On Mon, 31 Dec 2018 09:28:28 -0700, Chris L Peterson
wrote:
But we must be inside the 4D sphere or else we would have no
future.

No, we are on the surface. The surface is "now". The center is t=0
(actually, it is (0,0,0,0), the location of the Big Bang). The past
is
inside the sphere, where it is not accessible to us.

Which means that in one second we will be almost one lunar distance
outside this sphere? Since outside the sphere is where the future is.