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

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Dark matter: Will Special Relativity hold?

Part 1: It’s been said that dark matter makes up about 26 % of the universe. The restart of LHC would be dealing with the existence of dark matter also. Consider a situation that the results are ...
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Why dark matter and general relativity?

My knowledge on this subject is minimal, so sorry if my question is obvious. But why is the current consensus that there is something called dark matter rather than that our current theory of gravity ...
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How do we know dark matter isn't curved spacetime?

Could Dark Matter actually just be spacetime with curvature "leftovers" from the big bang or the inflationary epoch?
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310 views

Is dark matter moving faster than light? [closed]

My way of thinking is as follows: Consider a balloon. Let this be blown into a nearly elliptical sphere. Now, the temperature inside the balloon is increased by some means; this leads to the ...
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346 views

How much of the universes mass is bound up in photons traveling between stars?

I was watching a Scott Manley video on youtube and he mentioned that the Sun was loosing 4 million tons of mass a second as it converts to energy. With a few trillion trillion stars also converting ...
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201 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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200 views

Relation between $\Lambda$ and $\Omega_\Lambda$ in $\Lambda\mathrm{CDM}$

In minimal $\Lambda\mathrm{CDM}$, there is a parameter labeled $\Omega_\Lambda$, and current fits place it at around $\left( \Omega_\Lambda \sim 0.73\right)$. Meanwhile, $\Lambda$ enters the Einstein ...
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Does it make sense to continue searching for dark matter on Earth?

The Large Underground Xenon Detector (LUX) recently released results1 that they have found no signs of dark matter2 after a ~3 month search this spring and summer. The LUX group plans to spend all of ...
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Has energy in 'transit' been incorporated into missing matter calcs.?

Has energy in 'transit' been incorporated into missing matter calcs. ?It would seem that, although very small in mass, the sheer number of particles shhoting about from one end of the universe to the ...
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263 views

Distribution and detection of dark matter

I feel in the dark (no pun intended :), I'm sure most of you are familiar with this image I pulled from wikipedia: The caption reads: "3D map of the large-scale distribution of dark matter, ...
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Is there a binary black hole system in the middle of the galaxy? [closed]

We have observed gravity effects from black holes in the center of galaxies, but galactic centers are dusty so we can’t tell if it’s one black hole or two black holes in a binary system in there. A ...
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106 views

Wouldn't dark matter throw off the calculation of Earth's 'light' mass and estimates of its composition?

The Cavendish experiment first determined the mass of the Earth and (arguably) the gravitational constant. However, given the ubiquitous nature of dark matter, it seems reasonable that at least some ...
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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

Missing Matter Problem and Galactic Kinematics

This is a re-wording of an earlier problem I posted. The standard example of the Missing Mass Problem comes from the rotational profiles of galaxies. By counting up the visible matter, we extrapolate ...
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114 views

Can you collide with dark matter?

Assuming dark matter has space and weight, can dark matter collide with others planet? If unlike normal matter, dark matter repels matter, Will it makes dark matter impossible to collide with normal ...
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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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140 views

Galaxy rotation curve

In calculating galaxies' rotation curve, it is assumed that masses outside the orbit has no contribution and masses inside the orbit can be deemed as if they were at the center, just like the case of ...
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163 views

On non-local physics in cosmology by prof. B.V. Alekseev

Recently I've encountered work by prof. B.V. Alekseev, in which he claims that some physical problems can be easily solved if we consider non-local interactions in kinetic theory (interactions of ...
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117 views

Can observations of cosmic super voids teach us anything about time, dark energy, or dark matter?

Can observations of cosmic super voids teach us anything about... Time - If gravity affects time is there a chance we could gain any further information from studying a region with lower than ...
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1answer
178 views

Do most physicists believe that axions exist? [closed]

Is the theoretical justification behind proposing axions sufficiently robust, like, say the Higgs boson prior to its detection, that one should consider the existence of axions as generally accepted ...
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176 views

Could Hyper-Massive Black Holes be due to Dark Matter in the Early Universe?

An interesting discussion started here: Is there a limit as to how fast a black hole can grow? I am curious if Thompson Scattering and Eddington Luminosity have the same effect on Dark Matter (or ...
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167 views

What is dark matter composed of? [duplicate]

They say that about 80% of the matter in the universe is dark matter -- some unknown substance that has mass. But what is this matter expected or speculated to be composed of? For example might it ...
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1answer
128 views

WIMPs - would they be charged?

I'm no expert in this stuff, it's just a hobby to me, but I've been reading up on the WIMP theory a bit - layman articles, not published research. From Wiki on Dark Matter: It also cannot ...
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129 views

How much dark matter is needed to gravitationally distort light?

I understand that dark matter only has a gravitational property. It does not interact directly with regular matter or EM radiation. The evidence for dark matter comes from observations that contradict ...
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225 views

Why does the amount of dark matter increase the further away from the galaxy's center?

Why isn't the dark matter just randomly distributed? How does it know where to go?
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What is meant by “shallow density profile” in the context of dark matter halos?

Evidently there is a consensus about the density profile of dark matter at large distances from the centers of galaxies, but it is not known whether their density profiles are "shallow" or "cuspy". ...
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How does mirror matter account for the faster than expected spin of gallaxies?

To explain dark matter, some physicists have postulated the existence of mirror matter as an alternative to WIMPs, where mirror matter particles could interact with one another in the same way as ...
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What is a reasonably accurate but simple model of the Milky Way's gravitational field?

I am putting together a toy program which shows how stars move around in the galaxy. To run the simulation I need to know strength of the Milky Way's gravitational field at any location in it. I'm ...
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What exactly is 'Dark Matter'? [duplicate]

There are many documentaries, forums, blogs and more dedicated to Dark Matter. I have been frantically searching for an answer to my question however none of my sources have clarity to the matter of ...
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292 views

Can curvature waves in f(R) theories explain gravitational lensing in cluster collisions?

The Einstein-Hilbert action leading to Einstein's equations is $$S\sim\int R \sqrt{-g}\, {\rm d}^4 x$$ There is a class of modifications of Einstein's relativity called $f(R)$ theories of gravity ...
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184 views

Dark matter, dark energy [closed]

As I understand dark matter and dark energy are quite theoretical . That modern theories require the existence of these phenomena. I read a lot of information about this. And I realized that ...
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99 views

Why is dark matter used to explain big movements but not small ones

Just read that there are perturbations of stuff in the outer solar system that suggest there are Earth sized planets far out from the sun, in the dark. When the same sort of effects are seen at the ...
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Could the dark matter sector be boring?

People always talk about finding good dark matter (DM) candidates of beyond Standard Model (SM) theories. To be a proper candidate the particles should not decay into the SM particles and could ...
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Why are neutrinos ruled out as a major (or even sole) component of dark matter?

A number of times I have encountered in text-books and articles that neutrinos might contribute only a small fraction to dark matter. The reason has to do with the fact that if all of the dark matter ...
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What physical processes can convert dark matter into dark energy?

In this news article, it is mentioned that it could be the case that some physical processes convert dark matter into dark energy ...
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260 views

Could dark matter/dark energy turn out to be tachyonic?

Today, I was watching the Inexplicable Universe with Neil deGrasse Tyson. He spoke about Dark Matter, Dark Energy, and then he spoke about Tachyons. Naively, I thought what if the reason we can't ...
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Has the idea of holeum been debunked?

Here is the wikipedia article. The basic idea is that the primordial density of microscopic black holes was high enough that many were able to form stable bound states before decaying through Hawking ...
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121 views

A Theory of Almost Everything? [closed]

Before I present this theory, I ask that you take the time to read this disclaimer. I do not claim to have an excellent knowledge of physics, it is actually rather limited. Therefore, I am not ...
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At what point do researchers in physics make the leap from wild theoretical ideas to physical experiments? [closed]

Dark Matter, on the surface, appears to be a wild idea... Some invisible thing that we can't see that controls the movement of most of the universe. Yet, we are searching for it. Why? What evidence ...
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Why can't dark matter be baryonic? [duplicate]

Here's what I know about dark matter: Astrophysicists realized the movements of galaxies and other astronomical bodies cannot be explained by the gravitational effects of matter known to be there, so ...
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1answer
98 views

How can we be Certain that Dark Matter Exists if we Cannot See it or Directly Detect It? [duplicate]

It seems very certain that dark matter exists and that it makes up 26.8% of the Universe today (along with 68.3% Dark Energy and 4.9% Atoms), but how can this be if we cannot see it or directly detect ...
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Isn't searches for dark matter crazy effort? [closed]

There are a lot of crazy quests in astrophysics, one of them is searches for dark matter. How someone could observe dark matter while it is far away?
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Why is the rotation curve of a galaxy lower if measured with CO rather than H?

I have a simple question regarding galactic rotation curves. I know they are studied mostly using 21 cm emission of Hydrogen in the outer regions and with CO emissions in the inner regions, but why do ...
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968 views

How much of a galaxy's mass is in stars?

I have been trying to find an answer for this question for a while without a success, so I guess it might not have a specific answer. But to make things easier, let's take the Milky Way galaxy as an ...
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What makes the stars that are farther from the nucleus of the galaxy go faster than those in the middle?

It has no sense that stars that have a bigger radius and apparently less angular speed($\omega$) goes faster than the ones near the center.
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Could the estimated stellar mass for the Milky Way galaxy include brown dwarfs?

Trying to find an estimate for the stellar mass of the MW galaxy, I found this paper and the estimated stellar mass is $~6.5 \times 10^{10} M_{\odot}$. I was also trying to understand the methods used ...
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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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102 views

How can the Andromeda Galaxy alone have more mass than the Local Group?

I was reading about the Local Group, and it is stated that the total mass of the group is $1.29±0.14 × 10^{12}$ Solar masses. The number actually felt a bit low to me because I know the Milky Way ...
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Why don't stars have Keplerian orbits?

In a comment to Rob Jeffries' answer to this question on spherical galaxies, Incnis Mrsi commented There should exist the entire range of orbits in a spherically symmetric system: near-circular, ...