Modified Newtonian dynamics

Let's start with altering gravity.

Modified Newtonian dynamics, or MOND.

Right, MOND.

This is a heavy physics concept.

Let's break MOND down.

What exactly is modifying Newton?

MOND is perhaps the most radical yet mathematically rigorous alternative.

It was originally proposed in 1983 by Israeli physicist Mordechai Milgram.

The new findings, reported in the journal Physical Review D, are focusing on the Bullet Cluster, which has so far been considered one of the strongest pieces of evidence for the existence of dark matter.

But according to a new analysis of data from NASA's Webb Space Telescope, the observations of the Bullet Cluster are also consistent with an alternative explanation that doesn't involve dark matter at all, namely modified Newtonian dynamics, or MOND.

This alternative hypothesis to dark matter was first proposed by Israeli physicist Mordehai Milgrom back in 1983.

It suggests that the laws of gravity and inertia depart from standard Newtonian physics when objects experience very low accelerations, which happens in the outer regions of galaxies, the same places dark matter was first identified.

As a result, unlike the gas clouds, it's not slowed down by friction and is also not separated from visible matter in the galaxy clusters.

However, technically, that's not evidence that dark matter exists.

Modified Newtonian dynamics, or MOND, has been considered a fringe theory for years, largely because previously it had been assumed that it simply can't explain the observations in the Bullet Cluster.

However, this new study by Kroupa and colleagues shows that, on the contrary, the Bullet Cluster is actually especially consistent with the MOND scenario.

There are three theories that people have been promoting.

M- my own theory, conformal gravity, uh, modify Milgrom's MOND theory, modified Newtonian dynamics, and John Moffat's MOG theory, modified gravity.

And all of us do these, fit these rotation curves with universal parameters.

And the reason that we do so is because the universal parameters are in the data.

Alternative theories.

Modified Newtonian dynamics.

Proposes changes to gravity to explain galaxy formation without dark matter.

Dynamical dark energy models suggest that the dark energy evolves potentially requiring new physics beyond the lambda CDM model.

Maybe it's not that there's more invisible stuff out there causing gravity, but that gravity behaves differently, and there isn't any dark matter.

This is called MOND, Modified Newtonian Dynamics.

Mm.

Now remember how we talked about some of these cold spots are due to the expansion of the universe as photons fall in and out of these voids or in and out of, of the neighborhood of a black hole? Well, that could also be explained in some models of modified gravity.