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.
Thursday, July 28, 2011
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
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