From: Paul Grant (shade999@optonline.net)
Date: Mon Jul 14 2003 - 10:17:59 MDT
On Sat, Jul 12, 2003 at 08:26:35PM -0400, ABlainey@aol.com wrote:
> In a message dated 12/07/2003 11:12:16 GMT Daylight Time,
> asa@nada.kth.se
> writes:
>
> > For a static field in such a "slow gravity" universe nothing would
> > change. But imagine sending out Voyager towards Jupiter. At first it
> > experiences the weak tug towards the place where Jupiter was a long
> > time ago, and is accelerated that way. As it approaches the region
> > where Jupiter is, the acceleration will change direction and move
> > towards the current position, and as Voyager continues beyond it
> > will shift back towards an old position.
> >
Actually it just occurred to me; from a biological pov,
given how important gravity is to every day use,
we'ld all be equipped with significantly better gravity
detectors :) Kind of like "use the force" stuff.
Amusing.
> I can see that. Wouldn't the gravitational force also be weaker than
> expected if the voyager past the planet on its sun orbital trailing
> end ? A kind of gravital doppler shift.
I think in general we're probably confusing things; as someone more
versed than I pointed out, gravity can either be static [ignoring
motion]
or dynamic (even in our current universe); what you're doing when you
make
the propogation speed slower than the speed of light is arbitrarily
converting all cases of "static" gravity into dynamic cases [at least
relative to the light data]...
So, you have a planet which used to be considered static gravity
[constant
gravity emittor], which means effectively that at any point in space
that it occupied it emitted a summative field. When it vacates a
position, the
area of space "springs back' to its original configuration + the
trailing end
of the planet...[anyone know what the resiliancy of space with respect
to gravity (SEPerate from the propogation speed of gravity) is btw?]
Now lets place an observer in front and behind of the planet relative to
its motion; the observer in front will see in an increase in gravity
(depending
on the propogation speed); the frequency shift (doppler effect)
observed,
would be a "speed up" of the gravity field changes [the equivalent of
jerk].
Suddenly gravity would start increasing, and the rate at which it
increases
[remembering that gravity in and of itself is acceleration], would be
accelerating.
When he would see this sudden acceleration of gravity (no doubt
unpleasant),
would be a ratio of the speed he was going versus the speed of
propogation.
This would be the equivalent of the sonic boom.
The observer in the back of the planet would at some point, see the
correct vacancy in terms of gravity... but it would take him some time
to see the vacancy for what it was (a shift in gravitational energies);
the reason being that the speed of the propogation would determine
when the final energies (relative to the motion) would be updated.
He would be seeing the equivalent of a gravitational "flicker";
2 sources of information (the universe, and this planet), would be vying
to update his respective environment... with the final result being
that of the universe winning, with relatively more time in between
for its frames...
Now thats with interleaving within a time frame; but try normalizing
back to a single frame, and what you end up getting is intense
periods of supergravity in front of the moving gravity "wave"
and slow update in the trailing field (where you feel the effects
of gravity where there's no clear source for that gravity, relative
to how our notion of the universe works)
> > Even worse, Jupiter is actually moving "supersonically" in this
> > setting!
> > If Voyager is approaching from straight ahead of the planet it will
not
> > experience any gravitational field since Jupiter is moving faster
than
> > the information about where it is is spreading through the gravity
> > field. So on one side of Jupiter you would actually be weightless!
<<cut>> on one side you could be *potentially* weightless, until the
gravity waves reach up and snag you. and then you would probably
be severely heavy, and if off-axis from the direction of motion,
probably sheared in half (or quarters or whatever :P).
> > On
> > the other side all the information is present and you get normal
> > gravity. And you get a discontinous bow shock where you go from no
> > gravity to a mix of several accelerations pointing towards many
former
> > positions (likely just causing an inward accleration into the shock
> > cone).
perhaps :) I'm considering the simple case of a planet moving
with observers directly in line with its motion....
<snip>
you: Hmm, interesting. An observer on the planet surface would, if
gravity
behaved like it does here, observe the same gravity all around the
surface regardless of where it was moving. An external observer would
not see the same.
me:
it all depends on:
the speed of propogation,
the distance from the source,
the decay of the gravitational attraction per meter,
the resiliancy of space (refraction period similar to a neuron),
and of course, the vector of motion relative to the observer's position.
if you really want to have some fun, consider the planet not as a point
source, but as a series of point sources...then look at it from the
observers point of view....(six gagillion gravitional shockwaves
all happening simoultaneously underneath said person).
I daresay given the eddy currents involved in front, you would never
really get a planet in the first place; at least not one that's stable.
you:
My model is based on having gravity disturbances move
relative to a fixed spacetime *at a constant speed relative to this
frame*.
There cannot be a fast or slow gravity wave in my model, all gravity
waves
move at the speed g. Just like light in relativity and sound in still
air. If we allow gravity waves of different speeds then things get
*really* messy and interesting. I guess a fast moving planet would have
a field that moved fast to a receiver, while a slowly moving planet
would have a slowly expanding field. I think we need extra assumptions
here, and the whole thing starts to look like the theory of nonlinear
waves. Very interesting, but confusing.
omard-out
This archive was generated by hypermail 2.1.5 : Mon Jul 14 2003 - 10:26:51 MDT