A guy sees images of himself, says 6 images in different places, in this case he suspects he lives in a finite space. So he starts to blow up a balloon and sees all of his ghosts images blow up balloons too. Eventually the balloon begins to collide with itself (and its ghost images) at six places around each image of his.
As the balloon continues to expand, a hexagon is traced out by the pressing edges. And then, we'll figure out the shape of the universe.
"If nature had made space as small as a room, we'd always have known the world was finite. If I stand in the middle of a compact universe with a light bulb that never burns out and spaces is so small as a room, the light from bulb will transit around the space. Some will make it back to me after winding once around the space, some won't get back until winding a few times, some will take nearly forever just to happen to scratch past me again. If I wait long enough, I'll see a copy of myself in all directions, so that the space is filled and bright with ghost images of me and my light bulb at different ages. I could watch myself growing up and growing old. There'd be no need for photo album, I could watch my own life before me beyond the images of my own (Levin, 2002)
"We wouldn't have to rely on memories or stories of History. We could use binoculars or telescopes to look back, point it to the right direction and watch that history plays itself out (Levin, 2002)".
The thing is, we wouldn't be there long enough to see that happen,
"We would see no copies of ourselves but we could see many copies of our solar system, which has been around for million years"
Old enough to see several ghost images of itself.
"We could watch the solar system in different ages, when it's formed from dust and coagulate into the star with collection of planet"
But if the space were so huge that not even galaxies are ancient enough for the ghost images to wrap around the cosmos, we'd have to look back to the beginning (Big Bang). (Levin, 2002)
So, the Big Bang is still the very important source of information. Anything happen in that seconds of Big Bang will be carefully studied.
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