Dark matter Definition and 935 Threads

Dark matter: The invisible force The temperature of space may hold the key to solve problem of missing matter Dark matter, the "invisible" mass that scientists believe makes up a large part of the universe, can be explained as being mass that is at one end of a cooling process that all matter...

Hello; What is dark matter? I have been told from numerous sources that it is simply an invisible form of matter that is undetectable by its electromagnetic radiation. However, that does not explain what it is, that just tells me that I can't see it. What particles does dark matter consist...

I was wondering if studies of individual galaxies predict the same amount and distribution of dark matter as do studies of galactic super-clusters.

if dark matter they believe is not made of atoms it must be made of some substence. is it made of basicly a big bubble of some kind of bubble of particles? and how can this be are the particles made of string also like atoms , according to string theory that is

A question for those of you who know about the distribution of dark matter in the galaxy: Do we know how "clumpy" dark matter is? Can we tell yet whether dark matter is distributed about as densly as a gas or whether it's possible that there are the equivalent mass distributions that might...

Since pure dark matter apparently does not have charge but has mass, might it be found in the galaxy's edge as something akin to uncharged black holes? Typically, pure dark matter is invoked as particles. Wouldn't they form aggregations under gravity? Extended (i.e., not particulate) dark...

It might be a dumb question, but why didn't any quantum model ever predict dark matter? I always hear about how current quantum theory is wildly successful, which might suggest that it does somehow represent the true underlying reality. So it seems that it should have predicted dark matter, and...

Dark energy is observed to constitute about 72% of the mass density of the universe, dark matter about 23%, and regular matter about 5%. Is this proportion always like this or does it change over time? If it does change, how does one reconcile it with the requirement that the cosmological...

Are there any different testable predictions of the DM (WIMPs) having different spin: 1/2 or 1? For example, if DM is *matter* (spin=1/2) then Pauli princliple can make dense DM cloulds 'degenerate', creating an additional pressure, even WIMPs don't interact with themselves.

First off, let me say that while I am an avid astronomer, I know very little about the mathematics of astrophysics. My specialty falls more under mechanical engineering. While initially they may not seem all that related, history shows that the mixing of varying disciplines often sparks...

Has gravitational collapse of cold dark matter been considered? Since it can't repel (can it? thro' what interaction?) shouldn't it always go to a BH? How can it get rid of ang. momentum if it can't radiate? Maybe thro' jets... Have these things been considered? Thanx

All the LCDM models with variations (see http://lambda.gsfc.nasa.gov/product/map/current/parameters.cfm ) have similar ratios of dark matter: baryonic matter density of very close to 5:1. Is this ratio determined from WMAP data such as angular size of a peak, or is it a not very tightly...

as exciting as it is, it will never get the press tiger woods is getting.. http://www.foxnews.com/scitech/2009/12/18/scientists-announce-possible-discovery-dark-matter/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%253A+foxnews%252Fscitech+%2528FOXNews.com+-+SciTech%2529 sorry...

Hi all, Apologies if my understanding is a bit simplistic but even if my question turns out to be idiotic, I'm sure I'll learn from your replies. Thanks in advance! So the reason dark matter was postulated in the first place is because the observed gravitational effects in the known...

According to an article that I read, an article came out today announcing that scientists had detected dark matter or at least a WIMP. How did they detect these particles? Did they do it the same way they detect neutrinos? If so, how do they know what they detected wasn't a neutrino?

My question is why do we even need dark matter to make things work ? E=mc2 so if ENERGY AND MASS are the same thing if MASS creates gravity why can energy not also create gravity can someone explain this to me? if Under general relativity any form of energy couples with space time to create the...

Ok,so I am a bit of a noob so go easy on me! i was having a chat recently with my uncle (whos an astro physicist here in the UK) and although he didnt really give me the time of day because he's a busy guy,he said that my idea wasnt too far fetched but to come back to him when its got a bit more...

I have a rather simple question. Dark matter was first proposed because galaxies appeared to have more mass than was observable. That's fine. But then later, supermassive black holes were discovered to be at the center of every galaxy. That's billions of solar masses more in each galaxy than...

Could the effect of "Dark Matter" be explained if in the formaul for Gravitational attraction: F = GMm/d^x Where x is considered 2 is wee bit less (may be 1.98 or some thing)

This is a snippet from a mock encyclopedia which i will not link to. While I am not endorsing this viewpoint, I want to understand, what is fundamentaly inaccurate about what is being said? " In reality, the highest level of education required to comprehend the theory of dark matter is...

I understand that astronomers often locate planets orbiting other stars. They do this by detecting the "wobble" of a star. They can't actually see the planet right? Isn't it true that dark matter is also detected by it's gravitational influence on nearby objects? Maybe this is a dumb question...

Could dark matter be neutrinos? I'm wondering, neutrinos are weakly interacting, but they do respond to gravity. So has anyone calculated how far out of a galaxy a typical galactiaclly produced neutrino would travel before coming back into the galaxy? Are some galactically produced neutrinos...

What is dark matter? How was dark matter formed? Any replies would be greatly appreciated.

I was wondering how verifiable is the escape velocity equation. V=SQRT(2GM/r) How accurately has this equation been verified? It does not take into account dark matter. (Related ramblings) The escape velocity from the earth’s surface is about 11.2 km/s But there is also air...

I suppose the real title should be, "can relativity explain the NEED for Dark Matter"? Now I'm not a physicist, so if I get a detail wrong here or there please do not get stuck on that but rather try to answer the question... It is my understanding that dark matter is "needed" (in one...

Hello I try to get stable dark matter halos with n-body simulations. I set up the halo following a NFW-profile and I define the velocity distribution with a Gauss distribution or Edington inversion (the result is the same). After approximately 2Gyr my cusp turns into a core...?? I use about...

It is my understanding that physicists hope to use conservation of energy in the LHC to determine if there are multiple dimensions AND if there is dark matter. Let's suppose that through conservation of momentum, we detect a particle that apparently only reacts through gravity, and there is some...

Can someone explain to me if there is any evidence besides the spreading of cosmological objects behind dark matter/energy? Because I have a pretty solid theory that could explain that without anything beyond relativistic physics. I've got quite a few solid ideas, but I don't have access to...

Hay I would like to calculate the potential energy of a particle which is within a big dark matter halo. The Newton shell theorem says that if I have a particle within a spherical mass distribution (let us say at radius r) the mass with R>r exert no net Force to the particle. But there is a...

Are there any theories of gravitation and spacetime that don't require the existence of dark matter to explain the peculiar rotation of galaxies and don't require dark energy to explain the expansion of space? I would love some links. These things just seem suspiciously like luminiferous...

Just to clarify, I am NOT talking about the Dark Energy, I am talking about the Dark Matter w=?

Recently there has been a lot of discussion in the science media about this article, and other similar ones. http://www.physorg.com/news160726282.html Could someone knowledgeable about this please write about what is actually going on here? I don't really trust the way this is being reported.

Hi! I'm sure this has been done before, but is it possible for dark matter to travel faster than light (at least some candidates for dark matter)? We know that ordinary matter is limited by the speed of light, but what about dark matter? For all we know, dark matter may not use c-limited...

Hello everyone. May I ask if it's possible dark matter consists of trans-Seaborg elements beyond atomic number 126? Seaborg hypothesized that these elements were an "island of stability" and may be stable. Would we know enough of the chemical properties of such new elements to say that this...

What I was thinking is that if dark matter particles don't interact electromagnetically or by nuclear forces then what is there to stop them coming arbitrarily close to each other thus forming microscopic black holes? And shouldn't we then be able to detect them by Hawking radiation? Does the...

Hi, I hope someone can help me, my question is What are the principal candidates for baryonic dark matter in clusters of galaxies and in galaxy halos, are they different? I just need a list for halos and clusters as it might make it simipler for me to understand thanks in advance

Besides keeping the whole of galaxies rotating at the same rate, and holding galactic clusters together, what are the other forms of evidence for dark matter?

Hi, I have an issue that I can not answer as I do not understand the subject matter. Would you be so kind and review [crackpot link deleted] and provide me your impressions.

It seems to me that an obvious source of dark matter (and possibly dark energy) might be the massive ejections of spent fuel from our sun in the form of the solar wind. If our sun regularly ejects spent fuel in the form of the solar wind, it follows that the same process must happen in billions...

Hello, I am currently doing a research project on alternative theories to dark matter. I have covered all the main candidates fairly well such as nonsymmetrical gravity, conformal gravity and MOND etc. But I would really like to include a section on how string theory or M theory could explain...

Would Dark matter form out of the primordial plasma at the same time as baryonic matter, did some thing special happen to form this weakly interacting particle?

This guy uses lattice to calculate how gravity would behave in a non commutative aproximation. His insight is interesting given that gravitons interact among themselves pretty much like gluons. http://arxiv.org/abs/0901.4005 I am extremely surprised of how well that describes the whole thing

Suppose dark matter is normal matter, in an exotic state. Superfluids have some interesting properties in common with "dark matter". Superfluids are quite restricted in how they interact with their surroundings. Because a superfluid is, quantum mechanically, a single entity, all of its...

http://cdms.berkeley.edu From the discussion in APS Viewpoints. The two experiments taken together—XENON10 superior at lower masses and CDMS II at higher—are now encroaching well into the region where discovery may be lurking, a marvelous feat considering that a scattering cross section of...

Okay, so being fourteen, I know that I'm way out of my league on this forum. I do my best to understand anything to do with physics and to at least get a vague idea of theories and ideas, both old and new. Please forgive me for my ignorance. Aside from one topic a while back, I havn't done...

From everything I have read so far, we only know of Dark matter by means of gravitational inconsistencies. My question is this: Why is it so outside of the box to suggest that our understanding of gravitation itself may be faulty? Why are we inventing mysterious particles that are distributed...

I have started reading "Reinventing Gravity" by John W. Moffat. He basicly presents the concept that, to my best understanding, Einstein may have been incorrect in his calculation on gravity because the stars are moving faster then they should be according Einstein's theory of gravity and that...

arXiv:0812.4561 [pdf] Title: On Dark Energy and Dark Matter (Part I) Authors: Shlomo Barak, Elia M Leibowitz Comments: 12 pages, 1 figure Subjects: Astrophysics (astro-ph) 2. arXiv:0810.4034 [pdf] Title: On Dark Energy and Dark Matter (Part II) Authors: Shlomo Barak, Elia M...

Rightly or wrongly, there's considerable excitement about a paper which a postdoc theorist at CERN, Bob McElrath, recently posted. One physics blogger headlined his comment "Dark matter is a quantum liquid." The headline may itself be a misinterpretation of what McElrath is saying but I couldn't...

The most relevant observation to date regarding dark matter is "Bullet cluster". "The Bullet cluster (1E 0657-56) consists of two colliding clusters of galaxies.[1] Studies of the Bullet cluster, announced in August 2006, provide the best evidence to date for the existence of dark matter.[2]...