What is the universe expanding into?

Difficult question? Wait until you hear this simple analogy
24 August 2021


An artistic image of travelling through space, with stars passing by surrounded by wisps of bright colours, and a bright star in the centre



If the universe is expanding, what is it expanding into? 


Jess Wade from Imperial College London explains...

Jess - It's such a good question with such an annoying answer because it's really expanding into itself!

If you think about the Universe as being the Universe, it's just expanding; if the universe is everything, what's on the edge of the Universe Is the Universe, and what's on the edge of that is also the Universe! And you go layers and layers and layers and can freak yourself out with how much Universe there is.

The way that we're taught it in undergraduate physics is you kind of imagine that you draw a grid of dots onto a balloon, and then you blow up the balloon and the space between the dots is expanding, right? But if you're standing at any one of those dots, which could represent a galaxy, you see everything else receding away from you, kind of traveling away from you really fast.

So, it's just like the Universe, it's just like blowing up a balloon. And I'm sorry that that's not a better answer, but you'll have to go to some general relativity lectures to understand probably why...


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