# What is at the edge of space, or does it go on forever?

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eugbugposted 12 years ago

What is at the edge of space, or does it go on forever?

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Let us distinguish what we can think of as possible from what is physical reality.
The physical reality is as follows: A satellite launched into orbit that follows the shape of a hyperbola will free fall; that is, no force is necessary to move it, This satellite will not impact on the earth because its trajectory matches the curvature of the earth. If you were riding on that satellite you would think you were getting further away from earth. The fact is that satellite is only circling the earth forever. The same thing would happen if a satellite were launched into orbit out of the universe instead of the earth. This satellite will free fall but circling the universe. That is why the statement "the universe is finite but boundless."
The possibility of an end of the universe is only in the mind. It is like building a bridge intended to be straight that would link the earth with Venus. The possibility of such a bridge is only in the mind. The physical reality is that that bridge would end at your feet. This is explained by the generalized theory of relativity. The straightest line is curved called geodesic.

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Caleb DRCposted 12 years ago

Fascinating question, Eugbug. There is a lot of evidence that space had a beginning, and is expanding right now. I believe it was Penrose  and Hawking who both proved mathematically that space had a beginning--in addition to the evidence-- therefore, with the expansion being finite we know that there is an end to space. So what is beyond that end?  I personally believe it is a higher dimension of space, as for example, the 4th spacial dimension. The 4th dimension could be permeating our space, and the expansion of our 3D space is simply the expansion of a speck in 4D space. The way my dog eats, I have a big bang expansion going on right here in the house!

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