[meteorite-list] Slightly OT...but sttill space related!

From: MexicoDoug <MexicoDoug_at_meteoritecentral.com>
Date: Sun Nov 12 15:46:28 2006
Message-ID: <007501c7069b$9653f290$c25186ac_at_thedawning>

Chris wrote:

"What I'd expect to happen in space is that the individual oil droplets
will gradually coalesce as they collide (a statistical process).
Eventually, you'll have a single blob of oil drifting around in (or on)
a single blob of water."

Hi, I think Dave has not defined the question enough, and maybe Chris has
made the additional assumptions for him for a case with low gravity at an
earthly room temperature and pressure.

In Dave's question's pure form, this sounds much more like a thought
experiment rather than a practical question. The reason I say this is
because you have so many factors to worry about:

1-mean temperature (need to be in liquid range for the question to make
sense)
2-pressure and whether the system is closed (at low pressure in an open
system, e.g., space, it will simply all evaporate away before you have to
worry about it - very different than in the ISS.)
3-absorption, emission characteristics vs. radiative wavelengths applied
(oil and water are relatively transparent at most wavelengths compared to
forming meteoroids)
4-gravity (zero gravity, corrected to micro-gravity according to Chris'
assumption, would be impossible since any system has mass - especially a
closed one)
5-surface tensions (dependent on which oil you choose, and water purity and
temperature)
6-heat flux and gradient (heat from one side, rotisserie style, etc.)

not to mention a dozen more secondary factors.

Temperature is loosly behind the assumption for what causes Chris' droplet
collision and coalescence, and the gradient is behind the dynamics of
formation (how it "shakes out" :)).

In my thought experiment what happens follows:
God magically prepares a smoothie of oil and water and tells the water and
oil they are infinitely immiscible, and that he hath put a stop to concept
of evaporation; he makes an open system and puts them in outer space away
from any outside gravitational influences, and tells the oil and water thou
shalt not absorb or emit radiation; though shalt not freeze at absolute zero
... but thou shalt retain surface tension in the range known to Earthly
humans. Thus the surface tension causes a sweating preferentially of the
lower surface tension material multiply beading to the surface of the
perfect sphere the initial blob assumes under these hypothetical conditions.

Then you get an amazing phenomenon something like an hour glass where the
initial spherical blob creates many tiny spherical sweat beads on the
surface. In the absence of rotational motion of any kind, you'd get a
uniform migration to the surface, and at the surface as it got crowded and
contacts were made among alike materials, you'd get growing new spheres
until the initial sphere was much smaller and purified, or gone, and two
contact spherical balls were formed in this strange space hourglass. (If
there really was no rotational motion you might even get more than two)
spheres, depending on the realtive concentrations, too.

Back to reality which is a crockpot, depending on how you crock it you could
get any strange but plausible property you want out of the materials by
picking suitable conditions. That would include a slow plum pudding
formation, or a formation into rinds migrating outward in the hourglass,
Chris's cellulitic blob scenario, or God's perfect kissing sphere scenario.

So the question isn't silly at all. I think you are just sensing your own
bias and trying to overcome it - a bias in which you and essentially all men
view the physical reality at earthly conditions (temp, pressure, gravity,
radiative, closed, etc.) but something inside says that materials subjected
to different conditions might yield properties and phenomena that are very
different. I'm not sure about women, though. And I wouldn't go so far as
to have oil and water as a favorite model for mesosiderites beyond
illustrating the basic concept of immiscibility, if you just as well could
talk about other materials like liquid iron and sand, more appropriate at
the thought experimental phase, which have much lower evaporative
tendencies, and are less gravitationally challenged due to their own mass.

Hope this speculation helps,
Doug



----- Original Message -----
From: "Chris Peterson" <clp_at_alumni.caltech.edu>
To: "metlist" <meteorite-list_at_meteoritecentral.com>
Sent: Saturday, November 11, 2006 5:15 PM
Subject: Re: [meteorite-list] Slightly OT...but sttill space related!


> In microgravity, oil and water still won't mix, but they won't separate
> the way they do under gravity. The reason they don't mix is because oil
> has very low solubility in water. When you mix them vigorously, you get
> what's called an emulsion- in this case very small droplets of oil
> floating in the water. Unless you use special ingredients (as in mayo)
> to maintain the emulsion, the droplets will separate because of their
> buoyancy (which is meaningless in microgravity).
>
> What I'd expect to happen in space is that the individual oil droplets
> will gradually coalesce as they collide (a statistical process).
> Eventually, you'll have a single blob of oil drifting around in (or on)
> a single blob of water.
>
> Chris
>
> *****************************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>
>
> ----- Original Message -----
> From: "Dave Harris" <entropydave_at_ntlworld.com>
> To: "metlist" <meteorite-list_at_meteoritecentral.com>
> Sent: Saturday, November 11, 2006 3:04 PM
> Subject: [meteorite-list] Slightly OT...but sttill space related!
>
>
> > Hullo,
> > Well, I am a bit stumped by a question I was asked by one of my
> > sons...and I
> > couldn't answer it for certain - I've asked one chap, a good mate of
> > mine,
> > who has an astrophysics masters degree, and he proposed an answer to
> > my
> > query but I am not sure he's right...
> >
> > SO, we all know that oil and water don't mix - the oil will float on
> > the
> > water. What about in zero-g?
> > Would they mix? (think how easy it'd be to make mayo!) or would they
> > still
> > separate out if shaken together?
> >
> > It obviously has a relationship between certain meteorite classes (ie
> > mesos)
> > ie, whether molten silicates would float on molten iron...
> > but I just cannot visualise whether oil on water would still float.
> >
> > Seems a really silly question now I;ve written it down - but nope,
> > just
> > cannot figure what an oil/water mix would do.
> >
> > Any ideas (Bernd.....??)
> >
> > Dumbly....
> >
> > dave
>
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Received on Sun 12 Nov 2006 03:46:08 PM PST