I would like to know what is dark matter.
I would like to know what is dark matter.
The cosmological constant has nothing necessarily to do with dark matter. Furthermore, dark energy may or may not be a cosmological constant.It's a name for the cosmoligical constant from general relativity.
In astronomy and cosmology, dark matter is a conjectured form of matter that is undetectable by its emitted electromagnetic radiation, but whose presence can be inferred from gravitational effects on visible matter and background radiation.
Well Chalnoth is right.
Wikipedia is really a great database. Actually the thing is even I didnt know much about dark matter myself. Wiki helped!!
Here's the definition from wikipedia:
For more info go to
The cosmological constant has nothing necessarily to do with dark matter. Furthermore, dark energy may or may not be a cosmological constant.
I think questions as broad as "What is dark matter" are best researched on one's own outside the forum. When you have a basic understanding, come back and ask more specific questions. Then we'd be happy to help.
This was an early proposed solution, but detailed investigation showed that it didn't work. In particular, dark matter has a very different distribution from the normal matter: normal matter can lose energy by radiating, and so collapses into things like stars and galaxies. By contrast, dark matter loses very little energy with time, and so doesn't tend to collapse nearly as much as normal matter.Ok Thanks for redirecting me to Wikipedia. But now I would like to ask (only to those who is interested in giving answers, of course) if this emission criteria for defining dark matter may be interpreted as celestial bodies far enough and emitting so small an amount of radiation (planets, for instances) that we cannot detect it due to scattering or absortion in the midway.
It seems that there is another possibility, namely: a different patern (species) of matter.
And the simple answer is – No one knows, it's a mystery!I would like to know what is dark matter.
Hot gas detected by Chandra in X-rays is seen as two pink clumps in the image and contains most of the "normal," or baryonic, matter in the two clusters. The bullet-shaped clump on the right is the hot gas from one cluster, which passed through the hot gas from the other larger cluster during the collision. An optical image from Magellan and the Hubble Space Telescope shows the galaxies in orange and white. The blue areas in this image depict where astronomers find most of the mass in the clusters. The concentration of mass is determined by analyzing the effect of so-called gravitational lensing, where light from the distant objects is distorted by intervening matter. Most of the matter in the clusters (blue) is clearly separate from the normal matter (pink), giving direct evidence that nearly all of the matter in the clusters is dark.
The hot gas in each cluster was slowed by a drag force, similar to air resistance, during the collision. In contrast, the dark matter was not slowed by the impact because it does not interact directly with itself or the gas except through gravity. Therefore, during the collision the dark matter clumps from the two clusters moved ahead of the hot gas, producing the separation of the dark and normal matter seen in the image. If hot gas was the most massive component in the clusters, as proposed by alternative theories of gravity, such an effect would not be seen. Instead, this result shows that dark matter is required.
Comparing the optical image with the blue emission shows that the most of the galaxies in each cluster are located near the two dark matter clumps. This shows that the galaxies in each cluster did not slow down because of the collision, unlike the hot gas.
Thanks Orion1 for a thorough explanation.The current leading candidate for dark matter is supersymmetry (SUSY) particles, called neutralinos.
If supersymmetry exists close to the TeV energy scale, it allows for a solution of the hierarchy problem of the Standard Model, i.e., the fact that the Higgs boson mass is subject to quantum corrections which — barring extremely fine-tuned cancellations among independent contributions — would make it so large as to undermine the internal consistency of the theory. In supersymmetric theories, on the other hand, the contributions to the quantum corrections coming from Standard Model particles are naturally canceled by the contributions of the corresponding superpartners.
Hi Chalnoth! What's up (with "planck s")!Oh, no, not at all. SUSY models most definitely include Higgs bosons.
Well, since we don't know what the dark matter particle is, we obviously can't say for sure. However, that said, in quantum field theory, even SUSY, there remains a fundamental problem: if you insert a non-zero fundamental mass for any particle in the theory, it leads to a mathematical contradiction. This means that all masses must arise from interactions. For single particles, that interaction is modeled by an interaction with one or more Higgs fields. For composite particles (like protons and neutrons), it's a complex combination of interactions between the Higgs fields and the binding energy of the component particles.So what do you say about this:
Does the Higgs boson interact with DM to give it mass?
And if so – Will we then have an indirect 'link' to DM through Higgs?
And if so – Why does DM interact with the Higgs boson, and no other boson?
If not so – What gives DM mass?
I know that the Higgs boson is expected at LHC, but also that prominent scientist like http://vimeo.com/4062801" [Broken] – "Well, I think it'll be a lot more exciting if we don't find it."This means that all masses must arise from interactions. For single particles, that interaction is modeled by an interaction with one or more Higgs fields.
Okay, but isn't it 'weird' that DM does not interact directly with itself (except through gravity)? Electrons and photons (must?) do. Well, maybe neutrinos don't...Finally, if you think it strange that DM would interact with the Higgs and not other bosons, consider this:
Well, yes, in part because it would point us in an entirely new, unexpected direction of high-energy physics. Finding new information is always interesting, but finding things that nobody expected are often more interesting.Thanks Chalnoth, interesting answers as always.
I know that the Higgs boson is expected at LHC, but also that prominent scientist like http://vimeo.com/4062801" [Broken] – "Well, I think it'll be a lot more exciting if we don't find it."
Sadly I worry that the energy available at the LHC may simply be dramatically insufficient to say much about dark energy, or even about much of high-energy physics. As for dark matter, the LHC just won't be good at either producing or detecting such particles, so it's somewhat unlikely that we'll see them.I have absolutely no clue about the complicated math behind all this. But I do know there are some 'difficulties' in getting all 'pieces in place', like the measured cosmological constant, that is smaller than the calculated quantum field vacuum energy by a factor of 10-120. And we don't know what DM really is. And 90% of the mass in nucleons comes from quantum fluctuations (virtual particles), etc.
If dark matter is a WIMP -- a weakly interacting particle, then it interacts through the weak force as well as gravitationally. Thus, it would couple to W/Z as well as with itself through neutral currents.Okay, but isn't it 'weird' that DM does not interact directly with itself (except through gravity)? Electrons and photons (must?) do. Well, maybe neutrinos don't...
So far as I know, the "weak" in WIMP doesn't specifically relate to the weak nuclear force. Rather it's just a statement that its interactions with itself and other matter, whatever they may be, are rather weak. We don't yet know what those interactions are: they could be the weak nuclear force, they could be something else. But they aren't electromagnetism or the strong nuclear force (as with those interactions they'd simply interact too strongly with normal matter).If dark matter is a WIMP -- a weakly interacting particle, then it interacts through the weak force as well as gravitationally. Thus, it would couple to W/Z as well as with itself through neutral currents.
Thus, it would couple to W/Z as well as with itself through neutral currents.
The hot gas in each cluster was slowed by a drag force, similar to air resistance, during the collision. In contrast, the dark matter was not slowed by the impact because it does not interact directly with itself or the gas except through gravity.
Okay, so if LHC find (confirm) the Higgs boson, we can say nucleons get 90% of its mass from Quantum Chromodynamics, and 10% from Higgs.The mass of nucleons, on the other hand, is, I believe, a rather well-understood consequence of quantum chromodynamics.
Probably, as electrons, neutrinos, and the W/Z bosons are expected to.Okay, so if LHC find (confirm) the Higgs boson, we can say nucleons get 90% of its mass from Quantum Chromodynamics, and 10% from Higgs.
Would it then be 'safe' to predict that the 'voluminous' Dark Matter gets 100% of its mass from Higgs?