The evidence that there is dark matter beyond the disk of a spiral galaxy is the stellar mass which is distributed does not account for the rotation curve of galaxies.
Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe.
The most clear evidence of the existence of dark matter in spiral galaxies comes from their rotational velocities.
It has been shown from latest observations that the universe is not only expanding but that the expansion is accelerating and therefore, this could be the main evidence of the dark matter that the force it is exerting leads to universe expansion.
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