From: Lee Corbin (lcorbin@tsoft.com)
Date: Tue Jul 22 2003 - 23:09:12 MDT
Anders wrote
> [mailto:owner-extropians@extropy.org]On Behalf Of Anders Sandberg
> Sent: Saturday, July 12, 2003 3:03 AM
> > Can you clarify what you imagine this world would be like. To me I can't
> > really see that the propagation speed would make any observable difference as the
> > effective force levels would still be the same in any region.
>
> 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.
I don't agree (or more probably, don't understand). Let's
just discuss gravity influences moving at speed c. It would
seem to me that if a large object (like Jupiter) were moving
through interstellar space (somewhere between Alpha Centauri
and Sol, for example), that its gravitational field (i.e.
space curvature) would extend in front of it just as much as
it extended behind it. I say that mostly because from its
reference frame, there *is* symmetry.
But perhaps it has to be *really* traveling to generate the
effect you are discussing. Very well, assume that this large
object a couple of light years from Sol is traveling with
respect to the Big Bang or wrt our galaxy at c/10. To observers
moving with the planet, of course its field would be symmetric;
satellites would orbit it in the predictable fashion.
But what about to those of us at rest wrt the Big Bang? This is
a lot like railroad cars and lightning strikes, perhaps. Anyway,
what say you?
Later, Anders writes
> I made a matlab program (included at the end for those of you who like
> to play with it), and it seems to say the opposite (assuming I coded
> right, which is anybody's guess :-). The trailing side has a stronger
> force compared to the non-moving case. It looks more like a sonic boom
> than a doppler shift. If the planet is releasing gravity waves, they
> will of course be doppler shifted.
I guess that this program will depend a lot more on our relativistic
assumptions than what we would actually learn from running it. Or
did you find it enlightening in some way?
Lee
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