In 1929, Edwin Hubble published his discovery
that the universe is expanding!
All of the galaxies in the universe are moving away from Earth.
Galaxies that are twice as far away are moving away twice as fast!
The straight line is the Hubble law: v = H0 r
For each 3.26 million light years of distance, a galaxy moves away
about 65 km/s faster (Hubble parameter H0).
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