Dark Matter and Dark Energy Differences
Location: Outside U.S.
Date: Spring 2013
What is the difference between dark matter and dark energy?
If our understanding of gravity is correct, many stars move in patterns that require more mass than we can see. They curve around positions where we do not see the very massive stars required to cause the curved path. If our understanding of physics and astronomy are correct, and if gravity is the cause of the rotational paths we see, then there needs to be much more mass than we can detect. This is dark matter.
The universe as a whole is expanding, getting larger. All the galaxies are moving apart from each other. This is what we expect from the big bang theory. However, gravity pulls inward. The expansion should be slowing down. When we look at the universe, we find that the expansion is actually speeding up. Gravity slows down the expansion, taking energy away from the motion. There seems to be an unknown source of energy speeding things up. This is dark energy.
Dr. Ken Mellendorf
Illinois Central College
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Update: November 2011