Talk:Nordtvedt effect

Quantify

"Thus far, the results have failed to find any evidence of the Nordtvedt effect, demonstrating that if it exists, the effect is exceedingly weak."

Can we quantify that? How weak must it be (or if you prefer, how strong can it be) before conflicting with experiment? RJFJR 19:06, 21 April 2007 (UTC)

It can be quantified, but it's a bit messy. Directly, the difference in acceleration between the Earth and the Moon in the Sun's gravity is no more than about 1 part in 10^13. But the whole idea is that the difference is due to the gravitational self-energy, which is a tiny fraction of the Earth's total mass - about 1 part in 10^9. So when you divide out to get the "Nordtvedt parameter" (η) you get a limit - gravitational self-energy falls differently from other mass by at most (about) one part in 10^3. There have been some tests with pulsars (one is in progress right now), where the self-energy is 10-15% of their mass, but things get more complicated when you're in this strong-field regime. Exact numbers and discussion are available in section 4.3.1 of this review. Anne (talk) 00:36, 5 January 2018 (UTC)

Merger proposal

I propose to merge Nordtvedt effect into Free energy suppression conspiracy theory or Kenneth Nordtvedt. ToddGrande (talk) 08:28, 14 May 2020 (UTC)

Something is wrong with the first sentence of the article.

"In theoretical astrophysics, the Nordtvedt effect is the rejected hypothesis that relative motion between the Earth and the Moon which would be observed if the gravitational self-energy of a body contributed differently to its gravitational mass than to its inertial mass."

Something is missing: "is the rejected hypothesis that relative motion" what?

The effect is the relative motion due the difference. I put the first sentence back to its original wording. Multiple revisions had left it confusing. StarryGrandma (talk) 20:48, 15 August 2021 (UTC)