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

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30
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6answers
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Why isn't dark matter just matter?

There's more gravitational force in our galaxy (and others) than can be explained by counting stars. So why not lots of dark planetery systems (ie without stars) ? Why must we assume some undiscovered ...
35
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2answers
2k views

Are modified theories of gravity credible?

I'm a statistician with a little training in physics and would just like to know the general consensus on a few things. I'm reading a book by John Moffat which basically tries to state how GR makes ...
38
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4answers
7k views

How do we know Dark Matter isn't simply Neutrinos?

What evidence is there that dark matter isn't one of the known types of neutrinos? If it were, how would this be measurable?
15
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5answers
2k views

Dark matter and dark energy references

I've been looking for questions about dark matter, and I've read some very interesting answers. However, I desire too look into it deeply. This is not actually a question. I'm asking the community ...
22
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1answer
1k views

How can dark matter collapse without collisions or radiation?

I understand that dark matter does not collapse into dense objects like stars apparently because it is non-interacting or radiating and thus cannot lose energy as it collapses. However why then does ...
6
votes
4answers
684 views

Theory that gets rid of dark matter/energy

Is there any physics theory that either groups together gravity and dark energy/dark matter or eliminates dark energy/dark matter by modifying standard understanding of gravity or any force? If so, is ...
1
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2answers
257 views

Possibility of making dark energy equivalent with dark matter

I was curious whether it is possible to make dark energy equivalent to dark matter. Can this unification be done? If it can, why do scientists prefer to separate dark energy from dark matter?
3
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2answers
239 views

How does the friedmon solution to Einstein's equations resolve paradox of bounded infinities?

This article talks about a potential explanation of dark matter based on something called the "friedmon." I have no interest in the dark matter question, but the article has made me curious about ...
1
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2answers
132 views

Relativity and Galaxy Rotation Speed

If time travels slower nearer gravity wells, why can't the galaxy rotation speeds being faster on the outer edges than the inner areas be explained by relativity? What necessitates dark matter?
23
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3answers
3k views

How do people calculate proportions of dark matter, dark energy and baryonic matter of the universe?

The Wikipedia page on dark matter mentions that the Planck mission had revealed that in our universe ordinary baryonic matter, dark matter and dark energy are present in the ratio: 4.9%, 26.8% and 68....
11
votes
2answers
732 views

How does dark matter halo outside a galaxy help to explain galaxy rotation curve?

How does a dark matter halo outside a galaxy help to explain a galaxy rotation curve? Suppose for simplicity we use a model of a star rotating about a more massive star in a fixed circular orbit. For ...
3
votes
2answers
792 views

Dark matter and dark energy [duplicate]

Possible Duplicate: Dark matter references I have recently read about dark matter and dark energy, and why physicists think it must exist (dark matter: mass of galaxies are far bigger than ...
19
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2answers
5k views

How do we know Dark Matter is non baryonic? [duplicate]

It seems widely stated, but not thoroughly explained, that Dark Matter is not normal matter as we understand it. Wikipedia states "Consistency with other observations indicates that the vast majority ...
15
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1answer
363 views

Distribution of Dark Matter around galaxies

It is well-known that measurements of the velocity profile in galaxies are not compatible with Newtonian laws. A way to circumvent the problem is to assume that galaxies are surrounded by a spherical ...
5
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2answers
114 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?
2
votes
2answers
438 views

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 ...
4
votes
2answers
203 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?
25
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5answers
3k views

Why doesn't dark matter affect planetary motion?

If the universe is made up of ~95% dark matter, and it interacts only gravitationally then why didn't Newton and Kepler discover it before ? Why does it show itself only in the radial velocity profile ...
6
votes
4answers
612 views

How do we know that dark matter is dark?

How do we know that dark matter is dark, in the sense that it doesn't give out any light or absorb any? It is impossible for humans to be watching every single wavelength. For example, what about ...
6
votes
2answers
572 views

Is dark matter really present around the sun?

Recently I read an article that there is dark matter around the sun but if it is so, than why can we see it clearly. If it is called matter than it shall show some hindrance in radiation we receive ...
15
votes
5answers
4k views

Why can't dark matter be black holes?

Since 90 % of matter is what we cannot see, why can't it be black-holes from early on? Is is possible to figure out that there are no black holes in the line of sight of various stars/galaxies we ...
5
votes
2answers
759 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 ...
5
votes
2answers
480 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 ...
-3
votes
2answers
447 views

why is dark matter the best theory available to explain missing mass problems?

Why is dark matter the best theory to explain the missing mass problem? Why is dark matter mathematically necessary to explain the missing mass problem? On a side not I believe dark matter is ...
22
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4answers
3k views

How did the universe shift from “dark matter dominated” to “dark energy dominated”?

In order to get dark energy to dominate, wouldn't you first need another form of energy to push the expansion until dark energy could dominate? Otherwise I don't understand how the universe could ...
10
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5answers
3k views

Is Dark Matter expected to be equally distributed in our solar system?

If dark matter winds up being roughly equally distributed in our solar system would this mean it has no net gravitational influence? Furthermore, do we expect dark matter to be less dense out in ...
9
votes
5answers
595 views

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.
6
votes
1answer
279 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?
4
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1answer
691 views

What is a flat rotation curve?

Was reading about dark matter and the distribution of it throughout the galaxy. it said "For example, if rotation curves are flat this means-" what exactly does this mean?
10
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2answers
1k views

Mass density of dark matter in solar system near us

What is the approximate mass density of dark matter in our solar system at the radius of the Earth's orbit? I would like some idea of the mass of dark matter going through each cubic meter of ...
10
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2answers
1k views

Could Dark Matter form black hole?

Some people speculate that the mysterious dark matter in the universe could be tiny black holes. But on the other side, could dark matter particles attract each other by gravity and finally form a ...
5
votes
2answers
1k views

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 ...
5
votes
1answer
195 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 ...
4
votes
5answers
2k views

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 ...
4
votes
2answers
914 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.
2
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2answers
384 views

Where is all the Dark Matter? Theoretical Question

In my Physics Class we had to look into possible areas where Dark Matter could be "hiding." Such as Black Holes and so on. Dark matter really can be "seen" through its gravitational effects, and we ...
13
votes
2answers
420 views

Is there evidence of dark matter in our galaxy?

Is there evidence of dark matter in our galaxy? How can we measure this, say, how many percent of the center of our galaxy is dark matter? I did not find the answer in the question What's Dark ...
8
votes
2answers
348 views

Is it possible that all “spontaneous nuclear decay” is actually “slow neutrino” induced?

This thought was inspired by a comment from the current leading answer, by @Sentry, to the question Where are all the slow neutrinos? This [slow-neutrino induced nuclear decay] will still be an ...
4
votes
4answers
305 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 ...
4
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2answers
753 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?
3
votes
2answers
347 views

Do alternate theories for Dark Matter (like MOND) explain its effect on gravitational lensing?

For a long time, I was sceptical about the evidence for dark matter. To me, it seemed like a pretty big leap to make when we have no idea whether or not our current models of gravity should apply ...
-2
votes
1answer
255 views

Gravitational constant, $G$, What if it is not Constant?

The question is on title; What if Gravitational Constant, $G$, is not constant? Let's skip all the local consequences if it would suddenly change, like asked here; Can gravitational constant be ...
-2
votes
4answers
282 views

Dark energy and dark matter [duplicate]

Our galaxies are speeding apart from each other and that is because of dark energy, but we don't know where it comes from right? If I'm not mistaken could dark matter have dark energy? (If they are ...
59
votes
5answers
7k views

If dark matter only interacts with gravity, why doesn't it all clump together in a single point?

I'm a complete layperson. As I understand, dark matter theoretically only interacts with the gravitational force, and doesn't interact with the other three fundamental forces: weak nuclear force, ...
30
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3answers
3k views

Can the Sun capture dark matter gravitationally?

I think my title sums it up. Given that we think the dark matter is pseudo-spherically distributed and orbits in the Galactic potential with everything else, then I assume that its speed with respect ...
11
votes
1answer
232 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. ...
15
votes
2answers
470 views

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 ...
11
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2answers
429 views

Does the Milky Way have dark matter satellite galaxies?

This recent paper by Weinberg et al. discusses that one potential problem with our current model of Cold Dark Matter (CDM) is that is predicts a greater number of satellite galaxies for the Milky Way ...
12
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2answers
2k views

Is dark matter repulsive to dark matter? Why?

I think I saw in a video that if dark matter wasn't repulsive to dark matter, it would have formed dense massive objects or even black holes which we should have detected. So, could dark matter be ...
10
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3answers
633 views

What current alternatives are there to the standard concordance model of cosmology?

The current "standard model" or concordance model of cosmology is Lambda CDM which includes late time acceleration due to a cosmological constant, cold dark matter as the missing matter component and ...