THE NEW STORY STARTS with, gets its framework from, the cosmic story – the new understanding of the universe and of the natural world developed, especially during the 20th century, by disciplines such as physics, astronomy, geology, biology, ecology, archaeology, anthropology, and history. This article provides a brief retelling of that story, from the birth of the universe up to the emergence of humans. (For a more detailed, but highly readable, telling of this story, I recommend Timescale, by Nigel Calder (New York: Viking, 1983)).
THE MICRO STORY
For the first few hundred years of modern science, from Galileo to the beginning of the 20th century, scientific discovery seemed to be a process of replacing mystery with common sense. Phenomenon after phenomenon was studied, analyzed, and explained as just elaborate mechanisms, like the workings of a clock, made up of simple parts and simple forces that could be interpreted in ways that were familiar from everyday life. Success piled upon success, and encouraged the belief that eventually all of existence would be explained in this common sense way. While some bemoaned the loss of mystery, many others felt liberated by the intelligibility and "rationality" they saw in the world around them.
Yet just as the world seemed on the verge of being thoroughly tamed and explained, the most respected of the modern sciences, physics, by probing the microworld of atoms, uncovered phenomena that could only be explained in ways that seemed totally bizarre to the 19th-century mind – light "waves" acted in some ways like particles (concentrated in space and carrying a fixed "quantum" of energy), while "particles" (electrons, protons, etc.) also acted like waves (spread throughout space and capable of resonance and interference). As quantum theory developed, even worse shocks were in store – simple quantities, like position and velocity, could not be measured with absolute precision even in principle. Uncertainty in measurement led to uncertainty in prediction, which now could at best only provide statistical probabilities. Uncertainty also allowed "absolute physical laws," like the conservation of energy, to be violated for brief periods of time – allowing particles to simply appear (and then disappear) out of nothing.
It was not just that these results were surprising. They required a whole new attitude about the way the universe operated and what could be expected from science. Up to this time, science had used, with great success, the strategy of analysis, that is, understanding wholes by studying the properties of their parts. The hope (and to a large extent, the experience) was that a detailed knowledge of the parts would allow a complete reconstruction of the whole. For this to succeed requires that each part be knowable "in isolation" and in sufficient detail. In the microworld of quantum physics, these conditions just didn’t apply – quantum reality was both uncertain and an inseparable web. The process of observation had to be included as part of the experiment, inescapably helping to shape each outcome. This is seen most dramatically in the experiments used to test Bell’s theorem that suggest that observations at any one point instantaneously effect the whole rest of the cosmos!
The vision of science and of the physical universe that emerges from this is complex: Analysis continues to be an effective tool, but it is no longer absolute. Science can reveal a great deal, making the world around us more intelligible, but the ultimate mystery and unpredictability of life are affirmed, and if anything, deepened and reinforced. This spirit of simultaneous knowledge and mystery is at the heart of the New Story.
THE COSMIC STORY: THE PAST 13.5 BILLION YEARS
From the very small, we move to the very large. During the 20th century we have discovered a universe that is far larger and older than anything the Old Story imagined. It is also a universe with a story, a life, even a beginning.
Astronomers have developed four independent ways of estimating the age of the universe (the ages of the oldest stars, the ages of the oldest radioactive chemical elements, the age predicted by General Relativity based on the present density of matter in the universe, and the age determined from the expansion of galaxies away from us). These all agree that there was a "beginning" about 13.5 billion years ago (give or take a few billion). The story of that beginning, as we presently understand it, goes as follows:
It is hard for us to imagine the instant of beginning, for not only was there no matter, there was also no physical space or physical time. There may have been other dimensions of existence, but about these our physical sciences are silent. During the first second, the basic forces and particles of physics took form while space and time, as we know them, came into being. This initial "stuff" changed rapidly in time, but it was remarkably uniform in space – everywhere that there was space, there was also the same density of matter. The matter grew less dense with time – seemed to be expanding – but it did not "explode" into an empty surrounding space (nowhere was space empty). What it did was far more wondrous than that, for it actually "grew" more space within its midst – everywhere. As time went on and more space grew, the matter cooled. Within 3 minutes, the young universe was about as "cold" as the center of the sun, allowing about 1/4 of the hydrogen to be converted into helium.
The pace of the story then slows way down. It took a million years of growing more space and cooling the matter before the universe became transparent, and a billion years before stars and galaxies formed. These were able to form because matter was not quite perfectly uniformly distributed throughout space. The vigor of the young universe had included sound (pressure waves) as well as light and matter, and as the roar of creation cooled, it left slight clumpings that were the seeds of galaxies.
Once galaxies with their billions of stars formed, the next chapter in the cosmic story could begin. At first, the universe contained essentially only hydrogen and helium. But many of the first stars were bigger than the sun, and big stars burn hot and fast. Within as little as a hundred million years, they had transformed the hydrogen and helium in their cores into elements like carbon and oxygen, all the way up to iron. And then, at the end of their lives, they exploded in the extravagance of supernovas, creating elements as heavy as uranium and spewing them into the clouds of gas that traveled with the stars in these early galaxies. The elements that make up the sun and earth have an average age of about 10 billion years.
As time went on and space kept growing, the galaxies continued to be fertile breeding grounds for stars, and the larger stars kept enriching the gas in the galaxy with heavier elements. About 4.5 billion years ago (one third the age of the universe), our own sun was born, and from the scraps of that birth, the planets were formed.
THE EARTH STORY: THE PAST 4.5 BILLION YEARS
The cosmic story continues, of course, but its large scale events have changed little in the past 10 billion years. The interest shifts to smaller scales, for which we have real access to only our own Earth. How unique is the Earth? We do not know. We have observed Jupiter-sized planets around other stars, but beyond that, all is speculation. The best educated guesses are that planets are fairly common companions to stars, and that earth-like initial physical conditions are probably fairly common as well. Thus, while we are still a long way from proof, it would not be surprising if there are billions of earth-like planets throughout the universe.
The oldest rocks are about 3.9 billion years old, or about 700 million years younger than the Earth itself, leaving us with no direct record of those first 700 million years. We are able to piece together a remarkably detailed picture, however, from studies of the moon, studies of the solar system, and working backwards from the later history of the Earth.
It took only about 100 million years for the rocky Earth to be formed. The Earth began as a swarm of rocky debris circling the infant sun – debris that had been part of the interstellar gas cloud that collapsed to birth the sun. The inner solar system, home of Mercury, Venus, Earth, and Mars, was cool enough for materials like rock and even ice to survive as solids, but the lighter gases (hydrogen, helium, methane, etc.) were pushed further out, finding homes in Jupiter and the outer planets. Initial clumps in the ring of rocky material grew by gravitationally capturing smaller chunks. It took about 50 million years for the infant Earth to sweep up enough material to grow to about 5/6 of its present mass and another 50 million to essentially finish the process. The energy released by this bombardment, as well as by radioactive heating, melted the body of the Earth, allowing iron to sink into its core while lighter rocks rose to the surface.
The initial atmosphere was mostly carbon dioxide and water vapor. As the cosmic bombardment slowed, the surface of the Earth cooled, allowing water vapor to condense into clouds and rain, with seas gradually forming on the cratered surface. Somewhere in these seas, by 4 billion years ago and perhaps earlier, life began, evolving soon into simple bacteria. Within another 100 million years, some of these bacteria had learned how to live off sunlight and carbon dioxide (photosynthesis) just as modern plants do.
For the next 3 billion years, the life of the Earth is a monotonous tale of gradual geological processes and the slow evolution of single-celled organisms. The most notable event is the "oxygen revolution." Photosynthesis produces oxygen as a waste product, and all those little bacteria had been making lots of it for billions of years. Oxygen is chemically very active, and at first it all got absorbed by various minerals on the Earth’s surface. By 1.8 billion years ago, however, these oxygen absorbers were all used up, so the excess oxygen just accumulated in the atmosphere. Meanwhile continents of barren land drifted around, grouping and regrouping, all the while slowly growing in size.
Then 1 billion years ago, 3.5 billion after the formation of the Earth, life comes up with a brilliant invention – sex. Evolution accelerates through the more varied genetic combinations that sexual reproduction involves. It still takes another 600 million years, however, to get life onto land – first plants, then insects, and finally amphibians.
This brings us up to the most recent 10% or so of the Earth’s history. Most of what we usually think of as geological prehistory – the age of the dinosaurs, the formation of coal, the creation of present day mountain ranges, etc. – all took place in this last 10%. The details for this time period are rich, and in many cases fascinating. Continents shuffle around, species rise and fall, and even the cosmos gets into the act. On a number of occasions, massive extinctions coincide with evidence of a major cosmic impact (comet or planetoid). 245 million years ago such an event wiped out 96% of all marine species and all the large land animals. Then 67 million years ago, a similar event put an end to the age of dinosaurs. It is thought that these collisions produce large quantities of dust, darkening the atmosphere like a "nuclear winter" without the radioactivity.
To get to anything of more directly human interest, we have to look very recently indeed. The earliest ape/humans, walking upright, date from about 5 million years ago, or only 0.1% of the Earth’s life. The first species to get classified as fully human, Homo habilis, didn’t come for another 3 million years, or about 2 million years ago.
What messages does this cosmic story give us? Let me describe a few that I hear. First, change and evolution are a basic part of existence, even on its largest scales. Second, this change goes from simplicity and uniformity to increasing complexity and differentiation. Yet this differentiation is also democratic. There is no "center," no preferred location in the universe. Stars are everywhere very similar. This equality throughout space brings out a third message: a strong underlying unity pervades the universe. Everything in the universe started at the same beginning. Everywhere we look, the same physical laws are at work, the same physical constants apply.
These physical constants (that indicate the relative strengths of the basic physical forces of gravitation, electromagnetism, the weak interactions, and nuclear interactions) hold yet another message. As astronomers have experimented (theoretically) with how the universe might be different if these constants were different, they keep discovering that even small changes would make life as we know it impossible. Stars like the sun would not have formed, or they would have burned out too quickly for life to emerge. Likewise, without just the right balance of these constants, supernovas would not explode, and so there would be no heavy elements to create planets and life. Perhaps we were just lucky, but if you want to believe that this universe was designed to be a supportive home for life, the facts won’t contradict you.