Something that always got me thinking about is time is relative to the speed of the object (time dilation) how can we determine age of universe. Here is an example of what I'm thinking. When the big bang happened, imagine if certain parts of the big bang it got flung at different speeds (clumping?), lets group them into two different speeds 1, and 2. Group 2 equals somewhat near the speed of light, and 1 is moving at slow speeds (hardly moving.) Now group 1 is the slowest moving and will develop first into galaxies first at normal speeds, while group 2 will develop the slowest (last.) Now imagine a scenario where in group 2 finally gets to a stage to develop galaxies, and due to some large stars and/or black holes with gravitational slingshots (or some other event) that ends up slowing a set of star systems down to group 1 speeds, i.e. normal speeds. Now imagine life sprouting up on these set of star(s), from their perspective they will see galaxies, and stars systems that range from very old from group 1, to relative young ones in group 2. Now in reality there is just no group 1 or 2, as there will be groups in all ranges between 1 and 2. We can calculate rate of expansion of galaxies all we want, but how do we calculate the age of the galaxies when we don't have any previous speed history of what were looking at? I daydream a lot, so feel free to pick at all my logic holes on this.