How can the observable universe be over 90 billion light-years across when the universe is only 14 billion years old?

Question

How can the observable universe be over 90 billion light-years across when the universe is only 14 billion years old?

In: Physics

Answer 1

The universe is expanding at something like 72km per second, per megaparsec (about 3.3 million light years). So, something a megaparsec away from you appears to be moving 72km away every second.

You can kind of think of this like when a balloon is inflated and stretches out. You can make two dots on a deflated balloon and as you blow it up, the dots don’t necessarily move, but the space between them gets bigger. The further apart you make the dots, the bigger the space between them will be when the balloon is fully inflated.

So objects that are huge distances away, like other galaxies that are hundreds of millions or billions of lightyears away, have a huge amount of space expanding in between them, and with enough distance that expansion can appear to be moving them faster than the speed of light, creating a universe that is far bigger than light has had time to travel.