Dark matter Definition and 935 Threads

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!

What would a cosmological model without dark matter and dark energy look like? This requires imagining that the observational evidence for dark matter and dark energy are explainable by other means. In other words, absent of the idea that the universe is filled with 25%DM and 70%DE, but...

I was thinking about this and simply don't know enough about it all to answer my own question so was hoping someone could help me, is it possible that the dark matter we are searching so hard for are actually Nutrinoes, since they do indeed have mass, with their sheer numbers could it explain...

Hello all, I'm trying to do some research on dark matter and its effect on globular structures for my undergrad research project. I'm having difficulties gettin the ball rolling and need some help on where to look for journal papers on the topic. Unfortunately the professor that I will...

The way I understand it, non-baryonic dark matter can be thought of as matter that interacts gravitationally but not electromagnetically with other matter. Is there a dual type of matter that interacts electromagnetically but not gravitationally? And if there is, or can be, such matter, can it...

Could quantum mechanics be related to dark matter? As in new 'stuff" is being made therefore pushing the time space in between galaxies apart. Which to me makes sense as time and space is created (The Big Bang) wouldn't it be created on the quantum level? Couldnt this still be going on in the...

Photons must have a certain amount of energy to be absorbed by an electron. A photon with a little too much energy to be absorbed by one electron and not enough to be absorbed by another would be invisible to all electrons and everything else. However such photons still have energy so they would...

Dark matter, is it composed of... How can we be sure dark matter is matter, if it is, is it composed of Atoms? I thought if something was composed of Atoms it had to react to a magnetic field, which astrophysicists say it does not. Does it have a gravitational effect on other masses? Please...

What do we know about black holes swallowing dark matter? Dark matter exhibits gravitational effects, right [lensing and keeping star orbital speeds about galactic centers rouighly independent of their distance from a galactic center]? So it seems black holes should consume both normal and dark...

The science series currently on TV in the US called WORMSHOLES, narrated by Morgan Freeman (the actor) has a number of recent some new ideas. (Very worthwhile series, by the way.) The show last night discussed dark matter and dark energy and referred to a distant pair of galaxies colliding...

I hope a pointer to a speculative post on a blog is OK in this group. But as the posting rules at https://www.physicsforums.com/showthread.php?t=5374 reference a dead page, I was unable to check ;-) (It would be easy to copy and paste that article here, if that is considered desirable to...

How much dark matter is in the Sun, and does it have any effect on any process in the Sun? What percent of the total mass and volume of the Sun is DM by weight, and by volume? Does the high density of the Sun impede movement of DM? Is there a lot of DM trapped by the Sun's gravitational...

This theory just dawned upon as i feel asleep- In the same sense matter bends spacetime fabric to create the force of gravity (matter and light are attracted to it), is it possible for spacetime fabric to be inverted, so matter and light flow (repel) away from this 'negative gravity'? Instead...

How it's possible to discern dark matter from dark energy? Why do we need both things? How we can tell so accuratelly that the universe is made up 71.3% of dark energy and 27.4% of a combination of dark matter and baryonic matter. Thanks for answer.

im having a hard time understanding just what it actually is. I've heard about WIMPs and now quirks. But i know we can't see it, but how dose it affect us? Why does it emit no light? I've also heard about the big crunch saying that if there is too much matter in the universe it would...

If Dark Matter and Dark Energy are so abundant wasn't to be expected that they should be found on Earth? We can find elements such as uranium on our planet, which is one of the rarest elements fused on Stars, Dark Matter being estimated to account for roughly 20% of the total mass of the...

I have some questions that I have been wondering about for a while. I'm not a physicist, and I don't know the math behind anything. Just a guy who is thinking up some questions. Just think of me as a student asking some questions. I know these questions can be answered and have been thought of...

I wonder if there is any correlation between the weak coupling of a quantum field in the path integral and how it adds to or cancels out vacuum energy. If so, then how would weakly interacting dark matter effect the vacuum energy? Thanks.

A couple of decades ago, there were searches for proton decay basically looking at pure water over time, and these ruled out simplest non-SUSY GUT like SU(5) and SO(10). There are a variety of direct Dark Matter search experiments including CDMS II CRESST, EDELWEISS, and EURECA, DRIFT, MIMAC...

we all know of positive / negative mass, could the theorized "Dark Matter" actually be "Neutral" Mass? just a thought:)

I know that Newtonian mechanics predicts dark matter due the the fact that the sun (and other stars) is orbiting around the centre of the galaxy much faster than expected But i was just wondering if Einstiens general theory of relativity predicted this aswell? Does it "say" there is as much...

I have no quantitative understanding of current cosmology, so go easy. The intent of this post is to promote civil debate, not critisize current science. So basically, I look at astrophysicists and I think of them as saying "oh, because there are observations we don't understand, there...

I'm looking at this thread, https://www.physicsforums.com/showthread.php?t=403472 Dark Matter, On the Ropes? If there is no dark matter, could the neutralino of MSSM, SUSY and string theory, or the axion of GUT's exist? IF there is no dark matter, doesn't this imply there are no neutralinos...

What comes next if the dark matter hypothesis fails? A hypothesis that is fundamentally incorrect blocks any progress. The entire effort is trying to make a round peg fit in a square hole as opposed to looking for the correct mechanism. What theorist and modeler do is try to change the free...

Hi... Wikipedia says that only five percent of the universe is matter that we know... Can anyone tell me a paper where the percentages of visible matter, dark matter and dark energy in the universe are given?

Assuming gravity is matter curving space as Einstein says, isn't our theory of dark matter just an assumption that because more gravity is required to explain galaxy formation that it must be caused by unseen matter? Why do we assume that the curvature of space required must be caused by matter...

The thing we call dark matter its really just dark gravity. we don't know if its matter or something else, for example: -in ST it could have something to do with parallel universe -in QM maybe some quantum fluctuation in the higgs field -in GR it some matter that doesn't interact with...

are null to 90% If, as in searches for proton decay, the results continue to be null for experiments in the next several decades, as they have been for proton decay, at what point does the SUSY-neutralino space, or GUT axion, or other cold DM candidates, becomes constrained? Obviously a...

There are multiple fundamental problems with the explaining or the explaining away of observations related to the mass evolution with redshift of the super massive object that is believed to be found in almost all galaxies. Weight Gain Problem - Early Universe Fast Gain Problem SMB's at...

Dark Matter interacts only gravitationally. Stars and planets form by gravitational clumping. Clumping of whatever is there: gas and dust and presumably dark matter. By the cosmological principal we are at a typical generic location within the universe. Whenever the sun and Earth clumped...

If ordinary matter is related to energy per E=mc^2, then can dark matter also be similarly related, and if so, is there a name for this energy? I understand that "dark energy" (the cosmological constant in the expanding universe) and "dark matter" bear no relationship, so I'm wondering that if...

Could dark matter be the other universes posited by MWI. there has been speculation that the parallel universes remain weakly coupled by gravity after diverging, but we can't observe or communicate with them any other way. that sounds similar to the properties of dark matter, can't observe it...

If Dark Matter is made of particles, then wouldn't it be possible to have clumps of it collapse into a black hole? Would there be any radiation from that collapse that we could see? Would that radiation be distinct from the formation of normal black holes? Shouldn't we be able to measure the...

I'm just watching a lecture series with Mark Whittaker in and he states (while talking about primordial roughness and sachs-wolfe effect) "the property that atomic matter has dark matter does not, is that it can cool" but he leaves it at that and provides no further clarification,and I am...

Everyone points to the Bullet Cluster as the best proof of Dark Matter. But I have a few questions about the rationale. There are aspects of the proof I don't understand. 1) What is the mechanism which makes the interstellar gas visible at such a distance in this particular case? Is all...

Does anyone happen to know the average density of dark matter per unit volume in the milky way? I've seen at least one formula, but I'm not sure I fully comprehend it. Here is the equation I found: ρ0 = 4.5 × 10−2(r0/kpc) − (2/3)2x10^30kg pc−3 The only part of this equation that I can't...

Hi All, First question so please go easy on me. I'm currently reading 'Why Does E=mc2? at the moment and in an early chapter, Brian Cox referers to The Eather and how daft the concept was because it would cause drag in the universe and planets would lose orbital momentum etc, etc. Now...

Hi All, I would like to know what is dark matter. Thanks DaTario

If brane theory says that gravity is weak because it extends into another spatial dimension, is it also saying that the gravity attributed to dark matter might be due to matter in another spatial dimension?

From National Geographic: Daily News, by John Roach, March 22, 2010 http://news.nationalgeographic.com/news/2010/03/100322-dark-flow-matter-outside-universe-multiverse/" As if Dark Matter and Dark Energy aren't weird enough, now it seems we have verified proof of "Dark Flow". From the...

matter in The universe is thought to be made up of 75 percent hydrogen and helium is thought to make up 25 percent of helium; Dark matter is thought to make up 25 percent of the universe and 75 percent dark energy; that's an interesting coincidence. , and currently physicists are not certain...

I read that the distribution and proportion of dark matter to regular matter is different for regular-size galaxies and dwarf galaxies. Could you guys elaborate on that?

Hey guys, I was just pondering the idea of dark matter and a thought crossed my mind. I may be entirely off, but a few connections can be made between gravitons and dark matter. Neither can be detected directly with any classical methods (EM, pressure, etc..), and dark matter has no apparent...

Hi Clever People, I've been watching an amazing program about dark matter, dark energy and dark flow. I thought there were questions that should have been asked, but then I'm a website designer - what do I know! So... as an interested non-physicist, my apologies if this question is...