探寻宇宙 Stephen Hawking: Questioning the universe

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There is nothing bigger or older than the universe. The questions I would like to talk about are: one, where did we come from?

How did the universe come into being? Are we alone in the universe?

Is there alien life out there? What is the future of the human race?

Up until the 1920s, everyone thought the universe was essentially static and unchanging in time. Then it was discovered that the universe was expanding.

Distant galaxies were moving away from us. This meant they must have been closer together in the past.

If we extrapolate back, we find we must have all been on top of each other about 15 billion years ago. This was the Big Bang, the beginning of the universe.

But was there anything before the Big Bang? If not, what created the universe?

Why did the universe emerge from the Big Bang the way it did? We used to think that the theory of the universe could be divided into two parts.

First, there were the laws like Maxwell's equations and general relativity that determined the evolution of the universe, given its state over all of space at one time. And second, there was no question of the initial state of the universe.

We have made good progress on the first part, and now have the knowledge of the laws of evolution in all but the most extreme conditions. But until recently, we have had little idea about the initial conditions for the universe.

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