Why do we think there is a lot of dark matter in clusters of galaxies?
A.) Individual galaxies are moving so fast that they could not be held together by the gravity of visible matter.
B.) We've detected some of it with dark matter telescopes.
C.) Gravitational lensing lets us measure mass even when we can't see it.
D.) A, B, and C.
E.) A and C.
Ans: E.) A and C.
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C. Consistent D. Inconsistent
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