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Comment by bonzini | Hacker News Reader

But it's a coincidence, right? N*k=8.31 is pressure*volume/temperature for a mole of gas. Temperature has a relatively small range (100-1000) and there's no reason why the range of P*V couldn't be far from that range, for example 0.01–0.1, with a different definition of meter, second or kilogram.

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Meter, second, and kilogram were all chosen to be approximately the scale of a human, and the combined multiplicative units like Pascal, m^3, and Kelvin/Celsius are also numerically 1 in these units.

> Meter, second, and kilogram were all chosen to be approximately the scale of a human,

“Approximately the scale of a human” leaves so much wiggle room that I don’t see how one can defend that claim.

> and the combined multiplicative units like Pascal

You don’t explicitly claim it, but I wouldn’t say the Pascal is “Approximately the scale of a human”. Atmospheric air pressure is about 10⁵ pascal, human blood pressure about 10⁴ pascal, and humans can very roughly produce about that pressure by blowing.

Which is why I have always kinda hated kilogram. Such an ugly unit for it having prefix. Grav should have been correct answer, but instead we ended up with something that is too small... That is in reality gram. For grams we could simply have milligravs or decigravs for 100g equivalents... Not that hard considering decilitres are used and decimetres are kinda tried in schools.

A human is ~1 meter, 1e2 kilograms and 1e9 seconds.

Pascal is pretty small and m^3 is pretty large though. That's why we still often use millibar and liter. They just happen to largely cancel out.

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