Gravitational Interaction Between Two Regions Less Dense Than Surroundings

This didn't make it out of NTL's news server the first time (AFAICT), so
here goes again. Apologies if it ends up appearing twice:

Hello.

This originated from discussions in uk.sci.astronomy, but since I don't seem
to have any interest or any takers there, I'm now trying sci.physics.

It's unclear to me what would be the gravitational interaction between two
(let's say identical, spherical) regions in a denser medium, of less
mass-dense material.

Consider two such holes in proximity, say a few radii apart. What happens?
Do they attract, repel, or ignore each other? For some reason I have a vague
"feeling" (not that nature cares what I "feel") that they might still attract,
perhaps to minimise surface area somehow (one sphere volume 2V has less
surface area than two spheres volume V each). Physics does seem to like to
minimise surface area in many cases, but I'm not sure it's relevant in this
case.

Does it matter whether the spheres are "hard", when they spheres aren't
nearly touching? I guess so. Consider something like two spherical bubbles
of gas in a fluid; the bubbles can distort and coalesce; whereas if the
bubbles were rigid, they couldn't.

I am not interested in the fact that this couldn't be measured in the lab
because of the weakness of the gravitational interaction compared to the
other forces. I want to know what would happen at length scales where the
interaction would become significant.

Thanks for any informed, helpful responses.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk

Err - Fleetie mumbled something like:
This didn't make it out of NTL's news server the first time (AFAICT),
so
here goes again. Apologies if it ends up appearing twice:

Hello.

This originated from discussions in uk.sci.astronomy, but since I
don't seem to have any interest or any takers there, I'm now trying
sci.physics.


Err - Martin, there's something you should know ... :O)

Arthur



--
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http://www.ambermile.co.uk


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Err - Fleetie mumbled something like:
This didn't make it out of NTL's news server the first time (AFAICT),
so
here goes again. Apologies if it ends up appearing twice:

Hello.

This originated from discussions in uk.sci.astronomy, but since I
don't seem to have any interest or any takers there, I'm now trying
sci.physics.


Err - Martin, there's something you should know ... :O)

Arthur



--
--
52:30:25N, 1:17:51E
http://www.ambermile.co.uk


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.504 / Virus Database: 302 - Release Date: 24/07/2003

Err - Fleetie mumbled something like:
Err - Martin, there's something you should know ... :O)

Erm, what? Please tell me, because despite multiple efforts to
get this damn post out to uk.sci.astronomy, and sci.physics,
I've had a devil of a job, and only now have I managed to make it
appear. In fact I STILL haven't made it appear on sci.physics.

I have even checked that it didn't get out using www.deja.com,
as well as my usual news server, and my attempts didn't show up
on there either.

Why? Your tone implies that this is like, the 3rd or 4th time
it's shown up, but I haven't seen it, and people are maybe
getting tired of seeing it reposted again and again, etc.?

Is that what you're on about? I did my best to check first
before reposting each time.

Or did you mean something else? Like "No-one CARES! so shut up!"?

TIA.


Martin


OK - my original post was like this:

quote

This originated from discussions in uk.sci.astronomy, but since I
don't seem to have any interest or any takers there, I'm now trying
sci.physics.


Err - Martin, there's something you should know ... :O)

/quote

.... and I was pointing out that, although you *said* it was going to S.P, it
actually ended up here. As for my "tone" What tone? I had thought it
was a light-hearted comment. No matter (well, no *heavy* matter :O) )

Arthur



--
52:30:25N, 1:17:51E
http://www.ambermile.co.uk


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.504 / Virus Database: 302 - Release Date: 24/07/2003

Err - Fleetie mumbled something like:
Err - Martin, there's something you should know ... :O)

Erm, what? Please tell me, because despite multiple efforts to
get this damn post out to uk.sci.astronomy, and sci.physics,
I've had a devil of a job, and only now have I managed to make it
appear. In fact I STILL haven't made it appear on sci.physics.

I have even checked that it didn't get out using www.deja.com,
as well as my usual news server, and my attempts didn't show up
on there either.

Why? Your tone implies that this is like, the 3rd or 4th time
it's shown up, but I haven't seen it, and people are maybe
getting tired of seeing it reposted again and again, etc.?

Is that what you're on about? I did my best to check first
before reposting each time.

Or did you mean something else? Like "No-one CARES! so shut up!"?

TIA.


Martin


OK - my original post was like this:

quote

This originated from discussions in uk.sci.astronomy, but since I
don't seem to have any interest or any takers there, I'm now trying
sci.physics.


Err - Martin, there's something you should know ... :O)

/quote

.... and I was pointing out that, although you *said* it was going to S.P, it
actually ended up here. As for my "tone" What tone? I had thought it
was a light-hearted comment. No matter (well, no *heavy* matter :O) )

Arthur



--
52:30:25N, 1:17:51E
http://www.ambermile.co.uk


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.504 / Virus Database: 302 - Release Date: 24/07/2003

"A. Edwards" wrote in message
...
... and I was pointing out that, although you *said* it was going to S.P,
it
actually ended up here. As for my "tone" What tone? I had thought it
was a light-hearted comment. No matter (well, no *heavy* matter :O) )

Arthur

If there's no matter, surely there wouldn't be ANY gravitational
interaction! grin

Darren

"A. Edwards" wrote in message
...
... and I was pointing out that, although you *said* it was going to S.P,
it
actually ended up here. As for my "tone" What tone? I had thought it
was a light-hearted comment. No matter (well, no *heavy* matter :O) )

Arthur

If there's no matter, surely there wouldn't be ANY gravitational
interaction! grin

Darren