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TIL NASA calculated that you only need 40 digits of Pi to calculate the circumference of the observable universe, to the accuracy of 1 hydrogen atom (www.jpl.nasa.gov)

submitted 11 months ago by ripcord@kbin.social to c/TodayILearned@kbin.social

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[–] Umbrias@beehaw.org 2 points 11 months ago* (last edited 11 months ago) (1 children)

The observable universe is the size of forty of those circles (or pies, shortened to "pi").

No... Pi is a unitless number representing half a circles angular size.

Forty in the title is the number of digits, the title means that the relative size of the universe compared to a hydrogen atom is 1 followed by 40 zeros. Pi needs to be known to that accuracy to have a proper amount of significant figures.

Imagine trying to measure an ant with an unmarked foot long ruler. Not going to work super well. Your measurement uncertainty is +/- 6 in or 0.5ft. Well above the size of any ant.

Adding in inch marks improves that to +/- 0.5 in or +/- 0.042 ft. Closer to some ants, maybe about right, still not going to give you a measure of the ant but you'll be able to say if it's more or less than that. Now measure a circle with this ruler, to get the full accuracy of the ruler, you need only know pi to 4 digits., 3.142. Roughly. Actual uncertainty has some additional stuff going on, but without getting into it there you go.

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[–] ivanafterall@kbin.social 1 points 11 months ago

Six of one, half a dozen of the other.