Dark matter Definition and 935 Threads

I have been looking into dark matter recently, and I have three questions. When calculating what the gravitational pull of an object should be, do they account only for the mass of that object, or do they account for the total energy of that object? For example, a star will have a lot of mass...

Homework Statement I am struggling to calculate the gravitational force from a dark matter halo given that its density is given by ρ(r) = ρ0r02/r2. Once i have found the force i plan to equate it to the centripetal force, F = mv2/r, to find the velocity, v. Homework Equations Density...

Sorry if this has already been discussed. I just couldn't find it. So the main proof for dark matter comes from the anomalies of the gravitational interaction between galaxies and not being able to explain the near constant velocities of the rotating stars observed in a galaxy, independent of...

This article appeared March 2nd on Science Daily. Quite interesting. Any comments? http://www.sciencedaily.com/releases/2012/03/120302101413.htm

Thinking about how little we know even about the amount of mass in our own solar system (Oort Cloud etc), could the discrepancies in mass simply be a ton of space junk (asteroids, planets etc) and even objects like cold neutron stars that are all very explainable objects in terms of their...

Homework Statement We have been asked to calculate the density of dark matter in the solar system. I've used the following equation: Homework Equations rho= 3v^2/4gPir^2 The Attempt at a Solution V = 2.2*10^5 speed of solar system orbit around the galaxy G = 6.67*10^-11...

How did dark matter form? and is dark energy a result of dark matter like gravity is a result of ordinary matter?

If dark matter is actually there and not just some flaw in our understanding or mathematics then how can galaxies be made of both and not just one or the other. If dark matter doesn't interact with anything else like light then how can a dwarf galaxy be made of "mostly dark matter"?I know its...

Someone said that they are by mass-energy equivalence. Also, is it possible to say that dark matter is a indeed a form of matter, and dark energy is a form of energy?

So, I have been doing a lot of reading. I have an 8 year old girl that has renewed my interest in physics, chemistry, biology, etc. I find it interesting that we say that Electromagnetic Waves travel through a vacum. We know that mechanical waves like those propagated in liquids and gas...

What would be the distinguishing theoretical differences between gravitons with an infinitesimal rest mass (non-zero) and cold dark matter? Reference: Dark matter - Wikipedia Graviton - Wikipedia

Hello, since I am very interested in universe, I would like to know something more about dark matter and energy. There are too few information on Wikipedia for instance. Could you recommend me any great book which can bring me some light about this stuff? I am 1st year engineering student (for...

I read this article http://hitoshi.berkeley.edu/public_html/susy/susy.html and one of the things it suggested was that "One of the best candidates for Dark Matter is the lightest supersymmetric particle." So i have a question. (doesnt have anything to do directly with the article itself...

what's the status of that? also why not just look for two systems that have the same visible distribution but with a different dark matter content?

If it existed a particle that had such properties that it both pushed away other particles of the same kind and it pushed away ordinary matter ,could this then explain dark matter and dark energy ? If the big voids of the universe was filled with such a particle, the net force of the particles...

Hi All, I don't know whether to post this in quantum field theory or in cosmology. Maybe this stuff is one subject, not two. Hajdukovic published some papers recently which seem very intriguing even to an amateur like me who doesn't understand it. Here's the latest one...

I have a theory about what dark matter and dark energy is and so far my theory can explain the % of dark matter, atoms and dark energy for the present universe and the 380 000 old universe base on the Wilkinson Microwave Anisotropy Probe findings http://map.gsfc.nasa.gov/news/5yr_release.html...

1. Is the universe finite? 2. Could it be just the surface of a higher dimensional object? 3. If something travels across the universe will it reach the same point? 4. Could the effects of the accelerating universe, that scientist credit dark matter to, be just a side effect of some...

I read an article explaining how all the stars in the milky way revolve around the galactic center at the same velocity, which is obviously different than the way the planets in this solar system revolve around the sun. They say this is because the C.O.M. isn't located in the galactic center...

I was wondering two hings. First, does light's energy equate to mass and result in the bending of space time? The fact that it does follow the curve of space-time as well as mass-energy equivalence principle lead me to believe it would. Secondly, was that energy accounted for in calculating...

if there is dark matter every where, why it is noticed near galaxies? why can't we do some very sensitive lab experiments of gravity to find the effect of dark matter?

A thought experiment I have been thinking about this for twenty years and I would like to hear your opinions. It relates to black holes, dark matter, the expansion of the universe, and unifying theories. This is very simple and beautiful to me. Forgive my lack of formal training, my goal...

Accidently Posted this in the career guidance section earlier. Thought I should put it where its supposed to go. I am currently a physics major in my sophomore year of college. I have found that my interest really lies in Space, specifically Dark Matter and Dark Energy. Talking to a couple...

This has been discussed in other topics but not without leaving some issues unanswered. So DM has only gravity and does clump. Clearly even if it reached stellar density it would not intiate the usual nuclear 'burn' point because there are no electromagnetic/nuclear charges involved. But if it...

Hello, glad to be able to post my question ^^ ok I'm no scientist and I haven't looket at the math of quantum mechanics and such but i get the general idea that subatomic particles (like electrons) are like waves of probability, that they are more likely to pop "in and out of existence" in one...

Can someone explain why 'dark matter' is the dominate explanation for the 'excess' gravity seen around galaxies? It seems to me that we have made an assumption that mass causes gravity. Isn't it possible that gravity arises from some as yet not understood mechanism? I may be way off base...

Does it make sense to visualize dark matter as roughly spherical, or oblate, around a spiral galaxy? Perhaps incorrectly, I picture dark matter as analogous to a planet, or star, with the visible disk of the galaxy forming the equatorial plane. Is this reasonable picture of what we observe...

Dark Energy, Dark Matter, and "Empty Space" I'm new to this forum, and I've looked around but did not find this discussed. Apologies if I missed it. Has anyone in the research of Astrophysics considered the "missing mass" of the Universe to be contained in the structure of space-time itself...

I realize BBC science news is not a totally reliable source, but I'm wondering if any of the knowledgeable folks here have any comment on this: http://www.bbc.co.uk/news/science-environment-14948730 I tried to find if there had already been a thread on it, but I may have not looked hard...

I know that typical Black Holes don't feed on Dark matter because they are tiny, so the direct hit is unlikely. While normal matter has friction and can slow down close to the BH, Dark matter just pass it by. What's about supermassive (>10^10 solar masses) black holes? Do they consume...

I am a physician not a physicist, but I read Brian Green, Susskind, Thorne, Gamow, etc. I recently learned of the Blue Brain project as well. It has occurred to me that dark matter may represent a two dimensional sphere surrounding each galaxy which holds the information for that galaxy. The...

Dark matter...Waste? This may sound crazy (and probably is)...but. From my understanding "dark matter" is an unknown substance (?) that comprises most of the space(?) between planets, stars and galaxies, in our known universe. From what I have read the universe does not have near enough...

http://www.physorg.com/news/2011-08-dark-illusion-quantum-vacuum.html "His ideas (like those in the previous paper) rest on the key hypothesis that matter and antimatter are gravitationally repulsive, which is due to the fact that particles and antiparticles have gravitational charge of...

Far from any superclusters, is there a background of DM which hasn't yet clumped (at least to any great extent)? What is its density compared to the average DM density (which I think averages about 1 GeV/m3 in the present)?

Hi, I know that within the host halo there are smaller subhalos moving around. I was swondering that is their motion just random motion or does it follow some kind of pattern, e.g. circular motion centred at the centre of the dark matter halo? Thanks,

Why dark matter can not collapse into a black hole under it's own weight?

When it comes to dark matter; Has the mass of the super-massive black holes residing at the core of every galaxy been taken into consideration? Could the total mass of all black holes account for the missing mass in the universe?

Hi PF Would it be theoretically possible to create energy (for example photons) from matter-matter annihilation (not using anti-matter), so that we could create a powerplant based on this, without the need of producing anti-matter for the energy production? I know that Dark Matter WIMP's...

My question/thought is this... We know gravity is related to matter, could dark matter have "anti-gravity" Just like magnets have different polarities, one to attract and one to repel, could gravity have similar properties that we are unable to identify, perhaps related to types of matter...

If dark matter really does exist everywhere, and is constantly passing through our bodies, why doesn't this extremely dense matter affect regular matter? How are the atoms of our body not pulled by dark matter's gradational field? Also, if dark matter is thought to exist because stars in...

what is the temperature of cold & hot dark matter?

Here are some recent papers on attempts to detect dark matter directly or indirectly: a solar system test with a possible positive result: http://arxiv.org/abs/1001.1697 direct detection, with seemingly contradictory results: http://arxiv.org/abs/1106.1066 via gamma-ray astronomy...

Could it be possible that space-time curvature is not caused by matter but is an inherent characteristic of space-time? Wouldn't this explain dark matter?

It seems that we had the evidence, but no one had noticed except a team of Italian physicists who weren't taken seriously. At last, the data was confirmed by another team. http://www.technologyreview.com/blog/arxiv/26861/?ref=rss

Just curious to know what dark matter is. Thanks!

Hello everyone. I'm not a physicist however have been doing some research on the concepts behind dark energy and string theory and it has presented me with a question: Is it possible that dark matter could be the components of quarks that haven't pulled together to form the quarks. We can't...

I was watching a documentary the other day and this idea occurred to me. Here are links to the relevant portions on youtube... http://www.youtube.com/watch?v=4BRhjntvGoE&feature=related http://www.youtube.com/watch?v=2zgxvGaei6o&feature=related If gravity is not confined to 3 spatial...

What is our best knowledge on the mass and spatial distribution of dark matter in our galaxy? Could you give me a good reference?

Hello, I learned from Yahoo about the existence of many more "rogue planets" than stars. These planets are not bound to a solar system, they are "free floating". I found more information on wikipedia and jpl. I wonder now if these "rogue planets" could be an alternative to the "dark...

Hey guys, I'm a bit confused about how hot/cold dark matter plays into our theory of structure formation. Hot Dark matter is relativistic then it decouples in the early universe, and these particles are light and fast and do not form small structures since there is a large mass needed to keep...