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UrbanXrisis Oct25-04 11:38 PM

spacecraft traveled into space from Earth
is it true that if a spacecraft travled into space from Earth, it will ultimately reach the other side of the Earth (supposing it travled though the universe)?

James R Oct26-04 09:45 AM

It might eventually if our universe is topologically closed. Consider an analogy:

The Earth's surface is a 2 dimensional topologically closed surface. If you set out in a particular direction and travel far enough, eventually you'll go right round the Earth and end up back where you started.

Similarly, it is possible that our universe is a 3 dimension topologically closed space. If that is true, then if you travel out into space in a particular direction, eventually you will "wrap around" and end up back where you started.

Recent astronomical observations seems to suggest, however, that our universe is not actually closed.

UrbanXrisis Oct26-04 11:26 AM

What observations are those?

HallsofIvy Oct26-04 03:52 PM

Notice by the way that it would be incorrect to think that you would arrive at the "other side of the earth". I feel sure that the time required to "circumnavigate the universe" (assuming such a thing is possible), the earth would have rotated enough that you could might well arrive at any point!

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