I have heard many people say that the universe is possible infinite. But, if it takes time and energy to create bodies such as planets and stars and the universe has only existed for 13.7 billion years how could there be enough time to create something that is infinite in size. Is my logic flawed?

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    $\begingroup$ Possible duplicates: physics.stackexchange.com/q/9419/2451 and links therein. $\endgroup$ – Qmechanic Mar 13 '16 at 23:22
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    $\begingroup$ How long has the universe been around? What we "know" (in the sense of the models being self-consistent) is that the time that has elapsed since the "big bang" is 13.8 billion years. That doesn't tell us anything about the total lifetime of the universe. We aren't even sure that cosmological time is a good way of measuring anything that happened during the very early eras. As for the size... that's a "we don't know". Personally I am happy with a finite universe, albeit likely one that is much larger than the visible part. $\endgroup$ – CuriousOne Mar 13 '16 at 23:26
  • $\begingroup$ Besides that, "stars and planets" are not "the universe" and vice versa. The universe has always been infinite, as far as we know, and 13.8 billion years is plenty of time to form planets and stars. $\endgroup$ – Asher Mar 14 '16 at 6:37

Would it help if you knew that time can be curved too? It can. Spacetime is 4d, but if you had one spatial dimension than the spacetime is 2d and each point in the 2d object corresponds to a time and a place.

Imagine rolling a piece of paper into a cylinder. If time is the part that goes around a circle you could have a circular time but attaching the edges together, or you could have a big bang and a big crunch at the edges of the paper. But the unrolled end could be infinite in length. Always was and always will be be.

Or if you imagine rolling the piece of paper like a number six you could have the past be finite and the future go on forever. And the other unrolled direction can be flat and infinite in length, and again it always was and always will be.

And since spacetime isn't actually a surface in a larger space the kinds of curvature allowed are even greater than what you can imagine by rolling pieces of paper. Because its a more generalized kind of curvature.


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