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from the shedding-some-light-on-the-matter dept.
Dark Matter is Not Made Up of Tiny Black Holes:
An international team of researchers has put a theory speculated by the late Stephen Hawking to its most rigorous test to date, and their results have ruled out the possibility that primordial black holes smaller than a tenth of a millimeter make up most of dark matter. Details of their study have been published in this week's Nature Astronomy.
Scientists know that 85 per cent of the matter in the Universe is made up of dark matter. Its gravitational force prevents stars in our Milky Way from flying apart. However, attempts to detect such dark matter particles using underground experiments, or accelerator experiments including the world's largest accelerator, the Large Hadron Collider, have failed so far.
This has led scientists to consider Hawking's 1974 theory of the existence of primordial black holes, born shortly after the Big Bang, and his speculation that they could make up a large fraction of the elusive dark matter scientists are trying to discover today.
The scientists theorized that primodial black holes between Earth and the Andromeda galaxy. Were one to lie between us and a star, then it would cause the star to appear to brighten for a few minutes or hours.
From 190 images of the Andromeda galaxy taken over the course of a single, 7-hour observation, the researchers expected to see about 1000 events. They saw... just one. They haven't given up trying to locate the "missing mass" — mass we have not yet identified, but would be needed to explain the orbital properties of galaxies. To wit:
The researchers are now planning to further develop their analysis of the Andromeda galaxy. One new theory they will investigate is to find whether binary black holes discovered by gravitational wave detector LIGO are in fact primordial black holes.
Journal Reference:
Hiroko Niikura, et. al. Microlensing constraints on primordial black holes with Subaru/HSC Andromeda observations. Nature Astronomy, 2019; DOI: 10.1038/s41550-019-0723-1
(Score: 5, Interesting) by opinionated_science on Wednesday April 03 2019, @12:13PM (10 children)
There is a UK professors that has been working on an idea for a few years. He has developed a parameter free model that explains the data.
The theory is called Quantised Inertia [blogspot.com] and is a really interesting extension to the understanding of gravity.
There are some very easy to follow articles on the blog as well as peer-reviewed publications - highly recommended.
(Score: 0) by Anonymous Coward on Wednesday April 03 2019, @12:25PM
Yes, this also explains why MOND works right?
(Score: 4, Insightful) by Immerman on Wednesday April 03 2019, @02:01PM (7 children)
Does it also explain the recent galaxy discovered whose motion is accurately described without invoking dark matter?
It's anomalies like that that are the proving ground for scientific models - if your model can't describe the anomalies using the same theoretical constructs and constants as it uses for the normal samples, then it's almost certainly wrong.
(Score: 1, Informative) by Anonymous Coward on Wednesday April 03 2019, @02:35PM (4 children)
Probably, it gives predictions very similar to MOND.
MOND's predictions are so far consistent with both (NGC 1052-DF2 and NGC 1052-DF4). See table 2 here:
https://arxiv.org/abs/1901.02679 [arxiv.org]
Compare to:
https://iopscience.iop.org/article/10.3847/2041-8213/ab0d92/meta [iop.org]
https://iopscience.iop.org/article/10.3847/2041-8213/ab0e8c [iop.org]
(Score: 1, Informative) by Anonymous Coward on Wednesday April 03 2019, @02:40PM (3 children)
Source:
http://physicsfromtheedge.blogspot.com/2018/06/visit-to-julich-supercomputing-centre.html [blogspot.com]
(Score: 2) by Immerman on Wednesday April 03 2019, @07:31PM (2 children)
It's the adjustable "constant" that makes MOND really hard for me to take seriously. If you need to adjust the "constant" to fit different galaxies, all you have is a general empirical description, not a physical model.
(Score: 0) by Anonymous Coward on Wednesday April 03 2019, @08:19PM
There is one universal constant for all galaxies, but no one knows what exactly it is. It is heavily constrained to be about 1.2*10^-10 though, so usually people just use that value.
The quantitative inertia guy says his models do not even have that one universal value to measure. Compare to GR plus dark matter which has nearly infinite tunable parameters (at least one for each galaxy).
(Score: 0) by Anonymous Coward on Wednesday April 03 2019, @08:38PM
For example, in the MOND prediction paper linked above you can see they used the same a0 = 1.2e-13 km/s^2 value for all the galaxies that has been used since 1983. Units for my sister post are missing but were m/s^2.
(Score: 2) by opinionated_science on Wednesday April 03 2019, @09:10PM (1 child)
He posts regular updates, as data becomes available. I think he's really overworked, like most researchers not engaged in mainstream research.
He's got a bit of funding to measure the effects in the real world (from DARPA!) , but like most, I want to see the evidence first.
In the same way Einstein augmented Newton, it's entirely plausible for further augmentation to our understanding of gravity.
(Score: 2) by Gaaark on Wednesday April 03 2019, @10:39PM
Read my posts all over the place, lol. I'm glad you've joined me in the good QI fight!
Thumbs up!
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by Gaaark on Wednesday April 03 2019, @10:34PM
HEY! He's stealing Gaaarks thunder!
oh...wait. I'm Gaaark.
Welcome QI friend!
:)
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---