Dark matter Definition and 920 Threads

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...

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...

Ok so i don't know squat about either subject, so blame Nova for this post. The show was talking about reaching absolute zero and einstine's conensate theory. As they talked about using intense magnetic fields and shot light waves through these near zero gas clouds causing light to slow. one...

I’m new to these forums and indeed physics as a practice. Although physics has always interested me, it has only been later in life that I have started to invest time in it and started a degree course in my spare time. I do have a propensity for coming at things from odd directions and so please...

Does dark matter form orbits around stars ? Why would dark matter and "regular" matter, say, a dust belt not mingle and stick together? Just with black holes, with d.matter we are positing new objects with complex properties instead of simply admitting imperfection in gravity. Since it is...

Just a layman's question about dark matter. Dark matter, like regular matter, is associated with the gravitational force. Dark matter attracts other dark matter as well as regular matter. Regular matter attracts dark matter also. With that said, wouldn't dark matter be all around us...

Here's a question for the astrophysicists here: Is the commonly predicted amount of Dark Matter and its distribution in our solar system expected to be such that it has an appreciable effect on the orbital speeds of any of the bodies in our solar system?

Hey guys, I am taking a dietary supplement for lifting called dark matter, made by MHP. It was highly reccommended by a trusted website that i visit, so I figured since i had some extra cash i would dip into the honey jar of MHP. I was surprised to find that after mixing this with 20oz of water...

Since Dark Matter is by definition immune to electromagnetic forces, then it has no other way to interact except through gravity -- unless one wants to come up with some entirely new force, which has never been seen. If Dark Matter did have some force of its own, akin to electromagnetism...

And of course there's also been the other recent news about possible indications of a discovery of Dark Matter from detectors floating above Antarctica. http://www.iht.com/articles/2008/11/25/healthscience/25dark.php Could Dark Matter somehow permit new technologies or applications...

why is the temperature distribution of hot gases inside galaxies evidence for dark matter and why is Type 1a Supernovae evidence for dark energy