# B Does water pressure decrease in zero gravity?

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1. Sep 7, 2016

### allister109

me and my friend were talking on facebook and we couldn't think of an answer to the question, would water pressure decrease in zero G, you can see how far along we got before getting stuck in the picture below View attachment 105576

2. Sep 7, 2016

### Orodruin

Staff Emeritus
Your question is not really well defined. You need to specify the pressure of the surroundings and exactly what setup you are considering. If you pressurize the container, the pressure will be homogeneous throughout the liquid and equal to whatever pressure you put.

3. Sep 7, 2016

### Bandersnatch

So, we're the 'physics nerd forum'?

4. Sep 21, 2016

### Khashishi

Yes, it will decrease, all other things equal. You won't have the weight of the water contributing to the pressure. The water can still be pressurized by the container, but you also have that contribution with gravity.

5. Sep 21, 2016

### Chronos

There is no hyrostatic force in zero g, just like there is no bouyancy in zero g. A container full of water would float around like an astronaut on the ISS. There could be some nominal force due to surface tension and intermolecular adhesion of water but it would be negligible. The water would still have mass hence inertial resistance to motion, but, no pressure - unless you somehow apply compressive force to the water inside the cotainer. The pressure you would feel diving on earth would be absent because there is no gravity to provide column pressure.

Last edited: Sep 22, 2016
6. Sep 21, 2016

### Staff: Mentor

Yes, and proud of it too!

7. Sep 22, 2016

### Khashishi

Of course, with no pressure, the water will boil. If it is in a leakproof container like a spaceship, the water pressure will equal the air pressure.

8. Sep 23, 2016

### newjerseyrunner

Pressure = Force / Area. Put 0 in for force. :P. There would be negligible electromagnetic interactions as well as even more negligible gravity but for the most part if there was no other interactions, it'd just sit there slowly increasing in entropy with quantum fluctuations.

9. Sep 24, 2016

### Shreyas Samudra

In zero g weight of water is zero so
Zero pressure

10. Sep 27, 2016

### Chuck Keranen

So as I understand it, the atmospheric pressure surrounding a quantity of water will give it its globe shape. If that water is suddenly placed in a vacuum, such as space, it boils off?? Becoming what? Water vapor, or splitting into hydrogen and oxygen?

11. Sep 27, 2016

### jbriggs444

Suppose that you have an arbitrarily shaped blob of water. Does the volume of that blob decrease if you mold it into a sphere shape? If not, why would you expect atmospheric pressure to do anything to alter the shape?

Try Googling for "surface tension".

12. Sep 28, 2016

### Khashishi

Water vapor

13. Sep 29, 2016

### newjerseyrunner

Vapor. The molecules are held together by pressure, the atoms making the molecules are bound together and will not just drift apart.

14. Sep 29, 2016

Thank you...