sequence' star.
Main Sequence Stars
Main sequence stars are stars, like our Sun, that burn hydrogen to helium in their cores. For a given chemical composition and stellar age, a stars' luminosity, the total energy radiated by the star per unit time, depends only on its mass. Stars that are ten times more massive than the Sun are over a thousand times more luminous than the Sun. However, we should not be too embarrassed by the Sun's low luminosity: it is ten times brighter than a star half its mass. The more massive a main sequence star, the brighter and bluer it is.
For example, Sirius - the dog star, located to the lower left of the constellation Orion, is more massive than the Sun, and is noticeably bluer. On the other hand, Alpha Centauri, our nearest neighbour, is less massive than the Sun, and is thus redder and less luminous.
Since stars have a limited supply of hydrogen in their cores, they have a limited lifetime as main sequence stars. This lifetime is proportional to f M / L, where f is the fraction of the total mass of the star, M, available for nuclear fusion in the core and L is the average luminosity of the star during its main sequence lifetime. Because of the strong dependence of luminosity on mass, stellar lifetimes depend sensitively on mass. Thus, it is fortunate that our Sun is not more massive than it is since high mass stars rapidly exhaust their core hydrogen supply.
Once a star exhausts its core hydrogen supply, the star becomes redder, larger, and more luminous: it becomes a red giant star. This relationship between mass and lifetime enables astronomers to put a lower limit on the age of the universe.
Death of an "Ordinary" Star
After a low mass star like the Sun exhausts the supply of hydrogen in its core, there is no longer any source of heat to support the core against gravity. The core of the star collapse under gravity's pull until it reaches a high enough density to start converting helium to carbon. Meanwhile, the stars' outer envelope expands and the star evolves into a red giant. When the Sun becomes a red giant, its atmosphere will envelope the Earth and our planet will be consumed in a fiery death. The Sun will eventually evolve into a red super-giant as it exhausts the helium in its core. At this stage, it will have an outer envelope extending out towards Jupiter. During this brief phase of its existence, which last only a few tens of thousands of years, the Sun will lose mass in a powerful wind.
Eventually, the Sun will lose all of the mass in its envelope and leave behind a hot core of carbon imbedded in a nebula of expelled gas. Radiation from this hot core will ionize the nebula produces a striking 'planetary nebula', much like the nebulas seen around the remnants of other stars. The carbon core will eventually cool and become a white dwarf, the dense dim remnant of a once bright star. The final fate of low-mass dwarfs is unknown, except that they cease to radiate appreciably. Most likely they become burned-out cinders, or black dwarfs.
Death of a Massive Star
Massive stars burn brighter and perish more dramatically than most. When a star ten times more massive then Sun exhaust the helium in the core, the nuclear fusion cycle continues. The carbon core contracts further and reaches high enough temperature to burn carbon to oxygen, neon, silicon, sulphur and finally to iron.
Iron is the most stable form of nuclear matter and there is no energy to be gained by converting it to any heavier element. Without any source of heat to balance the gravity, the iron core collapses until it reaches nuclear densities. This high density core resists further collapse causing the in-falling matter to 'bounce' off the core.
This sudden core bounce (which includes the release of energetic neutrinos from the core) produces a supernova explosion. For one brilliant month, a single star burns brighter than a whole galaxy of a billion stars. Supernova explosions inject carbon, oxygen, silicon and other heavy elements up to iron into interstellar space. They are also the site where most of the elements heavier than iron are produced.
Future generations of stars formed from this heavy element enriched gas will therefore start life with a richer supply of heavier elements than the earlier generations of stars. Without supernova, the fiery death of massive stars, there would be no carbon, oxygen or other elements that make life possible.
The fate of the hot neutron core depends upon the mass of the progenitor star. If the progenitor mass is around ten times the mass of the Sun, the neutron star core will cool to form a neutron star. Neutron stars are potentially detectable as 'pulsars', powerful beacons of radio emission. A limit exists for the size of neutron stars, however, beyond which such stars are gravitationally bound to keep contracting until they become a black hole, from which light radiation cannot escape.
If the progenitor mass is larger, then the resultant core is so heavy that not even nuclear forces can resist the pull of gravity and the core collapses to form a black hole.
excerpt borrowed from http://www.astronomytoday.com/cosmology/evol.html
Sunday, September 13, 2009
The Brain
The brain has three main parts, the cerebrum, the cerebellum, and the brain stem. The brain is divided into regions that control specific functions.
THE CEREBRUM:
Frontal Lobe
* Behavior
* Abstract thought processes
* Problem solving
* Attention
* Creative thought
* Some emotion
* Intellect
* Reflection
* Judgment
* Initiative
* Inhibition
* Coordination of movements
* Generalized and mass movements
* Some eye movements
* Sense of smell
* Muscle movements
* Skilled movements
* Some motor skills
* Physical reaction
* Libido (sexual urges)
Occipital Lobe
* Vision
* Reading
Parietal Lobe
* Sense of touch (tactile senstation)
* Appreciation of form through touch (stereognosis)
* Response to internal stimuli (proprioception)
* Sensory combination and comprehension
* Some language and reading functions
* Some visual functions
Temporal Lobe
* Auditory memories
* Some hearing
* Visual memories
* Some vision pathways
* Other memory
* Music
* Fear
* Some language
* Some speech
* Some behavior amd emotions
* Sense of identity
Right Hemisphere (the representational hemisphere)
* The right hemisphere controls the left side of the body
* Temporal and spatial relationships
* Analyzing nonverbal information
* Communicating emotion
Left Hemisphere (the categorical hemisphere)
* The left hemisphere controls the right side of the body
* Produce and understand language
Corpus Callosum
* Communication between the left and right side of the brain
THE CEREBELLUM
* Balance
* Posture
* Cardiac, respiratory, and vasomotor centers
THE BRAIN STEM
* Motor and sensory pathway to body and face
* Vital centers: cardiac, respiratory, vasomotor
Hypothalamus
* Moods and motivation
* Sexual maturation
* Temperature regulation
* Hormonal body processes
Optic Chiasm
* Vision and the optic nerve
Pituitary Gland
* Hormonal body processes
* Physical maturation
* Growth (height and form)
* Sexual maturation
* Sexual functioning
Spinal Cord
* Conduit and source of sensation and movement
Pineal Body
* Unknown
Ventricles and Cerebral Aqueduct
* Contains the cerebrospinal fluid that bathes the brain and spinal cord
excerpt borrowed from http://www.enchantedlearning.com/subjects/anatomy/brain/Structure.shtml
THE CEREBRUM:
Frontal Lobe
* Behavior
* Abstract thought processes
* Problem solving
* Attention
* Creative thought
* Some emotion
* Intellect
* Reflection
* Judgment
* Initiative
* Inhibition
* Coordination of movements
* Generalized and mass movements
* Some eye movements
* Sense of smell
* Muscle movements
* Skilled movements
* Some motor skills
* Physical reaction
* Libido (sexual urges)
Occipital Lobe
* Vision
* Reading
Parietal Lobe
* Sense of touch (tactile senstation)
* Appreciation of form through touch (stereognosis)
* Response to internal stimuli (proprioception)
* Sensory combination and comprehension
* Some language and reading functions
* Some visual functions
Temporal Lobe
* Auditory memories
* Some hearing
* Visual memories
* Some vision pathways
* Other memory
* Music
* Fear
* Some language
* Some speech
* Some behavior amd emotions
* Sense of identity
Right Hemisphere (the representational hemisphere)
* The right hemisphere controls the left side of the body
* Temporal and spatial relationships
* Analyzing nonverbal information
* Communicating emotion
Left Hemisphere (the categorical hemisphere)
* The left hemisphere controls the right side of the body
* Produce and understand language
Corpus Callosum
* Communication between the left and right side of the brain
THE CEREBELLUM
* Balance
* Posture
* Cardiac, respiratory, and vasomotor centers
THE BRAIN STEM
* Motor and sensory pathway to body and face
* Vital centers: cardiac, respiratory, vasomotor
Hypothalamus
* Moods and motivation
* Sexual maturation
* Temperature regulation
* Hormonal body processes
Optic Chiasm
* Vision and the optic nerve
Pituitary Gland
* Hormonal body processes
* Physical maturation
* Growth (height and form)
* Sexual maturation
* Sexual functioning
Spinal Cord
* Conduit and source of sensation and movement
Pineal Body
* Unknown
Ventricles and Cerebral Aqueduct
* Contains the cerebrospinal fluid that bathes the brain and spinal cord
excerpt borrowed from http://www.enchantedlearning.com/subjects/anatomy/brain/Structure.shtml
Thursday, September 10, 2009
The Structure of the Brain
The nervous system is your body's decision and communication center. The central nervous system (CNS) is made of the brain and the spinal cord and the peripheral nervous system (PNS) is made of nerves. Together they control every part of your daily life, from breathing and blinking to helping you memorize facts for a test. Nerves reach from your brain to your face, ears, eyes, nose, and spinal cord... and from the spinal cord to the rest of your body. Sensory nerves gather information from the environment, send that info to the spinal cord, which then speed the message to the brain. The brain then makes sense of that message and fires off a response. Motor neurons deliver the instructions from the brain to the rest of your body. The spinal cord, made of a bundle of nerves running up and down the spine, is similar to a superhighway, speeding messages to and from the brain at every second.
The brain is made of three main parts: the forebrain, midbrain, and hindbrain. The forebrain consists of the cerebrum, thalamus, and hypothalamus (part of the limbic system). The midbrain consists of the tectum and tegmentum. The hindbrain is made of the cerebellum, pons and medulla. Often the midbrain, pons, and medulla are referred to together as the brainstem.
What do each of these lobes do?
* Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving
* Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli
* Occipital Lobe- associated with visual processing
* Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech
Note that the cerebral cortex is highly wrinkled. Essentially this makes the brain more efficient, because it can increase the surface area of the brain and the amount of neurons within it.
A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. Sometimes the right hemisphere is associated with creativity and the left hemispheres is associated with logic abilities. The corpus callosum is a bundle of axons which connects these two hemispheres.
Nerve cells make up the gray surface of the cerebrum which is a little thicker than your thumb. White nerve fibers underneath carry signals between the nerve cells and other parts of the brain and body.
The neocortex occupies the bulk of the cerebrum. This is a six-layered structure of the cerebral cortex which is only found in mammals. It is thought that the neocortex is a recently evolved structure, and is associated with "higher" information processing by more fully evolved animals (such as humans, primates, dolphins, etc).
The Cerebellum: The cerebellum, or "little brain", is similar to the cerebrum in that it has two hemispheres and has a highly folded surface or cortex. This structure is associated with regulation and coordination of movement, posture, and balance.
The cerebellum is assumed to be much older than the cerebrum, evolutionarily. What do I mean by this? In other words, animals which scientists assume to have evolved prior to humans, for example reptiles, do have developed cerebellums. However, reptiles do not have neocortex. Go here for more discussion of the neocortex or go to the following web site for a more detailed look at evolution of brain structures and intelligence: "Ask the Experts": Evolution and Intelligence
Limbic System: The limbic system, often referred to as the "emotional brain", is found buried within the cerebrum. Like the cerebellum, evolutionarily the structure is rather old.
This system contains the thalamus, hypothalamus, amygdala, and hippocampus.
Brain Stem: Underneath the limbic system is the brain stem. This structure is responsible for basic vital life functions such as breathing, heartbeat, and blood pressure. Scientists say that this is the "simplest" part of human brains because animals' entire brains, such as reptiles (who appear early on the evolutionary scale) resemble our brain stem. Look at a good example of this here.
The brain stem is made of the midbrain, pons, and medulla.
excerpt borrowed from http://serendip.brynmawr.edu/bb/kinser/Structure1.html#cerebrum
The brain is made of three main parts: the forebrain, midbrain, and hindbrain. The forebrain consists of the cerebrum, thalamus, and hypothalamus (part of the limbic system). The midbrain consists of the tectum and tegmentum. The hindbrain is made of the cerebellum, pons and medulla. Often the midbrain, pons, and medulla are referred to together as the brainstem.
What do each of these lobes do?
* Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving
* Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli
* Occipital Lobe- associated with visual processing
* Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech
Note that the cerebral cortex is highly wrinkled. Essentially this makes the brain more efficient, because it can increase the surface area of the brain and the amount of neurons within it.
A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. Sometimes the right hemisphere is associated with creativity and the left hemispheres is associated with logic abilities. The corpus callosum is a bundle of axons which connects these two hemispheres.
Nerve cells make up the gray surface of the cerebrum which is a little thicker than your thumb. White nerve fibers underneath carry signals between the nerve cells and other parts of the brain and body.
The neocortex occupies the bulk of the cerebrum. This is a six-layered structure of the cerebral cortex which is only found in mammals. It is thought that the neocortex is a recently evolved structure, and is associated with "higher" information processing by more fully evolved animals (such as humans, primates, dolphins, etc).
The Cerebellum: The cerebellum, or "little brain", is similar to the cerebrum in that it has two hemispheres and has a highly folded surface or cortex. This structure is associated with regulation and coordination of movement, posture, and balance.
The cerebellum is assumed to be much older than the cerebrum, evolutionarily. What do I mean by this? In other words, animals which scientists assume to have evolved prior to humans, for example reptiles, do have developed cerebellums. However, reptiles do not have neocortex. Go here for more discussion of the neocortex or go to the following web site for a more detailed look at evolution of brain structures and intelligence: "Ask the Experts": Evolution and Intelligence
Limbic System: The limbic system, often referred to as the "emotional brain", is found buried within the cerebrum. Like the cerebellum, evolutionarily the structure is rather old.
This system contains the thalamus, hypothalamus, amygdala, and hippocampus.
Brain Stem: Underneath the limbic system is the brain stem. This structure is responsible for basic vital life functions such as breathing, heartbeat, and blood pressure. Scientists say that this is the "simplest" part of human brains because animals' entire brains, such as reptiles (who appear early on the evolutionary scale) resemble our brain stem. Look at a good example of this here.
The brain stem is made of the midbrain, pons, and medulla.
excerpt borrowed from http://serendip.brynmawr.edu/bb/kinser/Structure1.html#cerebrum
Tuesday, September 8, 2009
My Personal View - Fred Hoyle
Fred Hoyle - A Personal View [1960]
Looking to the Future
I come now to an entirely different class of question. With the clear understanding that what I am going to say has no agreed basis among scientist but represents my own personal views, I shall try to sum up the general philosophic issues that seem to come out of our survey of the Universe.
It is my view that man's unguided imagination could never have chanced on such structure as I have put before you. No literary genius could have invented a story one-hundreth part as fantastic as the sober facts that have been unearthed by astronomical science. You need only compare our inquiry into the nature of the universe with the tales of such acknowledged masters as Jules Verne and H. G. Wells to see that fact outweighs fiction by an enormous margin. One is naturally led to wonder what the impact of the new cosmology would have been on a man like Newton, who would have been able to take it in, details and all, in one clean sweep. I think that Newton would have been quite unprepared for any such revelation, and that it would have had a shattering effect on him.
Is it likely that any astonishing new developments are lying in wait for us? Is it possible that the cosmology of 500 years hence will extend as far beyond our present beliefs as our cosmology goes beyond that of Newton? It may surprise you to hear that I doubt whether this will be so. If this should appear presumptuous to you, I think you should consider what I said earlier about the observable region of the Universe. As you will remember, even with a perfect telescope we could penetrate only about twice as far into space as the new telescope at Palomar. This means that there are no new fields to be opened up by the telescopes of the future, and this is a point of no small importance in our cosmology.There will be many advances in the detailed understanding of matters that still baffle us. Of the larger issues I expect a considerable improvement in the theory of the expanding Universe. Continuous creation I expect to play an important role in the theories of the future. Indeed, I expect that much will be learned about continuos creation, especially connection with atomic physics. But by and large, I think that our present picture will turn out to bear an appreciable resemblance to the cosmologies of the future.
In all this I have assumed that progress will be made in the future. It is quite on the cards that astronomy may go backward, as, for instance, Greek astronomy went backwards after the time of Hipparchus. And in saying this I am not thinking about an atomic war destroying civilization, but about the increasing tendency to rivet scientific inquiry in fetters. Secrecy, nationalism, the Marxist ideology- these are some of the things that are threatening to choke the life out of science. You may possible think that this might be a good thing, as we have obviously had quite enough of atom bombs, disease spreading bacteria, and radioactive poisons to last us for a long time. But this is not the way in which it works. What will happen if science declines is that there will be more work, not less. on the comparatively easy problems of destruction. It will be the real science, where the adversary is not man but the Universe itself, that will suffer.
Next we come to a question that everyone, scientist and nonscientist alike, must have asked at some time. What is man's place in the Universe? I should like to make a start on this momentous issue by considering the view of the out-and-out materialist. The appeal of their argument is based on simplicity. The universe is here, they say, so let us take it for granted. Then the Earth and other planets must arise in the way we have already discussed. On a suitably favored planet like the Earth, life would be very likely to arise, and once it had started so the argument goes, only the biological processes of mutation and natural selection are needed to produce living creatures as we know them. Such creatures are no more than ingenuous machines that have evolved as strange by-products in an odd corner of the universe. No important connection exists, so the argument concludes, between these machines and the universe as a whole, and this explains why all attempts by the machines themselves to find such a connection have failed.
Most people object to this argument for the not very good reason that they do not like to think of themselves as machines. But taking the argument at face value, I see not point that can actually be disproved, except the claim of simplicity. The outlook of the materialist is not simple; it is really very complicated. The apparent simplicity is only achieved by taking the existence of the Universe for granted. For myself there is a great deal more about the Universe that I should like to know. Why is the Universe as it is and not something else? Why is the Universe here at all? It is true that at present we have no clue to the answers to question such as these, and it may be that the materialist are right in saying that no meaning can be attached to them. But throughout the history of science, people have been asserting that such and such an issue is inherently beyond the scope of reasoned inquiry, and time after time they have been proved wrong. Two thousand years ago it would have been thought quite impossible to investigate the nature of the Universe to the extent I have been describing it to you in this book. And I dare say that you yourself would have said, not so very long ago, that it was impossible to learn anything about the way the universe is created. All experience teaches us that no one has yet asked too much.
And now I should like to give some considerations to contemporary religious beliefs. There is a good deal of cosmology in the Bible. My impression of it is that it is remarkable conception, considering the time when it was written. But I think it can hardly be denied that the cosmology of the ancient Hebrews is only the merest daub compared with the sweeping grandeur of the picture revealed by modern science. Is it in any way reasonable to suppose that it was given to the Hebrews to understand mysteries far deeper than anything we can comprehend, when it is quite clear that they were completely ignorant of many matters that seem commonplace to us? No, it seems to me that religion is but a desperate attempt to find an escape from the truly dreadful situation in which we find ourselves. Here we are in this wholly fantastic Universe with scarcely a clue as to whether our existence has any real significance. No wonder then that many people feel the need for some belief that gives them a sense of security, and no wonder that they become very angry with people like me who say that this security is illusory. But I do not like the situation any better then they do. The difference is that I cannot see how the smallest advantage is to be gained from deceiving myself. We are in rather the situation of a man in a desperate, difficult position on a steep mountain. A materialist is like a man who becomes crag-fast and keeps shouting: "I'm safe, I'm safe" because he doesn't fall. The religious person is like a man who goes to the other extreme and rushes up the first route that shows the faintest hope of escape, and who is entirely reckless of the yawning precipices that lie below him.
I will illustrate all this by saying what I think about perhaps the most inscrutable question of all: do our minds survive death? To make any progress with this question it is necessary to understand what our minds are. If we knew this with any precision then I have no doubt we should be well on the way to getting a satisfactory answer. My own answer would be that mind is an intricate organization of matter. In so far as the organization can be remembered and reproduced there is no such thing as death. If ordinary atoms of carbon, oxygen, hydrogen, nitrogen, etc., could be fitted together into exactly the structural organization of Homer, or of Titus Oates, then these individuals would come alive exactly as they were originally. The whole issue therefore turns on whether our particular organization is remembered in some fashion. If it is, there is no death. If it is not, there is complete oblivion.
I should like to discuss a little further the beliefs of the Christians as I see them myself. In their anxiety to avoid the notion that death is the complete end of our existence, they suggest what is to me an equally horrible alternative. If I were given the choice of how long I should live with my present physical and mental equipment, I should decide on a good deal more then 70 years. But I doubt whether I should be wise to decide on more then 300 years. Already I am very much aware of my own limitations, and I think that 300 years is as long as I should like to put up with them. Now what the Christians offer me is an eternity of frustration. ANd it is no good their trying to mitigate the situation by saying that sooner or later my limitations would be removed, because this could not be done without altering me. It strikes me as very curious that the Christians have so little to say about how they propose eternity should be spent.
Perhaps I had better end by saying how I should arrange matters if it were my decision to make. It seems to me that the greatest lesson of adult life is that one's own consciousness is not enough. What one of us would not like to share the consciousness of half a dozen chosen individuals? What writer would not like to share the consciousness of Shakespeare? What musician that of Beethoven or Mozart? What mathematician that of Gauss? What I would choose would be an evolution of life whereby the essence of each of us becomes welded together into some vastly larger and more potent structure. I think such a dynamic evolution would be more in keeping with the grandeur of the physical Universe than the static picture offered by formal religion.
What is the chance of such an idea being right? Well, if there is one important result that comes out of our inquiry into the nature of the Universe it is this: when by patient inquiry we learn the answer to any problem, we always find, both as a whole and in detail, that the answer thus revealed is finer in concept and design than anything we could ever have arrived at by random guess. And this, I believe, will be the same for the deeper issues we have been discussing. I think that all our present guesses are likely to prove but a very pale shadow of the real thing; and it is on this note that I must now finish. Perhaps the most majestic feature of our whole existence is that while our intelligences are powerful enough to penetrate deeply into the evolution of this quite incredible Universe, we still have not the smallest clue to our own fate.
Looking to the Future
I come now to an entirely different class of question. With the clear understanding that what I am going to say has no agreed basis among scientist but represents my own personal views, I shall try to sum up the general philosophic issues that seem to come out of our survey of the Universe.
It is my view that man's unguided imagination could never have chanced on such structure as I have put before you. No literary genius could have invented a story one-hundreth part as fantastic as the sober facts that have been unearthed by astronomical science. You need only compare our inquiry into the nature of the universe with the tales of such acknowledged masters as Jules Verne and H. G. Wells to see that fact outweighs fiction by an enormous margin. One is naturally led to wonder what the impact of the new cosmology would have been on a man like Newton, who would have been able to take it in, details and all, in one clean sweep. I think that Newton would have been quite unprepared for any such revelation, and that it would have had a shattering effect on him.
Is it likely that any astonishing new developments are lying in wait for us? Is it possible that the cosmology of 500 years hence will extend as far beyond our present beliefs as our cosmology goes beyond that of Newton? It may surprise you to hear that I doubt whether this will be so. If this should appear presumptuous to you, I think you should consider what I said earlier about the observable region of the Universe. As you will remember, even with a perfect telescope we could penetrate only about twice as far into space as the new telescope at Palomar. This means that there are no new fields to be opened up by the telescopes of the future, and this is a point of no small importance in our cosmology.There will be many advances in the detailed understanding of matters that still baffle us. Of the larger issues I expect a considerable improvement in the theory of the expanding Universe. Continuous creation I expect to play an important role in the theories of the future. Indeed, I expect that much will be learned about continuos creation, especially connection with atomic physics. But by and large, I think that our present picture will turn out to bear an appreciable resemblance to the cosmologies of the future.
In all this I have assumed that progress will be made in the future. It is quite on the cards that astronomy may go backward, as, for instance, Greek astronomy went backwards after the time of Hipparchus. And in saying this I am not thinking about an atomic war destroying civilization, but about the increasing tendency to rivet scientific inquiry in fetters. Secrecy, nationalism, the Marxist ideology- these are some of the things that are threatening to choke the life out of science. You may possible think that this might be a good thing, as we have obviously had quite enough of atom bombs, disease spreading bacteria, and radioactive poisons to last us for a long time. But this is not the way in which it works. What will happen if science declines is that there will be more work, not less. on the comparatively easy problems of destruction. It will be the real science, where the adversary is not man but the Universe itself, that will suffer.
Next we come to a question that everyone, scientist and nonscientist alike, must have asked at some time. What is man's place in the Universe? I should like to make a start on this momentous issue by considering the view of the out-and-out materialist. The appeal of their argument is based on simplicity. The universe is here, they say, so let us take it for granted. Then the Earth and other planets must arise in the way we have already discussed. On a suitably favored planet like the Earth, life would be very likely to arise, and once it had started so the argument goes, only the biological processes of mutation and natural selection are needed to produce living creatures as we know them. Such creatures are no more than ingenuous machines that have evolved as strange by-products in an odd corner of the universe. No important connection exists, so the argument concludes, between these machines and the universe as a whole, and this explains why all attempts by the machines themselves to find such a connection have failed.
Most people object to this argument for the not very good reason that they do not like to think of themselves as machines. But taking the argument at face value, I see not point that can actually be disproved, except the claim of simplicity. The outlook of the materialist is not simple; it is really very complicated. The apparent simplicity is only achieved by taking the existence of the Universe for granted. For myself there is a great deal more about the Universe that I should like to know. Why is the Universe as it is and not something else? Why is the Universe here at all? It is true that at present we have no clue to the answers to question such as these, and it may be that the materialist are right in saying that no meaning can be attached to them. But throughout the history of science, people have been asserting that such and such an issue is inherently beyond the scope of reasoned inquiry, and time after time they have been proved wrong. Two thousand years ago it would have been thought quite impossible to investigate the nature of the Universe to the extent I have been describing it to you in this book. And I dare say that you yourself would have said, not so very long ago, that it was impossible to learn anything about the way the universe is created. All experience teaches us that no one has yet asked too much.
And now I should like to give some considerations to contemporary religious beliefs. There is a good deal of cosmology in the Bible. My impression of it is that it is remarkable conception, considering the time when it was written. But I think it can hardly be denied that the cosmology of the ancient Hebrews is only the merest daub compared with the sweeping grandeur of the picture revealed by modern science. Is it in any way reasonable to suppose that it was given to the Hebrews to understand mysteries far deeper than anything we can comprehend, when it is quite clear that they were completely ignorant of many matters that seem commonplace to us? No, it seems to me that religion is but a desperate attempt to find an escape from the truly dreadful situation in which we find ourselves. Here we are in this wholly fantastic Universe with scarcely a clue as to whether our existence has any real significance. No wonder then that many people feel the need for some belief that gives them a sense of security, and no wonder that they become very angry with people like me who say that this security is illusory. But I do not like the situation any better then they do. The difference is that I cannot see how the smallest advantage is to be gained from deceiving myself. We are in rather the situation of a man in a desperate, difficult position on a steep mountain. A materialist is like a man who becomes crag-fast and keeps shouting: "I'm safe, I'm safe" because he doesn't fall. The religious person is like a man who goes to the other extreme and rushes up the first route that shows the faintest hope of escape, and who is entirely reckless of the yawning precipices that lie below him.
I will illustrate all this by saying what I think about perhaps the most inscrutable question of all: do our minds survive death? To make any progress with this question it is necessary to understand what our minds are. If we knew this with any precision then I have no doubt we should be well on the way to getting a satisfactory answer. My own answer would be that mind is an intricate organization of matter. In so far as the organization can be remembered and reproduced there is no such thing as death. If ordinary atoms of carbon, oxygen, hydrogen, nitrogen, etc., could be fitted together into exactly the structural organization of Homer, or of Titus Oates, then these individuals would come alive exactly as they were originally. The whole issue therefore turns on whether our particular organization is remembered in some fashion. If it is, there is no death. If it is not, there is complete oblivion.
I should like to discuss a little further the beliefs of the Christians as I see them myself. In their anxiety to avoid the notion that death is the complete end of our existence, they suggest what is to me an equally horrible alternative. If I were given the choice of how long I should live with my present physical and mental equipment, I should decide on a good deal more then 70 years. But I doubt whether I should be wise to decide on more then 300 years. Already I am very much aware of my own limitations, and I think that 300 years is as long as I should like to put up with them. Now what the Christians offer me is an eternity of frustration. ANd it is no good their trying to mitigate the situation by saying that sooner or later my limitations would be removed, because this could not be done without altering me. It strikes me as very curious that the Christians have so little to say about how they propose eternity should be spent.
Perhaps I had better end by saying how I should arrange matters if it were my decision to make. It seems to me that the greatest lesson of adult life is that one's own consciousness is not enough. What one of us would not like to share the consciousness of half a dozen chosen individuals? What writer would not like to share the consciousness of Shakespeare? What musician that of Beethoven or Mozart? What mathematician that of Gauss? What I would choose would be an evolution of life whereby the essence of each of us becomes welded together into some vastly larger and more potent structure. I think such a dynamic evolution would be more in keeping with the grandeur of the physical Universe than the static picture offered by formal religion.
What is the chance of such an idea being right? Well, if there is one important result that comes out of our inquiry into the nature of the Universe it is this: when by patient inquiry we learn the answer to any problem, we always find, both as a whole and in detail, that the answer thus revealed is finer in concept and design than anything we could ever have arrived at by random guess. And this, I believe, will be the same for the deeper issues we have been discussing. I think that all our present guesses are likely to prove but a very pale shadow of the real thing; and it is on this note that I must now finish. Perhaps the most majestic feature of our whole existence is that while our intelligences are powerful enough to penetrate deeply into the evolution of this quite incredible Universe, we still have not the smallest clue to our own fate.
Wednesday, August 19, 2009
The Standard Model of Particle Physics
Chemistry can be understood in the physics of 3 particles (proton, neutron and electron), and the influence of the electromagnetic force. Nuclear physics can be understood in the physics of 4 particles (proton, neutron, electron and electron neutrino), and the influence of the strong and weak nuclear forces together with the electromagnetic force. The Standard Model Theory (SM) of particle physics provides a framework for explaining chemistry and nuclear physics (low energy processes). It additionally provides an explanation for sub-nuclear physics and some aspects of cosmology in the earliest moments of the universe (high energy processes).
The Standard Model is conceptually simple and contains a description of the elementary particles and forces. The SM particles are 12 spin-1/2 fermions (6 quarks and 6 leptons), 4 spin-1 ‘gauge’ bosons and a spin-0 Higgs boson. These are shown in the figure below and constitute the building blocks of the universe. The 6 quarks include the up and down quarks that make up the neutron and proton. The 6 leptons include the electron and its partner, the electron neutrino. The 4 bosons are particles that transmit forces and include the photon, which transmits the electromagnetic force. With the recent observation of the tau neutrino at Fermilab, all 12 fermions and all 4 gauge bosons have been observed. Seven of these 16 particles (charm, bottom, top, tau neutrino, W, Z, gluon) were predicted by the Standard Model before they were observed experimentally! There is one additional particle predicted by the Standard Model called the Higgs, which has not yet been observed. It is needed in the model to give mass to the W and Z bosons, consistent with experimental observations. While photons and gluons have no mass, the W and Z are quite heavy. The W weighs 80.3 GeV (80 times as much as the proton) and the Z weighs 91.2 GeV. The Higgs is expected to be heavy as well. Direct searches for it at CERN dictate that it must be heavier than 110 GeV.
The matter and force particles of the Standard Model. Up and down quarks were observed for the first time in electron-scattering experiments at SLAC in the late 1960s. The 1990 Nobel Prize in physics for this discovery was awarded to SLAC's Richard Taylor and to Jerome Friedman and Henry Kendall from MIT. The charm quark was discovered simultaneously in experiments at SLAC and at Brookhaven in 1974. SLAC's Burton Richter and MIT's Samuel Ting shared the 1976 Nobel Prize in physics for this discovery. The tau lepton was discovered at SLAC in 1975, for which SLAC's Martin Perl was awarded the 1995 Nobel Prize in physics.
The SM particles are considered to be point-like, but contain an internal ‘spin’ (angular momentum) degree of freedom which is quantized and can have values of 0, ½ or 1. Spin-1/2 particles obey Fermi statistics, which have as a consequence that no 2 electrons can be in the same quantum state. This feature is necessary for forming atoms more complex than hydrogen. Spin-1 and spin-0 particles obey Bose-Einstein statistics, which prefer to have many particles in the lowest energy or ground state. This phenomenon is responsible for superconductivity.
The Standard Model says that forces are the exchange of gauge bosons (the force particles) between interacting quarks and leptons. Feynman diagrams are useful to describe this pictorially. As illustrated in the figures below, two electrons may interact by scattering and exchanging a photon; or an electron and positron may collide and annihilate to form a Z particle, which then decays into a quark and anti-quark. Electromagnetic forces occur via exchange of photons; weak nuclear forces occur via exchange of W and Z particles; and strong nuclear forces occur via exchange of gluons. Electromagnetic forces and interactions are familiar to everyone. They are responsible for visible light and radiowaves, and are the physics behind the electronics and telecommunications industries. All quarks and leptons can interact electromagnetically. Strong nuclear forces are responsible for holding protons and neutrons together inside the nucleus, and for fueling the power of the sun. Only quarks interact via the strong interaction. Weak nuclear forces are responsible for radioactivity and also for exhibiting some peculiar symmetry features not seen with the other forces. In contrast to electromagnetic and strong forces, the laws of physics (ie. the strengths of the forces) for the weak force are different for particles and anti-particles (C Violation), for a scattering process and its mirror image (P Violation), and for a scattering process and the time reversal of that scattering process (T Violation). All quarks and leptons can interact via the weak interaction. The Standard Model provides much more than simply a description of electromagnetic, strong and weak interactions. Its mathematics provides explicit and accurate calculations for the rates at which these processes take place and relative probabilities for decays of unstable particles into other lower mass particles (such as for a Z particle to decay into different types of quarks and leptons).
excerpt borrowed from http://www-sldnt.slac.stanford.edu/alr/standard_model.htm
The Standard Model is conceptually simple and contains a description of the elementary particles and forces. The SM particles are 12 spin-1/2 fermions (6 quarks and 6 leptons), 4 spin-1 ‘gauge’ bosons and a spin-0 Higgs boson. These are shown in the figure below and constitute the building blocks of the universe. The 6 quarks include the up and down quarks that make up the neutron and proton. The 6 leptons include the electron and its partner, the electron neutrino. The 4 bosons are particles that transmit forces and include the photon, which transmits the electromagnetic force. With the recent observation of the tau neutrino at Fermilab, all 12 fermions and all 4 gauge bosons have been observed. Seven of these 16 particles (charm, bottom, top, tau neutrino, W, Z, gluon) were predicted by the Standard Model before they were observed experimentally! There is one additional particle predicted by the Standard Model called the Higgs, which has not yet been observed. It is needed in the model to give mass to the W and Z bosons, consistent with experimental observations. While photons and gluons have no mass, the W and Z are quite heavy. The W weighs 80.3 GeV (80 times as much as the proton) and the Z weighs 91.2 GeV. The Higgs is expected to be heavy as well. Direct searches for it at CERN dictate that it must be heavier than 110 GeV.
The matter and force particles of the Standard Model. Up and down quarks were observed for the first time in electron-scattering experiments at SLAC in the late 1960s. The 1990 Nobel Prize in physics for this discovery was awarded to SLAC's Richard Taylor and to Jerome Friedman and Henry Kendall from MIT. The charm quark was discovered simultaneously in experiments at SLAC and at Brookhaven in 1974. SLAC's Burton Richter and MIT's Samuel Ting shared the 1976 Nobel Prize in physics for this discovery. The tau lepton was discovered at SLAC in 1975, for which SLAC's Martin Perl was awarded the 1995 Nobel Prize in physics.
The SM particles are considered to be point-like, but contain an internal ‘spin’ (angular momentum) degree of freedom which is quantized and can have values of 0, ½ or 1. Spin-1/2 particles obey Fermi statistics, which have as a consequence that no 2 electrons can be in the same quantum state. This feature is necessary for forming atoms more complex than hydrogen. Spin-1 and spin-0 particles obey Bose-Einstein statistics, which prefer to have many particles in the lowest energy or ground state. This phenomenon is responsible for superconductivity.
The Standard Model says that forces are the exchange of gauge bosons (the force particles) between interacting quarks and leptons. Feynman diagrams are useful to describe this pictorially. As illustrated in the figures below, two electrons may interact by scattering and exchanging a photon; or an electron and positron may collide and annihilate to form a Z particle, which then decays into a quark and anti-quark. Electromagnetic forces occur via exchange of photons; weak nuclear forces occur via exchange of W and Z particles; and strong nuclear forces occur via exchange of gluons. Electromagnetic forces and interactions are familiar to everyone. They are responsible for visible light and radiowaves, and are the physics behind the electronics and telecommunications industries. All quarks and leptons can interact electromagnetically. Strong nuclear forces are responsible for holding protons and neutrons together inside the nucleus, and for fueling the power of the sun. Only quarks interact via the strong interaction. Weak nuclear forces are responsible for radioactivity and also for exhibiting some peculiar symmetry features not seen with the other forces. In contrast to electromagnetic and strong forces, the laws of physics (ie. the strengths of the forces) for the weak force are different for particles and anti-particles (C Violation), for a scattering process and its mirror image (P Violation), and for a scattering process and the time reversal of that scattering process (T Violation). All quarks and leptons can interact via the weak interaction. The Standard Model provides much more than simply a description of electromagnetic, strong and weak interactions. Its mathematics provides explicit and accurate calculations for the rates at which these processes take place and relative probabilities for decays of unstable particles into other lower mass particles (such as for a Z particle to decay into different types of quarks and leptons).
excerpt borrowed from http://www-sldnt.slac.stanford.edu/alr/standard_model.htm
Wednesday, August 5, 2009
Conditioned Reflexes
Who was Ivan Pavlov?
The Russian scientist Ivan Petrovich Pavlov was born in 1849 in Ryazan, where his father worked as a village priest. In 1870 Ivan Pavlov abandoned the religious career for which he had been preparing, and instead went into science. There he had a great impact on the field of physiology by studying the mechanisms underlying the digestive system in mammals.
For his original work in this field of research, Pavlov was awarded the Nobel Prize in Physiology or Medicine in 1904. By then he had turned to studying the laws on the formation of conditioned reflexes, a topic on which he worked until his death in 1936. His discoveries in this field paved the way for an objective science of behavior.
Pavlov's drooling dogs
While Ivan Pavlov worked to unveil the secrets of the digestive system, he also studied what signals triggered related phenomena, such as the secretion of saliva. When a dog encounters food, saliva starts to pour from the salivary glands located in the back of its oral cavity. This saliva is needed in order to make the food easier to swallow. The fluid also contains enzymes that break down certain compounds in the food. In humans, for example, saliva contains the enzyme amylase, an effective processor of starch.
Pavlov became interested in studying reflexes when he saw that the dogs drooled without the proper stimulus. Although no food was in sight, their saliva still dribbled. It turned out that the dogs were reacting to lab coats. Every time the dogs were served food, the person who served the food was wearing a lab coat. Therefore, the dogs reacted as if food was on its way whenever they saw a lab coat.
In a series of experiments, Pavlov then tried to figure out how these phenomena were linked. For example, he struck a bell when the dogs were fed. If the bell was sounded in close association with their meal, the dogs learnt to associate the sound of the bell with food. After a while, at the mere sound of the bell, they responded by drooling.
Different kinds of reflexes
Reflexes make us react in a certain way. When a light beam hits our eyes, our pupils shrink in response to the light stimulus. And when the doctor taps you below the knee cap, your leg swings out. These reflexes are called unconditioned, or built-in. The body responds in the same fashion every time the stimuli (the light or the tap) is applied. In the same way, dogs drool when they encounter food.
Pavlov's discovery was that environmental events that previously had no relation to a given reflex (such as a bell sound) could, through experience, trigger a reflex (salivation). This kind of learnt response is called conditioned reflex, and the process whereby dogs or humans learn to connect a stimulus to a reflex is called conditioning.
Animals generally learn to associate stimuli that are relevant to their survival. Food aversion is an example of a natural conditioned reflex. If an animal eats something with a distinctive vanilla taste and then eats a tasteless poison that leads to nausea, the animal will not be particularly eager to eat vanilla-flavoured food the next time. Linking nausea to taste is an evolutionarily successful strategy, since animals that failed to learn their lesson did not last very long.
Why were Pavlov's findings given so much acknowledgment?
Pavlov's description on how animals (and humans) can be trained to respond in a certain way to a particular stimulus drew tremendous interest from the time he first presented his results. His work paved the way for a new, more objective method of studying behavior.
So-called Pavlovian training has been used in many fields, with anti-phobia treatment as but one example. An important principle in conditioned learning is that an established conditioned response (salivating in the case of the dogs) decreases in intensity if the conditioned stimulus (bell) is repeatedly presented without the unconditioned stimulus (food). This process is called extinction.
In order to treat phobias evoked by certain environmental situations, such as heights or crowds, this phenomenon can be used. The patient is first taught a muscle relaxation technique. Then he or she is told , over a period of days, to imagine the fear-producing situation while trying to inhibit the anxiety by relaxation. At the end of the series, the strongest anxiety-provoking situation may be brought to mind without anxiety. This process is called systematic desensitization.
Conditioning forms the basis of much of learned human behavior. Nowadays, this knowledge has also been exploited by commercial advertising. An effective commercial should be able to manipulate the response to a stimulus (like seeing a product's name) which initially does not provoke any feeling. The objective is to train people to make the "false" connection between positive emotions (e.g. happiness or feeling attractive) and the particular brand of consumer goods being advertised.
Pavlov's prize
Although the first image that comes to mind while mentioning Ivan Pavlov's name is his drooling dogs, he became a Nobel Laureate for his research in a different field. In 1904 he received the Nobel Prize in Physiology or Medicine for his pioneering studies of how the digestive system works.
Until Pavlov started to scrutinize this field, our knowledge of how food was digested in the stomach, and what mechanisms were responsible for regulating this, were quite foggy.
In order to understand the process, Pavlov developed a new way of monitoring what was happening. He surgically made fistulas in animals' stomachs, which enabled him to study the organs and take samples of body fluids from them while they continued to function normally.
excerpt taken from http://nobelprize.org/educational_games/medicine/pavlov/readmore.html
Thursday, July 16, 2009
Panspermia
An idea, with ancient roots, according to which life arrives, ready-made, on the surface of planets from space. Anaxagoras is said to have spoken of the "seeds of life" from which all organisms derive. Panspermia began to assume a more scientific form through the proposals of Berzelius (1834), Richter (1865), Thomson (Lord Kelvin) (1871), and Helmholtz (1871), finally reaching the level of a detailed, widely-discussed hypothesis through the efforts of the Swedish chemist Svante Arrhenius. Originally in 1903, but then to a wider audience through a popular book in 1908,3 Arrhenius urged that life in the form of spores could survive in space and be spread from one planetary system to another by means of radiation pressure. He generally avoided the problem of how life came about in the first place by suggesting that it might be eternal, though he did not exclude the possibility of living things generating from simpler substances somewhere in the universe. In Arrhenius's view, spores escape by random movement from the atmosphere of a planet that has already been colonized and are then launched into interstellar space by the pressure of starlight ("radiopanspermia"). Eventually, some of the spores fall upon another planet, such as the Earth, where they inoculate the virgin world with new life or, perhaps, compete with any life-forms that are already present.
Arrhenius's ideas prompted a variety of experimental work, such as that of Paul Becquerel, to test whether spores and bacteria could survive in conditions approximating those in space. A majority of scientists reached the conclusion that stellar ultraviolet would probably prove deadly to any organisms in the inner reaches of a planetary system and, principally for this reason, panspermia quietly faded from view-only to be revived some four decades later.
Sagan's analysis
In the early 1960s, Carl Sagan analyzed in detail both the physical and biological aspects of the Arrhenius scenario. The dynamics of a microorganism in space depend on the ratio p/g, where p is the repulsive force due to the radiation pressure of a star and g is the attractive force due to the star's gravitation. If p > g, a microbe that has drifted into space will move away from the star; if p less then g, the microbe will fall toward the star. For a microbe to escape into interstellar space from the vicinity of a star like the Sun, the organism would have to be between 0.2 and 0.6 microns across. Though small, this is within the range of some terrestrial bacterial spores and viruses. The ratio p/g increases for more luminous stars, enabling the ejection of larger microbes. However, main sequence stars brighter than the Sun are also hotter, so that they emit more ultraviolet radiation which would pose an increased threat to space-borne organisms. Additionally, such stars have a shorter main sequence lifespan, so that they provide less opportunity for life to take hold on any worlds that might orbit around them. These considerations, argued Sagan, constrain "donor" stars for Arrhenius-style panspermia to spectral types G5 (Sun-like) to A0. Stars less luminous than the Sun would be unable to eject even the smallest of known living particles. "Acceptor" stars, on the other hand, must have lower p/g ratios in order to allow microbes, approaching from interstellar space, to enter their planetary systems. The most likely acceptor worlds, Sagan concluded, are those circling around red dwarfs (dwarf M stars), or in more distant orbits around G stars and K stars. In the case of the solar system, he surmised, the best place to look for life of extrasolar origin would be the moons of the outer planets, in particular Triton.
Life-carrying rocks?
Many variations on the panspermia theme have been put forward. William Thomson (Lord Kelvin) proposed that spores might travel aboard meteorites ("lithopanspermia"), thus affording them better protection from high-energy radiation in space. Whether events violent enough to hurl rocks from the surface of a biologically active planet into interstellar space ever occur is not clear. But there is now overwhelming evidence that ballistic panspermia occasionally operates between worlds of the same planetary system. This follows the discovery of meteorites on Earth that have almost certainly come from the surface of Mars (see SNC meteorites) and the Moon. There is also controversial evidence for fossil remains aboard some carbonaceous chondrites, including the Orgueil meteorite.
Contamination
In the 1960s, Thomas Gold pointed out another way in which life might travel from world to world (see "garbage theory," of the origin of life). A team of explorers from an advanced, interstellar-faring race might land on the planet of a foreign star and, unwittingly, leave behind "bugs" which then adapt to the local conditions. He imagined, for example, the visitors having a picnic and not clearing up afterward. What effect microscopic alien fauna and flora might have on the indigenous species is impossible to predict, but such considerations were foremost in the minds of scientists receiving the first samples of rock and soil from the Moon. Precautions against alien contamination will be even more important when the first spacecraft return from Mars or Europa where the possibility of extant life is far greater ( back-contamination). And there is the reverse problem (forward-contamination). The remarkable case of Surveyor 3 makes it clear that some terrestrial microbes can survive for significant periods in hostile conditions on other worlds. What if such a world (like Mars) had life-forms of its own? What chaos might the "alien" microbes from Earth wreak? It would be tragic indeed if the very means of discovering the first examples of extraterrestrial life were also to be the vehicle of its extinction. On the other hand, as Carl Sagan pointed out, if Gold's "picnic scenario" had actually happened in the Earth's past "some microbial resident of a primordial cookie crumb may be the ancestor of us all." Just as the chance of accidental contamination arising from intelligent activity cannot be ruled out, there is the complimentary possibility of intentional or directed panspermia.
Life from space
Today, the panspermia hypothesis has finally achieved some measure of scientific respectability. Although it remains the orthodox view that life evolved in situ on this world and, possibly, many others, there is mounting evidence of at least some extraterrestrial input to the formative stages of planet-based biology. Prebiotic chemicals have been detected in interstellar clouds (similar to that from which the Solar System formed), comets, and meteorites (see astrochemistry). At the very least, it seems that some of the raw ingredients for life, such as amino acids, may have fallen from the sky in addition to being manufactured here on Earth. But some researchers have gone much further in their speculations. Most notably, Fred Hoyle and Chandra Wickramasinghe have argued persistently since the 1970s that complex organic substances, and perhaps even primitive organisms, might have evolved on the surface of cosmic dust grains in space and then been transported to the Earth's surface by comets and meteorites (see life, in space). The extraordinary durability of some extremophiles, bacterial spores, and even exposed DNA, lends credence to the view that simple life-forms may have originated between the stars or been capable of surviving long interstellar journeys.
excerpt taken from http://www.daviddarling.info/encyclopedia/P/panspermia.html
Arrhenius's ideas prompted a variety of experimental work, such as that of Paul Becquerel, to test whether spores and bacteria could survive in conditions approximating those in space. A majority of scientists reached the conclusion that stellar ultraviolet would probably prove deadly to any organisms in the inner reaches of a planetary system and, principally for this reason, panspermia quietly faded from view-only to be revived some four decades later.
Sagan's analysis
In the early 1960s, Carl Sagan analyzed in detail both the physical and biological aspects of the Arrhenius scenario. The dynamics of a microorganism in space depend on the ratio p/g, where p is the repulsive force due to the radiation pressure of a star and g is the attractive force due to the star's gravitation. If p > g, a microbe that has drifted into space will move away from the star; if p less then g, the microbe will fall toward the star. For a microbe to escape into interstellar space from the vicinity of a star like the Sun, the organism would have to be between 0.2 and 0.6 microns across. Though small, this is within the range of some terrestrial bacterial spores and viruses. The ratio p/g increases for more luminous stars, enabling the ejection of larger microbes. However, main sequence stars brighter than the Sun are also hotter, so that they emit more ultraviolet radiation which would pose an increased threat to space-borne organisms. Additionally, such stars have a shorter main sequence lifespan, so that they provide less opportunity for life to take hold on any worlds that might orbit around them. These considerations, argued Sagan, constrain "donor" stars for Arrhenius-style panspermia to spectral types G5 (Sun-like) to A0. Stars less luminous than the Sun would be unable to eject even the smallest of known living particles. "Acceptor" stars, on the other hand, must have lower p/g ratios in order to allow microbes, approaching from interstellar space, to enter their planetary systems. The most likely acceptor worlds, Sagan concluded, are those circling around red dwarfs (dwarf M stars), or in more distant orbits around G stars and K stars. In the case of the solar system, he surmised, the best place to look for life of extrasolar origin would be the moons of the outer planets, in particular Triton.
Life-carrying rocks?
Many variations on the panspermia theme have been put forward. William Thomson (Lord Kelvin) proposed that spores might travel aboard meteorites ("lithopanspermia"), thus affording them better protection from high-energy radiation in space. Whether events violent enough to hurl rocks from the surface of a biologically active planet into interstellar space ever occur is not clear. But there is now overwhelming evidence that ballistic panspermia occasionally operates between worlds of the same planetary system. This follows the discovery of meteorites on Earth that have almost certainly come from the surface of Mars (see SNC meteorites) and the Moon. There is also controversial evidence for fossil remains aboard some carbonaceous chondrites, including the Orgueil meteorite.
Contamination
In the 1960s, Thomas Gold pointed out another way in which life might travel from world to world (see "garbage theory," of the origin of life). A team of explorers from an advanced, interstellar-faring race might land on the planet of a foreign star and, unwittingly, leave behind "bugs" which then adapt to the local conditions. He imagined, for example, the visitors having a picnic and not clearing up afterward. What effect microscopic alien fauna and flora might have on the indigenous species is impossible to predict, but such considerations were foremost in the minds of scientists receiving the first samples of rock and soil from the Moon. Precautions against alien contamination will be even more important when the first spacecraft return from Mars or Europa where the possibility of extant life is far greater ( back-contamination). And there is the reverse problem (forward-contamination). The remarkable case of Surveyor 3 makes it clear that some terrestrial microbes can survive for significant periods in hostile conditions on other worlds. What if such a world (like Mars) had life-forms of its own? What chaos might the "alien" microbes from Earth wreak? It would be tragic indeed if the very means of discovering the first examples of extraterrestrial life were also to be the vehicle of its extinction. On the other hand, as Carl Sagan pointed out, if Gold's "picnic scenario" had actually happened in the Earth's past "some microbial resident of a primordial cookie crumb may be the ancestor of us all." Just as the chance of accidental contamination arising from intelligent activity cannot be ruled out, there is the complimentary possibility of intentional or directed panspermia.
Life from space
Today, the panspermia hypothesis has finally achieved some measure of scientific respectability. Although it remains the orthodox view that life evolved in situ on this world and, possibly, many others, there is mounting evidence of at least some extraterrestrial input to the formative stages of planet-based biology. Prebiotic chemicals have been detected in interstellar clouds (similar to that from which the Solar System formed), comets, and meteorites (see astrochemistry). At the very least, it seems that some of the raw ingredients for life, such as amino acids, may have fallen from the sky in addition to being manufactured here on Earth. But some researchers have gone much further in their speculations. Most notably, Fred Hoyle and Chandra Wickramasinghe have argued persistently since the 1970s that complex organic substances, and perhaps even primitive organisms, might have evolved on the surface of cosmic dust grains in space and then been transported to the Earth's surface by comets and meteorites (see life, in space). The extraordinary durability of some extremophiles, bacterial spores, and even exposed DNA, lends credence to the view that simple life-forms may have originated between the stars or been capable of surviving long interstellar journeys.
excerpt taken from http://www.daviddarling.info/encyclopedia/P/panspermia.html
Monday, July 13, 2009
Carl Gustav Jung
Amid all the talk about the "Collective Unconscious" and other sexy issues, most readers are likely to miss the fact that C.G. Jung was a good Kantian. His famous theory of Synchronicity, "an acausal connecting principle," is based on Kant's distinction between phenomena and things-in-themselves and on Kant's theory that causality will not operate among thing-in-themselves the way it does in phenomena. Thus, Kant could allow for free will (unconditioned causes) among things-in-themselves, as Jung allows for synchronicity ("meaningful coincidences"). Next to Kant, Jung is close to Schopenhauer, praising him as the first philosopher he had read, "who had the courage to see that all was not for the best in the fundaments of the universe" [Memories, Dreams, Reflections, p. 69]. Jung was probably unaware of the Friesian background of Otto's term "numinosity" when he began to use it for his Archetypes, but it is unlikely that he would object to the way in which Otto's theory, through Fries, fits into Kantian epistemology and metaphysics.
Jung's place in the Kant-Friesian tradition is on a side that would have been distasteful to Kant, Fries, and Nelson, whose systems were basically rationalistic. Thus Kant saw religion as properly a rational expression of morality, and Fries and Nelson, although allowing an aesthetic content to religion different from morality, nevertheless did not expect religion to embody much more than good morality and good art. Schopenhauer, Otto, and Jung all represent an awareness that more exists to religion and to human psychological life than this. The terrifying, uncanny, and fascinating elements of religion and ordinary life are beneath the notice of Kant, Fries, and Nelson, while they are indisputable and irreducible elements of life, for which there must be an account, with Schopenhauer, Otto, and Jung. As Jung again said of Schopenhauer: "He was the first to speak of the suffering of the world, which visibly and glaringly surrounds us, and of confusion, passion, evil -- all those things which the others hardly seemed to notice and always tried to resolve into all-embracing harmony and comprehensibility" [ibid. p. 69]. It is an awareness of this aspect of the world that renders the religious ideas of "salvation" meaningful; yet "salvation" as such is always missing from moralistic or aesthetic renderings of religion. Only Jung could have written his Answer to Job.
Jung's great Answer to Job, indeed, represents an approach to religion that is all but unique. Placing God in the Unconscious might strike most people as reducing him to a mere psychological object; but that is to overlook Jung's Kantianism. The Unconscious, and especially the Collective Unconscious, belongs to Kantian things-in-themselves, or to the transcendent Will of Schopenhauer. Jung was often at pains not to complicate his theory of the Archetypes by committing himself to a metaphysical theory -- he wanted the theory to work whether he was talking about the brain or about the Transcendent -- but that was merely a concession to the materialistic bias of contemporary science. He had no materialistic commitment himself and, when it came down to it, was not going to accept such naive reductionism. Instead, he was willing to rethink how the Transcendent might operate. Thus, he says about Schopenhauer:
I felt sure that by "Will" he really meant God, the Creator, and that he was saying that God was blind. Since I knew from experience that God was not offended by any blasphemy, that on the contrary He could even encourage it because He wished to evoke not only man's bright and positive side but also his darkness and ungodliness, Schopenhauer's view did not distress me. [ibid. pp. 69-70]
The Problem of Evil, which for so many people simply denuminizes religion, and which Schopenhauer used to reject the value of the world, became a challenge for Jung in the psychoanalysis of God. The God of the Bible is indeed a personality, and seemingly not always the same one. God as a morally evolving personality is the extraordinary conception of Answer to Job. What Otto saw as the evolution of human moral consciousness, Jung turns right around on the basis of the principle that the human unconscious, expressed spontaneously in religious practice and literature, transcends mere human subjectivity. But the transcendent reality in the unconscious is different in kind from consciousness. As Jung said in Memories, Dreams, Reflections again:
If the Creator were conscious of Himself, He would not need conscious creatures; nor is it probable that the extremely indirect methods of creation, which squander millions of years upon the development of countless species and creatures, are the outcome of purposeful intention. Natural history tells us of a haphazard and casual transformation of species over hundreds of millions of years of devouring and being devoured. The biological and political history of man is an elaborate repetition of the same thing. But the history of the mind offers a different picture. Here the miracle of reflecting consciousness intervenes -- the second cosmogony [ed. note: what Teilhard de Chardin called the origin of the "noosphere," the layer of "mind"]. The importance of consciousness is so great that one cannot help suspecting the element of meaning to be concealed somewhere within all the monstrous, apparently senseless biological turmoil, and that the road to its manifestation was ultimately found on the level of warm-blooded vertebrates possessed of a differentiated brain -- found as if by chance, unintended and unforeseen, and yet somehow sensed, felt and groped for out of some dark urge. [p. 339]
In other words, a "meaningful coincidence." Jung also says,
As far as we can discern, the sole purpose of human existence is to kindle a light in the darkness of mere being. It may even be assumed that just as the unconscious affects us, so the increase in our consciousness affects the unconscious. [p. 326]
However, Jung has missed something there. If consciousness is "the light in the darkness of mere being," consciousness alone cannot be the "sole purpose of human existence," since consciousness as such could appear as just a place of "mere being" and so would easily become an empty, absurd, and meaningless Existentialist existence. Instead, consciousness allows for the meaningful instantiation of existence, both through Jung's process of Individuation, by which the Archetypes are given unique expression in a specific human life, and from the historic process that Jung examines in Answer to Job, by which interaction with the unconscious alters in turn the Archetypes that come to be instantiated. While Otto could understand Job's reaction to God, as the incomprehensible Numen, Jung thinks of God's reaction to Job, as an innocent and righteous man jerked around by God's unconsciousness. Jung's idea that the Incarnation then is the means by which God redeems Himself from His morally false position in Job is an extraordinary reversal (I hesitate to say "deconstruction") of the consciously expressed dogma that the Incarnation is to redeem humanity.
It is not too difficult to see this turn in other religions. The compassion of the Buddhas in Mahâyâna Buddhism, especially when the Buddha Shakyamuni comes to be seen as the expression of a cosmic and eternal Dharma Body, is a hand of salvation stretched out from the Transcendent, without, however, the complication that the Buddha is ever thought responsible for the nature of the world and its evils as their Creator. That complication, however, does occur with Hindu views of the divine Incarnations of Vishnu. Closer to a Jungian synthesis, on the other hand, is the Bahá'í theory that divine contact is though "Manifestations," which are neither wholly human nor wholly divine: merely human in relation to God, but entirely divine in relation to other humans. Such a theory must appear Christianizing in comparison to Islam, but it avoids the uniqueness of Christ as the only Incarnation in Christianity itself. This is conformable to the Jungian proposition that the unconscious is both a side of the human mind and a door into the Transcendent. When that door opens, the expression of the Transcendent is then conditioned by the person through which it is expressed, possessing that person, but it is also genuinely Transcendent and reflecting the ongoing interaction that the person historically embodies. The possible "mere being" even of consciousness then becomes the place of meaning and value.
Whether "psychoanalysis" as practiced by Freud or Jung is to be taken seriously anymore is a good question; but both men will survive as philosophers long after their claims to science or medicine may be discounted. Jung's Kantianism enables him to avoid the materialism and reductionism of Freud ("all of civilization is a substitute for incest") and, with a great breadth of learning, employs principles from Kant, Schopenhauer, and Otto that are easily conformable to the Kant-Friesian tradition. The Answer to Job, indeed, represents a considerable advance beyond Otto, into the real paradoxes that are the only way we can conceive transcendent reality.
excerpt taken from http://www.friesian.com/jung.htm
Monday, July 6, 2009
Quasars
In the 1960s it was observed that certain objects emitting radio waves but thought to be stars had very unusual optical spectra. It was finally realized that the reason the spectra were so unusual is that the lines were Doppler shifted by a very large amount, corresponding to velocities away from us that were significant fractions of the speed of light. The reason that it took some time to come to this conclusion is that, because these objects were thought to be relatively nearby stars, no one had any reason to believe they should be receding from us at such velocities.
excerpt taken from http://csep10.phys.utk.edu/astr162/lect/active/quasars.html
Quasars and QSOs
These objects were named Quasistellar Radio Sources (meaning "star-like radio sources") which was soon contracted to quasars. Later, it was found that many similar objects did not emit radio waves. These were termed Quasistellar Objects or QSOs. Now, all of these are often termed quasars (Only about 1% of the quasars discovered to date have detectable radio emission).Quasars Are Related to Active Galaxies
The quasars were deemed to be strange new phenomena, and initially there was considerable speculation that new laws of physics might have to be invented to account for the amount of energy that they produced. However, subsequent research has shown that the quasars are closely related to the active galaxies that have been studied at closer distances. We now believe quasars and active galaxies to be related phenomena, and that their energy output can be explained using the theory of general relativity. In that sense, the quasars are certainly strange, but perhaps are not completely new phenomena.Quasar Redshifts Imply Enormous Distance and Energy Output
The quasars have very large redshifts, indicating by the Hubble law that they are at great distances. The fact that they are visible at such distances implies that they emit enormous amounts of energy and are certainly not stars.The Energy Source of Quasars is Extremely Compact
Quasars are extremely luminous at all wavelengths and exhibit variability on timescales as little as hours, indicating that their enormous energy output originates in a very compact source. Here are some light curves at different wavelengths illustrating the variability in intensity of some quasars and other active galaxies. Here is an explanation of these light curves. In all cases, the timescale for variability of the light from an active galaxy sets an upper limit on the size of the compact energy source that powers the active galaxy. These limits are typically the size of the Solar System or smaller.Some quasars emit radio frequency, but most (99%) are radio quiet. Careful observation shows faint jets coming from some quasars. The above images of the quasar 3C273 illustrate both a jet in the optical image on the left and radio frequency emission associated with the jet on the right. Here are some spectra of quasars and other active galaxies - see the following description.
Relationship of Quasars and Active Galaxies
The quasars are thought to be powered by supermassive rotating black holes at their centers. Because they are the most luminous objects known in the universe, they are the objects that have been observed at the greatest distances from us. The most distant are so far away that the light we see coming from them was produced when the Universe was only one tenth of its present age.The present belief is that quasars are actually closely related to active galaxies such as Seyfert Galaxies or BL Lac objects in that they are very active galaxies with bright nuclei powered by enormous rotating black holes. However, because the quasars are at such large distances, it is difficult to see anything other than the bright nucleus of the active galaxy in their case. As we have noted above, modern observations have begun to detect around some quasars jets and evidence for the surrounding faint nebulosity of a galaxy-like object.
Evolution of Quasars
The standard theory is that quasars turn on when there is matter to feed their supermassive black hole engines at the center and turn off when there is no longer fuel for the black hole. Recent Hubble Space Telescope observations indicate that quasars can occur in galaxies that are interacting with each other. This suggests the possibility that quasars that have turned off because they have consumed the fuel available in the original galaxy may turn back on if the galaxy hosting the quasar interacts with another galaxy in such a way to make more matter available to the black hole. Here is a recent survey of quasar host galaxies that sheds light on this issue.Abundance of Quasars in the Early Universe
Looking at large distances in the Universe is equivalent to looking back in time because of the finite speed of light. Thus, the observation of quasars at large distances and their scarcity nearby implies that they were much more common in the early Universe than they are now.This is one piece of evidence that argues against the steady state theory of the Universe but would be consistent with the big bang theory. We shall discuss this further below.
Hungry Black Holes
Notice that the greater abundance of quasars early in the Universe would be consistent with the mechanism discussed above whereby a quasar shuts off when its black hole engine has consumed the fuel available in the host galaxy. We would expect that generally in the early Universe there may have been more mass easily accessible to the black hole than later, after much of it had been consumed. Perhaps later quasars are more dependent on interactions between galaxies to disturb mass distributions and cause galaxies to begin to feed the hungry black hole.excerpt taken from http://csep10.phys.utk.edu/astr162/lect/active/quasars.html
Sunday, July 5, 2009
Dark Energy
The discovery in 1998 that the Universe is actually speeding up its expansion was a total shock to astronomers. It just seems so counter-intuitive, so against common sense. But the evidence has become convincing.
The evidence came from studying distant type Ia supernovae. This type of supernova results from a white dwarf star in binary system. Matter transfers from the normal star to the white dwarf until the white dwarf attains a critical mass (the Chandrasekhar limit) and undergoes a thermonuclear explosion. Because all white dwarfs achieve the same mass before exploding, they all achieve the same luminosity and can be used by astronomers as "standard candles." Thus by observing their apparent brightness, astronomers can determine their distance using the 1/r2 law.
By knowing the distance to the supernova, we know how long ago it occurred. In addition, the light from the supernova has been red-shifted by the expansion of the universe. By measuring this redshift from the spectrum of the supernova, astronomers can determine how much the universe has expanded since the explosion. By studying many supernovae at different distances, astronomers can piece together a history of the expansion of the universe.
In the 1990's two teams of astronomers, the Supernova Cosmology Project and the High-Z Supernova Search, were looking for distant type Ia supernovae in order to measure the expansion rate of the universe with time. They expected that the expansion would be slowing, which would be indicated by the supernovae being brighter than their redshifts would indicate. Instead, they found the supernovae to be fainter than expected. Hence, the expansion of the universe was accelerating!
In addition, measurements of the cosmic microwave background indicate that the universe has a flat geometry on large scales. Because there is not enough matter in the universe - either ordinary or dark matter - to produce this flatness, the difference must be attributed to a "dark energy". This same dark energy causes the acceleration of the expansion of the universe. In addition, the effect of dark energy seems to vary, with the expansion of the Universe slowing down and speeding up over different times.
Astronomers know dark matter is there by its gravitational effect on the matter that we see and there are ideas about the kinds of particles it must be made of. By contrast, dark energy remains a complete mystery. The name "dark energy" refers to the fact that some kind of "stuff" must fill the vast reaches of mostly empty space in the Universe in order to be able to make space accelerate in its expansion. In this sense, it is a "field" just like an electric field or a magnetic field, both of which are produced by electromagnetic energy. But this analogy can only be taken so far because we can readily observe electromagnetic energy via the particle that carries it, the photon.
Some astronomers identify dark energy with Einstein's Cosmological Constant. Einstein introduced this constant into his general relativity when he saw that his theory was predicting an expanding universe, which was contrary to the evidence for a static universe that he and other physicists had in the early 20th century. This constant balanced the expansion and made the universe static. With Edwin Hubble's discovery of the expansion of the Universe, Einstein dismissed his constant. It later became identified with what quantum theory calls the energy of the vacuum.
In the context of dark energy, the cosmological constant is a reservoir which stores energy. Its energy scales as the universe expands. Applied to the supernova data, it would distinguish effects due to the matter in the universe from those due to the dark energy. Unfortunately, the amount of this stored energy required is far more than observed, and would result in very rapid acceleration (so much so that the stars and galaxies would not form). Physicists have suggested a new type of matter, "quintessence," which would fill the universe like a fluid which has a negative gravitational mass. However, new constraints imposed on cosmological parameters by Hubble Space Telescope data rule out at least simple models of quintessence.
Other possibilities being explored are topological defects, time varying forms of dark energy, or a dark energy that does not scale uniformly with the expansion of the universe.
excerpt taken from http://imagine.gsfc.nasa.gov/docs/science/mysteries_l1/dark_energy.html
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