Because all motion is relative to the observer. The Earth moves...if we view it from a heliocentric model. The Earth is fixed, if we view it from a geocentric model. The Sun and Earth move if we view it from Sirius. The relationship and interaction is fixed in physics.
You do know the Big Bang was formulated by a priest. It’s meant to be a simplistic explanation to explain what is observed about the universe. If the Catholic Church says the Big Bang is a-okay...I don’t see what the hubbub is about.
Sorry but I don't accept something just because a priest formulated it.
"If the Catholic Church says the Big Bang is a-okay...I don’t see what the hubbub is about."
So was the Catholic Church correct when it supported geocentrism or is it correct now that it doesn't?