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ExtremeTech on MSNHow Old Is the Universe? A Massive Cosmic Mystery, ExplainedCepheid variables are an important rung on the cosmic distance ladder, a system astronomers use that builds one observation ...
In 1933, the Bulgarian-born astronomer Fritz Zwicky, working in the U.S., noticed unexpected motion in galaxies. Zwicky inferred gravitational effects of unseen material which he called Dark Matter.
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