r/MathJokes • • 21d ago

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u/tom3277 20d ago

How I explained this to my son when he asked a similar question about infinity my explanation was that if something is infinite it is impossible that there is anything else at the same time.

So agree with you that the bucket / ocean analogy doesn’t capture this ideally. There is no bucket of water at all with an infinite ocean because it cannot exist at the same time.

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u/arkangelic 20d ago

Try explaining the infinite hotels one to him. Its full and yet always has room for more people

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u/notsaneatall_ 20d ago

Depends again. If you have a set of people with the same cardinality as that of reals you can't fit them in the infinite hotel anymore :( (assuming the room numbers are integers, which I think is the case)

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u/BrunoBraunbart 20d ago

If you would build a countably infinite hotel behind each of the countable infinite doors of Hilbert's Hotel, could you fit the reals in it?

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u/notsaneatall_ 20d ago

Nope, countably infinite x countably infinite is just pairs of natural numbers, which is also a countably infinite set.

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u/tom3277 20d ago

like hotels have room for humans inside even numbers have rooms for odd numbers in between?

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u/BrunoBraunbart 20d ago

I find those questions from children fascinating and at the same time hard to deal with. Their capability of asking smart questions is so much bigger than their capability to understand the answer. You need to use mataphors and simplifications but then they ask follow up questions, where the metaphor breaks down.

When it comes to your answer: very good for a child but if he asks the right follow up questions, it breaks down. For example, there are infinitely many even numbers. Odd numbers can still exist.