What percentage of the mass required by the cluster's observed gravity,as shown by the speeds of galaxies in the cluster,is represented by the mass of the presently observable matter in a typical rich cluster of galaxies?
A) 10%
B) 100%,or all of the galaxy
C) About 1%
D) 90%

Question

Quizplus · Accepted Answer

The mass of the presently observable matter in a typical rich cluster of galaxies represents only about 10% of the mass required by the cluster's observed gravity, as shown by the speeds of galaxies in the cluster. This discrepancy is one of the pieces of evidence for the existence of dark matter, which does not emit light or radiation that we can currently detect.

What Percentage of the Mass Required by the Cluster's Observed