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Unformatted text preview: [2] (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 [59] 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. [60] At present, this cosmic event horizon is thought to be at a comoving distance of about 16 billion light years. [5] In general, the proper distance to the event horizon at time t is given by [59] where t max is the timecoordinate 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
 EmilyHoward
 Astronomy

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