Horizon BBC2 yesterday had a program on the shape of the Universe. Experts have checked triangulations of galaxies to see if the 3 angles add to anything different to 180 degrees - also using the CMB data. This has been done many times.
The answer they get is that there is no variation. The universe is Euclidean. That is - Flat. The Angles add to 180 degrees.
Can someone explain to me (what seems to me to be an obvious nonsense exercise) why any observation would produce a different result? We are looking back down a LIGHT CONE. Light cones are* FLAT. Looking back in time (any observation across any space does look back in time). NOTE the assertion 'Flat' is because you can (thought experiment) cut up the cone to the apex and lay the cone flat.
Is it not true that we can only observe the universe on the surface of a light cone? The light cone being a 2d representation of 3d - in a 4d universe incl. time