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James Webb Space Telescope finds evidence for alternate theory of gravity

(thedebrief.org)
355 points jchanimal | 6 comments | 16 Nov 24 18:33 UTC | HN request time: 1.059s | source | bottom
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samsartor ◴[16 Nov 24 20:21 UTC] No.42158987[source]▶
My hangup with MOND is still general relativity. We know for a fact that gravity is _not_ Newtonian, that the inverse square law does not hold. Any model of gravity based on an inverse law is simply wrong.

Another comment linked to https://tritonstation.com/new-blog-page/, which is an excellent read. It makes the case that GR has never been tested at low accelerations, that is might be wrong. But we know for a fact MOND is wrong at high accelerations. Unless your theory can cover both, I don't see how it can be pitched as an improvement to GR.

Edit: this sounds a bit hostile. to be clear, I think modified gravity is absolutely worth researching. but it isn't a silver bullet

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meindnoch ◴[16 Nov 24 21:39 UTC] No.42159582[source]▶
>We know for a fact that gravity is _not_ Newtonian, that the inverse square law does not hold

[citation needed]

The consensus is that gravity - outside of extreme mass/energy environments - works just as Newton described it to many many decimal places.

Emphasized part added because people in the replies thought that I literally think that General Relativity is somehow wrong. Don't be dense. All I'm saying is that gravity at galactic scales works as Newton described it. General Relativity has extremely tiny effect at those scales.

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1. auntienomen ◴[16 Nov 24 22:04 UTC] No.42159761[source]▶
Citation needed? That's ridiculous. The empirical evidence is well over century old at this point. Start with the anomalous precession of Mercury's perihelion. That already can't be accounted for by Newtonian gravity.
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2. bobmcnamara ◴[16 Nov 24 23:28 UTC] No.42160499[source]▶
I don't think they're saying the relativistic effects don't exist, just that they're still largely unimportant compared to Newtonian effects.

For precession of perihelion of Mercury we mostly noticed because any error is cumulative over time and we could integrate over an arbitrarily wide timebase. The relativistic effects are <10^-8 of the total, around 1/10th of the change imparted by Newtonian gravity of planets much, much further away. The BepiColombo orbiter should allow us to correct for the relativistic effects of other planets' pull on Mercury, but it's expected to be a change of <10^-12.

So I guess "many, many decimal places" is in the ballpark of 6-12.

3. ahazred8ta ◴[17 Nov 24 00:20 UTC] No.42160811[source]▶
Samsartor seems to think that the inverse square law does not hold at short distances (e.g. between the sun and mercury). Meindnoch agrees with mainstream physics that the inverse square law does indeed hold at short distances. You're confusing newtonian physics (busted) with the inverse square strength of gravity (still strongly supported); those are two different things. GR says gravity should be strictly 1/r^2, and this is what we observe in the solar system.
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4. Iwan-Zotow ◴[17 Nov 24 16:08 UTC] No.42164903[source]▶
"GR says gravity should be strictly 1/r^2, and this is what we observe in the solar system"

huh?!? there are GR corrections to Newton which include terms like 1/r^3 iirc

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5. ahazred8ta ◴[17 Nov 24 23:13 UTC] No.42168207{3}[source]▶
There are (ȓ/r^3) terms involving unit vectors, but that works out to 1/r^2 in practice. There are cubed terms in string theory and Quantum General Relativity (QGR) / Loop Quantum Gravity, but these do not apply at macroscopic distances. If you know of a url link to a non-theoretical inverse-cube effect which has actually been confirmed in lab experiments or actual observation, please post it.
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6. Iwan-Zotow ◴[18 Nov 24 05:15 UTC] No.42169894{4}[source]▶
Huh!?! Classic GR test of Mercury periphelon precession is mainly due to inverse cube correction to Newton