Given this links to a Penrose’s Hawking Points based diagram [1], i am constantly wondering why the universe - or its history is always depicted as a cone.<p>It’s hard to get my head around it since if there was a big bang, you’d expect a spherical visualization.<p>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.<p>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.<p>That works when showing the earth and its moon but is hard to follow once you add a galaxy, a cluster, etc…<p>Does anyone know of any good explanations and above all visual models that might make this more comprehensible?<p>Cheers and thanks!<p>[1] https://physicsworld.com/a/inside-penroses-universe/<p>Edit: Formatting.
The cone is a good way to explain it to add the flow of time, and the cone shape comes from the expansion of the universe. The tip is the big bang and the wide end of the cone today.<p>By taking a telescope and looking back in time we would be looking at a smaller universe heading towards the big bang in the cone, and hence the redshifted nature of what we see - since the universe is smaller.<p>If you were to take a slice of the top of the cone, that is your spherical view of the universe today - in 3d. The cone is 4d.
That Physics World article is excellent.<p>Nothing much else to say, but I’ll say that I rarely feel this way about most of the stuff I read on the web.