Where is Dark Matter?

[swansont]

You're not hiring particle phenomenologists, are you?

 

Not so much. Unless by particle phenomenologist you mean atomic physicist, with a background in laser cooling & trapping, femtosecond lasers and optical frequency combs.

[Severian]

For the dark matter doubters, you might like to explain how your favourite model can explain the Bullet Cluster better than Dark Matter.

 

 

Radiating matter is in red; gravitating matter is in blue.

[pioneer]

One can explain this with chemical affects. For example, the red spot on Jupiter shows that chemicals can and do segregate based on chemical selectivity. For example, I can take CH4 (methane) and NH3 (ammonia) in equal proprotions and then pass these over water. The Methane will enrich in the gas stream and the ammonia will preferentially dissolve into the water. If we add alcohol to the water the balance will shift.

 

Looking at that photo if we assume that the original cloud was blue and that central star was generating a new chemical that is different, than the blue reaction will change with the result being a color change. Based on the change from blue to red, if phenothalene was present it could be a simple pH change (just kidding) Or to get more complicated with the blue hotter, the new added chemical is sort of an inhibitor that lowers the reaction rate closer to the center of the pic resulting in the red emission. If we just focus on common atoms this could look like dark matter.

 

Another simple explanation is the central stars are evolving their output. Say if begins with H and C and then goes to H and N, the environment of the H gets different, such that the H emission reflects this change.

[insane_alien]

no you can't describe dark matter with chemical effects.

 

we discussed this here http://www.scienceforums.net/forum/showthread.php?t=28105&highlight=darkmatter

 

and this was the thread i was reffering to in the PM. could you answer the points raised there?

 

the origional cloud is RED as said. the blue stuff is the inferred mass distribution. this is currently the only way we can see darkmatter by observing the gravitational effects and calculating.

 

stars don't vary very much or very quickly in their chemical out put btw.

[Severian]

That cloud is not a star. It is two colliding clusters of galaxies. This is much much bigger scale.

[vincent]

Is it [dark matter]... in...my room?

 

Where do you live?

[Spyman]

Is it [dark matter]... in...my room? [/quote']Where do you live?

Some place that needs enlightenment...

[vincent]

Some place that needs enlightenment...

 

[GrandMasterK]

So basically, nobody knows?

[insane_alien]

yes there is very likely dark matter in your room. it just doesn't interact with anthing there in any noticable way.

[lakmilis]

yes there is very likely dark matter in your room. it just doesn't interact with anthing there in any noticable way.

 

wow, very likely....phew, guess you know more than most humans on this planet...

 

hell, since its so very likely, could you give me soem experimental data to back up such a 'well-recognised' claim?

[vincent]

...there is very likely dark matter in your room.

 

[Spyman]

So basically, nobody knows?

YES, and thats the reason to why it is called DARK Matter.

"Weve known that it exists for more than 25 years," says astronomer Virginia Trimble of the University of California Irvine. "But we dont know what the hell it is."

 

 

AFAIK, Dark Matter is not "stitched" to space, it moves around and interacts through gravity.

(Presumably Black Holes would consume Dark Matter too.)

 

 

Here is a popular science article for you: (Albeit somewhat old, from 2002)

Dark Matter: Hidden Mass Confounds Science, Inspires Revolutionary Theories

 

If you could see dark matter, say astronomers, most galaxies, including our own Milky Way, would appear 10 times larger than they do in telescopes. All the familiar inhabitants of the cosmos stars, galaxies, planets, and clouds of gas and dust are just a small fraction of whats out there.

 

And yet, for something so ubiquitous, dark matter has proved incredibly elusive. Here on Earth, dark matter could be passing by us or perhaps, through us but we dont notice. In part thats because dark matter rarely, if ever, interacts with normal matter. Its also far more widely scattered than normal matter. "Compared to anything that were aware of on Earth," says Trimble, dark matter is "incredibly diffuse."

http://www.space.com/scienceastronomy/astronomy/cosmic_darkmatt_020108-1.html

[Severian]

wow, very likely....phew, guess you know more than most humans on this planet...

 

hell, since its so very likely, could you give me soem experimental data to back up such a 'well-recognised' claim?

 

Do try not to be such a dick. We know there is plenty of Dark Matter in the universe, and it will cluster around ordinary matter, so it is 'very likely' that there is some in your room. If you want to claim that there is not then you will have to explain why it is not there, since its presence would be the natural assumption.

[insane_alien]

wow, very likely....phew, guess you know more than most humans on this planet...

 

hell, since its so very likely, could you give me soem experimental data to back up such a 'well-recognised' claim?

 

as severian said, it is a logical conclusion. DM interacts via gravity, it will be attracted to gravity sources. seeing as we are sitting in one gravity well inside an even bigger gravity well i think it would be safe to assume that there is some floating about. we just can't detect it.

[Fred56]

I grabbed someone else's post in a shameless ripoff (its about gravitomagnetics):

 

...let's clarify what the effect was. This was an experiment by Tajmar and deMattos looking for the gravitomagnetic analog of the London magnetic moment of a rotating superconductor. This is an effect of superconductors, ...Not all superconductors exhibit this behavior.

 

..to clarify ...what "gravitomagnetism" is. This is the gravitational analog of magnetic effects from electromagnetism. Electric charges exert forces directly on each other, called the electric or coulomb force, and these lead to a notion of an electric field. Magnetic forces are those [which] moving charges exert on each other. The forces are *velocity dependent*, and another way to express it is a force between electric currents.

 

Roughly, Newtonian gravity is the analog of the electric force, with mass playing the role of charge. ...Newtonian gravity had the same inverse square form as Coulombs law, save for a minus sign ("like" masses attract rather than repel, and there is no negative minus -- this is actually a huge difference when you get deeper into it, however).

 

So, one might wonder if there is [a] gravitational analog of magnetism, a force between moving masses, or mass currents.

 

There is, but it is extremely weak, normally. The force constant is proportional to G/c^2, where G is Newton's gravitational constant and c is the speed of light. That is a very small value.

 

Now, what Tajmar and deMattos discovered (and painstakingly verified, since it was such an amazing effect) was the gravitomagnetic field of certain rotating superconductors was much, much higher by orders of magnitude than this. What is interesting about this is it['s] direct evidence of some "quantum behavior" modifying normal gravitational behavior.

 

...Gravitomagnestism is insignificant on the galactic scale because it is so weak... -- the Milky Way isn't a giant superconductor. Now, gravitomagnetism does become important in the near field (close by) to very dense, rapidly rotating objects like neutron stars and black holes. But on the larger scale, it is insignificant. And this can be confirmed because if the Milky Way had a significant gravitomagnetic field, one that could produce forces on the order of the regular g (sometimes called "gravitoelectric" field by the Maxwell analogy), it would cause complex precessional behavior of the orbits and spins of the bodies in the solar system. The behavior is very complex about local detection, but this additional motion would [be] detectable against the stellar background.

 

Gravitomagnetism is actually merely an approximate, linear, weak field limit to the more complex full picture of General Relativity that is called "frame dragging". ...gravitomagnetism is an aspect of frame dragging. You may have heard of the "Gravity Probe B" experiment. That was a rather amazing feat of experimental engineering designed to measure the extremely weak frame dragging, gravitomagnetic effects, of the rotating earth.

..This... [is a] pretty good milestone, ...direct, "local observer" confirmation of frame dragging.

 

Now, gravitomagnetism does become important in the near field (close by) to very dense, rapidly rotating objects like neutron stars and black holes. And if this also turns out to be many orders of magnitude higher than expected (if the "matter" inside a black hole turns out to be the superfluid I've heard suggested would that make them superconductors?) would that increased figure need factoring into the mass calculations of the Universe when deciding if we need Dark Matter.

 

Well, "why we need dark matter" is beyond anything I'm qualified to speak to. But, the "exotic" effects of strong gravity are basically local phenomena that are too weak on the large scale.

 

Matter "inside" a black hole is not something physics can say anything about. Basically it is "gone" from our external universe and has just left its gravity behind.

 

...you've probably heard [about] superfluid/superconductor (and these are related) in *neutron stars*. I have seen speculation about how this "Tajmar effect" might play out in neutron stars. Far beyond my knowledge, but some are thinking about it. Now, is there any evidence of neutron stars we know about having this effect? ...

 

But in any event, these will be local. It might make for some very interesting, very wild stuff going on there, but I don't think there's anything there on the large scale.

-publius@bautforum.com 22-March-2007

[thedarkshade]

As far as I can understand it, Dark Matter is just like a gum that acts between all substances in the universe, and it makes it impossible for them to get away form each other (stop galaxies from running away form each other). I was thinking if I could look at it this way and I got a thought! If dark energy starts decreasing that means that dark matter will start increasing pulling everything closer to everything, until it gets to a state were density will be infinite and volume 0, that means the state before Big Bang. Possible???!!!

[fripro]

For the dark matter doubters, you might like to explain how your favourite model can explain the Bullet Cluster better than Dark Matter.

 

 

Radiating matter is in red; gravitating matter is in blue.

http://vmsstreamer1.fnal.gov/VMS/Samples/Cerenkov.ram

 

I guess I lost my way, however if my coment appears twice that is what happen.

 

With respect to the bullet photo above, could the blue light be Cerenkov Radiation?

 

To understand Cherenkov log on to: http://vmsstreamer1.fnal.gov/VMS/Samples/Cerenkov.ram

 

FRIPRO

[Klaynos]

http://vmsstreamer1.fnal.gov/VMS/Samples/Cerenkov.ram

 

I guess I lost my way, however if my coment appears twice that is what happen.

 

With respect to the bullet photo above, could the blue light be Cerenkov Radiation?

 

To understand Cherenkov log on to: http://vmsstreamer1.fnal.gov/VMS/Samples/Cerenkov.ram

 

FRIPRO

 

It's a false colour image I believe.

[insane_alien]

yeah, the blue part is where computer models suggest there should be clumps of darkmatter IIRC

[fripro]

I have seen this photo before from NASA's Hubble space telescope, and if it is the true color I would address it as a collision of two massive objects, both moving at near the speed of UV light in the dark matter (you have been refering to) to a collision.

 

This would cause the resultant residue to move in the dark matter at velocities greater than the velocity of light in that dark matter.

 

Thus the blue light. This light (or a form of it) can be seen in any atmosphere where a mass velocity exceeds the velocity of light in that matter.

 

It can also be explained as a cone of radiation similar to the sharp sound one hears in the earth's atmosphere when a airplane exceeds the sound barrier.

 

This is a form of and example of Chrenkov's light.

[Pete]

If you can't do calculations, then you can't make predictions. And if you can't make predictions, you are not doing science - just point

I see no reason to assume that's true in all areas of science in all situations. Some areas of science are non-mathematical in its very nature. There may be certain experiments which are analyzed with statistics but that is for verification purposes and not for predictions.

 

Pete

[Klaynos]

I see no reason to assume that's true in all areas of science in all situations. Some areas of science are non-mathematical in its very nature. There may be certain experiments which are analyzed with statistics but that is for verification purposes and not for predictions.

 

Pete

 

Some areas of science, yes, some areas of physics, no. Physics is by it's very nature mathematical.

[Pete]

YES, and thats the reason to why it is called DARK Matter.

Its called dark matter because it isn't luminous. It is detectable through its gravitational effects.

Some areas of science, yes, some areas of physics, no. Physics is by it's very nature mathematical.

Then it would be better in the future to say "physics" rather than "science" when it is physics that you are talking about.

Is it supposed to be in empty space or is it in clumps everywhere including my room?

Until we can determine what all forms of dark energy are it cannot be said where they are. Dark matter might consist of elementary exotic particles or it may consist of objects like black holes, cold stars, large gas giants, brown dwarfs etc.

Can anything be said about this stuff other then it generates gravity? For instance, how much could be clumped together into how small a space

Not yet.

and would a light matter object be able to pass through it?

Unknown as of yet.

When I caught a few minutes of a show on TV they were talking about how dark matter is just kinda stitched into the universe. If that's so, then it should only move as the universe expands. Dark matter is supposed to be the reason the galaxies are being held together in the first place so shouldn't a galaxy's location be dictated on on the concentration of dark matter?

The existance of galaxies doesn't depend on dark matter. It is the rotation curves which indicates its existance. The curves show that there is more matter there than can be accounted for my stars.

 

Pete

Edited July 11, 2008 by Pete
multiple post merged