Dark matter Definition and 935 Threads

Hello, I was just brainstorming for futuristic inventions with context for a sci-fi, high fidelity game (because I'm too cool to revise for exams) - and I thought of one, but my physics and engineering knowledge is at best sketchy when it comes to gravity and nuclear fusion combinations, I was...

I've been reading about black holes and dark matter and came across this theory: http://www.nature.com/nature/journal/v329/n6137/abs/329308a0.html where black holes don't completely evaporate, but evaporate until it hits an equilibrium where it's both unable to evaporate anymore (making it...

Usually, I like to bring up Dark Matter whenever I discuss cosmology or astronomy with someone, and whenever WIMPS (Weakly Interacting Massive Particles) are brought up, the person usually responds saying, "but there is no particle on the Standard Model that possesses all the particles of a...

In Dodelson's book, the equation for a scattering process ## a + b \Leftrightarrow c + d ## is given as ##a^{-3} \frac{ d (n_a a^3)}{d t}=-n^{\text{eq}}_a n^{\text{eq}}_b<\sigma v>(\frac{n_a n_b}{n^{\text{eq}}_a n^{\text{eq}}_b} - \frac{n_c n_d}{n^{\text{eq}}_c n^{\text{eq}}_d}) = - <\sigma...

Hey, I'm trying to look for a single test set-up for a dark matter-only simulation I and my friend are building. It's currently based on a particle-in-cell approach and we are calculating the Poisson equation and particle trajectories in a co-moving frame (so expansion of the Universe is taken...

The main evidence for the existence of dark matter is the flat rotation curve of galaxies, and high peculiar velocities of galaxies in galaxy clusters. The mass eclosed in a radius R is derived from the Keplerian equation M(R) = v2R/G . Also we know about the existence of gravitational...

This paper seems to be saying so. can the universe be logotripic, whatever that is? arXiv:1504.08355 [pdf, other] Is the Universe logotropic? Pierre-Henri Chavanis Comments: Submitted to EPJPlus Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum...

Wouldn't this explain why galaxies with no black holes are so small?

I am curious about mass of a galaxy without dark matter and with dark matter.I searched but I couldn't found.I ll be happy If you help me. Thanks

"Why do so many physicists believe there has to be a structure to the vast voids in space" ? Surely, Their thinking defies the basic principles of physics, i.e. in order to have something there has to be nothing ! to have a positive there also has to be a negative, so as for the positive to...

I need someone with more experience in the field who has knowledge of excel to check over my work. Given the gravitational attraction between two bodies is F = (GMm)/r^2, and the centripetal force required to keep a body in orbit is F = (mv^2)/r, therefore (mv^2)/r = (GMm)/r^2 therefore...

From what dark matter in space consist of?

http://phys.org/news/2015-04-potential-interacting-dark.html An international team of scientists, led by researchers at Durham University, UK, made the discovery using the Hubble Space Telescope and the European Southern Observatory's Very Large Telescope to view the simultaneous collision of...

This question straddles this forum and the "Beyond the Standard Model" one a bit, so if a mentor thinks it belongs better elsewhere, please feel free to move it. I've seen references in the "popular science" press about the possibility of indirectly detecting dark matter by looking for gamma...

Is there a non hypothetical particle [aka axion] that can be the make up of Dark Matter?

http://www.nasa.gov/press/2015/march/nasa-s-hubble-chandra-find-clues-that-may-help-identify-dark-matter/index.html The take away seems to be that some ideas about dark matter may have problems. The possibilities checklist of dark matter interactions has been shortened. There are some really...

Hello It is my understanding that the matter originally contained in a dying star which formed a black hole has been entirely converted to energy in the form of space time curvature. In other words the matter no longer exists and all that is left is the curvature of spacetime. Aside from my...

I've got a homework question that I'm particularly stuck on: Suppose that the halo, assumed spherical, of non-baryonic dark matter surrounding our galaxy has mass ~ 5 x10^12 M solar and radius 0.1 Mpc. What it its average density in Kg m-3? I think that I need to use the formula...

Hello there my name is Frank Pelsue. I am currently a senior in high school that is fascinated with physics. I have what I think is an interesting theory on dark matter that I would like to present to all of you. It is unsupported currently but I am just brain storming.

Hello, My problem is as follows I've tried differentiating to find the maximum and I've tried plotting E against m_{\chi} for a range of values and this did not suggest a maximum at m_N = m_{\chi}. Could someone explain why it is the case that the energy transfer is maximum when these masses...

Wondering if it's possible that black holes create dark matter and dark energy from the matter and energy they consume. Then, inflation might slow when supply is low. This would support author Tarō Gomi's theory that "everyone poops." What role would time dilation play if that's what's...

Could dark matter form structures the way matter does?

http://arxiv.org/pdf/1503.02320v1.pdf This paper discusses the emission of gamma rays from a neighboring dwarf galaxy. My understanding is that there is no conventional explanation of gamma ray emission. So there is interest in pursuing a possibility that these emissions are from dark matter...

I thought this was an interesting article on dark matter, what might this kind of DM be made from? I also wondered could DM help explain in some way where all the anti matter ended up? http://www.space.com/27794-dark-matter-destroying-neutron-stars.html

If we could observe a piece of dark matter with naked eye would it appear dark or invisible? Dark matter doesn't emit photons at all but it neither absorbs photons (it doesn't interact at all with photons right?) so it would appear invisible?

is a dark matter black hole possible, and what would it be like ?

Hey, I've a short question. Is there any research attempting to constrain models of dark matter by assuming stable solution for the universe? I'm interested in knowing whether this gives any sensible constraints on the dark matter models. I'm still fairly new to studying dark matter but as I...

Why did Dark Matter have less of an Impact on the Universe than Dark Energy? Under a different set of universal laws, do you think it would be possible for Dark Matter to have more of an impact than Dark Energy during an alternate big bang to create a infinitely dense point as a universe?

Why did dark energy overcome dark matter to create the expanding universe we live in today?

When we observe galaxy lensing of background objects taking place, is it possible to estimate the total mass of the galaxy carrying out the lensing and from that confirm that dark matter is needed to be present to provide sufficient mass to bend the light by the amount observed? Is there...

What is the evidence for dark matter being new particles as opposed to some modified form of gravity?

Hi, as an engineer i don't have much formal training in theoretical physics so bare with me. As most of you know, we can only understand 4% of our universe with the current models we have. The rest of the 96% is dark matter and dark energy (23% and 73%, respectively). Could these unexplained...

How massive would the neutrinos have to be so that relic neutrino from the big bang would account for all dark matter?

Dark Matter, Dark Energy. Is it possible that dark matter and dark energy are illusions caused by the fact that the equations of physics are only approximations? For example, in the falling body equation, F = mg, F (the initial weight of an object) is assumed to be constant, but in fact the...

I was thinking about the properties of dark matter - how it doesn't seem to interact with any of the forces of the universe except gravity and I was thinking about how neutrinos also don't have any charge and they don't interact with any other forces except the weak force and gravity. I thought...

How do we know that out of 100 percent, 4.96% is Matter, 0.42% is Neutrinos, approx 25% Dark matter and rest 70% is dark energy. How do we know about these percentages if we don't know how large the universe is? Or are these calculations based on the spaces of the VISIBLE universe? Are Dark...

This is a video by the two of the researchers who found anomalous xray emissions. These emissions may be related to dark mater, needs further verification. Edit 12/14/14 : preprint http://arxiv.org/abs/1402.4119

Can someone explain the disappearance of 57% of dark matter since the Big Bang? Is dark energy eating dark matter?

I have considered the possibility that dark matter is so hard to find because it exists in extra dimensions. Before posting here I googled this, and found that some scientists postulate this exact possibility, while others consider that extra dimensions themselves cause the effects that are...

I have been wondering about how the universe created itself from nothing and it seems in spacetime, the time dimension must have come first followed by multidimensional space. Following this, matter and dark matter must have been created. While matter and dark matter both underwent timelike...

I know MACHOS and WIMPs are leading candidates for Dark Matter, but is there any convincing evidence to support them?

With http://xxx.lanl.gov/pdf/0705.4298v2.pdf and http://arxiv.org/pdf/1410.2236.pdf I have found some interesting information that there is a lot of empirical evidence to exclude a lot of CDM candidates. All what is necessary is some cross section for interaction with standard matter and the...

As I understand "Dark Matter" is an _assumption_ of existence of matter in certain space, to explain gravitational effects on the matter around that space. But when it comes to "Dark Energy" it is another assumption to explain why universe is expanding. But by Einstein's theory, mass and energy...

It seems like most sci-fi hasn't really touched much upon dark matter. Instead of making up all sorts of fantastical new dimensions or universes, why not focus on dark matter, something we legitimately don't understand and really exists? There's far more dark matter than baryonic matter. Is it...

I would love some suggestions about my undergraduate research, thought it may be improper to ask here. I apology if I break the group rules. My undergraduate research topic is dark matter. My plan so far is to study important observations before making other progress. I have found an...

I saw an interesting article on dark matter possibly explained by axions and wondered what others thought of this? http://io9.com/curious-signal-could-be-dark-matter-pouring-from-the-su-1647581644

Note: this is a re-post because my initial post had problems, no one could reply to it. Ok this is my second in the series about dark matter. In a previous thread I asked where is dark matter https://www.physicsforums.com/threads/where-on-earth-is-dark-matter.764693/ The main response to my...

What theories attempt to explain the dark matter today? The force of gravity is the only thing that interacts with dark matter, the fundamental force "weaker" is gravity however, if she is not weak just reach dimensions that do not have access, dark matter could not be these heavenly bodies...

Dear Friends! I have read that in early universe in the inflationary phase the average density of matter was equal to critical density and now it is 10 percent of that due to which it is probably inferred that there must be hidden dark matter. Please correct the information if wrong or...

http://arxiv.org/pdf/1409.6302.p It is argued in this paper that Dark Matter does not exist, what do you think.