What hold galaxies together?

Einstein spent part of his life looking for the laws that apply to quantum physics and his theory of relativity, and he did not find them. It seems that the laws of physics are not universal or at least as postulated until a few decades ago.

 

Yes indeed, and thank you for your thoughtful post.
You highlight a number of places where I need to improve the language. I am encouraged to revisit the wording in order to respond to your observations.
Stay tuned.

 

"Universal"(capital U) is the name of a movie studio.

 

Once again, theories being thought of as laws. It isn't your fault, TANSL, most people, especially teachers, treat the current accepted and working theories as laws. If the universality of a theory wasn't expected to be so, we wouldn't work so hard to reconcile the problems of theories that only work sometimes.

-Will

 

Grasping at straws?

 

Scientists Tested Einstein's Relativity on a Cosmic Scale, And Found Something Odd https://www.sciencealert.com/scientists-tested-einsteins-relativity-on-a-cosmic-scale-and-found-something-odd

A very ingesting read.

You remember learning about the Ptolomaic system?!
Deferent and epicycle - Wikipedia https://en.m.wikipedia.org/wiki/Deferent_and_epicycle

The system needed to be tweaked.

Note how we don't simply abandon an imperfect model, but first attempt to add more inexplicable elements to it until the model more closely approximates our observations.

Like adding more epicenters to get closer to our observations, we simply suggest another sub-set of unknown "dark matter" to bring our observations together with the fundamental concepts of our model. We thus prove our model correct, yet again.

Easy peasy lemon squeezy.

This is a lesson that has much wider and far ranging applications than Astrophysics. We can apply this approach to any model that comes close but doesn't exactly fit all points.

-Will

 

I have to be a bit sceptical when blatant advertising sites like sciencealert.com are being quoted. We go to those for entertainment and tittilation, and treat their claims with large amounts of salt.
Similarly Wikipedia. Whilst a very useful site for introductions to ideas, no-one seriously offers Wikipedia as a source.
I think you are saying that the mystery of Dark Matter will be solved by incremental changes, evolution, to existing concepts. You may be right.
I'm suggesting that maybe the solution will not be incremental, at all but may require a major rethink.

 

I had a Galaxy. Made by Ford. I think it was mostly faith and machine screws that held it together.

 

By comparing the approach to solving the inadequacies of the dark matter theories to the approach to solving the inadequacies of the geo-centric Ptolomaic model, I was suggesting that both theories would prove, in the end, to be equal in their accuracy of describing reality. We have this concept of how the Universe works and if our theory to explain it doesn't prove accurate, we just add more parts and more parts, all based on the same fundamental concept, until our theories do match. It is an exercise in the absurd. Dark Matter is as legitimate an idea to explain what holds galaxies together as epicycles were to explain how planets and the Sun orbited around the Earth.

I don't know about ScienceAlert, they seemed like they were reporting on mainstream and current science reports. As for Wikipedia, I chose them to reference and describe a well known historical fact about the Ptolomaic System that I could have described without a reference. It shows the basic approach I wanted to illustrate at the same time acting as an example of how well known the history is.

I certainly wasn't trying to legitimize the concept of Dark Matter by comparing it to the use of epicycles in the Ptolomaic System. That wouldn't have the effect I would want at all.

-Will

 

Is it possible also to say that curved space-time is the force itself. It brings no alteration in the idea of the coriolis force Coriolis force - Wikipedia https://en.wikipedia.org/wiki/Coriolis_force as part of the expression the gravitationnal tensor Gravitational tensor - Wikiversity https://en.wikiversity.org/wiki/Gravitational_tensor. It makes sense with maths although cg, which represent the group celerity of the gravitationnal wave, couldn't be equal to the greatest speed of all, namely the speed of the light. These are the disturbing bounds of the Minkowski space I guess. Interessant idea also bringed onto the table by the astrophysicist Jayant_Narlikar,in 1967, with his concept of variable mass. His explanation of the redshift his fertile. Theoritically, though.

It may be interessant to examine deeper how astronomers measure the rotation speed or the mass.

 

No

 

I think that the term "gravitational attraction" is the source of misunderstandings. As far as we know, and use for calculations, gravity is an acceleration. There is no real force involved, but there is a pseudo-force.

 

How do we equate F=ma, a=F/m, m=F/a with gravity being an acceleration without a force behind it?

-Will

 

F in that equation is a pseudo-force.

 

And that’s the difference between an engineer and a scientist. Only an engineer could utter “pseudo-force”.