Dark matter is an ad hoc

[hypervalent_iodineisstupid]

Dark matter is just an ad hoc explanation for when our theories of gravitation don't create accurate predictions. Although it has already been proposed, and I did not come up with it, I agree with a modified form of Newtonian gravity where gravity is proportional to the inverse of the radius as opposed to the inverse square of the radius.

[Raider5678]

Dark matter was created to explain why the universe is expanding I thought... Though, I might be wrong.

[ajb]

Dark matter is just an ad hoc explanation for when our theories of gravitation don't create accurate predictions.

We essentially have two choices

 

i) Stick with the idea that general relativity is okay (for the scales we are talking about) and add some 'dark matter'.

ii) Look at modifying general relativity.

 

Both have been suggested and looked.

 

Although it has already been proposed, and I did not come up with it, I agree with a modified form of Newtonian gravity where gravity is proportional to the inverse of the radius as opposed to the inverse square of the radius.

Modified versions of Newtonian gravity are generally thought not to work properly. For one they seem not to account for all rotation curves. Secondly, one needs ad-hoc corrections to general relativity to get a non-Newtonian non-relativistic limit - the theory is not so nice in this respect.

 

Other kinds of modifications to general relativity have been thought about also. However, it is known - and known for a long time for f[R] theories - that Lagrangians build from the standard curvature tensors are equivalent to general relativity + matter - they can always been reformulated in this way, but the matter may be exotic. So it is generally thought that modifications of general relativity in this way are not really going to answer the question of dark matter. The general thinking today is that particle physics has the answer.

 

 

Dark matter was created to explain why the universe is expanding I thought... Though, I might be wrong.

You maybe thinking of dark energy - this is the root of the acceleration of the expansion that we see today.

 

But there is some loose connection here - details of the Cosmic Microwave Background Radiation (CMBR) seem to fit the Lambda CDM model. This model has both some form of dark energy and dark matter.

 

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Edit: The person who made the initial post has been banned. But we can still discuss some of this if anyone is interested?

Edited July 23, 2016 by ajb

[Strange]

Although it has already been proposed, and I did not come up with it, I agree with a modified form of Newtonian gravity where gravity is proportional to the inverse of the radius as opposed to the inverse square of the radius.

 

 

I doubt very much that a model where gravity follows a simple inverse law has been proposed. Basically, it would not fit any of the observational data. Could you even have stable orbits?