From the Big Bang to Humankind

Conversation 11, Socrates Worldview 8/22

SOCRATES. Well, Critobulus, you look a little flushed, or should I say you have a healthy glow about you. I told you that a brisk bike ride would blow the negativity out of your system. How do you feel?

CRITOBULUS. I confess to feeling stimulated, Socrates, but do you have to ride so fast?

S. I promise you, Critobulus, in a week or two, as your fitness improves, the ride will be a breeze. You can vouch for that, Adeimantus?

ADEIMANTUS. It is true, Critobulus. Soon you won’t know yourself.

C. I am not sure that’s the goal I’m seeking, Adeimantus, but I take your words as kindly meant. So now, Socrates, you are going to give us a ‘potted summary of the whole scope of science and our understanding of the physical universe’. I have mentally braced myself for your onslaught.

S. Brave man, Critobulus. My summary will, of necessity, be sketchy and will omit whole areas of science that are of great interest, but I hope it will demonstrate three things: firstly that the scope of what science has to say about the physical universe and its history is breathtaking in its expanse; secondly that the coherence of this story and its foundation in experiment suggest that no reasonable person should doubt its essential truth; thirdly that the story of the history of the universe that science provides is not tied to any human culture, unlike other origin stories. I also hope that my summary will give us a basis for understanding what science has to say about the human person, and what science does not tell us about the universe, that is to say, about the limits of science. Now, where shall I begin?

A. Why not start with Democritus, as we did yesterday?

S. Good thought, Adeimantus, why not indeed! You will remember that Democritus is said to have proposed that the ‘stuff’ of the universe is made of atoms and that the apparent qualities of matter are products of the arrangement or the motion of the atoms. The first evidence for atoms was indirect. Alchemists and chemists had observed that certain chemicals combined to form other chemicals, and that they always combined in the same proportions in making a given product. What is more, some chemicals could be broken down into other chemicals and, again, the products always appeared in the same proportions. Some chemicals could not be broken down into constituents: these were called ‘elements’. Other chemicals that could be broken down, or made by combining elements, where called ‘compounds’. A simple explanation of all these observations was that elements are made of one kind of atoms, which cannot be broken down. Compounds are made of molecules, combinations of the atoms of elements, always in the same proportion. For example, water was found to be made of one part oxygen and two parts hydrogen, so it was supposed that water was made up of molecules, each containing one atom of oxygen and two atoms of hydrogen.

S. Chemists observed the properties of the elements and developed the concept of valency to describe the propensity of an element to combine with other elements in certain proportions. Thus, an oxygen atom was said to have a valency of two, so it would combine with two atoms of hydrogen, each of valency one. A carbon atom with valency four likes to combine with two oxygen atoms of valency two to make a molecule of carbon dioxide, and so on. Chemists arranged a table of the elements according to their valency and other properties. This table, called the Periodic Table of the Elements, is one of the great achievements of science. Chemists also observed that compounds tended to crystallise into structures that suggested their molecules had a certain shape, and that the shape was related to the valency. The explanation for the periodic table and the shapes of molecules was a mystery until quantum mechanics came along.

S. Meanwhile, physicist studying radioactivity found that the radiation consisted of small particles that caused discrete clicks in a Geiger counter or flashes on a screen. Aiming a beam of these particles at a thin foil, they found that nearly all the particles passed straight through. Occasionally, a particle would be deflected at a large angle. This suggested that the atoms of the foil where mostly empty space, with most of the mass of an atom concentrated in a small nucleus at its centre. The idea of the planetary model of the atom emerged. In this model, there was a small, heavy, positively charged nucleus at the centre of an atom, and a number of very light, negatively charged particles called electrons orbiting around it. Unlike the solar system, which is held together by the force of gravity, the atom is held together by the electrical attraction between positively and negatively charged particles. Also, unlike the planets in the solar system, Newtonian mechanics could not be used to derive the orbits of the electrons. Because of their tiny size, the electrons where subject to the newly discovered laws of quantum mechanics.

S. Using quantum mechanics, physicists were able to derive the orbits of the electrons in atoms, with spectacular success in explaining the observations of the chemistry and properties of the elements. They found that that the orbits could only be described by a set of discrete functions, called orbitals, which were solutions of the quantum mechanical equations. Each orbital could accommodate only two electrons. The valency of an element was found to be related to the emptiness or population of the outer-most orbitals of its atoms. Thus, the whole periodic table was explained. Furthermore, some orbits where spherical, while others had preferred directions for the electrons to be in. The shapes of the orbitals explained the shapes of the molecules and the crystal structure of compounds containing those elements.

S. Another success of the quantum model of atoms was that it explained why the atoms would emit or absorb light of only certain discrete colours. Associated with each orbital was an energy level for the electrons in the orbital. If an electron absorbed energy and transitioned to a higher-energy orbital, it could only absorb an amount, or quantum, of energy equal to the difference in the energy levels of the two orbitals. When the electron reverted to the lower energy orbital, it emitted the same quantum of energy in the form of light of a specific colour. Thus, the emission and absorption spectra of elements, which appeared in spectrographs as sets of discrete coloured ‘lines’, where explained to high accuracy by quantum mechanics. This proved to be a major importance in astronomy, as I will describe later.

S. Physicists studied the newly discovered atomic nucleus, mainly by scattering particles from radioactive materials or electron from cathode ray tubes from them. They used the law of conservation of momentum and the observed scattering angles in conjunction with other techniques to measure the masses and electric charges of the atomic nuclei. They found that nuclei are made of positively charged particles called protons and electrically neutral particles called neutrons. The atoms of a given element all have the same number of protons. For example, carbon atoms all contain six protons and have six electrons orbiting around the nucleus. Carbon atoms may differ in the number of neutrons they contain. Most contain six neutrons and are referred to as the isotope carbon-twelve, twelve being the atomic weight, calculated by summing the numbers of protons and neutrons. Another isotope, carbon-fourteen, contains eight neutrons. The nucleus of carbon fourteen is unstable and decays by a process called beta decay. In beta decay, one of the neutrons in the nucleus turns into three particles: a proton, an electron, and an antineutrino. The electron and the antineutrino are ejected from the nucleus, converting it to the nucleus of a nitrogen atom. Thus, this radioactive process converts one element into another. The antineutrino is very hard to detect. Its existence was initially posited to conserve momentum and was later confirmed by more elaborate experiments.

S. One may ask what holds the nucleus together, since the positively charged protons repel each other electrically. Did that question occur to you, Critobulus?

C. It was just beginning to form in my mind, Socrates.

S. Well done, Critobulus. Scientists posited a new force, call the strong nuclear force, which is attractive between protons and neutrons at short distances. They also needed another force, called the weak nuclear force, to explain why some particles are unstable and decay, for example, by beta decay. The strong and weak forces fit into a very elegant theoretical framework which unifies them together with the electromagnetic force. As we discussed in a previous conversation, quantum field theory links forces with particles. Many experiments have confirmed the properties of the forces and the existence and properties of the particles predicted by the theory.

S. Now, some unstable nuclei, like that of uranium, split in a process called nuclear fission. It turns out that the sum of the masses of the fission fragments is slightly less than the mass of the original uranium atom. Where did the missing mass go, you ask? Special Relativity tells us that E=mc2, and the missing mass is converted into energy, mostly in the form of the kinetic energy of the fragments as they fly apart. This kinetic energy can manifest as heat, as we discussed yesterday. In a nuclear fission power station, the heat is used to make steam which drives turbines to generate electricity.

S. Another form of nuclear reaction occurs when two light nuclei collide and fuse into a heavier nucleus. Not surprisingly, this is called nuclear fusion. The colliding particles have to be moving very fast to overcome the repulsive electrical force between the two positively charged nuclei and to get close enough to each other for the strong nuclear force to take over and bind them together. You remember that material in which the particles are moving very quickly has a high temperature, so nuclear fusion only occurs at very high temperature.

S. One place where the temperature is high enough for nuclear fusion to occur is at the centre of stars. Nuclear fusion is what powers the heat and light of stars, like the sun. Observations of the light spectra of stars and interstellar gas clouds show that they contain mainly hydrogen, the simplest atom consisting of one proton and one electron. The understanding of nuclear fusion allowed scientists to develop a model of the life cycle of stars, which fits a host of astronomical observations. It goes like this. The early universe was made up mostly of hydrogen gas. The gas started to form into clumps under the influence of gravity. As gravity pulled the hydrogen atoms inwards, their gravitational potential energy was converted into kinetic energy. (Remember we talked about that yesterday, Critobulus?) The temperature of the hydrogen gas increased, and also the pressure. Collisions between the hydrogen nuclei became more frequent and eventually the temperature became high enough for fusion to occur, producing helium nuclei. As the contraction continued and the temperature increased further, helium fused with hydrogen, and so progressively heavier elements were produced. This process created all the elements up to iron. A nucleus of iron contains twenty-six protons and about thirty neutrons, depending on the isotope.

A. Why did fusion stop at iron, and where did the heavier elements come from?

S. Good question, Adeimantus. Iron happens to be the heaviest stable nucleus that can be produced in the conditions existing in most stars. Heavier elements are produced in the cataclysmic explosions of supernovae, which many stars undergo when they reach the end of their life. Since the Earth and other planets contain these heavy elements, the planets must have coalesced from the residue of gas and dust left over from the explosions of older stars.

S. In the light spectra of stars and interstellar gases we recognise the spectra of elements that exist on Earth, and no others. This observation supports our initial supposition that the laws of the physics are the same everywhere. They are also the same for all time, since some of the light we see originated in deep space billions of years ago. And the light spectra have more to tell us. Astronomers have observed that the spectra of objects that are far from us are red shifted. This means that the light appears shifted in frequency towards the red end of the spectrum, or lower frequency of oscillation. The effect is called the Doppler shift. The same thing can be observed with sound. When an ambulance comes towards you, its siren sound higher in frequency, or pitch, than it does when it is going away from you. The conclusion from the red shift is that objects in space are moving away from us, and the further they are away, the faster they are receding. This is the observation that leads scientists to conclude that our universe underwent a ‘big bang’ about thirteen billion years ago and grew from something that was very tiny.

A. But how do they measure how far away things are in space?

S. The distances to stars that are not more than a few light years away have been measured by the parallax method. Are you familiar with parallax, Critobulus?

C. Yes, Socrates, I suffer from it frequently.

S. I see, Critobulus. You are referring, of course, to the way nearby objects appear to move against their background when you move your head from side to side. As the Earth moves around the sun, nearby stars appear to move a little against the background of more distant stars. By measuring this parallax shift and using simple geometry, astronomers can calculate the distance to the nearer stars. Then, fortuitously for astronomy, Cepheid variable stars were discovered. These are stars that pulsate in brightness. It turns out that the period of pulsation is related in a measurable way to the absolute brightness of a Cepheid variable. The measurement required the distance of some Cephid variable stars to be known from parallax measurements. Once the relationship was established, the distance to far-away Cepheid stars could be estimated from their apparent brightness, since their absolute brightness could be determined from their pulsation rate. Cepheid stars have even been identified in distant galaxies, allowing the distance to those galaxies to be determined. When combined with red shift measurements, it was then possible for astronomers to determine the relationship between red shift and distance. Consequently, red shift, which can be measured even for extremely distant objects, can be used as a proxy for distance.

S. The methods for calculating astronomical distances exemplify how science builds on past observations and inferences. The whole of science is an edifice, built layer upon layer. All parts of the structure must be consistent with each other, or the whole edifice falls down.

A. Impressive!

S. This brings us to cosmology. Cosmology deals with the structure and evolution of the whole universe, or at least the part of it that we can ever hope to receive influences from. As you know, the prevailing scientific model of the universe is the Big Bang. In the beginning, according to this model, the entire universe was crowded into a tiny space, from which it expanded rapidly. There are popular accounts of the Big Bang (Weinberg, 1977), (Hawking, 1988), which you can read if you are interested. The tiny universe was a very hot fireball, teeming with high-energy photons. At such a high energy, the four fundamental forces of nature, the Strong and Weak nuclear forces, the electromagnetic force, and gravity, were all of similar strength. Quantum mechanics and gravity were both at play, so a mathematical description of this state would require a unified theory of quantum mechanics and gravity, something which has so far eluded physicists, for reasons which I may discuss another time. The early universe was opaque because the photons could not travel far before colliding with others. As the universe expanded it cooled. Soon the conditions were gentle enough for particles to survive. You could say that they precipitated out of the soup of photons. Soon the universe became transparent as the density decreased and allowed photons to travel longer distances. Photons from the big bang still persist, however. Their energy level has decreased, and they are now at microwave frequencies. They form what is called the cosmic microwave background, which was discovered by astronomers a few years ago. This cosmic microwave background is almost uniform, but it does have an observable pattern of speckles. Interestingly, the pattern closely matches theoretical predictions. Quantum mechanics tells us that empty space is not really empty. Particles and photons can bubble up randomly from apparently empty space and then disappear again, producing fluctuations in density on a predictable scale. The scale of fluctuations, allowing for the expansion of the universe, matches the scale of the speckles in the cosmic microwave background. So, quantum mechanics seems to work from very near the beginning of the universe.

S. The first particles to appear soon settled into electrons, protons, and neutrons. With further expansion and cooling, the electrons and protons paired off to form hydrogen atoms. The occasional neutron combined with a hydrogen nucleus to form the heavier isotope of hydrogen, called deuterium. At this stage, the early universe consisted of a vast, nearly uniform, cloud of hydrogen gas. The quantum density fluctuations meant that the hydrogen gas was slightly denser in some places than in others. Gravity pulled the hydrogen towards the areas of higher density, amplifying them and depleting the less dense areas. Galaxies and groups of galaxies formed from the contracting clumps of hydrogen gas. Within galaxies, gravity continued to pull together denser balls of hydrogen gas. As I described earlier, these balls of hydrogen gas became the first stars. Gravitational potential energy was converted to kinetic energy of the hydrogen atoms as the stars contracted. They got hotter and nuclear fusion reactions began, producing atoms of the heavier elements up to iron and giving off the heat and light which allowed the stars to shine.

S. Stars go through a life cycle, the length of which is mainly determined by their mass. Bigger stars burn hotter and brighter, and they use up their hydrogen faster than smaller stars. Eventually, most stars become unstable, and they explode as the energy from nuclear reactions overpowers the gravitational attraction. The exploding stars appear in the sky as supernova. In the very hot conditions that prevail briefly in supernova, atoms of the elements heavier than iron can form. Clouds of these heavy elements and dust spray out from exploding starts. As they disperse, gravity can pull clumps of the star dust back together and second-generation stars can form. Swirling clouds of star dust held by gravity around stars clump to form planets, asteroids, and comets. That is how the Earth came to contain elements as heavy as uranium. We are all made of stardust, as Joni Mitchell sang in that wonderful song of hers.

A. I didn’t know you are a Joni Mitchell fan, Socrates.

S. Let us not be distracted, Adeimantus, I am nearly at the end of my story for today.

C. Thank God!

S. As for the role of God in all this, we will come to that later, Critobulus. Right now, having got as far as the formation of planets, I must talk about the appearance of life. Many people, when they think about life, naturally leap to thoughts about consciousness and the spirit. But that is not our concern today. We are concerned with the living body and how it could have been produced by the mechanistic natural processes we have been talking about. For I am sure you will not have failed to notice that nowhere in the story of the evolution of the cosmos have I mentioned God or an intelligent designer, or anything to do with intention or purpose. It is all understandable in terms of the mechanistic operation of the natural laws we have discovered through the scientific endeavour. Now we must consider whether the same applies to the emergence of life. I contend that it does.

A. You somewhat surprise me, Socrates. I thought you would be arguing the opposite since you are always talking about God.

S. Wait and see, Adeimantus. Now, living organisms are very complex and some people are perplexed by how they could have come together spontaneously. The answer is that they did not come together spontaneously as complete, complex organisms. To cut a very long story short, complex organisms emerged through a series of steps, each step in itself a simple enough advancement on the steps that had gone before (Sagan, Margulis, & Sagan, 2022). It was like building a ladder by climbing up the steps you have already made and adding new steps at the top. Some years ago, scientists did experiments in which they took a mixture of simple chemical compounds containing carbon, oxygen, and hydrogen and supplied them with energy in the form of electrical discharges, simulating lightning, or ultraviolet radiation, simulating sunlight. Under these conditions, more complex ‘organic’ compounds like sugars and nucleic acids were produced. These compounds are the building blocks of the proteins and DNA from which living organisms are made.

S. So, we can see how the building blocks of living organism could have arisen naturally, but we are still a long way from life. One thing we have to remember is that life is a continual battle against the second law of thermodynamics, which I am sure you will remember Critobulus, says that left to themselves, things tend towards increasing entropy, which is a way of saying that they become less ordered, more chaotic, or more random. Iron rusts, and living things die and turn into dust. But the growth of a living organism is a process of increasing order. How can this be? The answer is that order can be increased locally, provided the overall entropy, or disorder, is increased. So, for example, when ice crystallises out of water, the water molecules move into a more ordered structure. In the process, a large amount of energy is given off by the water, increasing the temperature of the surrounding environment and making the molecules in the environment move in a more disorderly fashion. Overall, the entropy increases. Now, it always takes energy to reduce entropy and make a thing more orderly. You have to do work, which means expend energy. To cool water so it freezes, we put it into a refrigerator. A refrigerator is a heat pump. It uses energy to pump heat out, cooling and reducing the entropy inside, while heating and increasing the entropy inside. And consider a plum left on a table. After a while it begins to decay. A mould, which is a living organism, may form on the rotting plum. The mould is busy organising itself and increasing its order, and it needs energy which it gets in the form of chemical energy by digesting the plum. The plum becomes more disordered. Overall, disorder increases.

A. Life is a continual struggle against the forces of disorder.

S. Precisely, Adeimantus. How did early life win out over the forces of disorder on the ancient Earth? There may have been relatively few places in the expanding universe where the conditions where suitable for life to emerge. The planet Earth just happened to be one such place. It was neither too hot nor too cold. It has water and the right abundance of the necessary elements: carbon, oxygen, and hydrogen. In a few places, powered by energy from lightning or the sun, those elements must have combined to form the building blocks I spoke about. In even fewer places, by chance over hundreds of millions of years, the conditions must have been just right for those building block molecules to combine into more complex organic molecules, including RNA and DNA. This might have required the molecular soup to be concentrated, perhaps as a result of the molecules sticking to a clay substrate, which could also have provided the trace elements like phosphorus, sodium, potassium, and calcium necessary for life. A gradient of temperature or the concentration of chemicals could have provided energy to power chemical reactions. Over time, the new proteins organised themselves into structures, like membranes, that helped to preserve the conditions needed to produce and power more of themselves. Scientists refer to systems like this as cyclic metabolic systems. Within some of them, over very long periods of time and again by chance, molecules and processes emerged that carry genetic code and allow organisms to replicate themselves. The DNA/RNA system is one such coding system. Others could be imagined, but the DNA/RNA system won out. Once the coding system emerged, evolution took care of the rest.

C. But isn’t evolution just a theory, Socrates? You talk of it as if it was a certainty.

S. Evolution is a fact, Critobulus. We can see it happening before our eyes. We understand and can even manipulate the DNA genetic code, to produce vaccines, for example. We know how generic mutations can occur and can observe them happening in populations of organisms. And we know that the ‘survival of the fittest’ mechanism is a method of natural selection. We see this happening right now in the evolution of the coronavirus that is causing the current pandemic. We see mutations causing the emergence of new variants and the process of natural selection causing new variants to displace the old. All those things are facts from observation. We get into theories when we consider the historical routes that evolution took. Did the whole human race descend from one small group of people in Africa, or did different populations of humans spring up independently from different ancestors and then mingle later? Questions like that refer to theories about the path of evolution and they can only be settled by collecting evidence from the fossil record, which is often hard to find.

C. Fair enough. Are we done yet?

S. Nearly, Critobulus. It is remains for me to say a little about the emergence of humankind. Some of these self-replicating molecular structures developed surrounding membranes that allowed them, in effect, to carry their life-sustaining environment around with them. Thus, we had single-celled organisms which already had a quite complex structure. Some of these were able to clump together into multicellular groupings. Some developed the ability to generate their energy requirements from photosynthesis and were in essence primitive plants. Others needed to move around and gobble up other organisms to obtain their energy. They were like animals, although the division into plants and animals was not clear, as some could do both. After a very long period of time, more complex single-celled organisms emerged that had their DNA encased in a nucleus, as well as distinct energy-generating structures, inside the cell. Some of these developed the ability to unite into multicellular organisms in which cells differentiated to perform specialised functions, like blood cells, nerves, bones, sensory cells, and so on.

C. It seems incredible that complex structures like the human eye could have emerged by chance.

S. Incredible as it seems, Critobulus, the fossil record tells us that eyes evolved independently at least a dozen times. The eyes of an insect or crustacean, for example, are structurally very different from mammal eyes, although they perform a similar function. We must bear in mind the enormous number of random trials that evolution has had to work with. The fossil and geological record tells us that simple life forms emerged nearly four billion years ago, only a few hundred million years after the Earth coalesced from the stardust. It took about another billion years or more for complex multicellular organisms to evolve. During this immense time, every individual organism was at least slightly different from its parents, and those differences that conferred a survival and reproductive advantage came to predominate, and so new structures and functions emerged. Our inability to comprehend this process is really a symptom of our inability to imagine the vast span of time involved and the immense number of variations that have been tested in the cauldron of evolution.

C. My brain is already hurting without trying to imagine a billion years!

S. Relief is at hand, Critobulus. All I have left to say is that over the fullness of time, the human species evolved, and here we are! So tell me, Critobulus, what have you learned, if anything, from my long diatribe?

C. I confess that I feel somewhat enlightened about the scope of science, but I am not totally convinced that there could not be other expositions of the history of the universe that are equally true or plausible.

S. Remember that I said I wanted to demonstrate three things. The first thing was that the scope of what science has to say about the physical universe and its history is breathtaking in its expanse.'

A. We accept that as proven, Socrates. No doubt you could have talked all day, filling in details and exploring lesser branches.

S. Indeed I could have. The second thing was that the coherence of this story and its foundation in experiment suggest that no reasonable person should doubt its essential truth. Have I succeeded on that point?

A. The story certainly seems to be coherent. We will have to take your word for it that there is nothing contradictory in it, and nothing that conflicts with experimental observations.

S. I urge you to think about the magnificence of the achievement of humankind, that from this one tiny pocket of the vast cosmos we could have developed a coherent explanation of everything that we can observe in the physical universe. Of course, there are phenomena around the edges where the explanation is patchy and alternative theories may have credence, but let me assure you that scientists search like hounds for observations that appear to contradict the accepted story. It is only by finding cases where the theory seems inadequate that progress can be made in science. Everything in the story is well tested. Even you, Critobulus, can go up in an aeroplane and confidently expect that you will not fall down because our understanding of the laws of physics is wrong!

C. I admit to that Socrates, somewhat grudgingly.

S. That is good enough for now, Critobulus. The third thing I hoped to show was that the story of the history of the universe that science provides is not tied to any human culture, or to Western culture in particular.

C. I still have a feeling that the scientific story of the cosmos is specific to Western culture.

S. The creation story specific to Western culture is the story in Genesis. In common with the creation stories of most other cultures, it attributes the acts of creation to a supernatural agent, or agents. In respect of these mythical elements, the Genesis story is on a par with the stories of other cultures, whatever one might think about other aspects, such as moral content. The Genesis story is as much at odds with the scientific story as any other creation myth. The scientific story is unique among creation stories in specifically denying the participation of any supernatural agent. It makes no attempt to explain how and why the universe came into being, but what it uniquely does is to offer an explanation of how the universe evolved from very near the beginning to the present day by purely mechanistic processes governed by natural laws which we have discovered through the scientific method. The scientific story is in an entirely different class from other creation stories in terms of the standards of truth that it apples to itself. The scientific story must be compatible with all accepted scientific theories and all accepted scientific observations. That is an extremely rigorous standard, which it is not appropriate to apply to mythical stories. In saying that, I do not make any value judgment about the relative merits of any of the stories. The scientific and the mythical stories have very different purposes, and it is wrong to apply the same standard of truth to them. I hope to discuss the relationship between the scientific story and the Genesis story on another occasion.

S. But you ask, Critobulus, whether the scientific story of the cosmos is specific to Western culture, and by inference, whether it could be seen as an imposition on other cultures. I say it is not. Science grew out of Western culture, with its roots in the interplay between Greek philosophical speculation and the law-making Judeo-Christian God. But for the last century or two when most of the progress has been made, it has been practiced by people in all parts of the world and from many cultural backgrounds. Eskimos and Hottentots would get the same results for the same experiments. These days, the scientific endeavour is a truly global one embraced by most of humankind. Can you think of any human endeavour with the same global appeal?

A. I agree that not even football has such a global following.

S. Let me also be clear that I do not denigrate knowledge about the natural world that is specific to some cultures. The Eskimos and Hottentots may have inherited knowledge specific to their culture, like how to find food and judge the seasons in a harsh environment. The local indigenous people of the place where we now sit identified seven seasons instead of our four. Knowledge of this type is not dogma, but the distillation of careful observations made over countless generations. Our scientific weather and climate models, if they are accurate, should give predictions in line with those observations. The cultural knowledge may be interwoven with mythical stories which give them meaning and a moral force within the culture, whereas our scientific explanation relies on naturalistic processes. The scientific approach gives testable explanations, and the mythical stories do not, but that is hardly the point. The purpose of the explanation is different in the two cases. Are you with me now, Critobulus?

C. I confess that I find your exposition convincing, Socrates.

S. I am much relieved to hear it, Critobulus. Now, finally, I say again that my purpose today was to show you how much science has to say about the physical world. There is very little about the physical world in the sphere of human experience for which science cannot give a cogent explanation. It does this without invoking God and at a standard of proof that verges on certainty. It is not absolutely certain because it relies on the method of induction, but as my old maths teacher Claude Bogg, God rest his soul, would have said, ‘You can bet your bottom dollar on it, sonny boy!’

S. Despite what I have just said, I have to tell you now that there is much in human experience that science has little to say about. In our future discussions, I propose to explore the limits of science. We will start next time by looking into what science has to say about the human person.

A. I look forward to it Socrates.

C. No doubt you will have even more to say about the human person than about the whole universe!

S. That is possible, Critobulus.

References

Hawking, S. (1988). A Brief History of Time.

Sagan, C., Margulis, L., & Sagan, D. (2022). In Encyclopaedia Britannica. Retrieved January 10, 2023, from https://www.britannica.com/science/origin-of-life.

Weinberg, S. (1977). The First Three Minutes: A Modern View of the Origin of the Universe.