space topic
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okay.
Feb 17, 2008
0
#3
The universe - is it infinite or finite but unbounded (no edges) or finite and bounded (you can fall off the edge)?
some say it's infinet because it's expanding but there has to be a boundery
Feb 19, 2008
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#5
shadowslayer wrote:
some say it's infinet because it's expanding but there has to be a boundery
We know the universe is finite because of Olber's Paradox and the Big bang and a few other indicators. However, a finite space does not necessarily have an edge. If I think of the universe as a flat piece of paper then it has an edge. If I think of it as the surface of a sphere then it is finite but unbounded.
I thought about that too but we are not flat
Feb 20, 2008
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#7
shadowslayer wrote: I thought about that too but we are not flat
Depends on what you mean by flat.
as in if you go one way you have the opposite to go but you can still go up and down it's not like the earth, in the earth you can go into the sky or into the ground, how's that for a 13 year old mind.
Feb 21, 2008
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#9
Your 13 year old mind is thinking which is considered to be unusual by many adults. I'm a teacher so I don't think it is so unusual.
I think you are treating flat as meaning two dimensional, like a piece of paper. In mathematical terms something is flat if it is not curved. Einstein (and others before him) considered the curvature of three and four dimensional spaces. To get a handle on this idea you could have a look at a book called Flatland, it is available for free on the internet!
I ment you can go left and right and it makes sence but when you are talking about space everything changes there is no up and down, left or right just nothing. that's why I thought of the earth example
Feb 22, 2008
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#11
shadowslayer wrote: I ment you can go left and right and it makes sence but when you are talking about space everything changes there is no up and down, left or right just nothing. that's why I thought of the earth example
That is true in general. You can only define directions by using a frame of reference. On the earth we use the equator and poles as fixed points of reference. We also use the Greenwich meridian but that is completely arbitrary. The same applies to space. We pick a point, hopefully marked by a star or some other reasonably fixed reference marker and measure everything from there. In the end there are no absolute directions, even on the earth. Say I set out from the north pole in a straight line going south. I could pass through London, New York or any city I choose. Without the arbitrary Greenwich meridian I have no way to define my direction at all.
here post as many random facts or questions as you want.