Dark matter Definition and 919 Threads

Guys - I need some help here. I am just an interested layman, so i don't have deep understanding of the math involved in gravitational theory, but I remain quite confused regarding the concept of dark matter and dark energy. I understand that this is a result of large-scale gravitational...

I have not yet read anything about special relativity, so these questions may be naive. Here are my questions (very much related to each other): 1) Is it assumed in the physics community that dark matter is really matter? If so, why? 2) Can't it be that "dark matter" is just a dent in...

[b]1. Homework Statement [/b where i can find articles and paper on the subject of dark matter and the most recent experimental resolts on this subject? Any suggestions on bibliography? Homework Equations The Attempt at a Solution

Could someone help explain how these are related? I kind of understand the Higgs particle/field. It is believed to be the reason why fundamental particles (fermions and bosons) have mass. So, then I read that one of the problems with the Higgs field is that if it is true things should be...

Could you be more specific? You suggest that there are methods by which dark matter can dispose of kinetic energy, but can you show a method that is purely a gravitational interaction? If dark matter particles ineract with each other non gravitationally then do you agree that the dark matter...

I heard that dark matter could be the CMB mass corresponding, but I am not satisfied from that. What about this?

Can't it just be planets, asteroids, dust or gas which do not emit enough light to reach us?

I've recently come across some doubters as to the existence of dark matter. If you find yourself among that group, please read the following article on New Scientist and my comments. Then you can jump on the DM bandwagon with me! Dark matter and normal matter 'divorce' in cosmic clash...

If dark matter is evenly distributed throughout the galaxy then how much should be within the orbit of neptune?

http://agenda.albanova.se/contributionDisplay.py?contribId=389&sessionId=257&confId=355 This came out at the Identification of Dark Matter (IDM-2008) meeting in Stockholm on 18-22 August PAMELA - an experiment searching for dark matter with cosmic antiparticles "The PAMELA satellite...

Hello: I`ve heard that supersymmetry predicts new fundamental particles that may explain dark matter, and that dark matter and dark energy is 95 percent of the total mass of the universe... What are these fundamental particles predicted by supersymmetry?, and how...

how is dark matter different from the old "ether" theory

A year ago we had a HW problem about galactic rotation curves: If the dark matter density is \rho= \frac{\rho_0}{1+\left(\frac{r}{r_0}\right)^2}, Then how does velocity depend radius at large r ( r>>r_o)? You want to use the virial theorem here, so you calculate M(r) and then finally...

I have been thinking about this for a while, and I am not sure about how I can visualize this. Lets imagine that there can exist clouds of primordial matter, far away in space. 1. Can it be possible for a cloud to exist and be made out of strictly protons at 0 kelvins? I don't...

this topic relates to my post in a threat relating to GLAST https://www.physicsforums.com/showthread.php?t=240620 Super massive black holes eject jets of matter back out into space. The matter in these jets shoot out of the black hole at 99% the speed of light. However the escape velocity...

I was reading the wiki page on dark matter, and have trouble visualizing how galaxies keep their shape if most of the stars rotate at the same rate. If I try to imagine this (ie: without any sort of math modelling of the gravity interactions involved) I picture everything just merging into a...

The flyby anomalies, you may remember, are a set of fascinating data indicating that spacecraft flying past Earth undergo a strange, step-like change in their acceleration. The Galileo, Near, Cassini and Rosetta spacecraft all seem to have been hit by this weird phenomenon and while...

I recently had some thoughts about the big "space" between electrons and the nuclei and how weird it would be if that space were truly "empty". This led me to try to understand exactly what was empty space and the more I thought about it, the more I began to think about dark matter. I know empty...

My question is this: Why are we (as a community) so eager to disregard modifying Newtonian Dynamics (MOND)? Of course it's incredibly accurate on macroscopic scales, but isn't science meant to be progressive? Since Zwicky's observation of galactic cluster rotation in 1922 and the...

I was curious if dark energy will one day tear everything apart in the universe. Since dark matter is what keeps everything in the universe in place and not scientist have found out that the acceleration of the universe is caused by dark energy, so basically one day it will overcome the dark...

The whole solar system is orbiting the center of the Milky Way at about 250 kilometers per second. But the Earth is also orbiting the Sun. When the Earth is at one part of its orbit, its velocity (30 kps) adds to that of the solar system, but six months later it’s headed the other way, and its...

So you discover the dark matter particle... Now what? When, or if we ever discover the dark matter particle, how can that knowledge be applied to every day life? Fermi's nuclear reactions allow great fuel sources and weapons to be built. And Hubble opened the door to the universe. Will this...

Didn't Einstein say that mass and energy were interchangeable quantities? Electromagnetic waves transport energy - Does this therefore mean they also transport mass? Could, therefore, all the radiation coming out of every decaying atom in the universe, every star and every accelerating...

If dark matter only interacts with baryonic matter gravitationally, would it pool at the center of stars, planets, and other ordinary mass objects? That is, suppose there was a particle of dark matter, whatever that is, at rest at the surface of the earth. Since it would not interact with...

Kind of a newbie question that may have an easy answer, but if the observable universe IS the entire universe, and assuming 96% dark matter (which is the current estimate, no?), would the resultant mass (I saw 3 x 10 to the 55th power g/cm3 somewhere) make the universe continue to expand, or...

Huge filaments of dark matter have been detected in a survey of thousands of distant galaxies. The discovery supports the idea that dark matter drove the formation of galaxies and larger cosmic structures and resolves a discrepancy in previous studies about how much dark matter the universe...

The observation on the bullet cluster collision was stated as direct evidence for dark matter. http://apod.nasa.gov/apod/ap060824.html But could there be a possibility that it's just some molecules that are too dark to be seen ?

I keep hearing about how this exotic Dark Matter is supposed to be evenly spread out across the universe... and that it doesn't interact with normal matter, only through gravitation, etc... My question is, how is this the valid conclusion from the fact that our Gravitation formulas don't...

I could not find much info on neutron degenerate matter. Only in reference to neutron stars. http://en.wikipedia.org/wiki/Degenerate_matter neutron degenerate matter Has anyone looked at the possible properties of a neuton liquid or solid to determine if it could act as dark matter? jal

At this point, i am not yet convinced that enough data is in on the subject of dark matter/dark energy to support expansion of the standard model to include them, but, then, i am just a lowly layperson... How do you guys see dark matter and dark energy fitting into the standard model? how...

The magnetic field as "dark matter" Is it possible that the magnetic field has energy? If so, how much would that energy be? Would the energy have an impression on the space-time continuum? Since they extend infinitely, could the magnetic field of stars have more energy than the stars...

I was simply wondering if dark matter is most-likely a Solid, Liquid, Gas, or Plasma.

If I was traveling 60% of light speed in one direction, and you were traveling 60% of light speed in another direction We would be invisible to each other correct ? Is that all that dark matter is? matter in which the distance between us is increasing faster than light speed?

Why do we think there is a significant amount of Dark Matter in the universe? a) Descibe at least 3 independent situations which require Dark Matter to understand observations. b) Why don’t we think that Dark Matter is baryonic? c) What do we think is might be?

Suppose one measures the total mass of a galaxy somehow and its total luminosity. What mass to light ratio (in solar units) is considered a signal for dark matter and why? For example if M(galaxy)/L(galaxy) = 10 M(sun)/L(sun), is that considered 'too high' and a signal of dark matter? My...

I have just encountered an interesting hypothesis on the nature of dark matter. The author proposes that electrons, stripped from matter falling into black holes, comprises dark matter. THis is my first post, so I respectfully ask two questions: -How would electron clouds interact with photons...

An interesting review paper of the search for DM particle(s): Direct Detection of Cold Dark Matter. The search continues. Garth

Thinking about the hypothetical dark matter, I came to the following (primitive) thought experiment. Consider a large sphere (say radius R) filled uniformily with matter and a small test mass located at radius R1. This test mass will experience a force to the centre of the sphere and the...

So I'm running a superhero game on another forum and I am trying to keep comic book physics to a minimum. Problem is...I've never taken a physics class (I'm a high school student, I've taken Biology and Chem but Physics is next year). I was wondering how dark matter and dark energy work and...

http://www.space.com/scienceastronomy/071029-mm-mog-theory.html

Does anyone know if gravitational lensing confirms the existence of Dark matter?

No, not really, however my question is why has not dark matter been discovered, observed directly in the cosmic background radiation? [/Color] Reference: http://en.wikipedia.org/wiki/Dark_matter

"black hole the video". see what you think. go to a google video window. video feedback loop shows a black hole in real time. is the center rotation dark matter?

Why does cold dark matter imply a bottom-up scenario of structure formation? and why does hot dark matter imply a top-down scenario of structure formation? is it simply because cold dark matter is slow moving (non-relativistic) and slow moving things are more likely to clump together to form...

A nice review of Dark Matter and Dark Energy, including discussions of the CMB and Inflation, arrived today at the arXiv: http://arxiv.org/abs/0706.2986 I think some people here would find it quite interesting.

Hi everyone, I have just read an article about the discovery of a ring of a dark matter. In fact I do not understand this matter very much, except that it has great gravitational field in space. Can anyone explain shortly about that or just give me some web links that I can read about that...

Could Dark Energy and Dark Matter be ...? Time? I am sure that there is hundreds of reasons why this could not be possible but, it seems to me that there is some kind of synergy in this hypothesis. Imagine for a moment that time is a form of energy that we have not yet managed to quantify...

I've heard much talk of dark matter and the universe being more massive (according to calculations) than it should be given the amount of observable matter in it. Or something to that effect. But I am thinking that since black holes pretty much consume matter and gain mass and are...

this just out: a survey of efforts to detect DM particles. http://arxiv.org/abs/0705.3345 Direct Dark Matter Searches N. J. Spooner Submitted to JPSJ, 20 pages, 5 figures "For many working in particle physics and cosmology successful discovery and characterisation of the new particles that...

I was wondering, if dark matter (DM) halos are spherical in nature and increase in density as a function of distance from the galactic core, why does the density drop off so suddenly and why would stars on the edge of a galaxy feel an inward pull? To elaborate on the 2nd question, if DM...