There are two places in the scientific view of the beginning of things as they now are where the command “Let there be light” might seem to have an application.
First, consider the formless, chaotic mass of dust and gas slowly collapsing on the way to the formation of the solar system. As the mass collapses inward, its energy of motion is converted into heat, and the center of the whole, where the gathering matter is densest, grows hotter and hotter. The temperature rises into the thousands of degrees and, eventually, into the millions of degrees.
As the heat at the center rises, the atoms of which the matter is composed move more and more quickly and smash into each other in random collisions with greater and greater force. The outer shells of electrons boil off and are smashed off. The bare nuclei at the centers of the atoms smash into each other without being impeded by intervening electrons and fuse with each other into more complex nuclei. This “nuclear fusion” produces a great deal of energy that is in part, converted into electromagnetic radiation that streams out from the central regions of the cloud, which has now condensed into the sun. The electromagnetic radiation streaming out from the sun in all directions, we can detect, in part, as light.
In short, as the cloud condenses to form the sun, there comes a point when the sun ignites with a central nuclear fire and begins to shine. At that point, the sun “turns on,” perhaps quite rapidly, and it is as though there were the command of “Let there be light.”
Secondly, there is an earlier and an even more dramatic point at which we might view the command as having been given.
The solar system was formed nearly five billion years ago and the Galaxy, of which it forms part, billions of years before that. The Galaxy, however, is only one vast conglomeration of stars among many others like itself. There may be, in the Universe, as many as a hundred billion different galaxies, each containing many billions (or, in some cases, trillions) of stars.
In the 1920s, it was discovered that these galaxies exist in clusters that are receding from each other. It was found to be consistent with Einstein’s General Theory of Relativity (advanced in 1916) that the Universe was steadily expanding.
This means that, in the future, the Universe will be larger than it is now and that the matter within it will be spread out more thinly. It also means that, in the past, the Universe was smaller than it is now and that the matter within it was less spread out.
In fact, if we look far enough back in time, we can imagine a period when all the matter in the Universe was clumped together into a single body. The first to propose this was the Belgian astronomer (and Catholic priest) Georges Lemaitre in 1927. Calling the single body that existed at the beginning “the cosmic egg,” he suggested that its explosion led to the formation of the Universe as we now know it and that the galactic clusters recede from each other as part of the effect of that long-ago explosion.
Since Lemaitre’s time, astronomers have done their best to figure out what the cosmic egg was like and what the stages of its explosion were like.
If we imagine the Universe running backward in time, then we see all the galaxies coming together, and the effect is just that of the matter in a cloud of dust and gas coming together. The center grows hot.
Just as the sun grew hot as it formed forward in time, so the cosmic egg must grow hot as it forms backward in time. The heat of the sun, which resulted from the contraction of just one star’s worth of matter, is nothing at all compared to the heat of the cosmic egg formed from the contraction of the matter making up a billion trillion stars.
The cosmic egg was therefore inconceivably hot.
Suppose we begin with this super-hot cosmic egg and imagine time flowing forward again. The cosmic egg explodes in the largest conceivable explosion (the “big bang”), and its fragments are at first entirely too hot for matter, as we know it, to exist. Initially, the products formed in the explosion are energy. In tiny fractions of a second, the temperature dropped precipitously, and the Universe became cool enough to form certain fundamental particles of matter. Today, however, the Universe is too cool to allow these particles to exist.
A full second after the big bang, the temperature of the Universe had dropped to ten billion degrees, about what it is at the center of the largest stars, and the ordinary subatomic particles we know today came into existence. Later, ordinary atoms formed.
It was, however, not until about a million years after the big bang, by which time the temperature of the Universe had dropped to five thousand degrees (that of the surface of the sun), that matter came to predominate in the Universe. Until then, it was energy that predominated.
(By now, fifteen billion years later, the temperature of the Universe has dropped to an average of three degrees above absolute zero, though, obviously, there remain hot spots.)
It is rather dramatic to imagine that “Let there be light” marked the big bang and the initial period of energy-dominance. Light, after all, is a form of energy.
In fact, we might paraphrase the first three verses of Genesis as follows to make them fit the scientific view of the beginning of the Universe:
“To begin with, fifteen billion years ago, the Universe consisted of a structureless cosmic egg which exploded in a vast outpouring of energy.”
There are some points that must be made, though. The cosmic egg may be structureless (as far as we know), but it apparently represented a very orderly conglomeration of matter. Its explosion represented a vast shift in the direction of disorder, and ever since, the amount of disorder in the Universe has been increasing. (Scientists have invented the term “entropy,” which, among other things, is a measure of the amount of disorder in a system.)
~~In the Beginning: Science Faces God in the Book of Genesis -by- Isaac Asimov
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