Physics Question #53

Serge Bellemare, a 52 year old male from Boston, MA, U.S.A. asks on August 23, 1999,

Where in the universe are we? We seem to know the dimensions of the Universe; so does it have the shape of a ball or a football? We must be off center so where are we in this "ball"?

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The answer

Doug Hube answered on August 23, 1999

The answer involves all those convoluted, apparently contradictory, philosophically amusing and confusing, aspects of cosmology. We are located at an apparent centre of the Universe, away from which all galaxies appear to be receding uniformly and isotropically in accord with Hubble's Law of Redshifts. The apparent edge (horizon) of our observable universe is defined by the distance at which the velocity equivalent of the redshift is equal to the speed of light. At the same time, we are located at the apparent edges (horizons) of the observable universes of all observers who are located at the apparent edge (horizon) of our observable universe. All of that is consistent with the Cosmological Principle which states that all points in the Universe are, except for local details, equivalent. There is no absolute/unique centre. All points/locations in the Universe, including our own, took part in the Big Bang and are carried in the cosmological Hubble flow as the Universe expands.

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