Gravity: A Theory under Crisis.

[Tina]

Sometimes it felt like we'd never see the day when cosmologists would admit that their ominous "dark matter" might not actually exist!

And:

Even if it does exist, dark matter would be unable to reconcile all the current discrepancies between actual measurements and predictions based on theoretical models.

Well I just got a news feed:

Here is some very, very good news indeed.

http://www.physorg.com/news160726282.html

[Solar]

Great find Tina!!

Good news yes. But, it looks like they're just going to move over to MOND - a theory that was "designed" to fit the galaxy rotation curve problem.

Both MOND and dark matter were invented to explain the presence of mass discrepancies in astronomical data, especially the flat rotation curves of spiral galaxies. It is often asserted that MOND is ad hoc (and therefore bad), but this is also true of dark matter. Once invoked, dark matter can be distributed in any way necessary to explain just about anything. It is difficult to test, and does not constitute a falsifiable theory. In contrast, once a modified force law is specified, there is no freedom to adjust its predictions. MOND can not fit any arbitrary rotation curve: it is tied down by the observed mass distribution. - The MOND pages

Sheesh!, what a major crash gravity only cosmology is having.

[Tina]

To go on and subscribe to MOND now would be like taking one step forward, then two steps back. But I get the impression that the movement will be away from Newtonian Dynamics rather than reconciliation through MOND. This is similar to what Capernicus had to do in reconciling his observerations with current cosmoligical theory of his time - It just didn't work and led to rejection of old theory....eventually. And I guess that just like in Capernicus' time it is now...we have to wait for the blessing of official science.

[altonhare]

Have either of you read "The Origin of Inertia and Extended Mach's Principle" by Ghosh? It's a short read and the idea is qualitatively accessible to anyone and mathematically accessible to those comfortable with DE's.

Therein he solves the problems dark matter was invented to solve by positing a "cosmic drag". It amounts to adding a velocity-dependent term to Newton's distance only equation.

It also turns out that this "cosmic drag" accounts for a host of other astronomical observations, not just galactic rotation curves and the like. It is also only a single parameter that applies universally at all scales. Unlike dark matter, which must increase in proportion to regular matter as we look at larger and larger scales.

In general it seems much, much more parsimonious.

[StevenO]

Well I just got a news feed:

Here is some very, very good news indeed.

http://www.physorg.com/news160726282.html

This article has been discussed before in another thread: Time For A New Theory Of Gravitation?. You can find some explanations there.