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Alan Guth mentioned in his lectures that to get the accurate linear relationship of Hubble's law, we need to subtract the velocity of the Earth with respect to the cosmic microwave background (CMB) when calculating the velocity of galaxies.
Question 1:
If space is expanding uniformly throughout, why does the Earth move with respect to CMB?
Question 2:
If the Earth is moving at a velocity with respect to CMB, then doesn't this mean there is a special point that we can consider the centre of the universe? Divide the Earth's velocity by the Hubble's parameter, we will get a displacement vector, which is the vector that points from the centre of the universe to the Earth. Doesn't this contradict the assumption that the universe has no centre?
Guth's lecture:
Question 1:
If space is expanding uniformly throughout, why does the Earth move with respect to CMB?
Question 2:
If the Earth is moving at a velocity with respect to CMB, then doesn't this mean there is a special point that we can consider the centre of the universe? Divide the Earth's velocity by the Hubble's parameter, we will get a displacement vector, which is the vector that points from the centre of the universe to the Earth. Doesn't this contradict the assumption that the universe has no centre?
Guth's lecture: