Tuesday, May 01, 2007

Our future?

In this story from Apace.com, the author presents a new study of the far-future fate of the Universe, given what we know today. The basic gist of the article is that, if Dark Energy is real and behaves like Einstein's cosmological constant, in the distant future, all other galaxies and light from outside our galaxy will be accelerated away from us at beyond the speed of light, meaning that we will never be able to see anything outside our galaxy again. (We're talking 100 billion years from now, or 10 times the current age of the Universe.) In that sense, we are lucky to live when we do, as astronomers in that future time will not be able to figure out the history of their universe.

Many scientific predictions exist about the end of the Universe. Some are fairly mundane, in that they take the Universe as we know it and let it evolve into the future (the story above is one of these). Others hypothesize new physics (such as the "Big Rip," where the Universe expands so fast that it rips itself and everything within it asunder, or the ekpyrotic brane model, where a set of hyperdimensional membranes collide, destroying our Universe while spawning a new Universe).

One thing we learn as students is that extrapolating (or predicting future results based on what we know now) is very risky. You might stay close to the right answer for a long time, but eventually you can be quite wrong. One example is the prediction of asteroid orbits in our Solar System. We can predict very precisely where an asteroid will be a hundred years from now, and reasonably well a thousand or more years from now. But using almost exactly the same models of the Solar System with tiny differences (perhaps due to the uncertainty in where a planet is by as small as a mile or two) and looking forward millions of years, the positions of asteroids will be completely different, such that you'd never guess the original models were almost identical.

When astronomers predict the ultimate fate of the universe, we are making wild guesses. Guesses based in science and physics, yes, but still guesses. Tiny forces that we don't yet know about may eventually determine the ultimate fate of everything in our Universe. So whenever you read about the ultimate fate of the Universe, remember that these are more like descriptions of possibilities rather than hard predictions.

No comments:

Post a Comment