There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. ~Mark Twain
(Originally appeared in Gog's Blog 5/12/06; slightly revised)
Sometimes it's remarkable to see how scientists will attempt to repackage an old theory and try to make it sound like a new idea. Recently, a couple of scientists proposed what was purported to be a new idea [http://www.space.com/scienceastronomy/060508_mm_cyclic_universe.html]
about the fate of the universe. To do so, they tried to put a new wrinkle something Einstein called his greatest mistake: The good ol' cosmological constant.
When Einstein was developing his General Theory of Relativity, he ran into a problem. In folding gravity into his Special Theory of Relativity, he found that the equations stubbornly insisted that warped space would result in stars and galaxies drifting together, which in turn meant that space itself would be shrinking. Obviously, Einstein thought, any fool could see that the universe was static. After all, it was billions of years old, although how old was still a subject of spirited debate in his time. So the great theorist inserted a fudge factor, a repulsive force, which he called the cosmological constant.
He hated that.
Fortunately, along came Edwin Hubble whose spectra of distant galaxies showed that, while the velocity of stars might seem to be low, galaxies were moving like bats out of hell. Moreover, the farther away they were, the faster they went. Einstein happily scrapped the constant.
However, the durned thing just wouldn't go away. It turns out that continued observations indicate that something a bit weird is going in the universe. The galaxies should be slowing down. It turns out that the expansion is speeding up, at least according to current interpretations of the data. The only way to explain that is to postulate some sort of repulsive force, an antigravity, as it is called in the popular press.
Now, one of the ongoing conundrums of cosmology concerns the fate of the universe. If there's enough mass, the expansion would halt, and gradually all the stuff in the universe would come back together in a “big crunch.” If there isn't, then the universe will expand forever, getting more diffuse and eventually becoming a haze of elemental particles.
Despite the fact that either of these events is billions of years in the future, people seem bothered by either outcome. Perhaps it's because that a non-eternal universe is disturbing to those who look forward to spending an eternity in some sort of afterlife. Maybe it's just a matter of being depressed by the thought of a cooled down, lifeless void.
The crunch seems to be the preferred option, because, if the current universe started out from some primordial point source, maybe once it finishes crunching, it'll start over again with another big bang. Hence, we have cosmologists invoking dark matter, dark energy, and all manner of other exotica to show that there must be more mass than we can see.
Now the idea of the cyclical universe is not anything new. Hindu religion has postulated such a cycle as part of its own creation stories. In scientific circles, one can find the theory being espoused in the 1970's (Nigel Calder mentions the possibility in Einstein's Universe; Carl Sagan did so in Cosmos). That's why I'm a bit mystified as to what is so new and wonderful about yet another theory of crunch-bang.
The scientists mentioned in the article have dressed up their theory with a cute spin on the cosmological constant, saying in previous universes it was bigger. Their math, which I'm sure I wouldn't understand, must be fascinating. While a cyclic universe works intuitively, it is difficult to see how the universe could come back together with an even bigger repulsive force than is seen today.
The problem is that their conclusions fly in the face of recent findings that seem to indicate that, given the continuing increase in the expansion rate and the fact that no one seems to be able to find sufficient mass to reverse it, the universe's fate would appear to be of the fuzzy void variety. So, if the repulsive force was greater in previous incarnations of the universe, but it's great enough now to prevent the current universe from collapsing, how could it have collapsed previously?
The fact is, we don't know the fate of the universe. And, while the big bang makes an excellent model, we don't really know for sure how the whole ball of wax got rolling in the first place. This is not trivial stuff. We want to know this badly. If we didn't, we wouldn't have string theorists doing mindbending mathematics to come up with an 11-dimension universe coexisting with other universes, each on its own M-brane.
And you though science fiction was weird.
But, the search for the answer is worth it. We find out a lot about who we are when we try to find out about the universe around us. Whether there are parallel universes, Brahma cycles, or pudgy neutrinos, every step we take in searching for them is a step toward our own growth.
When we stop caring about our universe, we'll stop caring about ourselves.