Quote:
Originally Posted by CraigS
Ok … interesting …
So in our holographic universe, it seems overlapping 'Cosmic Horizons' can't occur either (for the same reason) …
(Just thought I'd say that … even though the term 'holographic universe' appears to arouse concerns).
Cheers |
There are similarities between a black hole's event horizon and a cosmic event horizon. To an observer at distance from the black hole or an observer at the centre of the cosmic horizon, velocity = c and change in time = 0 at the horizon.
However, I think there are differences.
With black holes, the event horizon is created by mass "compressed" into a critical volume by gravity. Light does not have enough energy to escape from the horizon's surface. Combining two black holes increases the mass and the size of the event horizon but the effect is the same. I'm not sure if Steven is suggesting that the merger would be instantaneous if the horizons touch. I wonder if this is the case, as the event horizons would be gravitationally distorted first with perhaps an ill-defined contact point.
Cosmic event horizons are brought about by objects exceeding the speed of light due to expansion away from the observer's location. I don't see any reason that these event horizons could not overlap (but not merge) for observers in two separate frames of reference. If each observer's universe can be defined by their cosmological horizon, as in the holographic principle, then it is still possible for information to be passed from one observer's universe to the other where they intersect.
Regards, Rob