From: ABlainey@aol.com
Date: Sat Jul 12 2003 - 18:26:35 MDT
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.
>
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.
> 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! 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).
>
I can't quite agree with this, although very nearly. I can see what you are
saying and I am probably nit picking.
My take would be that the gravitational force would be normal on the leading
side of the planet and you would 'appear to be' weightless on the other side.
The fact really is that you would not be weightless, rather that the planet
itself would be moving away from you faster than it is attracting you. so you
would still be constantly falling towards the planet surface, but getting
further away.
As for the sides of the planet !! I would imagine that gravity would be
pulling you at an angle perpandicular to a point somewhere behind the center of the
planet's mass. behind as in, behind its position along the planetary orbital
path. so you would be standing at an angle. If the planet was moving fast
enough and gravity propogated even slower, you may even be able to walk up
buildings :o)
Alex
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