>Since people are talking about Humphreys' theories I thought some might
>want to see what the Young-earth press is saying about Starlight and Time.
>It ain't favorable.
>
>
>The best critique of that book comes from a creationist source--Starlight
>and Time is the Big Bang" Conner and Page, "Starlight and Time is the Big
>Bang," Creation Ex Nihilo Technical Journal 12(1998), p. 174-194.
It should be pointed out that although this artiicle appeared in the
"Young-earth press" its authors are *not* of the YEC persuasion. They
merely submitted their criticisms to the venue that would likely reach
most of the supporters of Humphreys' theory (nearly all of whom, I think,
are YECs). Also, I understand that this past summer CENTJ published
Conner's follow-up criticism of Humphreys' recently modified theory:
"New Vistas of Spacetime Rebut the Critics" theory (which also originally
appeared in the same issue of CENTJ that Glenn referred to above) where
Humphreys took his opportunity to answer/rebut Conner and Page's
criticisms of his _Starlight_and_Time_ theory and made major
modifications in his original _Starlight_and_Time_ scenerio by appealing
to *classical signature change* rather than differential gravitational
time dilations to keep the time on the Earth much younger than the
distant cosmic matter. Essentially, the new "theory" claims that the
center of the cosmic expansion, i.e. the "earth", is much younger than
the distant matter because of a difference in *starting times* for clocks
there compared to clocks on distant matter. The old (S&T) theory relied
on a gravitationally induced difference in the *rates* at which those
clocks supposedly tick. The new (NV) theory admits that these different
clocks actually tick at the same rate, but they don't start together
because of differences in 'when' they emerged from a timeless Euclidean
zone. Needless to say, this new theory is also fatally flawed in that
Humphreys' model can be shown to not actually contain such a
Euclidean-signatured region that Humphreys claims it has. Humphreys has
misunderstood and misapplied the mainstream literature on classical
signature change in a failed attempt to fix his theory. Humphreys
essentially, mistook a coordinate singularity in a (physically not
useful) coordinate system which had a region where the time-like
coordinate became complex-valued and which made the metric *look* like
it had undergone a signature change when, in fact, it had not. The
unphysical coordinate system merely had a pathology.
<SNIP abstract and quotes of C&P's paper and quotes from Humphreys' S&T
book what illustrate Humphreys' misunderstanding of event horizons>
>The problem with this is that when you travel through ANY event horizon,
>the passage of time for you goes to zero.
This can be somewhat misleading. It only *looks* like time has stopped
for one falling through the horizon to a fixed *outside* observer. The
actual time elapsed for the falling observer is finite, smooth and
nonsingular when passing through the horizon, and that observer's world
line remains in tact until the observer is destroyed at the r = 0
singularity that occurs in the falling observer's future. This (r = 0)
singularity *seems* to be a central point in *space* (i.e. the spatial
origin of the standard coordinate system), but, in fact, it is a
singularity *in time* for all observers internal to the horizon. Inside
the event horizon the r coordinate no longer measures radial spatial
distance, but rather, (nonlinearly) measures *time* for internal
observers such that going to smaller r values means going into the
observer's future and increasing r values means going backwards in time.
This is really why observers inside the horizon cannot escape from the
hole; they would have to go *backwards in time* to get out. The reason
why they must be destroyed at the singularity at r = 0 (for a simple
Schwarzschild-type hole) is simply because they cannot avoid going into
their own future (where, er, *when* the singularity is).
The main physical defining property for an event horizon is not anything
about time stopping there. Rather, it is merely a boundary in spacetime
that divides a region of spacetime from where emitted null signals (i.e.
light rays) *can* asymptotically reach flat asymptotic future 'infinity'
from a region where such null signals *cannot* reach flat asymototic
future infinity.
Also, in the case of a Schwarzschild black hole where there exists a
spherically symmetric static metric on one side (i.e. outside of the
event horizon) the event horizon also is the limiting region where there
requires an infinite non-gravitational station-keeping force (e.g. rocket
motor thrust) to prevent an observer from moving (e.g. falling) with
respect to the coordinates of the static metric on that side. IOW, for
an observer exterior to the event horizon around a Schwarszchild black
hole, that observer must require an ever greater station-keeping thrust
to oppose the hole's gravity in order to continue to hover at rest above
the hole as the observer gradually lowers himself closer to the event
horizon. As the observer approaches and sneaks up on the even horizon
the required station-keeping force approaches infinity. This is related
to the fact that inside the hole there is no static metric at all.
Even though an observer falling through the event horizon of a black hole
doesn't experience any singular effects at the moment the horizon is
crossed, but merely can no longer send a signal to an external observer
and cannot keep from monotonically approaching the r=0 singularity with
r ever decreasing as the observer ages, this does *not* mean that there
is *no* sense in which time is dilated near (but external to) the event
horizon relative to greater external distances from it. For two station-
keeping observers each hovering at different fixed radial distances above
the event horizon, it is true that the observer nearer the horizon
experiences time more slowly than the observer which is farther from it.
Both observers can continuously communicate with each other and can
compare the radio-transmittted ticks of the other observer's clock with
their own local clock's ticking. Both observers will agree that the
clock of the observer closest to the event horizon ticks more slowly than
that of the more external observer. The closer the inner observer is to
the event horizon the more dilated his time is relative to the more
distant fixed observer. In the limit of the inner observer approaching
the horizon by sneaking up on it slowly with ever more gravity-countering
thrust (to prevent falling) the time scale of the inner observer is
dilated to the point that the external observer considers the inner
observer's clock coming to a halt, and the inner observer considers the
clock of the external observer as ticking infinitely fast.
In the case of a rotating (Kerr) black hole things are more complicated.
First, the central singularity acquires the topology of a ring. Second
there are two distinct closed horizon/boundary surfaces surrounding the
singularity. The inner surface is the ordinary event horizon that marks
the boundary of the regions from where emitted null signals can and
cannot reach asyomptotic flat future infinity. Again any observer
crossing this horizon from the outside in can never come back out. But
immediately outside the event horizon is another special region (called
the ergoregion) bounded by another outer boundary surface called the
"stationary limit surface". In the ergoregion between the event horizon
and the stationary limit surface the relativistic effect of the dragging
of inertial frames is so intense that no observer can remain at rest by
using any finite amount of thrust for station keeping purposes. In this
region, all observers tend to be carried around the hole no matter how
hard they try to resist this "rotation of space". Outside the stationary
limit surface an observer can keep fixed in space by using enough rocket
thrust to oppose gravity. Inside this surface stationarity is impossible
for the observer. But it is possible for the observer (and null light
signals, too) to remerge through the stationary limit surface to the
normal outer region given, enough thrust. The spatial separation of the
radial gap between the stationary limit surface and the event horizon is
latitude-dependent and greatest at the hole's 'equator' and is least at
its poles where the ergoregion thins to zero thickness and the stationary
limit surface just barely touches the event horizon at a single point
along each polar axis. In the limit of the angular momentum of the Kerr
black hole decreasing toward zero (for fixed mass) the hole's properties
continuously approach those of a nonrotating Schwarzschild black hole
with the ergoregion thinning out to zero thickness all around the hole,
and the stationary limit surface nestles down onto the event horizon.
Thus, for a rotating black hole the surface of infinite force for
station-keeping (stationary limit surface) is distinct from the surface
of no return (the event horizon). Only in the limit of a nonrotating
hole are these two surfaces everywhere coincident. Time does not stop
for an observer falling through *either* of these surfaces.
>Thus when at the event horizon,
>an infinite amount of time passes for the external universe outside of the
>black or white hole. If you stand outside of a black hole watching a
>friend fall into it, you never actually see him fall into it. His motion
>gets slower and slower and then appears to freeze and grow dim.
This effect is essentially due to the propagation problems that signals
such as the null signals of light/radio waves experience in trying to
escape the hole's gravitational potential well rather than actually due
to a stopping of the falling friend's time scale which continues to tick
normally at the event horizon.
>One author I
>read a few years ago, said this would be like the frozen grin of Alice's
>Cheshire cat. What he sees is that the outside universe is speeding
>up--going faster and faster until it is all a blur. Thus we should not see
>a universe of a few billion years old, we should see one that is infinitely
>old! Humphreys is wrong. Hope this helps.
>
>glenn
I do not think that this is correct. (The part before the statement that
Humphreys is wrong, I mean. Glenn is *correct* that Humphreys is wrong.)
If the friend was not falling, but only station-keeping at rest very
close to the event horizon, then the friend *would* see signals from
outside universe as *very* blue-shifted and all external processes would
seem to go very fast. The closer the friend is to the horizon the more
extreme the effect would be. *But*, for a friend actually *falling*
through the horizon the friend is moving at a local speed (relative to a
sequence of concentric fixed station-keeping observers) that is
approaching c as the horizon is approached. The Doppler redshift from
this inward speed (as the falling observer's motion tends to *try* to
outrun the incoming signals from farther out in the universe) will tend
to cancel out the blueshift (seen by the station-keepers) of signals
coming from the distant processes in the outer universe. I think I
recall that the effects will cancel out to the point that the falling
friend will *not* see anything unusual going on in the outside world as
he/she crosses the event horizon.
Regarding where James Gruetzner wrote:
> A collegue of mine here at Sandia Labs (where Humphreys works) is a
>friend of his. A couple of years ago he related to me that Russ Humphreys
>had abandoned this theory and states that it was wrong.
I think your collegue means that Humphreys no longer defends his
*original* _Starlight_and_Time_ scenario. As far as I know he still
defends his "New Vistas of Spacetime Rebut the Critics" modification of
the theory where he appeals to different emergence times from a Euclidean
zone as the mechanism of having wildly different ages of the Earth and
the very distant matter in the universe. At least he was still defending
it as of this past summer ('99).
David Bowman
David_Bowman@georgetowncollege.edu