Dark Matter ?

[interested]

Dark matter is theorized to be the most abundant substance in the universe.

If there is no dark matter is relativity wrong? 

If relativity is wrong what other theories might be valid? 

I understand various modern theories do not need dark matter to explain the movement of the outer planets, does anyone have a inside view regarding which alternative to relativity is the best option, in the event that dark matter is not detected?  

This is one link there are hundreds.

https://arxiv.org/pdf/1612.03034.pdf

Edited September 27, 2017 by interested
added link

[Strange]

5 minutes ago, interested said:

If there is no dark matter is relativity wrong? 

If relativity is wrong what other theories might be valid? 

That is (or was) certainly one of the possibilities; that "dark matter" could be explained by modifying the way gravity works. There are a whole class of modified gravity theories. The most well-known is MOND (Modified Newtonian Dynamics) and there are various versions of this which attempt to match General Relativity (but still account for the effects of dark matter and/or dark energy).

However, none of these have been very successful. The same modifications do not work for both  rotation curves within galaxies and the orbits of galaxies within galaxy clusters. Also, they cannot explain the fact that we can see the distribution of dark matter around and between galaxies by means of gravitational lensing.

Also, recent attempts to simulate the evolution of the universe and reproduce the large scale structures we see only work if dark matter is included.

Then there is data from the CMB ("baryon acoustic oscillations") which also requires dark matter to be present.

All of these work with the same amount of dark matter. So this seems a better solution than ad-hoc modifications to gravity.

15 minutes ago, interested said:

I understand various modern theories do not need dark matter to explain the movement of the outer planets

As far as I know, dark matter has no measurable effect on the movement of the planets (it is too diffuse) so I am not sure what you are thinking of here ...

[interested]

12 minutes ago, Strange said:

As far as I know, dark matter has no measurable effect on the movement of the planets (it is too diffuse) so I am not sure what you are thinking of here ...

The outer edges of the galaxies I understand are not moving as they should without dark matter, so dark matter is introduced to make relativity work. The link I posted above claims not to need dark matter to explain gravitational lensing. 

There are many theories out there, that do not need dark matter, I am trying to find out which are the best to read. If space is full of entangled virtual particles or quantum fluctuations, like in a holographic universe or any one of the other theories out there. Outer space in none stretched space would be more dense, than stretched space at the centre of galaxies, if I read it correctly. 

Without attempting to use maths or fluid dynamics, could planets in more dense space have higher gravitational fields than those in less dense space giving the appearance of dark matter, due to them orbiting in more dense space.

  

 

[Strange]

8 minutes ago, interested said:

The outer edges of the galaxies I understand are not moving as they should without dark matter, so dark matter is introduced to make relativity work. The link I posted above claims not to need dark matter to explain gravitational lensing. 

Strictly speaking, this not to make relativity work but just make gravity work as expected. You don't need relativity to calculate the expected speeds, Newtonian gravity will do. 

I will look at the link later when I have more time. 

[captcass]

How did I end up here? The previous thread was blocked, but now I end up here? Explain that, Strange. WTF am I doing in this thread? Hello?

I did not search this out, so why am I here? Thought I got away from you!

15 hours ago, Strange said:

Strictly speaking, this not to make relativity work but just make gravity work as expected. You don't need relativity to calculate the expected speeds, Newtonian gravity will do. 

I will look at the link later when I have more time. 

Newtonian gravity does not work to predict the speeds as observed. GR should but also doesn't because we do not properly understand what GR describes. I mean, really, Strange, why was this page here on my browser instead of the dead thread page? Any idea? I am totally serious.....Totally freaky, man.....

[beecee]

18 hours ago, interested said:

I understand various modern theories do not need dark matter to explain the movement of the outer planets, does anyone have a inside view regarding which alternative to relativity is the best option, in the event that dark matter is not detected?  

This is one link there are hundreds.

https://arxiv.org/pdf/1612.03034.pdf

GR accommodates DM but as Strange has said, it does not really play a part in the movement of the planets which is described by GR. Although a fudge factor, when first proposed, it is now well supported by the bullet cluster observation and other examples of gravitational lensing by DM as explained here....http://scienceblogs.com/startswithabang/2011/04/20/how-gravitational-lensing-show/

 

here's another....https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3263800/

As mentioned the other day in a thread, the incredible success of GR and the validation of its predictions, always meant that it could not be thrown out due to the apparent anomalous rotations of galaxies, despite what some people with non scientific agendas would like us to believe.  GR of course does have limitations and parameters outside of which it doesn't work: That's why the professionals are searching for a validated QGT.

People, expert professionals are testing to the ultimate, the validity of GR every day, checking out its predictions, making further observations etc. Just last month the fourth gravitational wave was recorded on three instruments in two different continents. It's track record speaks for itself, and even when the long sort after QGT is found and validated, it will not invalidate GR...just as GR did not invalidate Newtonian: Each new model extends the zones of applicability of the former. We could use GR instead of Newtonian for our every day living and it will give the same results but with far better accuracy which is simply not needed and a waste of time and brain power in working through the maths.   

[Strange]

2 hours ago, captcass said:

Newtonian gravity does not work to predict the speeds as observed. GR should but also doesn't because we do not properly understand what GR describes. 

Newtonian gravity and GR will produce exactly the same results so it doesn't matter which you use.

Although it is possible, as I say, that it could require a modification to our understanding of gravity, that is looking increasingly unlikely. But, of course, various people with a great deal of detailed knowledge and in-depth understanding are still looking at that possibility. (So are a few uneducated idiots, but that is hardly relevant.)

Here is an article on some of the recent work on modified gravity to explain dark matter: What if dark matter is not a particle? The second wind of modified gravity.

[interested]

I fully appreciate Newtons Equations are still valid in most circumstances and Einsteins are in others.

Apart from perhaps being called an uneducated idiot for asking a question, the question still stands. If dark matter does not exist what are the options.

An after thought, If an idiot is educated does that make that person an educated idiot, rather than an uneducated idiot? There are lots of stupid educated people in this world and a lot of clever none educated people. ? 

[Strange]

54 minutes ago, interested said:

Apart from perhaps being called an uneducated idiot for asking a question, the question still stands. If dark matter does not exist what are the options.

That comment ("idiots") was absolutely not aimed at you - just people who pop up on science forums who present their half-baked ideas as new "theories".

Anyway, the alternatives to dark matter as some form of matter are various modifications of our theories of gravity:

MOND is the best known: https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics

But there are others: https://en.wikipedia.org/wiki/Alternatives_to_general_relativity, https://en.wikipedia.org/wiki/Erik_Verlinde#Emergent_gravity_and_the_dark_universe, https://en.wikipedia.org/wiki/Dark_matter#Alternative_theories, http://backreaction.blogspot.it/2016/10/what-if-dark-matter-is-not-particle.html, https://arxiv.org/abs/1204.5571, and on and on

 

Edited September 28, 2017 by Strange

[interested]

Thanks for the responses Strange and Beecee, having had a night to muse over your responses, and invoking both Occams razor, and the KISS principle (keep it simple stupid) ,just in case I am, and having read the links but not all the sub links to your responses.

I think it is safe to assume that at least some of those that propose dark matter does not exist, are not fools and Einstein may be partly wrong.

I also think it is safe to assume that gravity affects light causing gravitational lensing.  

I also think it is safe to assume the distortion or stretching of space causes gravity, and the distortion or expansion of space causes a repulsion effect (cosmological constant) 

Also assuming dark matter does not exist, the above still holds true

This then leads to a mixture of ideas being presented in Stranges threads, I am going to reject those ideas that try to support a smooth space and dark matter as it is possible it does not exist.

Do any theories agree  with the following amalgamation of ideas gleaned from Stranges links this forum and various other websites?.

Bearing in mind wave fluctuations permeate all of space ( Mordreds thread on what space is). The super fluid idea of space does not restrict the movement of space or fluctuations in the density or distortion of space (gravity), if this fluid is a quantum field of wave fluctuations (Mordred again) without which space does not exist. When these quantum fluctuations are lumped together they can be viewed as a fluid permeating all of space. Space is not stationery or smooth it is dynamic and moving like any other fluid. This movement in space could cause the lensing effect independent of mass. ie

Galaxies swirling around in space will if space is viewed as a fluid cause space around them to move. (Take a good glass of wine and swirl it around hold it to the light and you will see a lensing effect (if you drink a few of the swirling glasses of wine the lensing effect should increase)). If space is viewed as a fluid, like any other fluid swirling around it will cause fluid adjacent to it to move, causing compression or stretching ie distorting it, causing variations in gravity. When a galaxy moves through space, if space is fluid there is nothing to stop it swirling around once the galaxy has passed. Gravitational lensing could be caused by a a historic event in space still distorting the space an event occurred in.

etc etc

Does any one have a theory that could replace relativity that does not include dark matter. Could quantum fluctuations result in an expansion of space and mirror the cosmological constant in einsteins equations. 

 

[Strange]

1 minute ago, interested said:

Does any one have a theory that could replace relativity that does not include dark matter. 

Apart from all those already mentioned? 

[interested]

2 minutes ago, Strange said:

Apart from all those already mentioned? 

Can you narrow it down a bit. Some of those mentioned were assuming smooth space, others were trying to agree with dark matter.

[Strange]

18 minutes ago, interested said:

Can you narrow it down a bit. Some of those mentioned were assuming smooth space, others were trying to agree with dark matter.

Not really. If you are looking for a theory that fits certain criteria (preconceptions?) then you will have to see how well each measure up to that. I'm not sure anyone else can do tat for you. (Note that this does not seem a good way to approach science, through.)

[beecee]

10 hours ago, interested said:

Space is not stationery or smooth it is dynamic and moving like any other fluid. This movement in space could cause the lensing effect independent of mass. ie

Galaxies swirling around in space will if space is viewed as a fluid cause space around them to move.

We also often here about the fabric of spacetime: These are simply analogies, and like all analogies are mostly limited in their description and should not be taken too far. Just as an aside, I like the river/waterfall analogy of spacetime with regards to BHs and as proposed by Professor Hamilton...here....http://jila.colorado.edu/~ajsh/insidebh/waterfall.htmland his paper on this....https://arxiv.org/pdf/gr-qc/0411060.pdf

I'm not sure about any models re the absence of DM, other then MOND, but even that appears limited in its application when applying to all galaxies. And again, as I said previously, DM is now strongly evidenced as per the bullet cluster and other examples of gravitational lensing.

[Mordred]

Nicodem Poplowkii  uses torsion under GR to try to replace DM. There is others but MOND and Popolwkii's ECT Einstein Cartan based universe were always the two strongest competitors.

 

Coincidentally as I understood it, the same problem that effectively killed MOND also affected Poplowskii.

That being the early large scale structure formation.

[interested]

Thank you all for the responses, I particularly liked the black hole water fall analogy, but it left me wondering what happens when the black hole is full of space?. Space being made up of quantum fluctuations. Which lead to a line of speculation, which I think is mostly correct, and could be derived by a politician trying to please all sides, rather than a scientist trying to prove one way is the only way. 

Sticking with the KISS principle.

My speculation is everyone may be mostly correct, but are explaining the observed "effects" in different ways. All claiming the "cause" of the "effect" is something different ie dark matter quantum foam, fluid space etc etc. Quantum fluctuations or foam permeate all of space and exist temporarily as virtual particles. Dark matter is not detectable in space but is inferred to exist. Virtual particles exist and on average have particle like effects. Could virtual particles Quantum foam or quantum fluctuations existing in space be the elusive dark matter. Virtual particles do on average exist and on average through out the universe will have an average mass, could virtual particles existing in space be the elusive Dark Matter.

Am I right in thinking that Dark matter and Quantum fluctuations, or Quantum foam, could be the same thing but explained differently.? 

To answer my first question the black hole does not get full of space and overflow, because space is absorbed by the matter inside the black hole and disapears. Quantum fluctuations without which space would not exist are driven out of existence in contact with matter inside the black hole.

 

 

  

 

[beecee]

7 hours ago, interested said:

Dark matter is not detectable in space but is inferred to exist.  

I'm not sure if that is correct. from http://scienceblogs.com/startswithabang/2011/04/20/how-gravitational-lensing-show/
 

Quote

 

Well, we can recreate the distribution of matter, most of which is not accounted for by atoms! In fact, if we show those results from weak lensing in blue, and overlay the Chandra X-Ray observatory data in pink, you may recognize this as one of the most famous images ever…

The Bullet Cluster! You can not only measure the amount of total matter, with weak lensing, but you can compare it with where the hot gas is in the X-ray. This combination is a big part of how we know dark matter doesn’t collide with either itself or with normal, atomic matter.

 

Quote

Am I right in thinking that Dark matter and Quantum fluctuations, or Quantum foam, could be the same thing but explained differently.? 

I don't believe so: quantum fluctuations is explained via the Heisenberg uncertainty principle and is a property of spacetime itself. It may even be connected with DE which we believe accounts for the observed acceleration of the expansion rate, acting in opposition to gravity which is trying to attract and DM acts gravitationally as we know. At least that's the way I see it. 

Quote

 

but it left me wondering what happens when the black hole is full of space?

To answer my first question the black hole does not get full of space and overflow, because space is absorbed by the matter inside the black hole and disapears. Quantum fluctuations without which space would not exist are driven out of existence in contact with matter inside the black hole

 

Perhaps this is an example of taking the analogy too far? We could also ask where does the spacetime come from with the universal expansion....perhaps "stretching" of spacetime is a better concept and when it (spacetime) flows into the BH, that stretching contracts again? Or even more speculatively, perhaps as the mass and spacetime fall towards the center where the singularity (as in where our models fail) lies, an ERB and wormhole is formed and the spacetime exits into another "baby universe"?

[Strange]

9 hours ago, interested said:

I particularly liked the black hole water fall analogy, but it left me wondering what happens when the black hole is full of space?

Space is not "stuff" so a black hole cannot be filled with it. Don't stretch the analogy too far. Space isn't literally falling into the black hole (which isn't literally a black hole).

9 hours ago, interested said:

Space being made up of quantum fluctuations.

Space (in the context of GR, which we are talking about) is distances between things in three dimensions (and the geometry that relates them). 

It may be full of quantum fluctuations (because quantum fields have a non-zero value because they are quantised) but it is not made of quantum fluctuations.

9 hours ago, interested said:

Could virtual particles Quantum foam or quantum fluctuations existing in space be the elusive dark matter.

No. For one thing, it wouldn't have the right distribution. The non-zero background energy which gives rise to these virtual particles is the same everywhere. That is not the distribution of dark energy that we see.

It is thought that the quantum foam (non-zero background energy) could explain dark energy but it appears to be 10¹²⁰ times too large. 

 

[interested]

Summarizing I think I am correct in thinking the following

The effect claimed to be Dark Energy is possibly quantum fluctuations.

I never said Space is stuff it is quantum fluctuations, without which there is no space.

Quantum fluctuations are absorbed in hot environments and by matter. 

The effect claimed to be Dark matter which does not interact with matter but affects gravity, may have originated in the or one of many big bangs, which was initiated by quantum fluctuations OR in a zero energy universe which again came from quantum fluctuations.

Quantum fluctuations are the cause of the effect known as the Heisenberg uncertainty principle.

Everything is a result of quantum fluctuations.

From the above summary IF I am correct, I think it is fair to assume, the effect of dark matter in space is a result of quantum fluctuations, these fluctuations do not interact with matter because they may be being absorbed by it, as they would be in a black hole.

There are theories out there written by clever people that disagree with the claim that "It is thought that the quantum foam (non-zero background energy) could explain dark energy but it appears to be 10¹²⁰ times too large. " One such theory was posted under Itoeros Hologaphic universe thread by Handy andy https://arxiv.org/pdf/physics/0307003.pdf there are many other more recent papers along similar lines.

This paper is by MOND https://arxiv.org/pdf/1704.00780.pdf again it is a version of quantum gravity, and will add to my reading this week. There are dozens of links for Poplowskiiand I am not sure where to start with this fella https://arxiv.org/a/poplawski_n_1.html any clues would be appreciated.

Thanks all.

 

 

[Strange]

That is a very confused and slightly incoherent picture. Bits of it may have some connection to physics, large parts of it seem to be made up. But as you don't seem to be interested in anything unless it confirms your ideas, I will leave it at that.

[interested]

Thanks for your input anyway I do not think I was making up quantum fluctuations as the origins of everything, unless of course you believe god did it which I do not, so I will leave it at that also.

Edited October 1, 2017 by interested

[Strange]

OK. Lets try and pick out some of the obvious errors.

9 minutes ago, interested said:

I never said Space is stuff it is quantum fluctuations, without which there is no space.

Quantum fluctuations exist in space. Length, width and height can quite happily exist without them.

Quote

Quantum fluctuations are absorbed in hot environments and by matter. 

This appears to be completely baseless.

Quote

Quantum fluctuations are the cause of the effect known as the Heisenberg uncertainty principle.

Wrong way round. Quantum fluctuations are the result of the uncertainty principle.

Quote

Everything is a result of quantum fluctuations.

Just no. General relativity has nothing to do with quantum fluctuations but does an extremely good job of describing gravity.

12 minutes ago, interested said:

I think it is fair to assume, the effect of dark matter in space is a result of quantum fluctuations, these fluctuations do not interact with matter because they may be being absorbed by it, as they would be in a black hole.

Utterly erroneous conclusion resulting from a baseless assumptions.

It is almost certain that dark matter is some form of matter; it is not the background energy of the vacuum.

Quote

One such theory was posted under Itoeros Hologaphic universe thread by Handy andy https://arxiv.org/pdf/physics/0307003.pdf

Cahill is a complete crackpot. You should ignore anything by him.

7 minutes ago, interested said:

I dont think I was making up quantum fluctuations are the origins of everything

That is complete speculation.

[interested]

Trying Again !

Assuming Relativity is correct, could the big bang have some left over remnant in the form of dark matter?

Quantum fluctuations or waves produce field excitations which are particles. Dark matter has mass and is therefore a particle of sorts. Spin 0, 1/2, 1 etc 

All of space is full of quantum fluctuations. There is no empty space where there are no quantum fluctuations. Space is expanding possibly due to quantum fluctuations.

Is it possible that dark matter is a mixture of particle pairs. That appeared out of the vacuum still in an entangled state. 

Could this particle pair production still be ongoing in the colder parts of space. Particles do not stay Entanglement in a hot environment like a big bang. 

Fields gives rise to particle production of the particle/anti particle pairs, and prior to any heating in the universe as a result possibly of a big bang would have happened at near absolute zero.

Could dark matter be a leftover from the big bang or from a zero energy universe, something like an electron + positron pair. Would this be detectable as it would be electrically neutral and possibly not respond to electromagnetic waves. 

--------------------------------------------------------------------------------------------------------------------------------------

Ref the rest above, the flowing space analogy like a water fall reminded me of the Cahil paper, who might well be a crackpot. There are many crackpots in the world and I suspect there are a few on this forum also. He was working in Adelaide Australia in a University so I assume he was reasonably clever. I have not checked him out so do not know.

Quantum fluctuations were happening long before Heisenberg was born.

I hope I am more correct this time.

Thanks for the response.

After thought is a crackpot worse than an educated idiot.

 

[swansont]

28 minutes ago, interested said:

 Could dark matter be a leftover from the big bang or from a zero energy universe, something like an electron + positron pair. Would this be detectable as it would be electrically neutral and possibly not respond to electromagnetic waves. 

Dark matter does not interact electromagnetically. It is not made up of e-e+ pairs, or of any other particle we've already detected. That's why we call it dark matter.

[Strange]

55 minutes ago, interested said:

Is it possible that dark matter is a mixture of particle pairs. That appeared out of the vacuum still in an entangled state. 

Virtual particle pairs only exist temporarily. Also, they are evenly distributed but dark matter is not.

55 minutes ago, interested said:

Could this particle pair production still be ongoing in the colder parts of space.

Pair production requires a source of energy.

56 minutes ago, interested said:

Fields gives rise to particle production of the particle/anti particle pairs, and prior to any heating in the universe as a result possibly of a big bang would have happened at near absolute zero.

The Big Bang happened because the universe was hot. The universe is cooling. 

57 minutes ago, interested said:

Could dark matter be a leftover from the big bang

Most models have dark matter appearing in the early universe, like normal matter.

 

58 minutes ago, interested said:

something like an electron + positron pair. Would this be detectable as it would be electrically neutral and possibly not respond to electromagnetic waves. 

We can detect electron-positron pairs.