An ant on the surface of the Earth might believe that the Earth’s surface (“space”) is infinitely large. But because it can never look beyond the horizon, it can’t know. If it is intelligent, it has to assume that the surface might be curved and curve into a sphere, hence making it a finite surface.
Actual space and the universe is sort-of an analogy one dimension higher up. “Sort of”, because (1) we don’t imagine a surrounding four-dimensional space for curved space in the sense in which Earth’s surface is embedded in three-dimensional space, and (2) the cosmological horizon has a different cause (namely the speed-of-light limit) than the horizon of a planet.
Here is an alternative way to think about it: You can’t exclude the possibility that if you’d travel in a straight line in one direction through space, that you’d eventually end up where you started (i.e. like in the classic Asteroids game). Space might be connected like that, and then it would have a finite volume.
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An ant on the surface of the Earth might believe that the Earth’s surface (“space”) is infinitely large. But because it can never look beyond the horizon, it can’t know. If it is intelligent, it has to assume that the surface might be curved and curve into a sphere, hence making it a finite surface.
Actual space and the universe is sort-of an analogy one dimension higher up. “Sort of”, because (1) we don’t imagine a surrounding four-dimensional space for curved space in the sense in which Earth’s surface is embedded in three-dimensional space, and (2) the cosmological horizon has a different cause (namely the speed-of-light limit) than the horizon of a planet.
Here is an alternative way to think about it: You can’t exclude the possibility that if you’d travel in a straight line in one direction through space, that you’d eventually end up where you started (i.e. like in the classic Asteroids game). Space might be connected like that, and then it would have a finite volume.