Given this links to a Penrose’s Hawking Points based diagram, i am constantly wondering why the universe - or its history is always depicted as a cone. It’s ha

Given this links to a Penrose’s Hawking Points based diagram, i am constantly wondering why the universe - or its history is always depicted as a cone. It’s hard to get my head around it since if there was a big bang, you’d expect a spherical visualization. Plus I am aware of WMAP and even if the reality is a, b or c - it all goes back to the theory of a flat universe, thus space time. Since everything we see - on earth and through instruments in space - has three dimensions it is hard to understand gravity by showing a warped plane by spheres. That works when showing the earth and its moon but is hard to follow once you add a galaxy, a cluster, etc… Does anyone know of any good explanations and above all visual models that might make this more comprehensible? Cheers and thanks!