• Question: How does the theory that the whole universe could fit into the size of a sugar cube?

    Asked by isabelleharrison to Meeks, Pete, Stephen, Steve, Tom on 20 Jun 2010 in Categories: .
    • Photo: Steve Roser

      Steve Roser answered on 18 Jun 2010:

      Its all to do with the fact that most stuff is made of nothing – what I mean by this is that in a simple view of an atom has the electrons circulating around the nucleus like a planet round the sun. If you imagine all the space between teh earth and the sun being squashed up then you can see if you collapsed *EVERYTHING* it could go really really small

    • Photo: Marieke Navin

      Marieke Navin answered on 18 Jun 2010:

      I have heard that if you took away the empty space in an atom then the entire human race would fit into a sugar cube.
      There is a lot of space inside atoms – it’s weird to think that everything is mostly space! Hard to get your head around…

    • Photo: Stephen Curry

      Stephen Curry answered on 19 Jun 2010:

      Hi Isabelle,

      I think the universe would be bigger that that even when compressed! I have heard people say that compression of all the atoms in the human race would give you a lump that was no bigger than a sugar cube.

      This is because atoms are mostly empty space. They are made up of a nucleus (tiny!) surrounded by electrons (tinier!). So although the diameter of one atom is about 0.1 nanometre the nucleus is only about 0.000001 nanometres. So to reduce one atom to remove the empty space you compress by a factor of about 100,000.

      Let’s try the calculation:

      Assuming an average human is 1.5 x 0.4 x 0.2 = 0.12 cubic metres and there are 6 billiion people (6 x 10^9), the total volume of the human race is 6 x10^9 x 0.12 = 720,000,000 cubic metres.

      If we compress the volume by 100,000, you get 7200 cubic metres.

      My answer is much bigger than a sugar cube! However, there is plenty of empty space between the atoms in your average human. So what we need to do first — and this is going to hurt — is to put a human in a crusher to see how small we can compact them – to just reduce them to the close-packed atoms. Assuming that you can squash a human body by a factor of 100 (ouch!), that brings my answer down to 72 cubic metres.

      I’m still out—if the sugar cube answer is correct—but I’m not sure where I’ve gone wrong. Maybe you or one of the other scientists has an idea?

    • Photo: Tom Hartley

      Tom Hartley answered on 20 Jun 2010:

      Hi Isabelle,

      I am not quite sure what you mean by this question. My understanding is that shortly after the big bang the entire universe was very small, and was so dense that all the material (not sure if we could call it matter at this stage) would have fitted into the space now taken up by a sugar cube. However, space itself has expanded too, so I am not sure if this question makes any sense, really. I am not saying it is a bad question – in fact I think it is a very good one. I suppose the idea of “the size of a sugar cube” only makes sense in a universe the size of the one we have today. Size is relative. If there had been a sugar cube around at the time of the big bang (just after) it would surely be equally true to say that a sugar cube was as big as the entire universe. It’s hard to think about, and I would want to discuss this with a cosmologist, though I am not sure there is a right answer.

      Following on from the huge sugar cube idea – here’s one I’ve often thought about: instead of a big bang would it make sense for us to think of the Universe (space) staying the same, and everything in it shrinking and getting closer together (i.e., condensing into little shrinking blobs)? – probably not.

      Although this kind of question makes my head hurt, and I think my answers are probably a bit wacky I think it is a “scientific” way of thinking – always asking could it be another way than we think. Does The Big Bang idea really make sense? I’m not so great at figuring out these answers, but, like you, I enjoy asking the questions. And I think in general scientists are happy thinking about difficult questions, and knowing that there might be problems with the answers, because they point us towards places where we can find new things out.

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