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Originally Posted by Nuri
One of the issues I can't grasp is the expansion thing. Edwin Hubble proved that galaxies were physically moving away from each other at an increasing speed. Reversing the direction of the galaxies should lead us to the point where they all meet - the Big Bang, right? Well, cosmologists would say "no, the Big Band happenned everywhere simultaneously..." ...ummm, say again?  |
There is no contradiction there, Nuri, if we can just get that false notion of everything happening in an infinite flat three-dimensional Euclidian space out of our heads.
The 4-D space-time of general relativity (in which we live and navigate spacecrafts and satellites by) can fold back on itself and be finite, and it can be shrunk to an arbitrarily small measure (a point in the limiting case). We cannot visualise this because our senses and brains are tuned to think of objects being embedded in three (flat, i.e., not curved) spatial dimensions. But that is just the naive view dictated by our immediate everyday experience, which breaks down when we carefully examine the heavens, i.e. on cosmological length scales. The flat space picture does not work over astronomical distances any more than a flat Earth does across continents.