Dark matter and Shell Theorem by Isaac Newton

[David Levy]

Thanks.

 

For a 3D, we could consider a submarine instead of ship…

 

However, the key issue -

Is it a constant matter in the universe? or is it moving with the galaxies?

Edited March 18, 2015 by David Levy

[Strange]

For a 3D, we could consider a submarine instead of ship…

 

A better analogy might be dew forming on a cobweb: http://fc04.deviantart.net/fs70/f/2011/305/b/8/cobweb_by_drezdany-d4eqoy3.jpg

Where the web is the drak matter structure and the drops are galaxies (or galaxy clusters).

 

Look at the two pictures on the right here: http://www.mpa-garching.mpg.de/galform/virgo/millennium/#pictures

(This is the source of the dark matter picture)

 

The top picture shows the distribution of galaxies, the bottom one shows the distribution of drak matter. I think the dark matter structure forms and provides a place where there is enough gravity for gas clouds to collapse and form galaxies.

 

Is it a constant matter in the universe? or is it moving with the galaxies?

 

In the case of individual galaxies, the dark matter and the galaxy move together. (Otherwise we wouldn't see the consistent pattern of the density of dark matter in the centre of the galaxy.)

 

There is an example where two galaxies have collided and we can see that the dark matter has become separated from the galaxies (a bit like a passenger being thrown from a car crash).

http://chandra.harvard.edu/press/06_releases/press_082106.html

[David Levy]

In the case of individual galaxies, the dark matter and the galaxy move together. (Otherwise we wouldn't see the consistent pattern of the density of dark matter in the centre of the galaxy.)

 

There is an example where two galaxies have collided and we can see that the dark matter has become separated from the galaxies (a bit like a passenger being thrown from a car crash).

http://chandra.harvard.edu/press/06_releases/press_082106.html

 

How could it be that the dark matter moves with the galaxies, although each galaxy is moving at different direction and at different velocity?

Edited March 19, 2015 by David Levy

[pzkpfw]

Do you think dark matter is some kind of fixed background on which the rest of space sits?

[David Levy]

Do you think dark matter is some kind of fixed background on which the rest of space sits?

 

I have no idea.

Somehow we need to take a decision if the dark matter is fixed or not.

Edited March 19, 2015 by David Levy

[Mordred]

Nothing in space is static or fixed to a location. Everything moves

[David Levy]

Nothing in space is static or fixed to a location. Everything moves

 

 

Thanks

So dark matter moves, but in which direction and velocity?

Does it move in the direction of the Milky Way galaxy or Andromeda galaxy (which move in the opposite direction to each other).

Does it move in relativity slow velocity as the nearby galaxies or at ultra fast velocity as the far end galaxies?

This should be an important section of the dark matter theory. We must give answer to this issue.

Edited March 19, 2015 by David Levy

[Mordred]

Dark matter is a slow moving particle, it follows the rules of gravity just as regular matter does.

 

You also seem to misunderstand the movement of galaxies. All galaxies regardless of location move according to conservation of momentum and gravity.

 

Galaxies at the limits of our observable universe follow the same rules they don't move faster than our local regions.

 

I think where your getting confused is expansion and what is known as recessive velocity.

 

Hubbles law states the greater the distance the greater the recessive velocity.

 

This unfortunately leads to a lot of confusion.

 

Expansion is the same everywhere,

 

Roughly H=70 km/s/Mpc.

So if you were to measure two objects at 1 Mpc they will seperate 70 km/s/Mpc. Regardless of where you are in the universe.

 

Recessive velocity however depends on the seperation distance, it is the total accumulation of the above value.

 

So for example at 10 Mpc it will be 700 km/s

 

At 100 Mpc 7000 km/s. Etc.

 

[latex]v_{recessive}=H_0d[/latex]

 

However this is an apparent velocity, the galaxies gain no inertia or momentum due to expansion. The volume of space between non gravitational bound structures simply increases.

A good article covering this is the following.

 

http://www.phinds.com/balloonanalogy/: A thorough write up on the balloon analogy used to describe expansion

http://tangentspace.info/docs/horizon.pdf:Inflation and the Cosmological Horizon by Brian Powell

 

I included the balloon analogy even though the article also shows it.

 

In terms of how distance measures work in the FLRW metric I wrote a handy article.

 

I also did one on expansion and redshift.

 

http://cosmology101.wikidot.com/redshift-and-expansion

http://cosmology101.wikidot.com/universe-geometry

 

page two of the last link covers FLRW distance measures and breaks down the metrics in 2,3 and 4d which is handy to learn how the 4d works.

 

 

http://cosmology101.wikidot.com/geometry-flrw-metric/

The light cone calculator link in my signature is also a handy tool as one can use it to see how the universe expands over time

As well as graph the results

Edited March 19, 2015 by Mordred

[Strange]

So dark matter moves, but in which direction and velocity?

Does it move in the direction of the Milky Way galaxy or Andromeda galaxy (which move in the opposite direction to each other).

 

The dark matter around the Milky Way galaxy moves with the Milky Way galaxy.

The dark matter around the Andromeda galaxy moves with the Andromeda galaxy.

 

Just like all the other matter that makes up the galaxy.

[swansont]

How could it be that the dark matter moves with the galaxies, although each galaxy is moving at different direction and at different velocity?

I'm going to go out on a limb and guess "gravity". You know, the same reason the stars (etc.) that comprise the galaxy move along with it.

[imatfaal]

 

The dark matter around the Milky Way galaxy moves with the Milky Way galaxy.

The dark matter around the Andromeda galaxy moves with the Andromeda galaxy.

 

Just like all the other matter that makes up the galaxy.

 

 

When unimpeded yes just like other matter.

 

But crucially without the ability to interact and emit radiation electromagnetically the dark matter has no easy methods of slowing down. Your link earlier with the bullet cluster is an instance of this; the gas clouds interacted, got hotter and glowed, and slowed down - whereas the stars and the dark matter carried on at a pace only affected by gravity. In simple terms the gas and dust bumped into each other - but the dark matter does not slow down when it bump into things. EMR due to interaction can carry off momentum energy etc

[David Levy]

 

The dark matter around the Milky Way galaxy moves with the Milky Way galaxy.

The dark matter around the Andromeda galaxy moves with the Andromeda galaxy.

 

Just like all the other matter that makes up the galaxy.

 

 

Your simple explanation might lead to significant result.

If the dark matter is like all other matter, and if it moves with the galaxy, than it must have similar activity as all other matter. As the matter is concentrated in galaxies, then the dark matter should also be concentrated in the galaxies.

Therefore, in each galaxy there might be different concentration of dark matter. However, outside the galaxy (and even outside in the halo) the concentration of dark matter should decrease dramatically.

This might be a breakthrough understanding for dark matter.

As there is different density at different locations (in the galaxy and outside the galaxy) than the total quantity of the dark matter could be significantly lower than our expectation.

Do you agree?

Edited March 19, 2015 by David Levy

[Strange]

If the dark matter is like all other matter, and if it moves with the galaxy, than it must have similar activity as all other matter. As the matter is concentrated in galaxies, then the dark matter should also be concentrated in the galaxies.

Therefore, in each galaxy there might be different concentration of dark matter. However, outside the galaxy (and even outside in the halo) the concentration of dark matter should decrease dramatically.

 

Correct.

 

This might be a breakthrough understanding for dark matter.

 

Your understanding, maybe.

 

As there are different density at different locations (in the galaxy and outside the galaxy) than the total quantity of the dark matter could be significantly lower than our expectation.

 

The total amount of dark matter is calculated taking into account it's distribution (as is the total amount of non-dark matter).

[David Levy]

 

Correct.

 

 

Your understanding, maybe.

 

 

The total amount of dark matter is calculated taking into account it's distribution (as is the total amount of non-dark matter).

 

 

http://en.wikipedia.org/wiki/Dark_matter

It is stated:

"Much of the evidence for dark matter comes from the study of the motions of galaxies.^[25] Many of these appear to be fairly uniform, so by the virial theorem, the total kinetic energy should be half the total gravitational binding energy of the galaxies. Observationally, however, the total kinetic energy is found to be much greater: in particular, assuming the gravitational mass is due to only the visible matter of the galaxy, stars far from the center of galaxies have much higher velocities than predicted by the virial theorem. Galactic rotation curves, which illustrate the velocity of rotation versus the distance from the galactic center, show the well known phenomenology that cannot be explained by only the visible matter."

 

Therefore, the density of the dark matter in the galaxy had been set to meet the galactic rotation curve.

However, if the dark matter is moving with the galaxy, then it is accumulated in the galaxy. Hence, the density outside the galaxy could be significantly lower than the density in the galaxy.

Therefore, the total dark matter in the universe might be lower than our expectation.

Edited March 19, 2015 by David Levy

[Strange]

Therefore, the density of the dark matter in the galaxy had been set to meet the galactic rotation curve.

 

That is correct. (Also, simulations of the behaviour of dark matter confirm this.)

 

 

However, if the dark matter is moving with the galaxy, then it is accumulated in the galaxy. Hence, the density outside the galaxy could be significantly lower than the density in the galaxy.

Therefore, the total dark matter in the universe might be lower than our expectation.

 

Not if the expectations were based on there being a lower density outside the galaxy (which, as you say, was already known).

[David Levy]

Not if the expectations were based on there being a lower density outside the galaxy (which, as you say, was already known).

 

Sorry, what do you mean?

[imatfaal]

Sorry, what do you mean?

 

That cosmologists calculating the total mass of dark matter in the universe have a really good grasp of the distribution of dark matter (ie lots better than the average forum poster) and that they take into account the variations in density when they make their calculations.

 

BTW - have you ever met a research scientist? They are not the dysfunctional bellends of The Big Bang Theory - they tend to be driven and bright; they also have a tendancy to have thought through their topic more than random guys on the internet. You will not come up with an amazingly obvious insight that all the cosmologists somehow failed to notice - sorry.

[Strange]

 

Sorry, what do you mean?

 

You have stated, correctly, that the density of dark matter is greatest around and within galaxies.

 

The density of dark matter outside galaxies is therefore lower.

 

This is well known.

 

Therefore the total amount of dark matter is calculated using this information.

 

Therefore there is no conflict with expectations.

[David Levy]

 

You have stated, correctly, that the density of dark matter is greatest around and within galaxies.

 

The density of dark matter outside galaxies is therefore lower.

 

This is well known.

 

Therefore the total amount of dark matter is calculated using this information.

 

Therefore there is no conflict with expectations.

Thanks

 

I would like to get an overview how different densities had been set and what kind of evidences had been used.

Please direct me to the article which specify this subject.

[Mordred]

Those are numerous, yet tricky, start with virial theorem and the NFW profile.

 

Yes there is tons of alternative distribution models those two are the most common.

[Strange]

Thanks

 

I would like to get an overview how different densities had been set and what kind of evidences had been used.

Please direct me to the article which specify this subject.

 

https://astro.uni-bonn.de/~uklein/research/dm.html

http://web.mit.edu/redingtn/www/netadv/specr/012/node7.html

http://arxiv.org/abs/1308.1703

http://adsabs.harvard.edu/abs/2001MNRAS.323..285B

http://scholar.google.co.uk/scholar?q=distribution+of+dark+matter+in+galaxies

[David Levy]

Thanks

 

Unfortunately, I couldn't find any information about the density of the dark matter between the galaxies.

It is stated that the science doesn't know what the dark matter is and whole idea of its existence is only based on the rotation curve of spiral galaxies:

http://web.mit.edu/redingtn/www/netadv/specr/012/node7.html

"While we don't know what the dark matter (DM) is, we have a fairly reasonable idea as to how much of it there is in the Galaxy, how it is distributed, and how fast it is moving. This information comes from the rotation curve of the Milky Way, and is crucial to all the direct searches for dark matter."

However, the "fairly reasonable idea" is a direct product of simulation. So, there is no real evidence how much DM there is in the galaxy, how it is distributed and how fast it is moving.

The science is doing whatever it takes to discover some proofs for the dark matter:

http://arxiv.org/pdf/1308.1703v2.pdf

"The direct detection of dark matter (DM) is one of the most exciting and frontier pursuits of contemporary physics."

Therefore, they are improving the sensitivity of the detectors and lowering the thresholds:

"After many years of steady progress in enlarging target masses, improving detector sensitivities, and lowering energy thresholds, but concomitant lack of detections and only ever more stringent exclusion limits, the field may now at last be at the cusp of success."

 

Based on my long experience in engineering its quite clear that this action might lead to discovery of what we call: "white noise".

However, in the last years they start to get some signals:

"a number of additional experiments have in recent years reported signals that may be interpreted as DM scattering events."

 

"Finally, a recent analysis from the CDMS II collaboration of data obtained with their silicon detectors found three DM candidate events with a total expected background of 0.7 events (CDMS Collaboration et al. 2013). Taking into account the energies of the three events, the CDMS II Si data prefer a DM scattering interpretation over a known-background-only scenario at 99.81% probability, so slightly more than 3_."

 

However, the science do not except this discovery based on the following reasons:

 

"Despite these exciting developments, the case for a discovery of a DM particle is not yet closed, for two principal reasons. For one, the regions of parameter space (mass of DM particle m_ and (spin-independent) scattering cross section _SI) preferred by the tentative detections don't all agree with each other. They do generally favor a light DM particle (m_ . 10 GeV) with _SI around 1041{1040 cm2, but the published 2_ con- _dence intervals don't all overlap (for a recent summary, see e.g. Fig.4 of CDMS Collaboration et al. 2013). Secondly, the preferred parameters are nominally ruled out by the non-detections in XENON100 (Aprile et al. 2012) and the CDMS II Germanium detectors (CDMS II Collaboration

et al. 2010; Ahmed et al. 2011)."

Therefore, so far there is no real proof for the DM. Actually, all the assumption of the DM is only based on simulation:

"Numerical galaxy formation simulations can provide guidance for the expected local DM density and velocity distribution, and their spatial and halo-to-halo variance."

 

Therefore, when the science claims: "we have a fairly reasonable idea as to how much of it there is in the Galaxy, how it is distributed, and how fast it is moving." They mean that it is based on simulation.

Hence, it might be a misleading statement.

The science must highlight that this information is purly based on simulation. This isn't evidence.

Therefore, the whole idea of dark mass density and velocity distribution is not confirmed yet by any real evidence.

Hence, the science can't claim that the dark matter isn't evenly distributed in the universe. They could claim that based on their simulation they believe that…

However, simulation and believe aren't evidences. Therefore, there is good chance that if there is a dark matter, it's distribution might be evenly in the Universe. Hence, it might meet Isaac Newton shell theorem.

 

If this is correct, then outcome is quite clear.

Edited March 21, 2015 by David Levy

[Mordred]

Not quite your jumping ahead again lol here the figures you want for the mean mass density of DM is here

 

 

http://arxiv.org/pdf/astro-ph/0406095v2.pdf"The Cosmic energy inventory"

 

now ask yourself how science can come up with all these extensive figures?

I should actually link you to the Planck collaboration results. However wiki has the main ones posted.

 

http://en.m.wikipedia.org/wiki/Lambda-CDM_model

 

you want the physical dark matter density

[David Levy]

 

Not quite your jumping ahead again lol here the figures you want for the mean mass density of DM is here

 

 

http://arxiv.org/pdf/astro-ph/0406095v2.pdf"The Cosmic energy inventory"

 

now ask yourself how science can come up with all these extensive figures?

I should actually link you to the Planck collaboration results. However wiki has the main ones posted.

 

http://en.m.wikipedia.org/wiki/Lambda-CDM_model

 

you want the physical dark matter density

So, what should we understand from the following statement:

http://arxiv.org/pdf/astro-ph/0406095v2.pdf

"The largest entries, for dark matter and the cosmological constant, or dark energy, are well constrained within a cosmological theory that is reasonably well tested, but the physical natures of these entries remain quite hypothetical.

We understand the physical natures of magnetic fields and cosmic rays, but the theories of the evolution of these components, and the estimates of their contributions to the present energy inventory, are quite uncertain. The situation for most of the other entries tends to be between these extremes: the physical natures of the entries are adequately characterized, for the most part, and our estimates of their energy densities, while generally not very precise, seem to be meaningfully constrained by the observations."

 

Actually, why don't you reply to the extreme conclusions which I have presented?

Do you agree or disagree?

Is it correct that the science had used a simulation to estimate all the ideas about the dark matter?

Why it is not clearly informed that all the "fairly reasonable idea" about the dark matter is based on simulation?

What is the chance that the simulation isn't fully correlated to the real universe (or galaxy)?.

What is the chance that there are Inaccuracies in some assumptions of this simulation?

Edited March 21, 2015 by David Levy

[Strange]

Thanks

 

Unfortunately, I couldn't find any information about the density of the dark matter between the galaxies.

It is stated that the science doesn't know what the dark matter is and whole idea of its existence is only based on the rotation curve of spiral galaxies:

http://web.mit.edu/redingtn/www/netadv/specr/012/node7.html

"While we don't know what the dark matter (DM) is, we have a fairly reasonable idea as to how much of it there is in the Galaxy, how it is distributed, and how fast it is moving. This information comes from the rotation curve of the Milky Way, and is crucial to all the direct searches for dark matter."

 

You don't seem to read things very carefully. Perhaps this is why you are having a hard time grasping the basics.

 

That quote is about the amount of dark matter in the galaxy based on rotation curves in the galaxy.

 

The amount of dark matter in galaxy clusters is based on the orbits of galaxies.

 

The amount of dark matter in intergalactic space is based on gravitational lensing.

 

The total amount of dark matter is based on analysis of the CMB.

Why it is not clearly informed that all the "fairly reasonable idea" about the dark matter is based on simulation?

 

Because it is not true.

 

 

What is the chance that the simulation isn't fully correlated to the real universe (or galaxy). What is the chance that there are Inaccuracies in some assumptions of this simulation?

 

The simulations are tested against observation and produce the right results.