Ment
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The first explains expansion (if you take a camera from a ball, draw something on it, and start inflating it, the drawn object will begin to increase, and it will increase equally in all directions, and the larger it is, the faster it increases). All that remains is to figure out who that guy with the pump is... And how can we explain expansion using the second one?
What do you think about this?
Obviously, for the three-dimensional case, we have a sphere in 3D, not in 4D space.
But a geoid, by definition, has the shape of the Earth, right?