Higher Multipoles of the Cow

Discussion (7 Comments)Read Original on HackerNews

lhd1•about 1 hour ago

One of the cool facts about gravity is that the gravitational field of a body 'feels' spherical at a distance, even if those bodies are not spherical themselves. There are higher multipoles but they are increasingly suppressed the further you are from the body. So at least for gravity the spherical approximation turns out to be good and justified.

DroneBetter•38 minutes ago

for simulating gravity in particular you can do one better, since a sphere is in turn gravitationally indistinguishable from a point mass due to the https://en.wikipedia.org/wiki/Shell_theorem#Force_on_a_point...

lhd1•24 minutes ago

and you can do one better than that - Birkhoff's theorem, the relativistic analogue of the shell theorem.

https://en.wikipedia.org/wiki/Birkhoff%27s_theorem_(relativi...

turbostar•about 2 hours ago

Anna Cramling, women’s international chess master, should review this paper, having popularized the Cow Opening.

Bowes-Lyon•2 days ago

Hmmm… Today is Sep 1st, not Apr 1st. That cow is a bit out of season :)

jitl•about 2 hours ago

> Submitted on 1 Apr 2025 (v1), last revised 1 Apr 2026 (this version, v2)

colechristensen•about 1 hour ago

Submission history

From: Benjamin Lehmann [view email]

[v1] Tue, 1 Apr 2025 07:55:39 UTC (2,401 KB)

[v2] Wed, 1 Apr 2026 12:28:24 UTC (3,845 KB)

Higher Multipoles of the Cow

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Discussion (7 Comments)Read Original on HackerNews