# World's most sensitive dark matter detector set up

Discussion in 'Physics & Math' started by arauca, Jul 15, 2012.

1. ### araucaBannedBanned

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How do you detect something you do.'t know what it is ?
Apparently it dies not Emmit or absorb any wavelength .
Can you collect it into some container and observe some physical or chemical property ?
Anybody have some opinion , please.

3. ### AlexGLike nailing Jello to a treeValued Senior Member

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You detect it by it's effects.

Gravity.

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7. ### araucaBannedBanned

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Very impressive site I was at the mine 12 years ago, they used bacteria to decompose Cyanide in Gold recovery.

8. ### AlphaNumericFully ionizedModerator

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Dark matter affects things via gravity, hence why we have dark matter evidence via galaxy rotation curves, the CMB variations and the Bullet Cluster. If, as many models think, it also interacts via the weak force then it would be invisible to telescopes but would be detectable by the same telescopes we use to detect neutrinos, because neutrinos only interact via gravity and the weak force. For a long time people thought dark matter was neutrinos, till it was ruled out by arguments I can't remember right now. So the construction of the IceCube neutrino telescope at the South Pole will provide information on the centre of the Sun (since neutrinos formed there stream out without being hindered by the Sun's matter), supernova (which dump a significant fraction of their energy into neutrino heating), neutrino mixing and perhaps dark matter. Personally I think it's one of those experiments, up there with CERN, which sound so crazy when you hear it described it sounds like science fiction. A cubic kilometre of ice is used to observe the centre of the Sun!

9. ### chingluValued Senior Member

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I must confess.

I am afraid. Since dark matter is everywhere, I am concerned I will run into it and break bones or something.

I must be smart, because as of yet, dark matter is everywhere, but I have yet to have it rip me apart. I must be dodging it by magic or something.

10. ### AlphaNumericFully ionizedModerator

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Then you obviously don't know anything about dark matter. As I just said, as you quoted me saying, dark matter only interacts via gravity and perhaps the weak force. Neutrinos interact only via gravity and the weak force and trillions of them as currently passing through your body as you read this sentence. Things like walls or tables or chairs only feel solid to us because their interact via electromagnetism with our bodies. If something doesn't interact via electromagnetism it lacks any 'substance'.

But good job on showing you haven't learnt a damn thing about dark matter but you're willing to act like a condescending muppet about it. Just like every other thing you complain about.

11. ### chingluValued Senior Member

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Why is dark matter not here and since it is everywhere else?

And, if it is here, why do I not bump into it since it represents 90% of the matter of the universe?

12. ### AlexGLike nailing Jello to a treeValued Senior Member

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Do you read the posts you respond to? :wallbang:

13. ### AlphaNumericFully ionizedModerator

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I cannot tell if you're being deliberately obtuse or you're just plain thick. You quoted me explaining why you're mistaken and then you go and repeat precisely the same mistake. If you attempt to continue with this line of trolling where you attempt to make smart arse comments only to demonstrate your wilful ignorance then you'll be getting a holiday. Stick to the pseudo forum where you belong.

14. ### chingluValued Senior Member

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You are claiming where we are, there is no dark matter and hence we have the correct acceleration due to gravity.

Is that correct?

If not, we only have our local value.

Then, we cannot know the correct value unless we find a place without dark matter. Do you have said place?

This is simple logic.

Now, let's continue the logic.

Since it would be absurd to claim there is no local dark matter, then the question remains, why do we not interact with its mass?

You are then left in two positions.

1) There is no local dark matter, which you must prove it is not here and everywhere else.
2) There is local dark matter but it does not interact with light and it has no mass to interact with matter. So, it stimulates gravity but has no mass.

Do you have any other possibilities?

15. ### AlexGLike nailing Jello to a treeValued Senior Member

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chinglu just doesn't pay any attention to answers.

This should be moved to the cesspool.

16. ### AlphaNumericFully ionizedModerator

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As usual you completely fail to understand what you've been told. This isn't even something a layperson might struggle with (as might be the case with relativity or countability), it's very simple. Dark matter doesn't interact electromagnetically with anything. Therefore it will pass through you, just like neutrinos pass through you. There are more neutrinos in the room with you right now than there are protons and electrons. You don't notice any of the neutrinos because only, literally, one or two are interacting with the trillions of trillions of particles which make up your body. Dark matter, if it exists, is in the room with you right now and it's being as bad an interacter as neutrinos.

No, that isn't true.

Yes and you've failed to understand it despite being told twice, now three times.

Because it doesn't interact with photons! Neutrinos don't interact with you, neither does dark matter. This is why both of them are so hard to do experiments with! Neutrino telescopes using billions of tons of material detect less than 10 neutrino interactions a year.

Yes, the properties which the mainstream thinks dark matter has!! You've been told twice and then you make up 2 possibilities, ignoring the third possibility I JUST TOLD YOU. This isn't the first time you've tried this method of 'discussion'.

This is your last warning. There's no ambiguity or complex stuff here, it's simple and even a layperson can understand it. If you continue with this trolling behaviour you're getting a holiday. You have used up all your chances.

17. ### chingluValued Senior Member

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I am sorry AN, I am not seeing this.

Why are you claiming that dark matter does not interact electromagnetically with normal matter yet it simulates gravity?

As you must know, mass and gravity stimulation are related.

Why do you get so angry when issues are put forward to you?

18. ### brucepValued Senior Member

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It's called dark matter because if it interacts with matter electromagnetically at all it would interact as weakly as your brain does with logic. Actually I should have said goodbye.

Last edited: Jul 22, 2012
19. ### AlphaNumericFully ionizedModerator

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Because that's what we observe. It has gravitational effects, altering galaxy rotations or the Bullet cluster, and yet it doesn't absorb or emit photons, unlike normal interstellar dust.

An object's mass has nothing to do with it's electromagnetic interaction. The Z bosons has a mass of 90GeV but it doesn't interact with photons.

Firstly it isn't an issue, it's you not understanding something. And secondly, you have a regular tactic of posting "Here is a contradiction in your claims. I've proven it contradictory! Submit to my proof!" attitudes and in every case, including this one, you've been wrong and are just showing you haven't bothered to look anything up.

An object can have lots of mass but if it doesn't interact with normal matter then it can pass through normal matter easily. Normal matter, such as atoms and molecules, is almost entirely empty space. The only reason you can't walk through walls is because of electromagnetic interactions between the atoms in your body and the atoms in the bricks making up a wall. If you have 1 kilogram of neutrinos then it'll produce the same gravitational effects as 1 kilogram of normal matter like bricks. But unlike a brick you can fire the 1 kilogram of neutrinos at yourself and it'll pass through you without you noticing it. Just like there's trillions of neutrinos passing through you right now.

You obviously haven't bothered to find out what dark matter actually involves, you've just reached some ignorant conclusion that everyone else must be wrong since otherwise you don't understand something. It's precisely the same attitude you have when talking about relativity or Cantor. This just illustrates the lack of honest discussion you provide (or rather don't provide). If you haven't bothered to even do a simple Wiki or Google about dark matter to find out something a child can understand it illustrates how little effort you put into understanding something before denouncing it. Of course it was obvious before, when you've talked about relativity or Cantor, but now you've illustrated it for everyone.

20. ### chingluValued Senior Member

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OK, a neutron has no electrostatic interactions with the proton and electron.

But, it does interact with the strong nuclear force.

So, I think you left this off.

But, that's fine.
So, you have this particle that does not either reflect nor absorb light correct?

Clearly it does not reflect it since we would see it. If light operated on this particle, then we would detect it.

Further, it must have a small mass. Otherwise, it has no mass and stimulates gravity, but that would be a problem for GR.

If it has some large mass, it would knock out electrons and maybe protons, which we would detect.

On the other hand, if these particles have a small mass, then there must be many of them since 70=o0% of the universe is made up of them.

However, even at a small mass with so many, this would represent instability to the electron which means atoms would naturally be unstable, which they are not.

Do you have any corrections to the above?

21. ### araucaBannedBanned

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Alpha Numeric
You obviously haven't bothered to find out what dark matter actually involves, you've just reached some ignorant conclusion that everyone else must be wrong since otherwise you don't understand something. It's precisely the same attitude you have when talking about relativity or Cantor. This just illustrates the lack of honest discussion you provide (or rather don't provide). If you haven't bothered to even do a simple Wiki or Google about dark matter to find out something a child can understand it illustrates how little effort you put into understanding something before denouncing it. Of course it was obvious before, when you've talked about relativity or Cantor, but now you've illustrated it for everyone.

You are a very nasty person , according to this paragraph .
Do you know what dark matter is , How would you go around and collect some of it ? Is the dark matter only around galaxy or does she penetrate through the galaxy ? If she does not penetrate through the galaxy why not ,

22. ### rpennerFully WiredStaff Member

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Chinglu -- you are the only one to mention neutrons. Neutrons are composite particles, and interact via weak, strong, and electromagnetic forces because their quark constituents (fundamental in the Standard Model) interact via weak, strong, and electromagnetic forces.
Posts #5, #7, #13, #16 by Alphanumeric only mention the fundamental (under the Standard Model) particles called neutrinos, which do not interact via the strong or electromagnetic forces.
That you have confused the two means you are sadly ignorant of more than the last 50 years development of particle physics. This stuff was taught to high school students in the 1980's. This makes your position based in falsehood and therefore unreliable.

neutron = 中子 (roughly "neutral particle")
neutrino = 中微子 (roughly "neutral tiny particle")

AlphaNumeric is more than "fine" -- he's better informed than you and correct. He is, in fact, appearing to engage in a teaching dialogue with you.
Are you talking about neutrinos, which have been posited as possible components of a type of "hot (quickly moving) dark matter" or are you talking about WIMPs which have been posited as possible components of a type of "cold (slowly moving) dark matter."

WIMP = 大质量弱相互作用粒子 (roughly "Large-Mass Weak Mutual Effect Particles")

Does not reflect, does not absorb, does not emit -- it doesn't interact with electromagnetic radiation in any way -- that is why it is called "dark" -- not because it is black -- but because it is hidden, invisible, transparent.

Why would it be a problem for GR? The main reason we know details about dark matter is that it shows up as a significant gravitational effect in galactic dynamics, galaxy cluster dynamics, gravitational lensing from galaxies and clusters of galaxies, and, of course, cosmology. So we have reproducible estimates of the density of dark matter and we have maps of where it is denser than average.

The question facing physics is what is the nature of the majority of dark matter. Multiple lines of evidence favor cold dark matter. WIMPs are one hypothetical model for cold dark matter.

For it to knock electrons out of hydrogen atoms, it would have to dominate the dynamics of the electron, which would happen only without a certain interaction cross-radius. Heuristically $\frac{e^2}{4 \pi \varepsilon_0 a_0^2} = \frac{e^2}{4 \pi \varepsilon_0} \left( \frac{ \pi m_e e^2 }{\varepsilon_0 h^2} \right)^2 = \frac{e^6 \pi m_e^2 }{4 \varepsilon_0^3 h^4} \approx 10^{\tiny -7} \, \textrm{Newtons} \approx \frac{\pi G m_X m_p}{\sigma}$ so if $\sigma < 10 \, \textrm{pb} = 10^{\tiny -39} \, \textrm{meters}^2$ this would put a maximum limit on $m_X < 0.29 \, \mu \textrm{g} \approx 1.6 \times 10^{\tiny 17} \textrm{GeV}/c^2$ before this mass would represent a "problem" for GR.

You are confusing dark energy (~ 72%) with dark matter (~ 23% of the universe). But, yes, there would be a lot of particle no matter which and what mass.

This opinion of yours is founded on no facts, no observations, and no calculations. Therefore this opinion of Chinglu is unreliable and a worthless contribution to this forum.

23. ### AlphaNumericFully ionizedModerator

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I didn't say neutron, I said neutrino. The neutron does interact with light because it contains charged particles (it has a dipole moment).

Not true. If there was some particle which was neutral and massless it could still cause gravity. Photons have no mass but cause gravity.

Not if it didn't interact with them. You seem to be under the mistaken assumption particles will interact with one another regardless, if they have a large mass. This isn't the case.

Dark energy is not dark matter.

Not true.

Yes, you were wrong on just about everything.

Chinglu and I have been around the block a few times. Just look at his attitude in this thread. He came in all dismissive, implying there's obvious flaws in dark matter concepts yet yet in every post he's made a slew of basic mistakes someone could correct just by reading Wikipedia. He's obviously made no real attempt to understand what he is dismissing, he just has the mistaken assumption he's always right.

Looks like you haven't bothered to find out anything either. I'm happy to explain things to people who want to learn but you obviously don't, given your comments. Go you!