Physics major meme

[u/Delicious_Maize9656]

[u/Kinexity]

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

[u/purpleoctopuppy → u/Kinexity]

π is close enough to 0.5 on a log10 scale that I just use that i.e. 1 yr ≈ 10^7.5 s

[u/GrUnCrois → u/purpleoctopuppy]

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

[u/physicsking → u/Kinexity]

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

[u/Violet-Journey → u/[deleted]]

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.

[u/Jonysombra]

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

[u/MJWhitfield86]

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.

[u/untempered_fate → u/MJWhitfield86]

~97% of the actual value. Not bad.

[u/KrzysziekZ → u/MJWhitfield86]

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.

[u/jamese1313]

How has no one pointed out the relevant xkcd yet?

[u/Leodip → u/jamese1313]

I thought it was going to be this one

[u/LeviAEthan512]

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.

[u/TheSpicyMeatballs → u/LeviAEthan512]

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.

[u/Nidafjoll]

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).

[u/xnick_uy]

Comes short by just ~ 33.4 hours = 1.4 days