Reason • Reality • Philosophy • Science • Psychology • Spirituality
The Infinite and Eternal Cosmos
Most people today have at least heard of the “big bang” theory. This is the idea that the entire universe which we observe, i.e., the “observable universe,” with its myriad galaxies, each containing myriad stars and planets, was not always as unimaginably huge as it is today. In fact, according to the big bang theory, the entire observable universe was once smaller than a grain of sand – and perhaps even much smaller, possibly even as small as a “Planck unit,” which, as we will see later, is the smallest size which has meaning in physics.
It is not important for our purposes here, however, that we actually know with any great accuracy just how compact the observable universe was at the time of the big bang. It is enough for us to know that the entire universe was, some 13.8 billion years ago or so, in an unimaginably dense, compact state. It is simple enough to prove this, because relatively simple astronomical observations indicate that the universe is currently expanding, and working backwards we can calculate how long it would have taken for the universe to reach its current size, from the time of the big bang.
Once it was known that the universe was expanding, it was naturally assumed that this expansion must be decelerating, or slowing down, over time. This is because all the matter in the universe tends to attract all the other matter in the universe, and this universal mutual attraction would tend to slow down the expansion of the universe, after the expansionary forces present at the time of the big bang had subsided. In fact, for a few decades cosmologists wondered whether this expansion would slow enough to actually stop, and eventually reverse, causing the entire universe to collapse into itself in sort of a reverse of the big bang. This possibility is called the “big crunch.”
A number of candidates have been proposed to explain this “dark energy.” One of the most simple and elegant solutions involves a quantum process known as “virtual particle pair production.” While this is a quantum mechanical process, and while we will focusing on quantum mechanics in the next section, virtual particle pair production can be described in a way which is fairly simple to explain and understand.
“Quantum uncertainty” (which will be described in the next sections) manifests itself in many ways. One of these involves the uncertainty regarding the precise amount of mass or energy contained in any volume of space. This manifests in the constant production of pairs of complementary “virtual” particles which exist for the briefest of moments and then mutually annihilate each other. This happens everywhere, all throughout space, all the time. We don't normally notice this constant production and annihilation of particles, because it happens so extraordinarily quickly and its effects are generally quite small. Nonetheless, the production and annihilation of these virtual particles does have real-world consequences. They produce an extremely small “pressure” which pushes space very slightly outwards. This pressure is typically unnoticeable but is cumulative with distance and becomes significant over cosmic scales. It is this outward pressure, due to virtual particle pair production and annihilation, which seems to be the source of the repulsive force of dark energy.
As the universe expands, galaxies move further and further apart. The attractive force of gravity between galaxies decreases as they get further apart. The repulsive force of dark energy, on the other hand, remains constant, and eventually overcomes the decreasing force of gravity. This causes the universe to begin to expand faster. At first the effect is very small, but the more that the universe expands and the force of gravity decreases, the more that the speed of the expansion increases. Eventually this expansion will become as fast as the expansion at the time of the big bang! With nothing to counteract the repulsive force of dark energy, this second period of cosmic inflation would continue to accelerate out of control, eventually even tearing apart individual atoms themselves, in what has been very aptly called the “big rip.”
We now have a model of the universe which seems to have begun with a period of extreme expansion, and also seems destined to end in another period of extreme expansion. The beginning and the end of the universe thus look very similar in certain ways, but very different in others. The similarity is that both periods are characterized by enormously accelerated expansion. The difference, however, is that while the beginning was characterized by an extremely high density of matter and energy, the ending will be characterized by extremely low density. This model, however, is not quite complete.
There are certain conditions under which virtual particles are not immediately annihilated, but instead continue to exist for a very extended period of time. When this happens, such particles are no longer considered to be “virtual” particles, but instead are considered to be “real” particles. Stephan Hawking, the noted theoretical physicist, described a process whereby particle pairs which are produced just outside the event horizon (the “edge”) of a black hole can be “pulled apart,” with one of the particles escaping out into space, and the other particle falling into the black hole. (The virtual particles which escape out into space from a black hole in this way, subsequently becoming real particles, are known as “Hawking radiation.”)
There is another condition under which virtual particles can be “converted” into real particles. This is
This modifies our view of the future period of cosmic inflation, because as the expansion of the universe gets faster, more and more virtual particles will continue to live on as real particles. Eventually, so many real particles will be created so quickly that their mutual gravitational attraction will be strong enough to cause the expansion to stop accelerating, and to actually decelerate for a time – just as happened after the period of extreme expansion which characterized the big bang.
Now the past and future periods of extreme cosmic expansion in our model of the universe look even more similar – so similar, in fact, that it seems that the big bang was not a unique one-time event. Instead, it now seems that the life-cycle of the universe actually consists of an eternal series of “epochs.” Each of these epochs begins with a period of big-bang-like extreme cosmic expansion which then “settles down” into essentially the type of universe we see today, until the expansion of the universe increases over time to initiate another period of big-bang-like cosmic inflation (and the conversion of virtual particles into real particles) which then, in turn, serves as the beginning of the next epoch.
Thus the universe is eternal and infinite, and also always expanding on cosmological scales. This solves certain problems inherent in the big bang model, such as where the initial matter and energy required by the big bang model came from, and how it could ever have exploded at all (since such initial matter and energy would essentially have been compressed into a black hole with the mass of the entire universe). There simply was no “initial” matter and energy whose existence would need explaining: instead, matter and energy are “created” by the conversion of virtual particles in real particles during each cycle of cosmic inflation. (It should be noted that this “creation” does not violate the law of conservation of mass-energy, because the gravitational force of these “new” particles acts as a sort of “negative energy” which exactly balances the mass and energy of the particles which are created.) Furthermore, since there was no initial state of super-compressed matter and energy (with all the characteristics of an unimaginably massive black hole) there was never a time when it would have had to have inexplicably exploded.
Thus, this model of the universe responds to the question, “Where did the universe come from?” with the very simple, straight-forward, and logical answer, “The universe always existed.” We live in an infinite and eternally expanding universe, a bit less than 14 billion years into one epoch of an endless string of other such epochs, stretching infinitely into both the past a future.
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