Dark matter Definition and 920 Threads

question 1. i need some help understanding this. it is proven that the universe is infinitely expanding correct? what is the exact reason for that? question 2. i have a couple questions on dark matter. does dark matter give off its own gravity bending space-time, I am assuming ?

Dark matter really due to stars having some charge?? I have an acquaintance who has a physics doctorate who argued the (to me) novel idea that dark matter doesn't really exist; that a plausible explanation of the observations suggesting it is that stars are sufficiently not exactly electrically...

XENON 100 published today the results from a 100-day run, significantly tightening the constraint on WIMP spin-independent cross-sections. It seems that they are beginning to probe interesting parameter spaces. http://arxiv.org/abs/1104.2549

Hello, I'm a third year engineering physics student, and my team and I are trying to model how the rotation (V(r)) of a galaxy is affected by the possible existence of the dark matter halo. Here are my questions: Regarding the dark matter halo: The integral of the mass density function...

There were proposals that dark matter might be ultra-light scalar particles in Bose-Einstein condensation phase, but the idea doesn't seem to have caught on. What are the advantages / disadvantages of this model?

I have seen a few other similar posts but wanted to add my thoughts. Is gravity the space between bubbles of dark matter. Matter that we know and dark matter are like oil and water? Gravity is the force created in the structures between the bubbles. Is that why we see the current structure of...

is antimatter the same thing as dark matter? is antigravity the same thing as dark energy?

Okay, so I understand that galaxies spin more like a frisbee than the solar system, and that there is evidence for a lot of non-light-emitting mass (such as gravitational lensing) but how would dark matter account for the difference in the spin of galaxies? Gravity still decreases inverse to the...

Hello, Firstly, i would like to say that i am by no means an educated person (as in taking specialty courses or an university degree in cosmology or physics), at least regarding this subject. From this point of view, what i am about to ask might seem silly or just plain stupid, so feel free...

Has Dark matter really been proven? And if, so what does this mean for the future of our understanding of physics?

There is a picture on this site that I don't understand. http://csep10.phys.utk.edu/astr162/lect/cosmology/darkmatter.html It is used as evidence that dark matter exists, but what is it? Is it a MACHO, a WIMP or something else? Can someone also explain what a MACHO or a WIMP is without...

Why is dark matter distributed in a web rather than falling into clumps ? Under the action of gravity normal matter falls into galaxies, stars, planets etc. How is it that DM doesn't do the same but instead is in web form ?

Why doesn't dark matter fall into black holes ? Assuming it doesn't of course. If it did then surely huge amounts would have fallen into black holes. By now they'd be full of the stuff & more massive than they are. So I'm assuming for some reason dark matter doesn't fall into black holes. In...

Hi there... I believe my previous questions related to a specific topic has caused a stir here with many people complaining/advising me to study that field more properly before asking anything... So now i will change topic hoping everyone is happy with it... I want to discuss dark matter...

Interesting :o http://www.technologyreview.com/blog/arxiv/26316/?ref=rss

I’m sorry, but I find dark matter and dark energy problematic. It’s hard to think of a Universe made up of about 95 % of stuff we have no idea about, except that maybe dark matter and dark energy have some properties. So I’m thinking maybe there’s something wrong with the data, but I can’t...

Average density of universe is 9.3 x 10^-27 Kg-mass/M3. Volume of Cubic-Light-Year is 2.7 x 10^25 M3. Result is .25 Kg-mass/CLY. If Dark Matter is 5 x ordinary matter then 1.25Kg-mass of Dark Matter per CLY. What if there was a billion times more Dark Matter in a galaxy than in the space between...

First up, I am not a physicist (just a meek mathematician and engineer). I was watching a television show last night on Discovery Channel, where they were summarizing and simplifying the current train of thought in cosmology. Therein, the expounded how dark matter is needed to hold spiraling...

Is it true that, if there was enough dark matter in the universe it could stop the expansion of it? If it is, can someone explain to me how?

While pondering the concept of dark matter with my puny brain, I came to a question I was unable to answer which seems to have some significant implications: Is Dark Matter affected by gravity and therefore clumped up with other matter in the universe? or is it unaffected by gravity and...

Twenty first century dark matter reminds me of ninetieth century luminiferous aether. Without dark matter, current models of galaxies fall apart. What could happen if some of that dark matter mass was from stellar black holes? The supermasssive black hole at the center of our galaxy, the...

Tentative evidence supporting the possible existence of "sterile neutrinos" is reported in the current SciAm: http://www.scientificamerican.com/article.cfm?id=a-whole-lot-of-nothing If anyone can fill in details for us, or elaborate on points made in the short news article, please do. ==sample...

Does Dark Matter have a temperature - obey the laws of thermodynamics?

Does dark matter fall into a black hole, and create radiation as it falls in like normal matter? If not, why not? If so, can we use this to detect it directly?

I was wondering how to rule out the hypothesis that most of dark matter is due micro - MACHOS, that is, if a considerable part of it is due to objects like those of the Oort Cloud and Kuiper belt.

We are in the Universe and the Universe is in us. The Universe contains 23% dark matter and 4.6% visible matter; this means there is 5 times more dark matter than visible matter. If the Universe is in us where is the dark matter?

Why doesn't dark matter affect the movement of solar system bodies as it does with the galaxies and stars movement?. Is it possible that dark matter affects only at galaxies scales or that the heliosphere interferes with the interaction of dark matter at solar systems scales (I say this because...

hi, i don't know if this is in the correct place but I've got a question that has puzzled me. i know that the stars on the outer edge of galaxies are moving too fast to be in a stable orbit without flying off away from the galaxy, does this mean that the gravity that the outer stars...

I hope this is in the right section of the forum. I figured astrophysics and cosmology could also be acceptable places to ask this. I was watching Lawrence Krauss's talk about everything from nothing, the one with the richard dawkins introduction. He talked about methods for trying to detect...

The paper below suggests an alternative to dark matter, the strength of gravity is greater than is predicted by GR due to graviton-graviton self-interactions in regions of higher density of matter. Hence dark matter is unnecessary. The increase would be too small to be measured locally, hence...

Loeb at Harvard is a top cosmologist. For six years or so I've seen him come out with paper after paper that seemed unusually insightful over a broad range of topics. He and Neal Weiner (Princeton IAS) just posted a creative idea about DM, http://arxiv.org/abs/1011.6374 about how some minor...

I came across this http://scienceblogs.com/startswithabang/2010/11/the_simplest_argument_for_dark.php cutesy pop-sci-ish explanation of how we know there's dark matter. If you scroll about 1/3 of the way down, it shows plots of the CMB's power spectrum as a function of multipole moment, l...

Hello, I'm not sure if this is the right place to be posting this question, but since it is related to school I hope it will do. I am currently a senior in high school and I am required to write an 8-10 page paper on a topic of my choosing. The main requirement is that I must argue a point...

http://blogs.nationalgeographic.com/blogs/news/breakingorbit/2010/11/new-dark-matter-map-hubble.html?source=link_tw20101112hubble" i found this article interesting , so shared here

Dark Matter Can it be identified? First of all let me start off by saying dark matter is only a theory, it is not proven. Dark matter is a hypothesized form of matter particle that does not reflect or emit electromagnetic radiation. The existence of dark matter is inferred from gravitational...

Hi ! I'm trying to understand the Dark matter problem, because it scares me if clever people tell me they don't know out of what 23% of the universum is consisting. But let's start with a simple question on GR: GR is stating that a body moving at a speed close to c holds an almost...

http://www.nasa.gov/images/content/498884main_DF3_Fermi_bubble_art_labels.jpg http://www.nasa.gov/mission_pages/GLAST/news/new-structure.html Could these structures account for the dark matter, or is the density profile inconsistent with two big blobs of matter/energy on both sides of the...

A friend called my attention to an interesting paper by Abe Loeb and David Spergel and somebody else. It seemed to raise unresolved issues about the DM and globular clusters. Does anybody know the current mainstream thinking about this? In case anyone is new to this, Loeb and Spergel are...

Just an idea: Suppose dark matter has a repulsive force towards matter and dark matter which follows a yukawa potential. It would be consistent with the lack of it in globular clusters, galactic center besides its clustering in galaxies. In case it touches matter, it would just cause an...

Just read an article on Universe Today at: http://www.universetoday.com/77662/missing-milky-way-dark-matter/ The paper is at http://arxiv.org/PS_cache/arxiv/pdf/1011/1011.1289v1.pdf . It introduces what seems to be rather tight constraints on the dark disc. Any cosmologists care to...

I know that Dark Matter and Dark Energy are 2 different animals. My question is not related to the difference between the 2. My question is, if dark matter exists, and since matter has energy, then dark matter must have energy associated with it. So while I hear a lot about Dark Energy and Dark...

We know particles have mass. Thusfar we don't know of anything that has mass which is not a particle so we assume the likeliest explanation for apparent missing mass must be missing particles. This makes some good sense. But what if this assumption is wrong? Has anyone looked into the idea of...

Dark matter is believed to have a more homogenous distribution than normal matter, a bias of at least 2 is used in models of large-scale structure in order to justify large voids and superclusters in a homogenous universe. If Dark matter is so evenly distributed I have some difficulties to...

Hi. I just had to share this little gem. Regardless of your points of view on Dark Matter versus other ideas (ie MOND in this case), this webpage is so well done and funny if you're a geek like me. (a conversation between Arnold Schwarzenegger and a physicist)...

Does anyone know if there is an understood correlation between the amount of dark matter we suspect in a galaxy and the age of the galaxy? Basically, I am wondering if older galaxies tend to have more dark matter. But I need references to information on this, not just opinions :) Thanks.

There are a lot of "IF's" in the following, so this may be more a question of logic than of physics. Also, I have two questions revolving around the same themes; they are independent from one another so a response can be to one or both of them. (1) In...

Currently the WMAP results give a baryon:photon ratio of ~6.2x10-10, and a dark:baryonic mass ratio of ~5. When added to the energy density of photons + neutrinos (+dark energy at later times), the total density is then critical for a flat Universe. The BB nucleosynthesis analysis of the...

I would like to know the difference between dark energy and dark matter. The way i understand it they are both detected by the effect the have on other ojbects. So why are they different? Thanks

I saw an interesting video that showed the dark matter halo that exists around the milky way galaxy, the scientist described it as having a squashed beached ball sort of shape, which got me thinking. Is there any reason why galactic black holes might have something to do with dark matter...

Hello fellow Cosmology fans and professionals! Does Dark Matter form into Black Holes, and do regular Black Holes attract and trap Dark Matter? Thanks!