28
votes
Accepted
How would "dark matter", subject only to gravity, behave?
What you describe is the standard paradigm in cosmological physics, so it has been studied extensively. The basic consequence of dark matter not having significant nongravitational interactions is ...
- 4,260
15
votes
Accepted
Is there more dark matter than we previously thought?
Probably nothing changes
Several reasons for this:
The study actually asserts (last paragraph of main text) that:
The IMF variation also calls for an extensive revision of star formation rates and ...
- 3,992
8
votes
Is there more dark matter than we previously thought?
Barely, because the estimates of dark matter are not sensitive to the IMF, they use (a) the dynamics of objects in galaxies to estimate the total mass of that galaxy, (b) observations of kinematics in ...
- 146k
8
votes
Accepted
Have we discovered a Galaxy lacking in Dark matter?
I don't work in this field, but it looks like the answer is "yes". The paper in question is here. See also 2018 preliminary results (linked to in your OP) and 2022 follow-up.
My impression ...
- 3,992
7
votes
Can dark matter accumulate at Lagrange points?
If dark matter is dissipationless and only interacts gravitationally, then no it can't. How could it be brought to approximate rest$^1$ with respect to a Lagrangian point, its inertia would mean it ...
- 146k
7
votes
If a supernova explodes close to the centre of the milky way does its light get blueshifted by dark matter by the time it reaches the Earth?
Light from the Galactic Center is gravitationally redshifted (not blueshifted) by a little over one part in a million as it climbs the Galactic potential to reach us. While dark matter contributes, ...
- 4,260
7
votes
Is dark matter made from the particles that had charge but no mass in the early part of the Big Bang
Charged, massless particles would be a form of "hot" dark matter. i.e. A form of energy density that was relativistic at the epoch of structure formation and of course, still relativistic ...
- 146k
6
votes
Accepted
Dark Matter's effect on galaxy structure
The dark matter isn't directly responsible for the rotation of the Galaxy - that is a consequence of the initial angular momentum (or the angular momentum it has accrued during its formation).
Dark ...
- 146k
6
votes
Accepted
How can we measure the amount of Dark Matter in the universe to the level of a percent?
The most precise figures for the amount of dark matter in the universe arise from measurements of the cosmic microwave background and are supported by estimates of the primordial abundances of helium ...
- 146k
5
votes
Accepted
What is everything wrong with this theory of dark matter?
Sorry, but this is not correct. In the diagram, spacetime and hence the universe is the curved line. The sun, Earth, and any dark matter are not on spacetime, they are in it.
Visualising spacetime as ...
- 116k
5
votes
If w bosons can create dark matter neutrinos by decay, can they also create dark energy?
The W boson has a lifetime of $3\times 10^{−25}$ seconds. So any big bang W bosons will have long decayed. So they are not a dark energy source. Also, they produce "hot" relativistic decay ...
- 14.4k
4
votes
If a cluster of stars in dynamical equilibrium falls into a much larger blob of dark matter, will it get hotter and expand? Will it stop?
Yes, what you are proposing is essentially the accretion of dwarf galaxies/globular clusters onto larger bound objects. As the gravitationally bound cluster falls towards the more massive object, it ...
- 436
4
votes
Is dark matter made from the particles that had charge but no mass in the early part of the Big Bang
No, because if "dark matter" had no mass, it wouldn't be dark matter anymore.
Keep in mind dark matter needs to exert gravitational force, and massless particles do not exert gravitational ...
- 3,992
4
votes
Accepted
When did the first cold dark matter halos begin to originate?
The first dark matter halos typically originated in the redshift range 30-70, at a time of 30-100 million years. This is based on assuming that the initial variations in the density of the universe at ...
- 4,260
4
votes
Do black holes emit dark matter as Hawking radiation?
Black holes are expected to be able to radiate every particle. There is no connection to what kinds of particles fell into the black hole.
And indeed, evaporating black holes in the early universe ...
- 4,260
3
votes
Can the CMB Cold Spot be explained by dark matter redshifting photons?
Can the CMB Cold Spot be explained by dark matter redshifting photons?
More specifically, the explanation discussed by the linked article is that the CMB Cold Spot is (at least partially) explained ...
- 4,260
3
votes
The consequences and the mechanisms of a shift of the Earth away from the sun
Your idea of a planetary-mass black hole is on track. The real challenge here is that the black hole only gets one chance to change the orbit as it passes through the solar system. It would definitely ...
- 3,691
2
votes
Proportion of dark energy, dark matter, matter
Yes, all of these estimates have uncertainties. Table 2 of Planck Collaboration (2021) are the most recently compiled results. The exact values depend on which datasets go into the estimates.
There ...
- 146k
2
votes
When two galaxies with dark matter halos merge do they provide evidence for fermionic or bosonic dark matter?
There is no law of physics that prevents fermions getting arbitrarily close to each other. The Pauli Exclusion Principle says that no two fermions can occupy the same quantum state. Basically, this ...
- 146k
2
votes
Accepted
Why is the dark matter component of MOND important in central regions?
MOND, in generally, does not show a need for dark matter in the central regions of galaxies. The central regions of galaxies outside of galaxy clusters, in contrast, are a problem for cold dark matter ...
- 144
2
votes
Has anyone observed dark matter? what could we see?
I’m not a dark matter expert, but I think we have to clarify some fact about it.
First of all, the reason we called them dark matter is that they don’t interact with normal matters, photons, and ...
- 71
1
vote
Does dark matter exist because as Einstein said the laws of physics should be the same inside and outside a black hole?
The simple answer is: no.
The reason is that there is no mechanism preventing matter from speeding when falling into a black hole (it cannot move faster than light according to the local light cones, ...
- 14.4k
1
vote
Why are WIMP dark matter particles, if Majorana-like, expected to annihilate upon contact? But not neutrinos?
Gluons actually annihilate, so do neutrinos, just more rarely than Neutralinos.
Neutrinos, Gluons, WIMPS, Majorana particles are always neutral being a Truly Neutral Particle. These Majorana particles ...
- 1,208
1
vote
Are vacuum fluctuations that produce dark matter correlated to fluctuations that produce baryonic matter?
Yes. This question was only settled in the last decade or so, but initial variations in the baryon density and in the dark matter density seem to agree at the percent level. See for example "...
- 4,260
1
vote
Is the mass function of dark matter halos fundamental or an approximation based on experimental data?
Assuming you know the statistics of the cosmological initial conditions (e.g. the matter power spectrum), the halo mass function can be predicted from first principles using so-called excursion set ...
- 4,260
1
vote
Could dark matter be ordinary cool matter far away?
I think it is unlikely because of the importance of dark matter in more local dynamics.
Dark matter is necessary to be able to account for the dynamics of our galaxy, not just the behavior of distant ...
- 3,404
1
vote
The anomaly of spiral galaxies and the need for dark matter
Besides the fact that the central black holes really aren't all that massive compared to the galaxy, there is another more fundamental reason they can't explain the overly rapid revolution of the ...
- 3,691
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