Quote:
For the cosmological model postulated by CraigS it is possible the the two galaxies will blink out at the same time.
However, the entire universe can only blink out if Y is a photon from the galaxy furthest from us and X is a photon from the galaxy nearest to us and all galaxies are receding so fast that light cannot reach us. However some galaxies are not moving away from us. So the universe will not blink out all at once.
|
This is clearly not correct. It violates Hubble's Law which states the recession velocity is a function of the proper distance of the galaxy to the observer. If galaxy Y has "just" blinked out it has done so because it has exited the Hubble sphere. Galaxy X which is closer to the observer is still inside the sphere and is therefore still observable.
This is applicable if galaxies X and Y are formed during a period when the acceleration of the Universe began
and the expansion of the Universe is faster than the expansion of the Hubble sphere.
If on the other hand galaxies were formed during a period when the expansion of the early Universe may have been slightly decelerating, the Hubble sphere can expand faster than the expansion of the Universe. In this case those galaxies that are just beyond the Hubble sphere will eventually become visible. So we will never achieve a total and sudden blink out even if all galaxies were receding.
Quote:
|
Further, CraigS did not stipulate that Y is a photon from the galaxy furthest from us and X is a photon from the galaxy nearest to us. So the question as stated was flawed.
|
I must be missing something here. Photon Y is assumed to be emitted from galaxy Y and photon X is assumed to be emitted from galaxy X. Craig has clearly stipulated that galaxy X is closer than galaxy Y.