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Unformatted text preview:  (with comoving distance normally defined to be equal to proper distance at the present time, so a ( t ) = 1 at present), the proper distance to the particle horizon at time t is given by  The particle horizon differs from the cosmic event horizon in that the particle horizon represents the largest comoving distance from which light could have reached the observer by a specific time, while the event horizon is the largest comoving distance from which light emitted now can ever reach the observer in the future.  At present, this cosmic event horizon is thought to be at a comoving distance of about 16 billion light years.  In general, the proper distance to the event horizon at time t is given by  where t max is the time-coordinate of the end of the universe, which would be infinite in the case of a universe that expands forever....
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This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.
- Fall '10