Dark matter is more lumpy than expected

[Ags]

High density knots of dark matter have been observed in the core of large galaxy clusters, which was not predicted by current dark matter models.

https://www.spacetelescope.org/news/heic2016/

[Drifter]

Maybe the cause of lensing effects aren’t solely gravitational?
Chemicals, liquids between a light source can cause distortions

Imagine some mechanism out in space generating such pockets of refraction? 

Aren’t our observations ‘lensing’ through the ice fields of the Kuiper Belt?
 

Edited November 17, 2020 by Drifter
Pruning

[Gfamily]

On 10/09/2020 at 23:24, Ags said:

High density knots of dark matter have been observed in the core of large galaxy clusters, which was not predicted by current dark matter models.

https://www.spacetelescope.org/news/heic2016/

That's interesting.

I wonder how it's related to the 'Core Cusp Problem', which (as I understand it) says that for small galaxies, the Dark Matter should have high density knots, that we don't see.

This recent report seems to be a complementary problem affecting assemblies at the other end of the galaxy cluster scale.

https://en.m.wikipedia.org/wiki/Cuspy_halo_problem

Edited November 12, 2020 by Gfamily

[Drifter]

On 12/11/2020 at 08:51, Gfamily said:

That's interesting.

I wonder how it's related to the 'Core Cusp Problem', which (as I understand it) says that for small galaxies, the Dark Matter should have high density knots, that we don't see.

This recent report seems to be a complementary problem affecting assemblies at the other end of the galaxy cluster scale.

https://en.m.wikipedia.org/wiki/Cuspy_halo_problem

Is it possible the data/calculations making up the computer model simulation are erroneous... rather than there being some unknown factor interfering with the observation?

[saac]

On 12/11/2020 at 00:40, Drifter said:

Maybe the cause of lensing effects aren’t solely gravitational?
Chemicals, liquids between a light source can cause distortions

Imagine some mechanism out in space generating such pockets of refraction? 

Aren’t our observations ‘lensing’ through the ice fields of the Kuiper Belt?
 

That would be a simply unbelievable amount of liquid/chemicals to cause the extent of gravitational lensing recorded. Most improbable. 

Jim 

[Drifter]

On 24/11/2020 at 19:18, saac said:

That would be a simply unbelievable amount of liquid/chemicals to cause the extent of gravitational lensing recorded. Most improbable. 

Jim 

Good point. 
Just positing the idea that gravitational lensing could be caused by many things currently invisible to our telescopes ... I gave the Asteroid belt ice objects as an example ... interesting to know how much refraction is out there we can’t see ..... from the gravitational forces generating it’s shape and extent.
 

But there also might be other factors that might be invisible to our science eg: multiverse interferences .... if theoretical physicists have their say?

[michael.h.f.wilkinson]

Gravitational lensing by things not seen by our telescopes is almost the very definition of dark matter, apart from other gravitational effects like the motions observed in the outer parts of galaxies in H-I observations by Westerbork and other radio telescopes. Asteroids do not explain the effects seen.

 

The idea that the algorithms used in computation are wrong can be countered by the fact that many different pieces of code have been developed by different groups, and the different packages yield similar results. All the code used is open source and peer reviewed, so unless you can point to a particular error you have found (always possible), just saying the code must be wrong is not a good scientific argument.

[Drifter]

This might point to why there is a problem with the data:

https://www.nasa.gov/feature/goddard/2021/as-nasa-s-voyager-1-surveys-interstellar-space-its-density-measurements-are-making-waves
 

This extract:

“When one pictures the stuff between the stars – astronomers call it the “interstellar medium,” a spread-out soup of particles and radiation – one might imagine a calm, silent, serene environment. That would be a mistake.

“I have used the phrase ‘the quiescent interstellar medium’ – but you can find lots of places that are not particularly quiescent,” said Jim Cordes, space physicist at Cornell and co-author of the paper.

Like the ocean, the interstellar medium is full of turbulent waves. The largest come from our galaxy’s rotation, as space smears against itself and sets forth undulations tens of light-years across. Smaller (though still gigantic) waves rush from supernova blasts, stretching billions of miles from crest to crest. The smallest ripples are usually from our own Sun, as solar eruptions send shockwaves through space that permeate our heliosphere’s lining.

These crashing waves reveal clues about the density of the interstellar medium – a value that affects our understanding of the shape of our heliosphere, how stars form, and even our own location in the galaxy. As these waves reverberate through space, they vibrate the electrons around them, which ring out at characteristic frequencies depending on how crammed together they are. The higher the pitch of that ringing, the higher the electron density. Voyager 1’s Plasma Wave Subsystem – which includes two “bunny ear” antennas sticking out 30 feet (10 meters) behind the spacecraft – was designed to hear that ringing.”

[UKDiver]

On 27/11/2020 at 11:54, michael.h.f.wilkinson said:

Gravitational lensing by things not seen by our telescopes is almost the very definition of dark matter, apart from other gravitational effects like the motions observed in the outer parts of galaxies in H-I observations by Westerbork and other radio telescopes. Asteroids do not explain the effects seen.

 

The idea that the algorithms used in computation are wrong can be countered by the fact that many different pieces of code have been developed by different groups, and the different packages yield similar results. All the code used is open source and peer reviewed, so unless you can point to a particular error you have found (always possible), just saying the code must be wrong is not a good scientific argument.

Different pieces of code using different algorithms or using the same algorithm? If the latter, I'm not surprised they yield similar results. However, similar results does not mean they are right. After all, 'all models are wrong' etc. So maybe the models were good at replicating what had been initially observed, but were limited by the data selected/available for that model and thus not so great at predicting outside the source variations.

I realise that the above may sound obvious and even insulting, but I've seen it happen in a completely different domain. Over trusting of a model that well replicated responses of one set of observed events, but not a second set because the variations were not thought to be possible as they had not been observed. Only one set of algorithms exist based on 150 year old empirical formulae, yet modellers have used them inappropriately.

I agree that just stating 'the code must be wrong' is not very useful. So has it been used wrongly? What else is left if it's not the code and it's not the data?

Edited November 16, 2021 by UKDiver

[michael.h.f.wilkinson]

8 hours ago, UKDiver said:

Different pieces of code using different algorithms or using the same algorithm? If the latter, I'm not surprised they yield similar results. However, similar results does not mean they are right. After all, 'all models are wrong' etc. So maybe the models were good at replicating what had been initially observed, but were limited by the data selected/available for that model and thus not so great at predicting outside the source variations.

I realise that the above may sound obvious and even insulting, but I've seen it happen in a completely different domain. Over trusting of a model that well replicated responses of one set of observed events, but not a second set because the variations were not thought to be possible as they had not been observed. Only one set of algorithms exist based on 150 year old empirical formulae, yet modellers have used them inappropriately.

I agree that just stating 'the code must be wrong' is not very useful. So has it been used wrongly? What else is left if it's not the code and it's not the data?

As far as simulations are concerned, there are different algorithms (and different models). The idea that something that is not directly visible is exerting a gravitational pull on matter and light is well established by many different observations (like H-I velocity profiles mentioned before). Inferring the exact distribution from observation is quite a tricky (or ill-posed) inverse problem, and small perturbations in the input can cause large differences in the output, i.e. the results may change with more, and better data coming in. We will have to wait and see