Where does space begin and end?

Question: Where does space begin and end?
- Keywords:
  space
Asked by jellyman to Amy, Grant, Martin, Shawn, Usman on 9 Mar 2013.
- Grant Kennedy answered on 9 Mar 2013:
  
  That’s a really good question, and a really hard one to answer so I’m going to be honest: We don’t know how big it is.
  
  We do know that if we look out into space from the Earth that no matter how far we look there’s always something there, so the Universe goes at least farther than we can see, probably a lot farther.
  
  We think space began with what we call the “Big Bang”, when everything was created in a tiny dot 13.8 billion years ago. The Universe has been expanding ever since, and at the moment we think that it will never end, just keep on expanding forever.
  
  I hope that helps, not knowing things like this is the reason we do science!
  g
- Martin Archer answered on 9 Mar 2013:
  
  There’s no specific start to space as you go up and up from the Earth’s surface, the atmosphere just gets thinner and thinner. But scientists officially say that the Karman Line 62 miles above sea level is the start of space. This is actually higher than Felix Baumgartner did his skydive!
  
  We have no idea how big space/the Universe is, some people even think it’s infinite. However, the edge of the visible Universe is 13.8 billion light years away from us. Light coming from this distance has been travelling since the Big Bang to get to us. So it’s as far away and as far back in time that we can look.
- Usman Kayani answered on 9 Mar 2013:
  
  If space had a beginning and end, it would have a boundary and you then have to ask what is outside this boundary; what is outside the universe!? We are still not quite sure yet but recently there have been developments which have led physicists more inclined to believe that the universe is ‘flat’ and therefore infinite i.e space has NO beginning and NO end, it just keeps going on and and on from every direction.
  
  If you could find the centre of the universe you could figure out where it begins and ends; like knowing the centre of a square or a circle this allows you to find where the shape “starts” and “ends”. So where is the centre of the universe? This might sound crazy but its everywhere; This is called the cosmological principle. If you think of the expansion of a balooon, we are living on the surface of the baloon and not inside it.
  
  The observable universe is only the part of the universe that we can see, because light takes time to travel a distance just like anything else and so when we look further and further into the universe we are actually looking back in time! The limit to what we can see is 13.8 billion light years away, since the light travelling from there would have started its journey around the time of the big bang. We can’t see further than this!
- Shawn Domagal-Goldman answered on 12 Mar 2013:
  
  What everyone else said! And just to get a sense of scale here, 13.8 billion light years is 130,555,292,000,000,000,000,000,000 meters away. :-0

Question: Where does space begin and end?

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