Hacker News new | ask | show | jobs
by opwieurposiu 1303 days ago
Yes and the circumference of the earth is about 40 million meters. This is because a meter was originally supposed to be 1/10E6 the distance from the equator to the north pole through Paris.
2 comments

Earth’s circumference around the poles is now given as 40,007.863 km [1]. So when the French Academy of Sciences defined the metre in the 1790s [2] the distance they measured from equator to North Pole was off by less than 2 km.

[1]: https://en.wikipedia.org/wiki/Earth's_circumference

[2]: https://en.wikipedia.org/wiki/Metre#Meridional_definition

I have read that the atronomers at the time actually knew that they were a bit off due to a mistake that was done by one of them.

They spent several years making lots of smaller measurements that were added up.

Each measurement was done twice to ensure correctness. One of the distances had two conflicting measurements, but due to a war, they could not return to make a third measurement and had to just choose one of them (the wrong one).

They chose not to tell anyone because they feared politicians would use it to discredit the metric system.

  >o their 1793 measurement of the distance from the equator to the North Pole was off by less than 2 km....
Or, like a lot of people, the Earth's put on a bit of wieght in the intervening 200+ years
Nitpick: 1/10⁷, not 1/10⁶. They picked the power of ten that gave a reasonably-sized unit of length.

They also made things complex by then picking a unit of mass that’s inconsistent with that: a gram isn’t the mass of 1m³ of water, but of 1/10⁶ m³ of water (a cubic meter is 10³ liters, and a liter of water weighs 10³ grams)

Centimeter-gram-second (https://en.wikipedia.org/wiki/Centimetre–gram–second_system_...) really is superior in that sense (but of course, that’s relative to the arbitrary choice of using water to convert between mass and volume, and from that, length)

The gram is the easiest to save by working backwards from Avogadro's number.

Avogadro's number is close to 24!, so we could redefine our mass unit as exactly 24! hydrogen atoms (or 4!!) and that comes out to within about 3% of a gram while being significantly easier to communicate to an extraterrestrial civilization.

Picking 1/10^9 would also have had the advantage of making the distance from the pole to the equator ~1 gigacentimeter.

Exploring a bit, picking 4 times that, as an estimate of the circumference, would give us a basic length unit of 4 cm (a pretty reasonable unit—bit over an inch and a half, fits right in with the variety of Chinese cun standards, for example). Then our immediate volume unit is 64 mL, which seems kind of small (on the scale of 2 floces), but ten of them make a decent "pint", so I think it can work—it's ~13% bigger than an imperial pint instead of ~12% smaller. the corresponding mass unit, at ~64 g, which again seems a bit small but manages to line up an average person's weight right around 1 kilo.

10E6 = 10×10⁶ = 10⁷, so you can unpick that nit!
Yep!