Why do astronomers attempt to limit or make predictions as to the size of the universe?
== All forms of science are about asking questions about the world and trying to find answers. If someone is curious about the size of the universe, science will try to find an answer. == If man knew the size of the universe, he 1) would be able to estimate the magnitude of the energy that created the universe, and 2) would be closer to determining the energy and composition of the early universe. == By determining the size of the universe, scientists might be able to make some predictions about the future of the universe! In our universe, everything is currently "expanding" and galazies are, in general, moving away from each other. If we had some idea of the volume of the universe, we might be able to make some guesses about its shape. And we might also be able to make some predictions about whether the universe will expand "to infinity" or not. Will there exist in the end enough gravity to "take hold" of all the galaxies and pull all the mass back together in the "Big Crunch" bringing everything full circle? Or will everything just continue to "fly apart" resulting in the reduction of the mass per unit volume of that universe to the point where everything just "dies" in the emptiness of seeming endless dimensions of spacetime? If we knew to some degree of certainty the volume of the universe, we might be able to look into the future of that universe and see where it's headed and how it might end. == And another reason is, because, since images travel at the speed of light, the size of the Universe that we can observe is linearly related to the age of the Universe, or at least the purported age. So, since we can't really deduce at all what's happening outside our sphere of visibility, it becomes quite imperative to place limits on the size of the Universe.
By the way, quite ironically, Earth is nearly at the Exact center of OUR observable Universe, in fact, any human being is at the center of his/her own personal observable Universe. Plato gets some credit after all, huh?
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