Dark Matter in the Universe

How did Galaxies Form

After recombination there were obviously pockets of density enhancements around which material accumulated

The exact mechanism for this is unclear and most of the mass is probably darkmatter. Gravitational coalescence of this dark material then built the galaxies we observe today. Below is an N-body supercomputer simulation of this process.

These eventually grow to form galaxies. Unfortunately, there is a rather wide range of different galaxy types, shapes and densities which means the formation process was not simple. Also most all galaxies today are embedded in some larger scale structure. The formation of these structures is unclear but here are a couple of possibilities:

Structure formation could have either occurred from fragmentation of very large regions into smaller regions or from the gravitational coalesence of sub-units into successively large structures. Both formation scenarios lead to a highly clustered Universe with structure on many different size scales.

However, no matter what form you are talking about, Dark Matter plays a central role.

The Dark Matter Universe

What is Dark Matter?

How do we know its there?

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