Astronomy
The Role of Cosmic Inflation in Solving the Flatness Problem
Quick fact
Inflation expanded the universe by a factor of at least 10^26 in less than 10^-32 seconds, smoothing out any curvature in the process.
Why this is interesting
If you blew up a balloon to the size of the observable universe, its surface would look flat. The same stretching happened to our universe — but what caused it?