On Thu, 03 Jan 2019 15:08:06 +0100, Paul Schlyter
wrote:

On Thu, 03 Jan 2019 06:57:40 -0700, Chris L Peterson
wrote:
On Thu, 03 Jan 2019 09:47:51 +0100, Paul Schlyter
wrote:

Every point in spacetime is defined by a single coordinate,
(x,y,z,t).
Relativity doesn't change that. There is only one surface; the
interior (that is, space in the past) isn't a surface.

There must be one surface for every t. Unless one claims that
every t
except the present "does not exist".

Every t except for the present is in the interior of the
hypersphere,
not on its surface.

That ought to re-introduce t as an absolute quantity like in the
Newtonian universe. For each pair of t1 and t2 one must then be able
to conclude if they are the same or, if they are different, which one
preceded and which one followed.

Could any two time surfaces t1 and t2 ever intersect one another?

t is an absolute quantity in the past. There is only one surface (it
isn't a "t surface", so I don't know what you mean.