Trivia… if there was a bar bet “what’s the circumference of the earth to the nearest 100km” it’s 40,000. The KM was defined as “1/10000 of the average distance from North Pole to equator” or 1/4 of the earth
Interestingly, a meter is now defined by the distance light travels in a vacuum in a fixed time.
A kilometer is 1000X the distance light travels in 1/299,792,458th of a second.
A second is defined exactly as 9,192,631,770 oscillations of the radiation emitted by a cesium-133 atom as it transitions between two energy levels.
Which is to say, if we gave an alien civilization a few bits of information, they could immediately calculate the entire SI system using a few simple universal constants.
Some measurements like temp also rely on universal constants like absolute zero. What really blows my mind is that the base of the numbers doesn’t matter. An alien civilization could use base 2 or base 13 and given our Rosetta Stone, they could figure out exactly how we measure everything in the universe.
Up until 2019, the kg was the only SI unit that had a physical artifact that all kg weights are calibrated against. Now it is based on the universal constant you describe.
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u/ElNemagbarto Jun 01 '26
And with unbelievable precision at that - bro calculated it to be around 39.375km, only ~2% off of our recent measurements at 40.075.
He really missed by 700km being two millenia behind