A quick thought:<p>Since the universe is expanding at an accelerating rate, there are or will be regions of the universe that are receding from each other at the speed of light. Hence any traveler or signal traveling at the speed of light in a straight line would never be able to return to it's point of origin, even in a closed topology. So the universe is infinite even if there is no infinite distances* in the universe at any one point in time.<p>Unless of course if the Universe is finite and the acceleration stops before there is any part of the universe that is receding from any other point at the speed of light.<p>* Of course two regions of space receding from each other at the speed of light, are in a very real sense separated by an infinite distance.