Question: do you know how big the universe is?

Jen Gupta answered on 16 Jun 2011:

Well we think that the universe is infinite so it’s infinitely big! But that seems like a rubbish answer so I’m going to tell you a bit about the furthest away things we’ve seen.

In astronomy, when we look at really distance objects like galaxies, we are actually looking back in time – light travels at a certain speed so if a galaxy is a million lightyears away, the light that we are seeing from the galaxy actually left that galaxy a million years ago. Last month some astronomers claimed that they have discovered the most distant object that has been seen so far (http://www.bbc.co.uk/news/science-environment-13539914). They claim this object (a gamma-ray burst) is 13.14 billion lightyears away.

The oldest “light” that we actually see is called the Cosmic Microwave Background Radiation. It’s the afterglow of the Big Bang and was emitted only about 300,000 years after the Big Bang. Something that’s pretty cool is that if you detune an analogue TV so you get a snowy screen, a few percent of that signal is actually this CMB emission!