Even in maths, the idea that something could have no limit is paradoxical. For example, there is no largest counting number nor is there a biggest odd or even number. Although it seems like there should be half as many odd or even numbers as there are numbers in total, if both sets are infinite, in some sense we have the same amount of each.

Contradictions are more palatable in the realm of the abstract than in the real world bound by physical laws. For example, you can’t accelerate to an infinite speed as the speed of light is the cosmic limit.

The universe could be infinite, both in terms of space and time, but there is currently no way to test whether it goes on forever or is just very big. The part of the universe we are able to observe is finite, measuring about 46 billion light years in diameter. Many physicists believe it goes out further than that, an idea supported by cosmological models of the big bang and inflation.

Others think we should ditch the never-ending story. Some mathematicians are trying to rebuild the foundations of mathematics without the infinite. But if there is a biggest number, what would happen when you add one to it? The solution could be thinking of numbers as a cycle rather than a linear series, some sort of loop where you revert back to the beginning. It’s a little strange, but then so is infinity.

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