3 ms·

> Cute asides: The meter is based on a miscalculation of the distance between the equator and North pole. The SI couldn't find anything absolute that actually m

> Cute asides: The meter is based on a miscalculation of the distance between the equator and North pole. The SI couldn't find anything absolute that actually matched their arbitrary size, so made it dependant on a bar in the SI building, and then realized the bar is changing sizes with time! (This is finally being rectified with some atomic measure.) Actually the definition has gone through a number of rounds of increasing precision. It did have an atomic definition for a period of time, but now it's based on the speed of light. (IE the distance light travels in a vacuum in 1/299792458 of a second.) Too bad we didn't know the exact speed of light before coming up with the definition, or we could have a nice round 300,000,000 m/s!

sam_goody 8y ago
That's exactly my point. It was first based on a miscalculation. When they realized that, they switched to a more accurate but still incorrect definition. They have gone through multiple iterations, each more accurate than the last, but none that are nice and round. Actually, if there wasn't so much politics (and fake science) involved, there are plenty of things they could have used from the get-go that would have been nice and round. The "nice round" figure that you offer from the speed of light, and suggest that they would have used had they known it then, is not nice and round and it is not related (and therefore would not have been used).
- nasredin 8y ago
  What other things to define a meter? (1cm = 2.54in IIRC)
  - sigio 8y ago
    the other way around 1 inch = 2.54cm
    - samatman 8y ago
      Huge missed opportunity. Imagine if 1 inch = 2.56 cm
      - krsdcbl 8y ago
        Hot damn, never thought about this!
- tempestn 8y ago
  But the original definition was arbitrary. Yes, it was chosen to be a "nice, round" measurement of something (distance from equator to pole), but it doesn't really matter; what matters is having a consistent unit of measure. Once it was chosen, it didn't make sense to change the physical length it referred to, because that would have caused inconsistencies between old and new measurements. Instead, new definitions allow the same unit of measure to be defined more precisely, thereby allowing greater consistency between results where extreme precision is required. My point about the speed of light was that if we were coming up with a unit of measure now, we would not arbitrarily base it on the distance from the equator to the pole, which is by nature imprecise, but rather on the speed of light, since that is the most fundamental and precise reference we have. And if we were basing it on the speed of light, we would pick a round number, because there is one available that results in a meter of useful length. (By chance, very close to the actual meter.)

sam_goody 8y ago

That's exactly my point. It was first based on a miscalculation. When they realized that, they switched to a more accurate but still incorrect definition. They have gone through multiple iterations, each more accurate than the last, but none that are nice and round. Actually, if there wasn't so much politics (and fake science) involved, there are plenty of things they could have used from the get-go that would have been nice and round. The "nice round" figure that you offer from the speed of light, and suggest that they would have used had they known it then, is not nice and round and it is not related (and therefore would not have been used).

nasredin 8y ago
What other things to define a meter? (1cm = 2.54in IIRC)
- sigio 8y ago
  the other way around 1 inch = 2.54cm
  - samatman 8y ago
    Huge missed opportunity. Imagine if 1 inch = 2.56 cm
    - krsdcbl 8y ago
      Hot damn, never thought about this!
tempestn 8y ago
But the original definition was arbitrary. Yes, it was chosen to be a "nice, round" measurement of something (distance from equator to pole), but it doesn't really matter; what matters is having a consistent unit of measure. Once it was chosen, it didn't make sense to change the physical length it referred to, because that would have caused inconsistencies between old and new measurements. Instead, new definitions allow the same unit of measure to be defined more precisely, thereby allowing greater consistency between results where extreme precision is required. My point about the speed of light was that if we were coming up with a unit of measure now, we would not arbitrarily base it on the distance from the equator to the pole, which is by nature imprecise, but rather on the speed of light, since that is the most fundamental and precise reference we have. And if we were basing it on the speed of light, we would pick a round number, because there is one available that results in a meter of useful length. (By chance, very close to the actual meter.)