Evidence of Dark Matter within the Solar System?

[greswd]

And within the near-galaxy too. If we can find some in close proximity, there's tremendous potential for research.


I found these two conflicting articles: (both a few months apart)

Survey finds no hint of dark matter near Solar System

Astronomers Detect Dark Matter Near The Sun


So what do you guys think? Is there a possibility of directly studying dark matter in the near-future?

 

[ZapperZ]

So what do you guys think? Is there a possibility of directly studying dark matter in the near-future?

Er... we are studying dark matter NOW! All the current possible candidates are being looked for!

Zz.

 

[greswd]

Er... we are studying dark matter NOW! All the current possible candidates are being looked for!

Zz.

Hmm...I mean directly obtaining a sample from some location in our solar system and studying it. Possible?

 

[DennisN]

As an example, the AMS-02 experiment is running at the moment, and the first results are expected this month (hopefully). EDIT: this was not a reply to post #3.

 

[ZapperZ]

Hmm...I mean directly obtaining a sample from some location in our solar system and studying it. Possible?

Why are you putting in such restriction in studying this dark matter? Do we HAVE to go to some location in our solar system to study such a thing if we can find it in our underground detectors or even in our particle colliders?

Zz.

 

[Mordred]

There are several projects currently underway to study dark matter. As pointed out. The results from the AMS are due for release this month. The other project is detectors far underground. Why underground has to do with how weakly interactive dark matter is considered to be. Similar in nature to neutrinos.
Though dark matter is not considered to be a neutrino.

LHC is also a possibility in creating dark matter thougj they have been unable to do so yet. Might be due to needing higher energy levels. However I'm not that familiar with that aspect to say for sure.

 

[Drakkith]

Hmm...I mean directly obtaining a sample from some location in our solar system and studying it. Possible?

Why do you believe this is possible? Perhaps our belief that dark matter doesn't interact through any other forces other than gravity is correct. This would mean that we couldn't obtain a sample, as it would pass through everything.

 

[Mordred]

Why do you believe this is possible? Perhaps our belief that dark matter doesn't interact through any other forces other than gravity is correct. This would mean that we couldn't obtain a sample, as it would pass through everything.

Just a side note. This is one aspect that's always confused me.
The statement dark matter only interacts via gravity leads me to ask how dark matter has mass. The Higgs field provides mass for quarks. So only accounts for a small percentage of mass. The strong nuclear force accounts for the remaining mass in baryonic particles. If dark matter does not interact or weakly interacts with the strong force. How do we account for its mass? Thats one
question I've had for awhile but
hadn't gotten around to asking.
However I also have no interst in stealing this thread so if any answers are provided keep it short I' ll ask related questions on another thread

 

[Jonathan Scott]

I found these two conflicting articles: (both a few months apart)

Survey finds no hint of dark matter near Solar System

Astronomers Detect Dark Matter Near The Sun

So what do you guys think? Is there a possibility of directly studying dark matter in the near-future?

As far as I can see, both of those are not directly about dark matter, but rather about measuring whether the motion of local stars within the Milky Way galaxy seems to be accounted for by the gravitational effect of ordinary matter (according to GR, probably using Newtonian gravity as a reasonable approximation) and if not trying to estimate what distribution of "dark matter" would be needed to account for the motion.

This tells us very little about the nature of the "dark matter" involved, and does not rule out alternative explanations such as modified gravity theories.

 

[ZapperZ]

Just a side note. This is one aspect that's always confused me.
The statement dark matter only interacts via gravity leads me to ask how dark matter has mass. The Higgs field provides mass for quarks. So only accounts for a small percentage of mass.

This is not correct. The Higgs field that we know of so far accounts for the mass in the leptonic sector. In fact, it accounts for the mass of the W and Z bosons.

The strong nuclear force accounts for the remaining mass in baryonic particles. If dark matter does not interact or weakly interacts with the strong force. How do we account for its mass? Thats one
question I've had for awhile but
hadn't gotten around to asking.
However I also have no interst in stealing this thread so if any answers are provided keep it short I' ll ask related questions on another thread

There are numerous models for the type of dark matter. Whether it will interact with the Higgs field or not is what needs to be tested. Whether is it WIMP, or sterile neutrinos, or some other species all will have different types and strength of interactions via the different mechanisms.

Zz.

 

[Mordred]

Thanks Zapper both for the clarification on the Higgs interaction and the explanation on dark matter mass. Glad to see that it is one of the questions yet to be answered. I can see from your explanation that it would require more information on dark matter identity that makes sense. Thanks for pointing that out.

 

[Chalnoth]

Why do you believe this is possible? Perhaps our belief that dark matter doesn't interact through any other forces other than gravity is correct. This would mean that we couldn't obtain a sample, as it would pass through everything.

I would put a lot more than a "perhaps" on this. CMB observations guarantee that dark matter cannot have an electric charge. And without an electric charge, it most definitely passes straight through normal matter all the time. Rather like neutrinos.

 

[ZapperZ]

I would put a lot more than a "perhaps" on this. CMB observations guarantee that dark matter cannot have an electric charge. And without an electric charge, it most definitely passes straight through normal matter all the time. Rather like neutrinos.

Actually, just so those who are not familiar with the subject matter (no pun intended) do not get the wrong information, the lack of charge is not a necessary and sufficient criteria for something to "pass straight through normal matter all the time". A neutron, for example, is one of the most biologically ionizing particle and also causes damage to solids. So it interacts extremely strongly with matter. Yet it is also electrical neutral!

So lack of charge is not the only criteria here for something such as a neutrino (and possibly dark matter candidates) to have such weak interactions (no pun intended here either).

Zz.

 

[Chalnoth]

Actually, just so those who are not familiar with the subject matter (no pun intended) do not get the wrong information, the lack of charge is not a necessary and sufficient criteria for something to "pass straight through normal matter all the time". A neutron, for example, is one of the most biologically ionizing particle and also causes damage to solids. So it interacts extremely strongly with matter. Yet it is also electrical neutral!

So lack of charge is not the only criteria here for something such as a neutrino (and possibly dark matter candidates) to have such weak interactions (no pun intended here either).

Zz.

Actually, neutrons do pass through matter pretty easily as well. You can't actually trap neutrons, except by joining them to atomic nuclei.

That said, if dark matter interacted through the strong nuclear force, we would have detected it a long time ago.

 

[ZapperZ]

Actually, neutrons do pass through matter pretty easily as well. You can't actually trap neutrons, except by joining them to atomic nuclei.

If that is true, the shielding we have at neutron sources are useless, neutrons would not be considered as ionizing radiation, the walls around nuclear reactors would not suffer neutron damage as easily, and thermalizing neutrons in water for fission reaction would not happen.

 

[Drakkith]

I look at a neutron kind of like I look like a neutral atom. Neither have a net electric charge, but both will interact with EM fields. It's not that Dark matter is just uncharged, it's that it doesn't interact through the EM force at all.

 

[ZapperZ]

I look at a neutron kind of like I look like a neutral atom. Neither have a net electric charge, but both will interact with EM fields. It's not that Dark matter is just uncharged, it's that it doesn't interact through the EM force at all.

You seem to have completely ignored the evidence I presented on neutron interaction with stuff. Is there a reason why?

Please note my original objection, that your characterization that it doesn't have any charge is the reason why it doesn't interact with matter. This is false because a neutron interacts quite well with matter. You would not want to stand in front of a neutron beam the way you would stand in front of a neutrino beam!

We are not debating the mechanism of how neutrons interact with matter. We are debating the false and misleading claim that was made regarding neutrons and their interaction with matter.

Zz.

 

[cepheid]

You seem to have completely ignored the evidence I presented on neutron interaction with stuff. Is there a reason why?

Please note my original objection, that your characterization that it doesn't have any charge is the reason why it doesn't interact with matter. This is false because a neutron interacts quite well with matter. You would not want to stand in front of a neutron beam the way you would stand in front of a neutrino beam!

We are not debating the mechanism of how neutrons interact with matter. We are debating the false and misleading claim that was made regarding neutrons and their interaction with matter.

Zz.

It seems to me that Drakkith was totally agreeing with you in the post that you are responding to here, saying that having no electric charge is not a sufficient condition for not being able to interact with ordinary matter.

 

[ZapperZ]

It seems to me that Drakkith was totally agreeing with you in the post that you are responding to here, saying that having no electric charge is not a sufficient condition for not being able to interact with ordinary matter.

Ooops.. you're right. I thought I was responding to Chalnoth.

My apologies, Drakkith.

Zz.

 

[Drakkith]

Ooops.. you're right. I thought I was responding to Chalnoth.

My apologies, Drakkith.

Zz.

It's cool. I'll just go borrow Bannenstein, Evo's legendary Banhammer. I'll be back in a few...

 

[Chalnoth]

If that is true, the shielding we have at neutron sources are useless, neutrons would not be considered as ionizing radiation, the walls around nuclear reactors would not suffer neutron damage as easily, and thermalizing neutrons in water for fission reaction would not happen.

Neutron shielding generally works by surrounding the source by lots of light nuclei that, when the neutrons bounce of said nuclei, will tend to slow down. Water is perfect for this, because it has a lot of hydrogen atoms (heavier nuclei aren't so good for this, because even though they are bigger, the neutrons don't slow down much bouncing off of a heavy nucleus).

But the fact remains that neutrons penetrate quite deeply into normal matter, because they completely ignore the electrons, and atomic nuclei are really, really tiny. For the same energy, a neutron will penetrate normal matter far more deeply than will a proton, specifically because of the lack of electric charge.

Of course, dark matter can't have a strong force charge either. If it did, then it would bounce off of atomic nuclei very readily, and we would have detected it long ago. And that means that it has more in common with neutrinos than neutrons.

As far as I'm aware, whether or not dark matter interacts with the weak nuclear force is still up in the air (I believe most dark matter models interact with the weak nuclear force, but not all). But as long as it only interacts with the weak force and gravity, we have a hope of eventually detecting dark matter particles. If it only interacts through gravity, then I'm not sure we have any hope of ever detecting the nature of dark matter.

 

[ZapperZ]

Neutron shielding generally works by surrounding the source by lots of light nuclei that, when the neutrons bounce of said nuclei, will tend to slow down. Water is perfect for this, because it has a lot of hydrogen atoms (heavier nuclei aren't so good for this, because even though they are bigger, the neutrons don't slow down much bouncing off of a heavy nucleus).

What you had just described is exactly neutron interacting with matter. Case closed.

Zz.

 

[Chalnoth]

What you had just described is exactly neutron interacting with matter. Case closed.

Zz.

*sigh*

Yes. I never said that neutrons don't interact with other matter. But they do interact much more weakly than particles with electric charge, and will pass straight through most matter with ease (meaning that neutron shielding has to be quite thick).

 

[ZapperZ]

*sigh*

Yes. I never said that neutrons don't interact with other matter. But they do interact much more weakly than particles with electric charge, and will pass straight through most matter with ease (meaning that neutron shielding has to be quite thick).

Read this again and remind yourself what I was trying to correct.

https://www.physicsforums.com/showpost.php?p=4302201&postcount=13

Zz.

 

[Drakkith]

So, when a neutron "bounces" off a nucleus, what force causes this?

 

[Chalnoth]

So, when a neutron "bounces" off a nucleus, what force causes this?

The strong nuclear force, I believe. Though perhaps the magnetic moment and the fact that neutrons are made up of charged particles also allows the electromagnetic force to play some role.

 

[ZapperZ]

The strong nuclear force, I believe. Though perhaps the magnetic moment and the fact that neutrons are made up of charged particles also allows the electromagnetic force to play some role.

Some role?

Look up the neutron scattering experiments that are used to study materials. The strong force plays zero role in such interactions.

Zz.

 

[Chalnoth]

Some role?

Look up the neutron scattering experiments that are used to study materials. The strong force plays zero role in such interactions.

Zz.

Ahh, sorry, guess I was mistaken on that. The magnetic dipole of the neutron is the primary factor there. But still, that's because the neutron itself is made out of charged particles. The dark matter particle can't be so composed, or else we would have detected it by now.

 

[ZapperZ]

Ahh, sorry, guess I was mistaken on that. The magnetic dipole of the neutron is the primary factor there. But still, that's because the neutron itself is made out of charged particles. The dark matter particle can't be so composed, or else we would have detected it by now.

I have no idea why you continue to want to teach me about the properties of dark matter. You also seem to not have any realization on what it means to have a necessary and sufficient criteria.

If you had looked at the post that I mentioned earlier, note that you were implying that not having charge is a necessary AND sufficient criteria for something to pass through matter easily, as easily as neutrinos. Why? Because that's all you stated! This is patently false.

While being neutral is a necessary criteria, it is NOT A SUFFICIENT CRITERIA! This is what is different between a neutral neutrino and a neutral neutron, where one has a mean free path of light years, while the other can be a few centimeters! I am puzzled why you don't get this. Is dark matter neutral? Sure, if not we would have seen EM interaction signatures. However, just as with the neutrino, that is NOT the only characteristics that it should have, and that is NOT the characteristics that allows it to pass through matter easily.

Is this finally getting through here? Because I'm tired of explaining something that I thought should be obvious to you.

Zz.

 

[Chalnoth]

I have no idea why you continue to want to teach me about the properties of dark matter. You also seem to not have any realization on what it means to have a necessary and sufficient criteria.

Honestly, you're just getting bent out of shape out of me simply not explaining every little detail. Yes, neutrons most definitely pass through matter far more easily than particles with net charge. No, they don't pass through matter as easily as neutrinos because they have a magnetic moment. They also sometimes bind to nuclei (due to the strong force). Obviously dark matter can't have any of these things.

You're confusing pedantry with science. Get a grip.

 

[ImaLooser]

The idea I liked about detecting dark matter was to look for effects inside neutron stars. The gravity of the star would attract the dark matter and there are a great many neutrons there, so if the dark matter interacts weakly it should have some effect, perhaps on the viscosity.

The trouble is that this is at best a second-order effect. We would have to understand neutron star physics so precisely that deviations of the viscosity from the model would be significant, and we are a long way from that.