Why are the kilogram, ampere, kelvin, and mole still considered base units and not derived? Given their current definitions, they're purely defined in terms of other units and cannot be independently measured, right?
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It has energy so it's just E = mc2 I guess? Just glad it's above my pay grade to think about these things
Right, that's how you get to J = kg*m^2*s^-1, but photons have no mass so wtf I should have gone to college
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All I'm saying is that we stopped using the mass of a litre of water because it was difficult to use in practice, and I'm not sure how determining the effects of a fixed numerical value for the Planck constant is somehow easier
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I guess no-one has to take special care of a lump of metal anymore is the main benefit
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I always wondered what happens when light travels through glass in a vacuum - does it lose energy whilst traveling through the glass only to gain it again?
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No. The glass will accelerate but that's not because the light slowed down, it's because it became less intense (e.g. some of the photons were stopped by the glass) This is basically how solar sails work
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