ratiocinator
Lightly seared on the reality grill.
Ok, back to the big bang!
Can anyone here tell me the shape of the post big bang beginning relative to the very start of time. Iow, if one imagines to be an observer at the starting point, what is the shape of the big bang expanding volume of space one would see?
My own guess is that the volume would be spherical as it creates more space in time, any takers?
I think you've got the wrong idea. It's unlikely that space has a boundary and hence a shape in that sense.
It's generally assumed that space has constant curvature, which gives basically three options for its geometry: positive curvature, negative curvature, and zero (flat). Its 'shape' depends on the topology, which is not known. We can, however, consider the simplest topology in each case.
If it's positively curved, then one can imagine the simplest topology as the (three-dimensional) surface of a four-dimensional sphere. So space would be finite but without an actual boundary (like the surface of the Earth). I emphasis, however, that that is a way to imagine it, it in no way implies that the fourth spacial dimension actually exists.
If it's flat, the simplest case is just that it's infinite Euclidean space. Although you can imagine other topologies (the surface of a torus, for example) which would make it finite.
If it's negatively curved, then there's no way to imagine it as a shape embedded in a higher dimensional Euclidean space (you can embed it in Minkowski space but that's not much help for the imagination) - you often see a saddle shape in books but that only really represents negative curvature right at the centre. Again, the simple case is that space is infinite.
Observation suggests that the universe is very close to being flat.