• Question: how big is the universe thought to be or is it just infinite and never ending.

    Asked by goldeyes202 to Dilwar, Lou, Rachel, Simon, Susan on 13 Nov 2013.
    • Photo: Simon Langley-Evans

      Simon Langley-Evans answered on 13 Nov 2013:

      The Universe is not infinite and we know roughly how big it is. When measuring distances in space people often talk about ‘light years’. That is confusing because a year sounds like a measurement of time and not distance. When people say light year, what they mean is the distance that light can travel in one year. As light moves pretty fast this distance is huge. A light year is 10 trillion kilometres (10 000 000 000 000 km). The Universe is estimated to be 150 billion light years across!

      To give you an idea of how far that is. If you could drive a car from one side of the Universe to another (not breaking the speed limit of 60mph!) it would take you 1 800 000 000 000 000 000 years to complete the journey.

      That is pretty huge I would say, so although it isn’t never ending, it might as well be…

    • Photo: Susan Skelton

      Susan Skelton answered on 14 Nov 2013:

      This is a brilliant question, because scientists just still don’t know. It might be infinite, or it might not be – we have no way of knowing!

      I’ll try to explain here why we don’t know. It’s a bit complicated but bear with me and I’ll try to explain as clearly as I can!

      So, firstly, how would we go about measuring the size of the universe? Well, we can get a rough idea of how big the universe is by measuring how far away the furthest star is. Stars that are close to us are much brighter than stars that are far away, so by measuring how bright the star is we can figure out how far away it is. Neat, eh?

      But some of these stars are really really far away – so far, in fact, that the light coming from these stars takes billions of years to get here! So the light that we see now actually left the stars billions of years ago! That means that when you look up at the stars on a dark winter’s night, you are actually looking back in time!!

      The further we look into space, the further back in time we go … and the very last thing we can see is the left-overs from the Big Bang. We cannot see anything that happened before the big bang (there was nothing to see!), so that means there is also a limit to how far we can see. Some parts of the universe may simply be too far away for the light coming from there to have had enough time to reach us yet, so we are unable to see these parts of the universe.

      The part of the universe that we can see is about 45 billion light years away, but it is getting bigger all the time.

      But we have no way of knowing what lies beyond that – is there more of the universe than we can see, does that part of the universe look the same as this part, or even, could there be more than one universe??

      I hope this all makes sense – please ask again if you want to know more!

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