Matter not observed directly but inferred to exist based upon its gravitational effects

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Can Dark Matter just be clumps of Neutrons

I was wondering about Dark matter, and it occurred to me that why could it not be just nuclei of Neutrons with no electron cloud. Is it possible for such things to exists. Can Neutrons bond to one ...
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756 views

If the universe is full of dark matter, why is it only 2.73 K cold?

people! I am just a physics layman, but I recently watched a documentary about the universe and it was told that the universe is full of dark matter and energy and the universe is empty, so that ...
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175 views

Does the term “dark matter” apply to nonluminescent bodies which still interact electromagnetically?

On the new Astronomy.SE site, I was having a short discussion on one of my answers. The basic discrepancy was; can MACHOs like black holes/brown dwarfs/neutron stars be termed "dark matter"? My ...
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Is most of the matter in the observable universe within galaxies?

Do we know, either through observations or through theory driven computer simulations, the location of the majority of the visible matter in the observable universe? That is, is it located within ...
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183 views

Experimental Data for Mass Distribution of a Galaxy

My goal here is not to discuss dark matter in general. I know there are many other observational clues that hint us towards Dark matter. My goal is simply to understand this argument here a little ...
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262 views

Why doesn't the dark matter halo co-rotate with the luminous disk? What keeps it from falling into the center if not angular momentum?

Why doesn't the dark matter halo co-rotate with the luminous disk? What keeps it from falling into the center if not angular momentum?
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620 views

7 GeV dark matter particle: how particle accelerators missed it?

This posting is regarding the recent confirmation of the DAMA results that might be due to underlying differences in proton and neutron cross section with the dark matter particles, which reflect on ...
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160 views

following up dark matter accretion in supermassive black holes

A while ago, there was some conspicuous evidence that supermassive black holes didn't seem to be eating dark matter at the expected rate of 70%-30%, in fact, only 10% of the black hole mass increase ...
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286 views

Experimental foundations of the “otherwise galaxies would not hold together” argument for dark matter

On the question of motivation and evidence for dark matter, there are some illuminating (so to speak) answers on this site. I'd like to understand in detail the foundations of one of the lines of ...
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481 views

Does conformal gravity explain the Bullet cluster lensing effects?

Conformal gravity is an "alternative" theory of gravity, where instead of using the Einstein-Hilbert action composed of the Ricci scalar, the square of the conformal Weyl tensor is used. It was ...
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174 views

Why hasn't warm dark matter replaced cold dark matter as the standard model of cosmology?

The $\Lambda\rm CDM$ (cold dark matter with cosmological constant) is the current standard model of cosmology because the model comes with a long list of phenomena successfully explained by it. ...
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337 views

Can dark matter be relativistic dust?

As far as I know the mass of an observed object increases as it approaches the speed of light. Is it possible that the excess mass called "dark matter" is due to relativistic dust? Surely, stars ...
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344 views

Dark matter is electrically neutral

I would like to know how come if dark matter was electrically charged it would reflect light. What are the equations or the logic behind it?
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How much light is there in space and how heavy is it?

Our night sky is filled with stars. On a dark night a significant fraction of the sky is light. This light, we are told, has been in transit for many millions of years. There must therefore be quite a ...
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113 views

Where would the dark matter particle fit inside a picture of the standard model of particle physics?

Where would the dark matter particle fit inside a picture of the standard model of particle physics? While I am particularly fond of the Sterile Neutrino, I have not been able to find any example of ...
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455 views

Dark Matter 'Stars'

I'm aware that the Milky Way has a dark matter 'halo' around it, presumably a spherically symmetric distribution. But I'm completely ignorant regarding the theories explaining dark matter... Is there ...
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359 views

How much does electromagnetic radiation contribute to dark matter?

EM radiation has a relativistic mass (see for instance, Does a photon exert a gravitational pull?), and therefore exerts a gravitational pull. Intuitively it makes sense to include EM radiation ...
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728 views

Is dark matter really matter?

Is dark matter really a form of matter? We know it has a gravitional attraction and we know that everything that has a gravitional force is made by matter. But maybe this is an exception? And if ...
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346 views

Does the dark matter halo rotate with the galaxy?

If the dark matter halo is stationary related to the arms of the galaxy then tidal effects should slow the galaxy rotation. If it rotates with the normal matter in the galaxy then shouldn't it ...
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106 views

Are there experiments taking place right now that might show evidence for or falsify dark energy or dark matter?

What experiments at quantum or cosmic level might provide the strongest supporting evidence for or, conversely, potential for falsifying, the existence of dark matter or dark energy?
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132 views

What fraction of baryonic matter is in stars?

We know from big bang nucleosynthesis that baryonic matter accounts for about 5% of the universe's total mass-energy density. What is the current best estimate of how much of this is in the form of ...
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2k views

How the CMB anisotropy is linked to the existence of cold dark matter and dark energy?

After the data from the cosmic microwave background has been collected by WMAP or Planck, what types of analysis is needed to conduct in order to deduce the cold dark matter density and the ...
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173 views

Can dark matter and energy be formulated as local perturbations of the metric

Note, my formal physics education ended over ten years ago so I may be missing some obvious piece of understanding. The relationship between space-time and matter/energy distribution is described by ...
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68 views

What do the latest FERMI results say about dark matter?

There was an announcement at a recent UCLA symposium on dark matter by the FERMI collaboration which hints at some evidence of dark matter. The results aren't yet published, but the symposium news ...
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Integrated Boltzmann equation for dark matter

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 ...
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Why can't “missing mass” (=dark matter) be photons?

After a star lives and dies, I assume virtually all of its mass would be photons. If enough stars have already lived and died, couldn’t there be enough photon energy out there to account for all ...
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741 views

Is cold dark matter made of Higgs bosons?

"Stable Higgs Bosons - new candidate for cold dark matter", by Yutaka Hosotani Has the hypothesis in the above article been proved? What about WIMPs?
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Is dark matter around the Milky Way spread in a spiral shape (or, in a different shape)?

Dark matter doesn't interact with electromagnetic radiation, but it, at least, participates in gravitational interactions as known from the discovery of dark matter. But does dark matter exist in a ...
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259 views

How can I add dark matter to my $N$-body simulation?

I've written a simple non-scientific N-body simulation for fun: http://magwo.github.io/fullofstars/ I expected to create something looking like spinning galaxies (there are two invisible very heavy ...
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304 views

Could Dark Matter particles that don't couple to quarks or leptons have been produced?

With what we know about physics, is it possible that when the universe 'began', around when quarks and leptons were produced, another particle, which doesn't couple to either quarks, leptons or ...
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186 views

can we have a parallel earth made of dark matter?

In the sense that the two planets move together and has intelligent beings with their own forces and particles, but they just do not interact with (are invisible to) us?
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376 views

Sterile Neutrinos as Dark Matter

There has been recent activity by astrophysicists to determine whether a fourth flavor of neutrino, a sterile neutrino, exists. It would likely be more massive than electron, muon or tau neutrinos. ...
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260 views

Assuming SUSY is found to be incorrect, what would then be the most compelling candidates for dark matter?

From what I've read, the only remaining candidates appear to be either sterile neutrinos or MOND (MOdified Newtonian Dynamics -- it does seem to keep changing.) Did I miss anything else plausible?
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Does Dark Matter interact with Higgs Field?

Dark matter does have gravitational mass as we know from its discovery. Does it have inertial mass?
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463 views

Sparticles: Relationship to supersymmetry and dark matter?

I was attempting to read this paper after watching a show with Brian Greene. As I understand it, sparticles are a prediction of supersymetry, so I was wondering: Wouldn't the discovery of ...
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55 views

Was the matter-energy content of our universe always distributed in the same ratios?

Currently, Dark energy (68.3%) and Dark matter (26.8%) together constitute about 95.1% total matter-energy content of the universe while only 4.9% is ordinary baryonic matter. Was this always the ...
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77 views

Dark Civilizations? [duplicate]

I just read that maybe the dark matter could have dark forces. Hence, I wonder: dark atoms, dark galaxies, dark intelligent beings. Basically a parallel, interpenetrating universe. Is this ...
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164 views

Proportion of dark matter/energy to other matters/energy at the beginning of the universe?

What was the proportion of dark matter/energy to other matters/energy at the moments after the beginning of the universe (standard Big Bang model)?
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845 views

What is currently incomplete in M-theory?

As it is, what is currently and seemingly incomplete in M-theory? One example I can give is explaining dark matter proportions and.. how do we perceive the world as 4-dimensional. Thanks everyone.
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141 views

What are wimpy particles?

Can anyone give a brief overview of what a wimpy particle is?
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70 views

How dark matter makes ordinary matter far from the center of a disc galaxy rotate faster?

I was reading several questions on this subject, incluiding duplicates, and even received the very useful help of Kyle Oman in this question to understand the behavior and distribution of DM. But I'm ...
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92 views

Distribution of dark matter in galactic halos

Often dark matter around galaxies is referred to as a 'halo'. I've seen the galactic rotation curves, but I'm having trouble visualizing how the dark matter is distributed for a typical rotating ...
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192 views

Relation of General Relativity to Dark Matter and Dark Energy

I was reading an elementary book on dark matter (in fact, a historical perspective) and there were mentioned how the scientific community react to the idea of dark matter proposed as a solution to ...
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403 views

Why is the dark matter density profile within the solar radius (and local density) uncertain?

It seems that we know the rotation curve inside the sun's galactic orbit fairly accurately. Then wouldn't we be able to just take the derivative* of this to get the DM density profile at smaller ...
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356 views

Could dark energy be the effect of gravity at great distances?

This may be a silly question, but is it possible that dark energy and gravity are related to each other? Space-time is deformed everywhere in space by objects with mass. The more massive the object, ...
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52 views

What is the analogous effect of cosmological redshift for particles with mass?

Due to the metric expansion of space, light emitted from earlier times in faraway parts of the universe and travels for a long time to reach us get progressively redshifted, decreasing the energy of ...
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518 views

Difference between baryonic, inertial and gravitational mass? (and relation to dark matter)

Inertial mass: determined from Newton's f = ma Gravitational mass: determined via Newton's law of gravity Baryonic mass: sum of mass of all baryons. Which ones ...
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97 views

Vacuum polarization of dark matter candidates

Can a dark matter particle (axions, for instance, but the question applies to any valid candidate for dark matter) induce QED vacuum polarization effects even if being electrically neutral and with no ...
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866 views

What is the formal definition of spin-independent vs. spin-dependent scattering?

In the search for WIMPs as the dark matter particle, there is an important distinction between spin-independent and spin-dependent scattering. Roughly, WIMPs scattering from nucleons through a ...
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Relation between dark matter and supermassive black holes located in the center of galaxies

This research (see link), conducted on 3000 elliptical galaxies (which are typically galaxy merger results), reports finding "distinct relationship between the mass of the dark matter halo and the ...