This question on quora discusses whether an infinite universe would allow for a repetition of patterns and arrangements of matter. The top answer gives a very convincing argument as to why this would be impossible because, he reasons, that spacetime is causally connected. However if the universe is infinite wouldn't that make two bits of space so far away that never could any interaction travel and effect any bit of space that lies within the observable region of another space? Is his reasoning plausible? Here is his answer: "No, there would be no copy of you, even with an infinite universe. Those who have answered by saying that there must be an infinite number of copies of you are flatly mistaken. If space is infinite, then the possible arrangements of matter within it is also infinite. The space between galaxies can be rearranged in an infinite number of ways, because there is always more space to be had, and so the assertion that there must be a copy of you is false. It is more than just probably false. It is demonstrably false. Imagine some distant space where there is an almost-copy of the Milky Way galaxy, with a very sun-like star and a very Earth-like planet. Gazing up at the night sky is an almost-copy of you. He looks at the almost-like-the-Andromeda Galaxy (if he lives in a dark enough area). Now imagine that the center of the almost-Andromeda galaxy is 0.0000000001 mm further from our clone galaxy that our true Andromeda galaxy is from us. The entire histories of the galaxies will diverge because of that almost-immeasurably small difference. Trillions upon trillions of neutrinos every second will follow different paths because of that tiny difference. And since the variability of distances between galaxies is INFINITE, there is NO mathematical certainty of duplication anywhere. If anything, there is almost a complete guarantee of NO duplication. Why? Complete duplication of Earth would require tiling of the entire universe. By tiling, I mean filling of space with patches that are identical to each other, much the way a tiled floor is covered by identical pieces. Unlike the case with a tiled floor, each tile in the universe is affected by adjacent tiles. Pick a tile size, as large or small as you want. Every photon from every galaxy in every direction that crosses into the next tile, affects the history of that tile. If there is a copy of you somewhere, in order for his life to proceed exactly as yours has, every photon from every direction, every neutrino, every cosmic ray, must have been identical. In other words, if you shift your gaze in any direction by the tiniest fraction of a degree, there must be an identical copy not just of Earth, but of the ENTIRE VISIBLE UNIVERSE in absolutely every direction, at some very great distance too large for us to see (because there is clearly no tiling of what we actually see), and they must mesh together perfectly like a tiled floor, and the same sort of perfectly symmetrical tiling must apply to every point of the universe (every point must be surrounded by infinite copies of itself, repeating at some regular distance). The idea that an infinite universe would guarantee a duplicate of you is just nonsense. It would require radial symmetry in an infinite number of directions, with that symmetry applying at every point of space. We can see that space is lumpy, irregular, chaotic. There is no tiling of the universe. There is no duplicate you. And don't get me started on the Uncertainty Principle. Even if there were a duplicate of you, he would no longer be a duplicate a microsecond later, because quantum mechanics has randomness built into it."