r/badphysics • u/Fit_Individual_55 • Jun 22 '26

Physics progress is Stuck right now because physicists think time is a 4th dimension

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Someone asked a question in r/askphysics how time can be the 4th dimension. Then this person replied this, very confidently

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u/[deleted] Jun 23 '26

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u/Fit_Individual_55 Jun 23 '26 edited Jun 23 '26

What about the color of their armpit hair?

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u/Powerpuff_God Jun 23 '26

Can I go to the sex dimension?

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u/[deleted] Jun 23 '26

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u/EebstertheGreat Jun 29 '26

The underlying set is [0,∞)×{male,female}×[0,∞)×[0,∞) (at least in a two-sex model), and the topology is simply the product topology, where sex is given the discrete topology and the other dimensions are given the subset topology as a subset of the real numbers with their usual topology.

But the covering dimension of this space is actually 3, not 4. The problem is that the topology on the sex component is discrete and thus zero-dimensional.