Stephen <mcavoys_at@aoldotcom> wrote:
> Nice but: ???These galaxies are rushing away from us, in some cases, 
> faster than the speed of light???.
> The images are awe inspiring but the words crap. IMO.

  And exactly what is wrong about that statement?

  Firstly, general relativity does not forbid the distance between two
points in space (and hence the distance between two particles, or two
galaxies) from growing faster than c. On the contrary, GR *predicts* this
to happen. What GR forbids is a particle *traveling* between two points
faster than c.

  The expansion of the universe causes galaxies which are sufficiently
far away from each other to recede from each other faster than c. This
does not contradict GR (but it is, in fact, a prediction of GR). In fact,
at the initial stages of the universe it is estimated that the expansion
rate was exponential, much much faster than it is today. Yet even today
there all parts of the universe which are farther away from us than a
certain distance are receding from us farther than c. This is the basis
for the concept of "cosmological horizon", which basically means that
the observable universe (ie. observable by us) is smaller than the entire
universe.

  The expansion of the universe is not the only situation where distances
growing faster than c is predicted to happen. Another situation is within
the so-called ergosphere of a rotating black hole (look it up). A particle
inside the ergosphere (but outside the event horizon) will be dragged to
a speed faster than c with respect to the rest of the universe. Again,
this does not contradict GR. On the contrary, this is a *prediction* of GR.

  Secondly, the expansion of the universe causes for the change in distance
between galaxies to accelerate. The speed at which some galaxy is receding
from us is today higher than it was a billion years ago.

  What we are seeing in the ultra deep field picture is what those galaxies
looked like billions of years ago. At this moment (in other words, billions
of years *after* the galaxies in question sent those photons which were
captured by Hubble) their recession speed has accelerated to the point
that they are receding from us faster than c.

  Again, not against GR, but supported by it.

-- 
                                                          - Warp

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