Newton's law of gravity passes its biggest test

GuB-42

If you follow Sabine Hossenfelder's channel, she has a MONDOmeter. With MOND (modified Newtonian gravity) on one side and dark matter on the other side. As new papers come out the needle goes back and forth, and I guess that she will make a new video if she hasn't already, with the needle moving one step towards dark matter. I find it interesting how it doesn't seem to settle. Dark matter is still the favorite, but there is a lot of back and forth between "MOND is dead" and "we found new stuff we couldn't explain with dark matter, but it matches MOND predictions".

Lvl999Noob

I thought newtonian gravity was already proven to be inaccurate with Einstein's Special Relativity (or General Relativity?) giving better results on cosmic scales (basically analogous to an approximation vs an exact formula)?

DivingForGold

just another nag screen ...

rappatic

When I see dark matter in the news I'm always reminded of the story of Vulcan. In the 1800s, detailed observations of the planet Mercury showed that its orbit was slightly different than Newtonian mechanics predicted-- a difference of about 43 arcseconds per century. The study was rigorous enough to rule out any observation errors. Le Verrier, the astronomer who made these observations, wondered how to explain the difference. A decade earlier, he had noticed a similar irregularity in the orbit of Uranus, which led to the discovery of Neptune, whose gravity caused these perturbations. So Le Verrier reasoned that something similar must be going on for Mercury, and he posited the existence of Vulcan, a tiny planet close to the Sun. Many attempts were made for decades to observe Vulcan. It was even included on some maps of the Solar System at the time ( https://www.loc.gov/resource/g3180.ct003790 ). But it was never conclusively observed. When Einstein published his theory of relativity in 1915, the mystery of Mercury's orbit was finally explained-- Newtonian mechanics were simply incomplete, and the irregularity of Mercury's orbit was due to relativistic effects. Could it be that something similar is happening today? Observations of gravity on galactic scales doesn't quite align with what relativity would predict, so we use dark matter to fill the gaps. We've tried for decades to detect dark matter, with no dice. Is our theory of gravity simply incomplete? MOND may not be the solution, but I'm still skeptical about dark matter.

ricksunny

If it had failed, would we be hearing about it in Science before the researchers continued testing it until it passed? (i.e. is this a blindspot in our collective epistemology?)

adrian_b

Free variant of this research paper: https://arxiv.org/abs/2604.14327

DoctorOetker

It's bizarre that Newton's law passes this test, when the linearization of general relativity predicts a gravitational equivalent of a magnetic analog for gravity. Gravity Probe B. There exists an even simpler derivation for a magnetic term, but its in my file drawer... (simpler in that it just relies on observations from special relativity)

tech_hutch

Newton's law of gravity passes its biggest test Yo momma