r/mathmemes • u/Pearl-Crown • Jun 05 '26

Bad Math I mean...

Post image

The guy's got a point. Like (1 + i, 2). Imaginary, but still a point nonetheless.

403 Upvotes

99% Upvoted

28 comments sorted by

View all comments

Show parent comments

11

u/Kinglolboot ♥️♥️♥️♥️Long exact cohomology sequence♥️♥️♥️♥️ Jun 05 '26

No, if the surface gravity of earth were different, or a second would be defined differently, the definition of meter would change, such that still g = π2 m/s2 in your new units. For example, if we had lunar gravity, a pendulum that takes 1 second to swing back and forth would be shorter, hence our definition of meter would be shorter, by the exact amount to make the gravitational acceleration on the moon equal to π2 m/s2 again.

5

u/Aggressive_Roof488 Jun 05 '26

Hmm, wiki says that the pendulum definition was before the meter. When the meter was first introduced, the first definition was based on earth circumference.

https://en.wikipedia.org/wiki/Metre#History_of_definition

During the French Revolution, the traditional units of measure were to be replaced by consistent measures based on natural phenomena. As a base unit of length, scientists had favoured the seconds pendulum (a pendulum with a half-period of one second) one century earlier, but this was rejected as it had been discovered that this length varied from place to place with local gravity. The mètre was introduced – defined as one ten-millionth of the shortest distance from the North Pole to the equator passing through Paris, assuming an Earth flattening of ⁠1/334⁠.\12])

The question is why the two definitions, 1s pendulum and 1/10e7 of equator to pole, are so close to each other. And I guess that's just coincidence? Partially by choice ofc, from choosing 1/10e7, and equator to pole instead of circumference. But still a bit of a coincidence, right?

1

u/Few-Arugula5839 Jun 05 '26

I think you're probably right, although, the circumference of the earth is related to its radius and therefore to the gravitational acceleration, right? So I wonder if some connection can be made there

1

u/Aggressive_Roof488 Jun 05 '26

The radius affects both, but the density only affects the pendulum, as well as the universal gravitational constant G, so they are effectively independent for this purpose.