Nature vs Values

by: Bertrand Russell

The philosophy of nature is one thing, the philosophy of value is quite another. Nothing but harm can come of confusing them. What we think good, what we should like, has no bearing whatever upon what is, which is the question for the philosophy of nature. On the other hand, we cannot be forbidden to value this or that on the ground that the nonhuman world does not value it, nor can we be compelled to admire anything because it is a "law of nature." Undoubtedly we are part of nature, which has produced our desires, our hopes and fears, in accordance with laws which the physicist is beginning to discover. In this sense we are part of nature; in the philosophy of nature we are subordinated to nature, the outcome of natural laws, and their victims in the long run.
The philosophy of nature must be unduly terrestrial; for it, the earth is merely one of the smaller planets of one of the smaller stars of the Milky Way. It would be ridiculous to warp the philosophy of nature in order to bring out results that are pleasing to the tiny parasites of this insignificant planet. Vitalism as a philosophy, and evolutionism, show in this respect, a lack of sense of proportion and logical relevance. They regard the facts of life, which are personally interesting to us, as having a cosmic significance, not a significance confined to the earth's surface. Optimism and pessimism, as cosmoc philosophies, show the same naive humanism; the great world, so far as we know it from the philosophy of nature, is neither good nor bad, and is not concerned to make us happy or unhappy. All such philosophies spring from self-importance and are best corrected by a little astronomy.
But in the philosophy of value the situation is reversed. Nature is only a part of what we can imagine; everything, real or imagined, can be appraised by us, and there is no outside standard to show that our valuation is wrong. We are ourselves the ultimate and irrefutable arbiters of value, and in the world of value nature is only a part. Thus in this world we are greater than nature. In the world of values, nature in itself is neutral, neither good nor bad, deserving of neither admiration nor censure. It is we who create value and our desires which confer value. In this realm we are kings, and we debase our kingship if we bow down to nature. It is for us to determine the good life, not for nature.

Edwin Hubble

was born in the small town of Marshfield, Missouri, USA, on November 29th, 1889. In 1898, His family moved to Chicago, where he attended high school. Young Edwin Hubble had been fascinated by science and mysterious new worlds from an early age, having spent his childhood reading the works of Jules Verne (20,000 Leagues Under the Sea, From the Earth to the Moon), and Henry Rider Haggard (King Solomon's Mines), Edwin Hubble was a fine student and an even better athlete, having broken the Illinois State high jump record. When he attended University, Hubble continued to excel in sports such as basketball and boxing, but he also found time to study and earn an undergraduate degree in mathematics and astronomy.

Edwin Hubble went to Oxford University on a Rhodes scholarship, where he did not continue his studies in astronomy, but instead studied law. At this point in his life, he had not yet made up his mind about pursuing a scientific career.

In 1913, Hubble returned from England and was admitted to the bar, setting up a small practice in Louisville Kentucky; but it didn't take long for Hubble to realize he wasn't happy as a lawyer, and that his real passion was astronomy, so he studied at the Yerkes Observatory, and in 1917, received a doctorate in astronomy from the University of Chicago.

Following a tour of duty in the first World War, Hubble took a job at the Mount Wilson Observatory in California, where took many photographs of Cepheid variables through 100 inch reflecting Hooker telescope, proving they were outside our galaxy, and determining the existence of several other galaxies such as our own milky way, which had until then been believed to be the universe.

Hubble had also devised a classification system for the various galaxies he observed, sorting them by content, distance, shape, and brightness; it was then he noticed redshifts in the emission of light from the galaxies, seeing saw that they were moving away from each other at a rate constant to the distance between them. From these observation, he was able to formulate Hubble's Law in 1929, helping astronomers determine the age of the universe, and proving that the universe was expanding.

It is interesting to note that In 1917, Albert Einstein had already introduced his general theory of relativity, and produced a model of space based on that theory, claiming that space was curved by gravity, therefore that it must be able to expand or contract; but he found this assumption so far fetched, that he revised his theory, stating that the universe was static and immobile. Following Hubble's discoveries, he is quoted as having said that second guessing his original findings was the biggest blunder of his life, and he even visited Hubble to thank him in 1931.

excerpt taken from http://www.edwinhubble.com/hubble_bio_001.htm

The Double Helix

The Discovery of the Double Helix, 1951-1953

The discovery in 1953 of the double helix, the twisted-ladder structure of deoxyribonucleic acid (DNA), by James Watson and Francis Crick marked a milestone in the history of science and gave rise to modern molecular biology, which is largely concerned with understanding how genes control the chemical processes within cells. In short order, their discovery yielded ground-breaking insights into the genetic code and protein synthesis. During the 1970s and 1980s, it helped to produce new and powerful scientific techniques, specifically recombinant DNA research, genetic engineering, rapid gene sequencing, and monoclonal antibodies, techniques on which today's multi-billion dollar biotechnology industry is founded. Major current advances in science, namely genetic fingerprinting and modern forensics, the mapping of the human genome, and the promise, yet unfulfilled, of gene therapy, all have their origins in Watson and Crick's inspired work. The double helix has not only reshaped biology, it has become a cultural icon, represented in sculpture, visual art, jewelry, and toys.

Researchers working on DNA in the early 1950s used the term "gene" to mean the smallest unit of genetic information, but they did not know what a gene actually looked like structurally and chemically, or how it was copied, with very few errors, generation after generation. In 1944, Oswald Avery had shown that DNA was the "transforming principle," the carrier of hereditary information, in pneumococcal bacteria. Nevertheless, many scientists continued to believe that DNA had a structure too uniform and simple to store genetic information for making complex living organisms. The genetic material, they reasoned, must consist of proteins, much more diverse and intricate molecules known to perform a multitude of biological functions in the cell.

Crick and Watson recognized, at an early stage in their careers, that gaining a detailed knowledge of the three-dimensional configuration of the gene was the central problem in molecular biology. Without such knowledge, heredity and reproduction could not be understood. They seized on this problem during their very first encounter, in the summer of 1951, and pursued it with single-minded focus over the course of the next eighteen months. This meant taking on the arduous intellectual task of immersing themselves in all the fields of science involved: genetics, biochemistry, chemistry, physical chemistry, and X-ray crystallography. Drawing on the experimental results of others (they conducted no DNA experiments of their own), taking advantage of their complementary scientific backgrounds in physics and X-ray crystallography (Crick) and viral and bacterial genetics (Watson), and relying on their brilliant intuition, persistence, and luck, the two showed that DNA had a structure sufficiently complex and yet elegantly simple enough to be the master molecule of life.

Other researchers had made important but seemingly unconnected findings about the composition of DNA; it fell to Watson and Crick to unify these disparate findings into a coherent theory of genetic transfer. The organic chemist Alexander Todd had determined that the backbone of the DNA molecule contained repeating phosphate and deoxyribose sugar groups. The biochemist Erwin Chargaff had found that while the amount of DNA and of its four types of bases--the purine bases adenine (A) and guanine (G), and the pyrimidine bases cytosine (C) and thymine(T)--varied widely from species to species, A and T always appeared in ratios of one-to-one, as did G and C. Maurice Wilkins and Rosalind Franklin had obtained high-resolution X-ray images of DNA fibers that suggested a helical, corkscrew-like shape. Linus Pauling, then the world's leading physical chemist, had recently discovered the single-stranded alpha helix, the structure found in many proteins, prompting biologists to think of helical forms. Moreover, he had pioneered the method of model building in chemistry by which Watson and Crick were to uncover the structure of DNA. Indeed, Crick and Watson feared that they would be upstaged by Pauling, who proposed his own model of DNA in February 1953, although his three-stranded helical structure quickly proved erroneous.

The time, then, was ripe for their discovery. After several failed attempts at model building, including their own ill-fated three-stranded version and one in which the bases were paired like with like (adenine with adenine, etc.), they achieved their break-through. Jerry Donohue, a visiting physical chemist from the United States who shared Watson and Crick's office for the year, pointed out that the configuration for the rings of carbon, nitrogen, hydrogen, and oxygen (the elements of all four bases) in thymine and guanine given in most textbooks of chemistry was incorrect. On February 28, 1953, Watson, acting on Donohue's advice, put the two bases into their correct form in cardboard models by moving a hydrogen atom from a position where it bonded with oxygen to a neighboring position where it bonded with nitrogen. While shifting around the cardboard cut-outs of the accurate molecules on his office table, Watson realized in a stroke of inspiration that A, when joined with T, very nearly resembled a combination of C and G, and that each pair could hold together by forming hydrogen bonds. If A always paired with T, and likewise C with G, then not only were Chargaff's rules (that in DNA, the amount of A equals that of T, and C that of G) accounted for, but the pairs could be neatly fitted between the two helical sugar-phosphate backbones of DNA, the outside rails of the ladder. The bases connected to the two backbones at right angles while the backbones retained their regular shape as they wound around a common axis, all of which were structural features demanded by the X-ray evidence. Similarly, the complementary pairing of the bases was compatible with the fact, also established by the X-ray diffraction pattern, that the backbones ran in opposite direction to each other, one up, the other down.

Watson and Crick published their findings in a one-page paper, with the understated title "A Structure for Deoxyribose Nucleic Acid," in the British scientific weekly Nature on April 25, 1953, illustrated with a schematic drawing of the double helix by Crick's wife, Odile. A coin toss decided the order in which they were named as authors. Foremost among the "novel features" of "considerable biological interest" they described was the pairing of the bases on the inside of the two DNA backbones: A=T and C=G. The pairing rule immediately suggested a copying mechanism for DNA: given the sequence of the bases in one strand, that of the other was automatically determined, which meant that when the two chains separated, each served as a template for a complementary new chain. Watson and Crick developed their ideas about genetic replication in a second article in Nature, published on May 30, 1953.

The two had shown that in DNA, form is function: the double-stranded molecule could both produce exact copies of itself and carry genetic instructions. During the following years, Crick elaborated on the implications of the double-helical model, advancing the hypothesis, revolutionary then but widely-accepted since, that the sequence of the bases in DNA forms a code by which genetic information can be stored and transmitted.

Although recognized today as one of the seminal scientific papers of the twentieth century, Watson and Crick's original article in Nature was not frequently cited at first. Its true significance became apparent, and its circulation widened, only towards the end of the 1950s, when the structure of DNA they had proposed was shown to provide a mechanism for controlling protein synthesis, and when their conclusions were confirmed in the laboratory by Matthew Meselson, Arthur Kornberg, and others.

Crick himself immediately understood the significance of his and Watson's discovery. As Watson recalled, after their conceptual breakthrough on February 28, 1953, Crick declared to the assembled lunch patrons at The Eagle that they had "found the secret of life." Crick himself had no memory of such an announcement, but did recall telling his wife that evening "that we seemed to have made a big discovery." He revealed that "years later she told me that she hadn't believed a word of it." As he recounted her words, "You were always coming home and saying things like that, so naturally I thought nothing of it."

Retrospective accounts of the discovery of the structure of DNA have continued to elicit a measure of controversy. Crick was incensed at Watson's depiction of their collaboration in The Double Helix (1968), castigating the book as a betrayal of their friendship, an intrusion into his privacy, and a distortion of his motives. He waged an unsuccessful campaign to prevent its publication. He eventually became reconciled to Watson's bestseller, concluding that if it presented an unfavorable portrait of a scientist, it was of Watson, not of himself.

A more enduring controversy has been generated by Watson and Crick's use of Rosalind Franklin's crystallographic evidence of the structure of DNA, which was shown to them, without her knowledge, by her estranged colleague, Maurice Wilkins, and by Max Perutz. Her evidence demonstrated that the two sugar-phosphate backbones lay on the outside of the molecule, confirmed Watson and Crick's conjecture that the backbones formed a double helix, and revealed to Crick that they were antiparallel. Franklin's superb experimental work thus proved crucial in Watson and Crick's discovery. Yet, they gave her scant acknowledgment. Even so, Franklin bore no resentment towards them. She had presented her findings at a public seminar to which she had invited the two. She soon left DNA research to study tobacco mosaic virus. She became friends with both Watson and Crick, and spent her last period of remission from ovarian cancer in Crick's house (Franklin died in 1958). Crick believed that he and Watson used her evidence appropriately, while admitting that their patronizing attitude towards her, so apparent in The Double Helix, reflected contemporary conventions of gender in science.

excerpt taken from http://profiles.nlm.nih.gov/SC/Views/Exhibit/narrative/doublehelix.html

Dinosaur Extinction

By: A. Buckley

There have been many mass extinctions throughout the history of the Earth. Probably the most famous is the extinction that finally saw the end of the dinosaurs reign on the Earth, 65 million years ago. It wasn't just the dinosaurs that died out in this extinction. Whatever caused the death of the dinosaurs also caused the death of around 70% of all of the species on the Earth. Although the dinosaurs had been in a period of decline, it is thought that their recovery was prevented by some sort of catastrophic event. There are many theories about why the dinosaurs finally became extinct, some of which are more than a little outlandish.

The two main 'serious' theories are the asteroid and volcano theories, both of which make some use of the analysis of the rocks in and around the K-T boundary (the Cretaceous - Tertiary boundary). The use of K comes from the Greek word for chalk (Kreta) which is found in great quantities in the rocks of the Cretaceous.

The K-T Boundary and Iridium 

In the late 1970's Luis and Walter Alvarez (father and son) along with a team of scientists from the University of California were making a study of the rocks around the K-T boundary in Gubbio, Italy. In particular they were looking at an unusual layer of clay at the boundary point which contained an unusual spike in the amounts of the rare element iridium. This spike revealed that the levels of iridium contained in the clay were roughly 30 times the normal levels. In parts per million iridium is present in the following amounts, 

(The term diabase is used to describe certain types of gabbro.) From these figures it can be seen that iridium is an extremely rare element, so it's discovery in 'large' amounts indicates that something serious happened. There are 2 sources of iridium, the main source comes from outer space in the form of cosmic dust which is constantly showering the planet. A second source is the Earth's core when there are eruptions of certain types of volcano. It is believed that the iridium, plus many other rare elements, were carried down and concentrated in to the Earth's core while the Earth was still largely molten. During this time certain types of primitive chondritic meteorites were formed where no concentration could have taken place due to rapid cooling. This means that it is possible that within the primitive chondritic meteorites there could be reasonable levels of iridium. From this information it can be seen that there are only two possible theories to explain the increased presence of iridium in the clay layer either an asteroid strike or a massive volcanic eruption.

Asteroid Signature

The thin clay layer that marks the boundary between the Cretaceous and Tertiary rocks. This layer has been found at many localities around the Earth. (Courtesy of Canadian Museum of Nature, Ottawa)

Of the two more serious theories perhaps the most well supported theory is concerned with the impact of a large asteroid type body. It is a well-known fact that throughout the history of the planet there have been many thousands of impacts some large and some small. The results of these impacts can have a wide variation. Two recent (in geological time) events show these differences in results very well. The results are known as the Tunguska Fireball and the Barringer Meteor Crater. 

  

Tunguska Fireball 

On June 30, 1908, the area near the Tunguska River in Siberia was the site of a remarkable explosion. The explosion, which took place at an altitude of roughly 8 km, had a force that was roughly equivalent to a 10-megaton atomic bomb. The explosion caused a shock-wave that flattened forests covering an area of more than 1000 square kilometers and killed herds of reindeer and other animals. No crater was formed, and aside from some microscopic nodules extracted from the soil, no recognizable fragments of the object remain. Scientists generally believe that the explosion was caused by an object with an approximate weight of 100,000 tons. 

  

 Barringer Meteor Crater 

Barringer Meteor Crater in northern Arizona, is a bowl-shaped depression 180m deep and 1.2km in diameter. It was named after American scientist Daniel M. Barringer who in 1905 theorized that the crater was meteoric in origin. The crater was the first impact site of an object to be identified on the Earth. Scientists think that the crater was formed sometime between 25,000 and 50,000 years ago by an iron meteorite, somewhere between 30 and 100m in diameter, weighing roughly 60,000 tons. The energy released by the impact was roughly equivalent to 3.5 million tons of TNT. Most of the object vaporized, but about 30 tons of fragments have been collected. There are other craters on the planet but due to erosion and plate movement it takes a trained eye to find them. From these two examples it can be seen that when large objects enter the atmosphere a great deal of energycan be released causing large amounts of damage. This evidence helps to support the Asteroid theory.

Barringer Meteor Crater, Arizona, USA

A photograph of the 50,000 year old crater in Arizona. (Courtesy of United States Geological Survey) 

The Asteroid Theory 

The first people to suggest the asteroid theory were the team lead by Luis and Walter Alvarez. It has been calculated that a chondritic asteroid approximately 10km in diameter would contain enough iridium to account for the iridium spike contained in the clay layer. Since the original discovery of the iridium spike other evidence has come to light to support the asteroid theory. Analysis of the clay layer has revealed the presence of soot within the layer. It is thought that the presence of the soot comes from the very large global fires that would have been the result of the large temperatures caused by an impact. Something else that was found within the clay were quartz crystals that had been physically altered. This alteration only occurs under conditions of extreme temperature and pressure and quartz of this type is known as shocked quartz. Despite all of this evidence many geologists did not believe in this theory and many were saying 'show us the crater'.

Blasted Rock

The parallel lines on this sample of quartz show what happens when this particular mineral is subjected to extremely high temperatures and pressures such as those obtained from meteorite impacts or nuclear explosions. (Courtesy of United States Geological Survey)

In 1990 a scientist called Alan Hildebrand was looking over some old geophysical data that had been recorded by a group of geophysicists searching for oil in the Yucatan region of Mexico. Within the data he found evidence of what could have been an impact site. What he 'found' was a ring structure 180km in diameter which was called Chicxulub. The location of this structure was just off the northwest tip of the Yucatan Peninsula. The crater has been dated (using the 40Ar/39Ar method) as being 65 million years old. The size of the crater is comparable to that which would have been caused by an impacting body with a diameter of roughly 10km.So we now have some of the proof of the asteroid theory. We know that a chondritic meteorite with a diameter of 10km contains enough iridium to cause a spike. We also know that about 65 million years ago there was an impact of a large object. The big question is what were the results, and how did they effect the dinosaurs.

The Yucatan Peninsuka

A map showing the probable location of the crater formed by the impact of the K-T meteorite.

Chicxulub, Yucatan Peninsula, Mexico

This three-dimensional map of local gravity and magnetic field variations shows a multi-ringed structure called Chicxulub named after a village located near its center. The impact basin is buried by several hundred meters of sediment, hiding it from view. This image shows the basin viewed obliquely from approximately 60° above the surface looking north, with artificial lighting from the south. (Courtesy of V. L. Sharpton, LPI)

If a 10km diameter object impacted at the point at which it struck it would have a velocity of roughly 100,000 km/h. At this velocity there would have been an initial blast (with an estimated force of many millions of tons of TNT) which would have destroyed everything within a radius of between 400 and 500km, including the object. At the same time large fires would have been started by the intense shock wave which would have traveled long distances. Trillions of tons of debris (dust, gases and water vapour) would have been thrown into the atmosphere when the object vaporized. Many enormous tidal waves would be started causing even more damage, the evidence of such waves has been found all the way round the Gulf of Mexico. Along with the tidal waves the blast would also start a chain reaction of earthquakes and volcanic activity there would have also been very high winds caused by the blast. In the days and weeks following the impact the cloud of debris would have been carried over large distances by the post blast high winds. This will have caused months of darkness and a decrease in global temperatures. After this there would have been an increase in temperatures caused by the large amounts of CO2 released by what would have been global fires. Eventually this would cause chemical reactions that would result in the formation of acid rains.

Dino Killer?

An artists impression of the meteorite that was responsible for the death of the dinosaurs. 
Artist: Don Davis (No Copyright-see NASA "USE" policy)

On the land the effects of the impact on the flora and fauna would have been devastating, especially on the large animals which would need large food supplies and on the dinosaurs which would need sun light to keep warm. The global fires would have destroyed considerable amounts of vegetation (by the analysis of the soot in the K-T boundary it is estimated that 25% of the vegetation cover was destroyed), the immediate effect of this would have resulted in the death of the large herbivores. A knock on effect of this would have killed off the large carnivores. Only the small active scavengers, like birds and mammals with the ability to find food from a wide range of sources would have survived. Analysis of the K-T boundary fossils shows that there was a short term takeover of the land by the hardy ferns, which moved into the areas were there had been fires.

In the sea the effects would have been just as dramatic. There would have been a decrease in the oxygen levels in the seawater as low oxygen deep seawater would have been brought up by massive under water currents. This would have resulted in a massive disturbance of the marine food chain through the death of much of the plankton. This would have resulted in the eventual death of the marine reptiles which would have relied on the food chain. There would also have been a massive death rate amongst the shelled sea animals like the ammonites. There could also have been a serious increase in the acidity of the seas caused by the acid rains. This may have also killed off some of the sea species.

The period of recovery would have seen the surviving species moving into the ecological niches left vacant by the dead species. After a short period of time some of the plants that had been burnt down would have regrown from buried seeds or rootstock. As is common with all mass extinctions there would have a sudden evolutionary burst as new species developed. The age of the mammals was beginning.

except taken from http://web.ukonline.co.uk/a.buckley/dino.htm

  

Life in the universe

LIFE IN THE UNIVERSE
S. W. Hawking

In this talk I would like to speculate a little on the development of life in the universe,and in particular the development of intelligent life. I shall take this to include the human race, even though much of its behaviour throughout history has been pretty stupid and not calculated to aid the survival of the species. Two questions I shall discuss are: what is the probability of life existing else where in the universe, and how may life develop in the future.

It is a matter of common experience that things get more disordered and chaotic with time. This observation can be elevated to the status of a law, the so-called Second Law of Thermodynamics. This says that the total amount of disorder or entropy in the universe always increases with time. However, the Law refers only to the total amount of disorder. The order in one body can increase provided that the amount of disorder in its surroundings increases by a greater amount. This is what happens in a living being.One can define Life to be an ordered system that can sustain itself against the tendency to disorder and can reproduce itself. That is, it can make similar, but independent, ordered systems. To do these things the system must convert energy in some ordered form, life food, sunlight or electric power, into disordered energy in the form of heat. In this way the system can satisfy the requirement that the total amount of disorder increases while at the same time increasing the order in itself and its offspring.

A living being usually has two elements: a set of instructions that tell the system how to sustain and reproduce itself. And a mechanism to carry out the instructions. In biology these two parts are called genes and metabolism. But it is worth emphasizing that there need be nothing biological about them. For example, a computer virus is a program that will make copies of itself in the memory of a computer and will transfer itself to other computers. Thus it fits the definition of a living system that I have given. Like a biological virus, it is a rather degenerate form because it contains only instructions or genes and doesn't have any metabolism of its own. Instead it reprograms the metabolism of the host computer or cell. Some people have questioned whether viruses should count as life because they are parasites and can not exist independently of their hosts. But then most forms of life, ourselves included, are parasites in that they feed off and depend for their survival on other forms of life. I think computer viruses should count as life. Maybe it says something about human nature that the only form of life we have created so far is purely destructive. Talk about creating life in our own image. I shall return to electronic forms of life later on.

What we normally think of as life is based on chains of carbon atoms with a few other atoms such as nitrogen or phosphorous. One can speculate that one might have life with some other chemical basis, such as silicon, but carbon seems the most favorable case because it has the richest chemistry. That carbon atoms should exist at all with the properties that they have requires a fine adjustment of physical constants such as the QCD scale, the electric charge and even the dimension of spacetime. If these constants had significantly different values either the nucleus of the carbon atom would not be stable or the electrons would collapse in on the nucleus. At first sight it seems remarkable that the universe is so finely tuned. Maybe this is evidence that the universe was specially designed to produce the human race. However, one has to be careful about such arguments because of what is known as the Anthropic Principle. This is based on the self evident truth that if the universe had not been suitable for life we wouldn't be asking why it is so finely adjusted. One can apply the Anthropic Principle in either its Strong or Weak versions.For the Strong Anthropic Principle one supposes that there are many different universes each with different values of the physical constants. In a small number the values will allow the existence of objects like carbon atoms that can act as the building blocks of living systems. Since we must live in one of these universes we should not be surprised that the physical constants are finely tuned. If they weren't we wouldn't be here.

The strong form of the anthropic principle is not very satisfactory. What operational meaning can one give to the existence of all those other universes. And if they are separate from our own universe how can what happens in them affect our universe. Instead, I shall adopt what is known as the Weak Anthropic Principle. That is, I shall take the values of the physical constants as given. But I shall see what conclusions can be drawn from the fact that life exists on this planet at this stage in the history of the universe.

There was no carbon when the universe began in the Big Bang about 15 billion years ago. It was so hot that all the matter would have been in the form of particles called protons and neutrons. There would initially have been equal numbers of protons and neutrons.However, as the universe expanded it would have cooled. About a minute after the Big Bang the temperature would have fallen to about a billion degrees, about a hundred times the temperature in the Sun . At this temperature the neutrons will start to decay into more protons. If this had been all that happened, all the matter in the universe would have ended up as the simplest element, hydrogen, whose nucleus consists of a single proton.However, some of the neutrons collided with protons and stuck together to form the next simplest element, helium, whose nucleus consists of two protons and two neutrons. But no heavier elements, like carbon or oxygen, would have been formed in the early universe. It is difficult to imagine that one could build a living system out of just hydrogen and helium,and anyway the early universe was still far too hot for atoms to combine into molecules.

The universe would have continued to expand and cool. But some regions would have had slightly higher densities than others. The gravitational attraction of the extra matter in those regions would slow down their expansion and eventually stop it. Instead, they would collapse to form galaxies and stars starting from about two billion years after the Big Bang. Some of the early stars would have been more massive than our Sun. They would have been hotter than the Sun and would have burnt the original hydrogen and helium into heavier elements such as carbon, oxygen and iron. This could have taken only a few hundred million years. After that some of the stars would have exploded as supernovae and scattered the heavy elements back into space to form the raw material for later generations of stars.

Other stars are too far away for us to be able to see directly if they have planets going round them. But certain stars called pulsars give off regular pulses of radio waves. We observe a slight variation in the rate of some pulsars and this is interpreted as indicating that they are being disturbed by having Earth sized planets going round them. Planets going round pulsars are unlikely to have life because any living beings would have been killed in the supernova explosion that led to the star becoming a pulsar. But the fact that several pulsars are observed to have planets suggests that a reasonable fraction of the hundred billion stars in our galaxy may also have planets. The necessary planetary conditions for our form of life may therefore have existed from about four billion years after the Big Bang.

Our solar system was formed about four and a half billion years ago, or about ten billion years after the Big Bang, from gas contaminated with the remains of earlier stars.The Earth was formed largely out of the heavier elements, including carbon and oxygen.Somehow some of these atoms came to be arranged in the form of molecules of DNA. This has the famous double helix form discovered by Crick and Watson in a hut on the New Museum site in Cambridge. Linking the two chains in the helix are pairs of nucleic acids.There are four types of nucleic acid: adenine, cytosine, guanine and thymine. An adenine on one chain is always matched with a thymine on the other chain, and a guanine with a cytosine. Thus the sequence of nucleic acids on one chain defines a unique complementary sequence on the other chain. The two chains can then separate and each act as templates to build further chains. Thus DNA molecules can reproduce the genetic information coded in their sequences of nucleic acids. Sections of the sequence can also be used to make proteins and other chemicals that can carry out the instructions coded in the sequence and assemble the raw material for DNA to reproduce itself.

We do not know how DNA molecules first appeared. The chances against a DNA molecule arising by random fluctuations are very small. Some people have therefore suggested that life came to Earth from elsewhere and that there are seeds of life floating round in the galaxy. However, it seems unlikely that DNA could survive for long in the radiation in space. And even if it could it would not really help explain the origin of life because the time available since the formation of carbon is only just over double the age of the Earth.

One possibility is that the formation of something like DNA that could reproduce itself really is fantastically unlikely. However, in a universe with a very large or infinite number of stars one would expect it to occur in a few stellar systems but they would be very widely separated. The fact that life happened to occur on Earth is not however surprising or unlikely. It is just an application of the Weak Anthropic Principle: if life had appeared instead on another planet we would be asking why it had occurred there.

If the appearance of life on a given planet was very unlikely one might have expected it to take a long time. More precisely one might have expected life to appear just in time for the subsequent evolution to intelligent beings like us to have occurred before the cutoff provided by the life time of the Sun. This is about ten billion years after which the Sun will swell up and engulf the Earth. An intelligent form of life might have mastered space travel and be able to escape to another star. But otherwise life on Earth would be doomed.

There is fossil evidence that there was some form of life on Earth about three and a half billion years ago. This may have been only 500 million years after the Earth became stable and cool enough for life to develop. But life could have taken 7 billion years to develop and still have left time to evolve to beings like us who could ask about the origin of life. If the probability of life developing on a given planet is very small why did it happen on Earth in about one 14th of the time available.

The early appearance of life on Earth suggests that there's a good chance of the spontaneous generation of life in suitable conditions. Maybe there was some simpler form of organisation which built up DNA. Once DNA appeared it would have been so successful that it might have completely replaced the earlier forms. We don't know what these earlier forms would have been. One possibility is RNA. This is like DNA but rather simpler and without the double helix structure. Short lengths of RNA could reproduce themselves like DNA and might eventually build up to DNA. One can not make nucleic acids in the laboratory from non living material let alone RNA. But given 500 million years and oceans covering most of the Earth there might be a reasonable probability of RNA being made by chance.

As DNA reproduced itself there would have been random errors. Many of these errors would have been harmful and would have died out. Some would have been neutral, that is they would not have affected the function of the gene. Such errors would contribute to a gradual genetic drift that seems to occur in all populations. And a few errors would have been favorable to the survival of the species. These would have been chosen by Darwinian natural selection.

The process of biological evolution was very slow at first. It took two and a half billion years to evolve from the earliest cells to multi cell animals, and another billion years to evolve through fish and reptiles to mammals. But then evolution seemed to have speeded up. It only took about a hundred million years to develop from the early mammals to us.The reason is fish contain most of the important human organs and mammals essentially all of them. All that was required to evolve from early mammals like lemurs to humans was a bit of fine tuning.

But with the human race evolution reached a critical stage comparable in importance with the development of DNA. This was the development of language, and particularly written language. It meant that information can be passed on from generation to generation other than genetically through DNA. There has been no detectable change in human DNA brought about by biological evolution in the ten thousand years of recorded history.But the amount of knowledge handed on from generation to generation has grown enormously. The DNA in human beings contains about three billion nucleic acids. However,much of the information coded in this sequence is redundant or is inactive. So the total amount of useful information in our genes is probably something like a hundred million bits. One bit of information is the answer to a yes no question. By contrast, a paperback novel might contain two million bits of information. So a human is equivalent to 50 Mills and Boon romances. The University Library contains about five million books or about ten trillion bits. So the amount of information handed down in books is a hundred thousand times as much as in DNA.

Even more important is the fact that the information in books can be changed and updated much more rapidly. It has taken us several million years to evolve from the apes.During that time the useful information in our DNA has probably changed by only a few million bits. So the rate of biological evolution in humans is about a bit a year. By contrast,there are about 50,000 new books published in the English language each year containing of the order of a hundred billion bits of information. Of course, the great majority of this information is garbage and no use to any form of life. But, even so, the rate at which useful information can be added is millions, if not billions, times higher than with DNA.

This has meant that we have entered a new phase of evolution. At first evolution proceeded by natural selection from random mutations. This Darwinian phase lasted about three and a half billion years and produced us, beings who developed language to exchange information. But in the last ten thousand years or so we have been in what might be called an external transmission phase. In this the internal record of information handed down to succeeding generations in DNA has not changed significantly. But the external record in books and other long lasting forms of storage has grown enormously. Some people would use the term evolution only for the internally transmitted genetic material and would object to it being applied to information handed down externally. But I think that is too narrow a view. We are more than just our genes. We may be no stronger or inherently more intelligent than our cave man ancestors. But what distinguishes us from them is the knowledge that we have accumulated over the last ten thousand years and particularly over the last three hundred. I think it is legitimate to take a broader view and include externally transmitted information as well as DNA in the evolution of the human race.

The time scale for evolution in the external transmission period is the time scale for accumulation of information. This used to be hundreds or even thousands of years. But now this time scale has shrunk to about 50 years or less. On the other hand, the brains with which we process this information have evolved only on the Darwinian time scale of hundreds of thousands of years. This is beginning to cause problems. In the 18th century there was said to be a man who had read every book written. But nowadays if you read one book a day it would take you about 15000 years to read through the books in the University Library. By which time many more books would have been written.

This has meant that no one person can be the master of more than a small corner of human knowledge. People have to specialize in narrower and narrower fields. This is likely to be a major limitation in the future. We certainly can not continue for long with the exponential rate of growth of knowledge that we have had in the last three hundred years. An even greater limitation and danger for future generations is that we still have the instincts, and in particular the aggressive impulses, that we had in cave man days.Aggression in the form of subjugating or killing other men and taking their women and food has had definite survival advantage up to the present time. But now it could destroy the entire human race and much of the rest of life on Earth. A nuclear war is still the most immediate danger but there are others such as the release of a genetically engineered virus. Or the green house effect becoming unstable.

There is no time to wait for Darwinian evolution to make us more intelligent and better natured. But we are now entering a new phase of what might be called self designed evolution in which we will be able to change and improve our DNA. There is a project now on to map the entire sequence of human DNA. It will cost a few billion dollars but that is chicken feed for a project of this importance. Once we have read the book of life we will start writing in corrections. At first these changes will be confined to the repair of genetic defects like cystic fibrosis and muscular dystrophy. These are controlled by single genes and so are fairly easy to identify and correct. Other qualities such as intelligence are probably controlled by a large number of genes. It will be much more difficult to find them and work out the relations between them. Nevertheless I am sure that during the next century people will discover how to modify both intelligence and instincts like aggression.

Laws will be passed against genetic engineering with humans. But some people won't be able to resist the temptation to improve human characteristics such as size of memory resistance to disease and length of life. Once such super humans appear there are going to be major political problems with the unimproved humans who won't be able to compete.Presumably they will die out or become unimportant. Instead there will be a race of self designing beings who are improving themselves at an ever increasing rate.

If this race manages to redesign itself to reduce or eliminate the risk of self destruction it will probably spread out and colonize other planets and stars. However long distance space travel will be difficult for chemically based life forms like DNA. The natural life time for such beings is short compared to the travel time. According to the theory of relativity nothing can travel faster than light. So the round trip to the nearest star would take at least 8 years and to the center of the galaxy about a hundred thousand years. In science fiction they overcome this difficulty by space warps or travel through extra dimensions.But I don't think these will ever be possible no matter how intelligent life becomes. In the theory of relativity if one can travel faster than light one can also travel back in time.This would lead to problems with people going back and changing the past. One would also expect to have seen large numbers of tourists from the future curious to look at our quaint old fashioned ways.

It might be possible to use genetic engineering to make DNA based life survive in-definitely or at least for a hundred thousand years. But an easier way which is almost within our capabilities already would be to send machines. These could be designed to last long enough for interstellar travel. When they arrived at a new star they could land on a suitable planet and mine material to produce more machines that could be sent onto yet more stars. These machines would be a new form of life based on mechanical and electronic components rather than macro-molecules. They could eventually replace DNA based life just as DNA may have replaced an earlier form of life.

This mechanical life could also be self designing. Thus it seems that the external transmission period of evolution will have been just a very short interlude between the Darwinian phase and a biological or mechanical self design phase. This is shown on this next diagram which is not to scale because there's no way one can show a period of ten thousand years on the same scale as billions of years. How long the self design phase will last is open to question. It may be unstable and life may destroy itself or get into a dead end. If it does not it should be able to survive the death of the Sun in about 5 billion years by moving to planets around other stars. Most stars will have burnt out in another 15 billion years or so and the universe will be approaching a state of complete disorder according to the Second Law of Thermodynamics. But Freeman Dyson has shown that despite this life could adapt to the ever decreasing supply of ordered energy and therefore could in principle continue forever.

What are the chances that we will encounter some alien form of life as we explore the galaxy. If the argument about the time scale for the appearance of life on Earth is correct there ought to be many other stars whose planets have life on them. Some of these stellar systems could have formed 5 billion years before the Earth. So why is the galaxy not crawling with self designing mechanical or biological life forms. Why hasn't the Earth been visited and even colonized. I discount suggestions that UFO's contain beings from outer space. I think any visits by aliens would be much more obvious and probably also much more unpleasant.

What is the explanation of why we have not been visited. One possibility is that the argument about the appearance of life on Earth is wrong. Maybe the probability of life spontaneously appearing is so low that Earth is the only planet in the galaxy or in the observable universe in which it happened. Another possibility is that there was a reasonable probability of forming self reproducing systems like cells but that most of these forms of life did not evolve intelligence. We are used to thinking of intelligent life as an inevitable consequence of evolution. But the Anthropic Principle should warn us to be beware of such arguments. It is more likely that evolution is a random process with intelligence as only one of a large number of possible outcomes. It is not clear that intelligence has any long term survival value. Bacteria and other single cell organisms will live on if all other life on Earth is wiped out by our actions. There is support for the view that intelligence was an unlikely development for life on Earth from the chronology of evolution. It took a very long time two and a half billion years to go from single cells to multi cell beings who are a necessary precursor to intelligence. This is a good fraction of the total time available before the Sun blows up. So it would be consistent with the hypothesis that the probability for life to develop intelligence is low. In this case we might expect to find many other life forms in the galaxy but we are unlikely to find intelligent life.

A third possibility is that there is a reasonable probability for life to form and to evolve to intelligent beings in the external transmission phase. But at that point the system becomes unstable and the intelligent life destroys itself. This would be a very pessimistic conclusion. I very much hope it isn't true. I prefer a fourth possibility: there are other forms of intelligent life out there but that we have been overlooked. There is a project now on called SETI the search for extraterrestrial intelligence. It involves scanning the radio frequencies to see if we can pick up signals from alien civilizations. I think this project is worth supporting. But we should be wary of answering back. Meeting a more advanced civilization might be a bit like the original inhabitants of America meeting Columbus. I don't think they were better off for it.