Quote (duffman316 @ Jun 27 2013 06:53am)
ah so there is infact a way to detect it aside from needing it to exist to prevent holes in modern physics?
We detect dark matter from graviational effects that should not be there based on current theories. Basically, approximetly 25% of the universe is made up of dark matter.
I should have thought about this long ago, but here is the NASA site on dark matter:
http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/Quote
By fitting a theoretical model of the composition of the Universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter. What is dark matter?
We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the Universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.
However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs". But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles).
Where I reiterate: we dont know what it is, but we know something is there. This "something" is termed dark matter.
This post was edited by khemist on Jun 27 2013 10:34am