Where is dark matter?

[DerpenWolf]

I know that we believe that there is a large amount of dark matter in the middle and on the outer edge of our galaxy but apart from that where else do we find it? Also how do we know where it is? Just trying to get a better understanding on this bit if physics!

[Xannari Ferrows]

Dark matter is hypothetical, so it's not really known where it resides. However, for the sake of argument, Dark Matter is believed to exist everywhere in a metaphysical state.

Very little is known about it, except for this:

Dark Matter makes nearly 80% of our universe, but doesn't interact with it. At least, not in a way that directly affects us

[Bill Phil]

Isn't it called Dark because it doesn't interact in many ways? Except for gravitationally, right?

[Ralathon]

Isn't it called Dark because it doesn't interact in many ways? Except for gravitationally, right?

Yea, it doesn't seem to react to anything but gravity. A good bit of evidence for this (Although they're still discussing it) is the Bullet Cluster. In essence you have 2 colliding clusters, due to radiation pressure etc the gas of the colliding galaxies is getting slowed down. Dark Matter doesn't react to electromagnetism so it flies on. So if you use gravitational lensing to detect mass concentrations you see a bulge of dark matter with the gas lagging behind it.

[Steambirds]

Probably behind the couch, it's dark back there.

[YNM]

"Dark Matter" is an amount of mass that's calculated to exist via gravitational observations (empty areas gravitational lensing within clusters, superclusters or around interacting galaxies, then rotation speed in the disk of spiral galaxies), but can't be observed visually, or through other means (yet, hopefully). There have been speculations what is it actually. It may be an usual particle (baryonic), matter that's normally present (consider brown dwarf, planemo, gas cloud, white dwarf, red dwarf etc. that's not easily observable on distant galaxies), but it's harder to think how could there be a lot of these things between two faraway galaxies, as to those within clusters and superclusters; hence why there're also non-baryonic (unusual particles, protons neutrons quark lepton etc. are considered normal / baryonic) solution such as WIMPs (weakly interacting massive particles, the name reflects what is it supposed to be - a particle that interacts only via gravity and weak force). Neutrinos are also proposed, as they do interact gravitationally.

Other explanation is called MOND (modified newtonian dynamics), where they propose it's because the characteristics of gravity itself. But it mostly fails over explaining the empty area lensings, other part of the explanations still makes some sense (even it tries to address out dark energy).

Edited December 1, 2014 by YNM

[FenrirWolf]

Isn't it called Dark because it doesn't interact in many ways? Except for gravitationally, right?

I forget if it's theorized to interact Weakly as well or not.

[kerbiloid]

And whether it indeed exists. Or gravity field is not a simple GM/r^2 in a galaxy scale of distance. The only direct experiment we have are 2 Voyagers and 2 Pioneers  just 100 AU far from here.

For example: electromagnetic and gravitational fields are 1/r^2. But do you have any simple formula for weak and strong interactions?

And as we presume, all four interactions are the same in a proper distance and time range.

[dansmithers]

Wherever it likes. It can't be detected, so it could be anywhere.

[mpc755]

There is evidence of dark matter every time a double slit experiment is performed; it's what waves.

The Milky Way's halo is not a clump of stuff anchored to the Milky Way. The Milky Way is moving through and displacing the dark matter.

The Milky Way's halo is the state of displacement of the dark matter.

The Milky Way's halo is the deformation of spacetime.

What is referred to geometrically as the deformation of spacetime physically exists in nature as the state of displacement of the dark matter.

A moving particle has an associated dark matter displacement wave. In a double slit experiment the particle travels through a single slit and the associated wave in the dark matter passes through both.

Q. Why is the particle always detected traveling through a single slit in a double slit experiment?

A. The particle always travels through a single slit. It is the associated wave in the dark matter which passes through both.

What ripples when galaxy clusters collide is what waves in a double slit experiment; the dark matter.

Einstein's gravitational wave is de Broglie's wave of wave-particle duality; both are waves in the dark matter.

Dark matter displaced by matter relates general relativity and quantum mechanics.

Edited December 3, 2014 by mpc755

[PB666]

Tagging this post onto this old thread

There is new evidence concerning Dark Matter and Dark Energy.

First the XENON100 experiment is a large container of Xenon buried deep in a Western US desert to avoid contamination with Cosmic rays. It is basically a gigantic scintillation counter.

The evidence from this site suggests no interactions of Dark Matter with leptonic material. The argument here is that if Dark Matter was a WIMP and WIMP interact with electrons it would be detected. Some evidence from Itally suggested this might be true, apparently it is not. So either DARK matter is not a WIMP, or it almost never interacts with leptons, which means that if it interacts with anything it would be Bosonic material (i.e. black holes and the Higgs).

https://theconversation.com/the-search-for-dark-matter-and-dark-energy-just-got-interesting-46422

http://phys.org/news/2015-08-theoryif-dark-approach.html

So what we learn from these two article. We can't see DM electron collisions, because DM just flies right through the electromagnetic fields

They can annihilate, and we can see this happen, maybe, but we haven't seen it happen.

What if dark matter also exhibits asymmetry the antiparticles are elsewhere?

The first article also brings up the issue of dark energy, that maybe dark energy is a chameleon, pushing space around when little matter is present but being less pushy around gravitational objects. It apparently is not a chameleon, its simply enigmatic

For whatever reason, dark energy, the stuff that is speeding up galaxies does not interact with the matter in galaxies,

can't say if it interacts with dark matter, and in may interact with space-time and push space-time around (like cosmic inflation).

Whatever it is, it remains as elusive today as the day it was first theorized to exist.

[Glaran K'erman]

In your bum

or, http://www.scientificamerican.com/topic/dark-matter/

[K^2]

Isn't it called Dark because it doesn't interact in many ways? Except for gravitationally, right?

It's called dark matter to distinguish it from luminous matter. Id est, stars. Technically, planets and asteroids contribute to dark matter fraction of the universe. The problem is that there aren't nearly enough of these to add up. So usually, when people talk about dark matter, they just talk about the missing fraction, which happens to be most of it.

Whether or not it interacts with other stuff is still debated. Weakly interacting dark matter is one of the hypotheses. Another is that dark mater is very compact. Tiny black holes all over cosmos, or some such.