Brian Lucas asked:
It was only during the enlightenment that it was established that the Earth was not at the centre of the Universe. And only decades since we discovered other galaxies and of our location within the Milky Way. We have since discovered galaxy clusters, the acceleration of the expanding universe, mapped the microwave background and most recently witnessed gravitational pull among certain clusters. Assuming there is no infinity and using the inflating balloon' analogy, do we have any idea where we are located within the universe that we know exists (both visible and theorised)? Or on this level, is physical location simply an illusion?
Joanna Kerr asks astrophysicist Dr Sean McGee from the University of Birmingham...
Because there is no center and no observable edge to the universe, we will need a reference point. How about the Earth as a reference point? For all intents and purposes, it is the "center" of the observable universe for us earthlings. Therefore, we are located at the following address: Earth, Solar System, Orion Arm, Milky Way galaxy, local galactic group, Virgo Supercluster, Laniakea Supercluster, Observable Universe, Universe. The location can be further defined if necessary. The minimum diameter of the observable universe is 28,000 megaparsecs and the universe appears the same in all directions. My guess is that there is a lot more out there, but the light either has not reached us yet or the universe is expanding faster than the speed of light at distances greater than 14,000 Mpc.
As the universe appears from here to be fairly isotropic and populated with sparse random dots of matter, it seems that we are at the centre. As we have no reason to believe that our position is in any way special, it is equally true that any other point can be considered to be the centre.
This often asked question never gets an answer acceptable to either the layman or common sense. Ron Maxwell, Sun, 20th Dec 2015
The universe is centered on me... you're off to one side.
Are you saying then that everything that exists now in the universe existed at the first moment of the big bang? And that at that moment it had no size? Ron Maxwell, Thu, 24th Dec 2015
I understand that the universe came into existence after 10^-43 seconds (Planck time) when everything was separated by one Planck length. Space moved over the next Planck second and some separation took place. Here is where I have a problem, my reference to common sense if you like. One particle did not move relative to the others, the one at the centre. Or are you saying that everything moved away from any (possibly undefineable) centre and there is just a hole there, like the balloon analogy? Ron Maxwell, Thu, 24th Dec 2015
Neither Ron. That's the beauty of it. No particle moved.
Thank you, I do get your explanation. One last question though. Taking the balloon analogy, there is no centre to it's surface but it does have a centre in three dimensions. That could mean that if you include the timeline (arrow of time of the universe?), there is a centre, that of the space that has expanded. Probably not traceable though or of any particular import. Ron Maxwell, Thu, 24th Dec 2015
Ron, Any analogy can only carry an explanation so far. In the Balloon analogy the Balloon surface represents everything that is, was and ever will be.