Is Dark Matter Real?

[Itoero]

• Scientists have long assumed that some invisible “dark matter” particles must accompany the normal matter in the universe to explain how stars orbit in galaxies and how galaxies orbit in clusters. An alternative idea that there is no extra matter and that our equations of gravity need updating has received much less attention.
• But numerous experiments have failed to find evidence for dark matter particles, and the possibility remains that gravity must be modified.
• Lately, in fact, some astrophysical evidence, such as recent observations of gravitation in galaxies, favors modified gravity theories over dark matter. It is time that physicists let go of their prejudices and reexamined this underdog idea.http://www.nature.com/scientificamerican/journal/v319/n2/full/scientificamerican0818-36.html

Dark matter is deemed essential for describing galaxy dynamics. A prominent alternative theory can make the same predictions without dark matter, by introducing a universal acceleration constant. Recent high-quality observations of galaxies are used to investigate whether this constant is really a constant.http://www.nature.com/articles/s41550-018-0547-4

You have to pay to read entire articles. But what do you think of this?

[quiet]

Within the concert of ideas of the cosmological community, are the adjectives dark and undetected synonymous? Example without pretense of taking it seriously. A cloud of positrons, in thermal equilibrium with the microwave background, would be indistinguishable from that background for typical observation methods. It is not a dark cloud. It irradiates the thermal spectrum corresponding to the equilibrium temperature, but what radiates is identical to the cosmic background and by the usual means is indistinguishable. Now I think about it and I notice that, from time to time, some of those clouds would collapse producing a burst of gamma rays, like those called explosive sources of gamma rays. But I only put it to give an idea of how something present can be indistinguishable.

[Strange]

On 22/08/2018 at 8:04 PM, Itoero said:

It is time that physicists let go of their prejudices and reexamined this underdog idea

Luckily, science is not some sort of dogmatic belief system so there are a great many people looking at many different models for dark matter including many types of modified gravity and many possibilities for some type of matter (and other more esoteric ideas). 

On 22/08/2018 at 8:04 PM, Itoero said:

You have to pay to read entire articles. But what do you think of this?

It doesn’t seem to be available on arxiv or anywhere else so I can’t comment. It will be interesting to see if anything comes of it. 

1 hour ago, quiet said:

are the adjectives dark and undetected synonymous?

No

[Itoero]

I just found another paper.

Researchers at Johannes Gutenberg University Mainz (JGU) have now presented a novel theory of dark matter, which implies that dark matter particles may be very different from what is normally assumed. In particular, their theory involves dark matter particles which are extremely light—almost one hundred times lighter than electrons, in stark contrast to many conventional models that involve very heavy dark matter particles instead.

https://phys.org/news/2018-02-theory-dark-based-unusual-x-ray.html#jCp

[Eise]

Wikipedia is your best friend. The article lists all the observations that hint at the existence of dark matter:

• Galaxy rotation curves
• Velocity dispersions
• Galaxy clusters
• Gravitational lensing
• Cosmic microwave background
• Structure formation
• Bullet Cluster
• Type Ia supernova distance measurements
• Sky surveys and baryon acoustic oscillations
• Redshift-space distortions
• Lyman-alpha forest

It also explains why alternative theories are not very probable:

Quote

A problem with alternative hypotheses is that the observational evidence for dark matter comes from so many independent approaches (see the "observational evidence" section above). Explaining any individual observation is possible but explaining all of them is very difficult. Nonetheless, there have been some scattered successes for alternative hypotheses, such as a 2016 test of gravitational lensing in entropic gravity.

The prevailing opinion among most astrophysicists is that while modifications to general relativity can conceivably explain part of the observational evidence, there is probably enough data to conclude there must be some form of dark matter.

But as you see, as Strange already said, science is not as dogmatic as you seem to imply. Other approaches are tried, and sometimes successful, but alas, just for one of the observations. Maybe, maybe, when after many years still no dark matter is found directly, someone will come up with an alternative theory that explains more or less all of the above phenomena.

I think you should read Imre Lakatos, for some viable philosophy of science. In his terms, when the research programme for finding dark matter fails, other research programmes might pop up.

Edited September 13, 2018 by Eise

[Strange]

14 hours ago, Itoero said:

I just found another paper.

Researchers at Johannes Gutenberg University Mainz (JGU) have now presented a novel theory of dark matter, which implies that dark matter particles may be very different from what is normally assumed. In particular, their theory involves dark matter particles which are extremely light—almost one hundred times lighter than electrons, in stark contrast to many conventional models that involve very heavy dark matter particles instead.

https://phys.org/news/2018-02-theory-dark-based-unusual-x-ray.html#jCp

Interesting. The trouble is that at the moment, there are too many interesting ideas!