Thread: Dark Matter question

This question come from the following information:
1) Dark matter does not electromagnetically interact with normal matter.
2) There are underground experiments to detect dark matter
directly. The hope is that a dark matter particle would hit the nucleus
of an atom. I assume that this means that there is potently a strong
force interaction between normal matter and dark mater.
3) Dark mater and normal matter interact via gravity.

If we are surrounded by a sea of dark mater that some times interacts
with the nucleus of atoms in the earth I would expect that it would be
possible that some of these dark matter particles would settle into
orbit around the earth and every other object in the universe. (Dark
matter particle on a hyperbolic orbit hits a nucleus loses some energy
and is now in an elliptical orbit.) Therefor if dark matter really does
interact with the nucleus of atoms I would expect that very sensitive
measurement of satellite orbits could revile if the earth has been
collecting orbiting dark matter for the last 4.5 billion years.

Black hole question:
If dark matter falls into a black hole will it say within the event
horizon? If so with the slow evaporation of a black hole via Hawking
radiation can a black hole turn into a pure dark matter black hole?

You're assuming dark matter and ordinary matter interact. In fact, they don't. Otherwise, quite a lot of planets would be banging into dark matter and their orbits would be radically altered.

It is true dark matter interacts with ordinary matter through gravity. It's a bit like the neutrino, however: the neutrino couldn't be detected for a long time because it interacted very weakly with matter. However, dark matter doesn't interact at all.

So, if dark matter does fall into a black hole, it'll just go through the singularity, assuming that the singularity consists of ordinary matter. It'll be stuck inside the hole, but as the black hole loses mass through Hawking radiation, the black hole will never collapse to form a pure dark matter black hole because the singularity doesn't consist of it. When the black hole finally explodes, the dark matter will be free to go anywhere it wishes.

Originally Posted by Liongold

You're assuming dark matter and ordinary matter interact. In fact, they don't. Otherwise, quite a lot of planets would be banging into dark matter and their orbits would be radically altered.

Take a look at these web sites:
http://xenon.astro.columbia.edu/
http://www.sciencedaily.com/releases...0504061536.htm

Here they are assuming that there is more than just a gravitational
interaction between ordinary matter and dark matter, albeit quite
small . So given
this cross section the question remains.

No one has a clue as to what dark matter is or where it is. If the redshift can be shown as wrong (ie: it has a large gravitational component which has not been taken into account), then stars in galaxies are not moving as fast as it is thought, then DM is not needed.

DM is supposed to work gravitationally so will behave like normal matter in that respect; in planets, stars, black holes, etc.