Description
explain what Hubble's Law is, in layman's terms. Why does this observed relationship imply the universe had to have a beginning?
Explanation & Answer
Hubble's Law is the expansion of other galaxies away from the Earth. Proof of this expansion is in the red shifts. Galaxies closer to the Earth have red shifts that are brighter but the galaxies farthest from the Earth have red shifts that are a fainter red. This means the further the galaxy the more quickly it is moving away from the Earth. This implies the Earth had a beginning because there was a departure place kicking of the expansion. In other words based on Friedman's equation and Hubble's Law the Earth can be dated by going backwards form the current expansion rate. Based on this measurement the Earth (universe) began 14 billion years ago.
http://www.physicsoftheuniverse.com/topics_bigbang_expanding.html
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