Originally Posted By: paul

if you pour out a gallon of water inside the ISS
a sphere of water will form.
if you push a ping pong ball into the sphere of water in the near zero g environment the pingpong ball will be pushed back out , because of the differences in the density of the water and the density of the ping pong ball.


No it won't. No gravity = no weight = no pressure = no pressure gradient = no buoyancy.
This air bubble has less density then the surrounding water: still in zero g it stays submerged:
http://www.youtube.com/watch?v=ZyTwLAW-Z8c&feature=related

The density difference between the ping pong ball and the water doesn't "do" anything. Exactly like the density difference of a ping pong ball and a brick wall at its side doesn't exert any force.

Also there wouldn't be any mentionable density difference in the water (even with gravity). Water is basically incompressible. You can read this in any boom about physics.


You dont have to believe me, just take a take a look here (same source you got your "density" picture from:
http://en.wikipedia.org/wiki/Buoyancy#Forces_and_equilibrium
Or:
http://www.answers.com/topic/buoyancy
Or:
http://answers.yahoo.com/question/index?qid=20100401145652AAtLQew

Or if you don't like reading watch this:
http://video.answers.com/Q/learn_about_fluids_-_part_5_99162287 (actually these videos of kahn academy are quite good).


Originally Posted By: paul

so all I would need to do to increase atmospheric pressure outside the bottle is to increase the water inside the bottle.


Now you are playing stupid?
Of course not.
It means you can't elevate the water more then the air pressure allowes you to.
If you elevate the straw further then 10 meter the water would still stay at 10m.
You could lift up a straw of any length, kilometers if you like, the water column in the straw would still be at a height of 10 meters.


Originally Posted By: paul

are you saying that the atmospheric pressure outside the bottle would become 2000 lbs or are you saying that the 2000 lb of water looses its weight and becomes 14.7 lbs?


I'm saying: You can't support 2000 lbs of water in the bottle. At least not by using the "suction of a vacuum".
The pressure of the weight of the water in the straw will always match the surrounding air pressure.
If you lift the bottle/straw further, the water will stay where it is, you will just have a bigger empty place at the top of the straw.

Strictly speaking you can support 2000 lbs of water in the bottle: AS LONG as the height of the water column is less then 10.3m. You could just make your straw wider.
It's a question of pressure: Weight of the water / Area of the straw = downward pressure <= atmospheric pressure.

Last edited by Momos; 05/01/10 09:39 PM.