Hubble he did not prove the universe is expanding at an accelerating rate.
He demonstrated that distant objects doppler shift toward the red spectrum.
Einstein pointed out is his theories of relativity that observers could not tell the difference between gravity or velocity causing a red shift.
It was shown that stationary quasars next to massive galaxies also show red-shifts.
All we know to date is that there is a redshift in distant objects.
It could be caused when we look through the mass of the universe.
It could because they are accelerating away.
Or even both.
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