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The Expanding Universe

Professor Carlos Frenk asks the age old brain bender: If the universe is expanding, what is it expanding into?

So that’s the same question as what was there before the Big Bang.  So let me tell you a story.  When I was about 13 years old, I don’t understand why I was there, I went to a lecture…I must have been a precocious child…I went to a lecture by a very famous physicist who I think already had the Nobel prize or soon got it after that, I can’t remember.  I won’t give the name.  Anyway, so I was sitting there as a 13 year old, listening to this wonderful talk about the Big Bang.  It wasn't even in my native language, it was in English and my first language is Spanish.  Still, I could understand what the man was saying. The lecture finished and the chairman asked for questions.  I was sitting there, 13 years old, my hand itching to go up, I felt like Dr Strangelove with my hand, like Peter Sellers, I was trying to control it, but before I knew it my hand was up.  The chairman says yes.  And then I asked the big question, ‘what was there before the Big Bang?’  The big physicist looks at me and says, well, that’s a stupid question because time began as part of the universe, time began with the Big Bang, there’s no time, there’s no sense in before or after, it doesn't make sense to talk about before or after, when time didn't even exist, that’s a stupid question.  Well, I felt myself shrink and becoming smaller and smaller and smaller and I never asked the question again for years.  I didn't even go to do physics at university, partly because my mother was telling me I wouldn't make a living out of physics, so all these things came together, I was traumatised.

Now that I’m a professional physicist, I now realise that the question ‘what was there before the Big Bang?’ is one of the most profound, interesting and fascinating questions and is one that falls very well within the remit of physics.  It’s a question that is there to be answered by physics; we don’t have the answer yet but that doesn't mean that we will never have it.  It’s exactly the same question, as it happens, as ‘what is the universe expanding into?’ except in this case we have a slightly better explanation.  So in the same spirit of this Nobel prize winner, I could’ve said to you well, look, the universe is all there is so there’s nothing for it to expand into. However, that would be again semantics and a vacuous explanation.  However, it’s a profound question, what does the expansion of the universe actually mean? The universe is not expanding into anything, what the expansion of the universe means is two points moving away from one another.  Space, if you like, is being created between these two points.  That’s what we measure when we’re talking about the expansion of the universe; all we’re talking about is that galaxies are moving apart from one another, but they're not moving apart into anything, they're just moving apart, new space is being created, if you like, between the particles.  The universe doesn't expand into anything, the universe really is all there is and it doesn't need to expand into anything because the universe as such is not expanding, it’s just that two points are moving away from one another.  Now that is a difficult question, my answer is just touching the surface of it, but it’s something like that.