Is there really dark matter?

[Helio]

.So a gap that needed plugging, which wasn't known about awhile back, now has "objective" evidence based on that gravitational need?

It was, actually, a while back (1933) that the strangeness was first detected. Zwicky found that galaxies revolved within a cluster much too quickly. No visible matter could be found to explain the additional gravity needed. Zwicky called the missing matter: dark matter.

But this was only one line of evidence.

Jumping forward several decades, Vera Rubin, with an improved spectrometer, measured the motion of stars moving in orbit around the center of the Andromeda galaxy. Keplerian motion, unexpectedly, was not found. A great deal of matter had to exist in a halo around the galaxy . This was now a second line of evidence.

Today, I think, there are only a small percentage of galaxies without this dark, but highly influential, matter.

There are also all those Einstein rings that add yet another line of evidence.

 

[whoknows]

It was, actually, a while back (1933) that the strangeness was first detected. Zwicky found that galaxies revolved within a cluster much too quickly. No visible matter could be found to explain the additional gravity needed. Zwicky called the missing matter: dark matter.

But this was only one line of evidence.

Jumping forward several decades, Vera Rubin, with an improved spectrometer, measured the motion of stars moving in orbit around the center of the Andromeda galaxy. Keplerian motion, unexpectedly, was not found. A great deal of matter had to exist in a halo around the galaxy . This was now a second line of evidence.

Today, I think, there are only a small percentage of galaxies without this dark, but highly influential, matter.

There are also all those Einstein rings that add yet another line of evidence.

All evidence for missing gravity, theory is fine, where is the objective proof for dark matter? My argument is not that dark matter is not real but that claims of objectivity that it is require justification.

 

[billslugg]

These are not evidence of missing gravity, they are evidence of missing mass. The only source of gravity, as we know it, is mass. We have excess gravity therefore there must be excess mass.
If you want to argue for new physics to explain it, that is fine but then you are just as unobjective as those of us positing missing mass.

 

[whoknows]

These are not evidence of missing gravity, they are evidence of missing mass. The only source of gravity, as we know it, is mass. We have excess gravity therefore there must be excess mass.
If you want to argue for new physics to explain it, that is fine but then you are just as unobjective as those of us positing missing mass.

I am not positing any new physics, just requesting that objective claims need to be justified.

 

[whoknows]

These are not evidence of missing gravity, they are evidence of missing mass. The only source of gravity, as we know it, is mass. We have excess gravity therefore there must be excess mass.
If you want to argue for new physics to explain it, that is fine but then you are just as unobjective as those of us positing missing mass.

How is/was it is determined that mass is missing or not, or in excess?

 

[billslugg]

We can see that galaxy clusters are orbiting some thing. We can see that galaxy stars are orbiting something we can't see. We can see Einstein Rings where there is no visible mass to cause the image. These are three independent indications of large masses we can't see.

 

[Helio]

What may be confusing is that the observations, though objective, are indirect evidence for DM. We always prefer direct observations of phenomena. But we are now beyond any reasonable doubt that DM is there and it’s not normal matter.

 

[G_x0a]

I think the current beautiful distances are enough to continue looking for the structure of space.
The dark matter hypothesis may be an observational error, going through many different derivatives (although I asked Grok and Grok concluded that scientists have considered most of the cases that lead to observational errors). But the way they came up with the quantitative number of 27% mass or 95% energy is amazing.

 

[Helio]

Observational evidence of the influence of DM on stars and galaxies since 1933 is likely in the thousands. Whatever DM actually is, its presence is “beyond a reasonable doubt”. Thus, alternative views are now ATM (Against The Mainstream) ones that will require significant argument to revise mainstream view.