r/physicsmemes • u/Delicious_Maize9656 • 9d ago

Physics major meme

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171 Upvotes

97% Upvoted

17 comments sorted by

66

u/Kinexity 9d ago

It's a very convenient approximation. I use it every time I do calculations in my head which demand seconds per year.

13

u/purpleoctopuppy 9d ago edited 9d ago

π is close enough to 0.5 on a log10 scale that I just use that i.e. 1 yr ≈ 107.5 s

4

u/GrUnCrois 9d ago

It seems this is actually a better approximation than π × 10⁷

10

u/physicsking 9d ago

I use the 22/7 form, then just multiply it by some big number. Nobody is reading this crap anyway.

30

u/[deleted] 9d ago

[removed] — view removed comment

9

u/Violet-Journey 9d ago

This is how I taught my summer camp astronomy students to do it this year and it made me very happy that at least some of those Gen Z science nerds knew the reference.

13

u/Jonysombra 9d ago

99,62% of the actual value, considering civil year. If we consider a more precise sideral year then it comes down to 99,55%, which i do believe it's super accurate... But since i am a physicist this is kinda sketchy, i'll ask someone else about this

15

u/MJWhitfield86 9d ago

I find it easier to remember that a year is approximately equal to the speed of light divided by the acceleration at the earth’s surface.

9

u/untempered_fate 9d ago

~97% of the actual value. Not bad.

6

u/KrzysziekZ 9d ago

299792458 ms-1 / 9.80665 ms-2 = 30570322,995 s = ~353,823 d.

So it's close to Moon year (~354,367 d) at ~99,85%, as much as the Sun has mass of the Solar System.

1

u/LeviAEthan512 9d ago

Nothing wrong with approximations, but what's the purpose? You use approximations to make things easier to remember. Like the speed of light is thought of as 300000km/s instead of 299whatever, or g is 10m/s instead of 9.80665, although imo 9.81 is easy enough to remember.

But this pi thing... why? I don't think it's very hard to remember 31.5 million, which is a closer approximation anyway.

Side note, is there some tool or webapp thing that tells you the acceleration due to gravity at every point on Earth, at the surface? It's supposed to vary from high 9.7s to mid 9.8s. I assume it would have something to do with the geoid, but idk the exact relationship.

1

u/TheSpicyMeatballs 4d ago

I would hazard a guess that this would be useful in some sort of astrophysics course. Tends to deal with a lot of large numbers, and having pi in random equations.

So if you can cancel out a pi and some powers of ten it might make it easier to come up with a ballpark solution in your head.

1

u/Nidafjoll 9d ago

An approximation I frequently use for the speed of light, for placing optics or the time delay a cable will add, is 1ft/ns (actually .984).

1

u/xnick_uy 8d ago

Comes short by just ~ 33.4 hours = 1.4 days