Archives for August 13, 2009

What Makes the Universe Expand?

So, the Universe started with a bang. Everything was hot, dense, and expanding. It’s 13.7 billion years later now, and our Universe is cold and sparse. The temperature of the leftover glow from the big bang — which used to be over 10^30 degrees — is now down to 2.7 Kelvin, just barely above absolute…