Man is on board of a spaceship with enabled artificial gravity swimming in a pool. Due to a malfunction gravity goes out. Pool liquid tends to form a sphere with the man locked inside.

  • Will it still be possible to swim out of the bubble given a weightlessness?
  • As for artificial gravity mechanism I would suggest two options:
    • There is some kind of gravity field, which could be turned on and off almost immediately.
    • There is more conventional spinning gravity that fill fail smoothly.

P.S. Situation plot is taken from a sci-fi movie Passengers (2016).

enter image description here

Video: https://youtu.be/IOVrvZ3aKt4

P.P.S. There is a similar question answered at WB: 0g pool: can I keep a big ball of water in space?

Still would like to keep a separate one, because it more focused on surviving a gravity failure while in a pool than the mechanics of a zero-g pool itself.

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    $\begingroup$ He's going to die (Also possibly duplicate) $\endgroup$
    – Separatrix
    Aug 1, 2017 at 7:36
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    $\begingroup$ Stopping "spinning gravity" will give radically different effects than just turning off switch. Which one do you really want? $\endgroup$
    – Mołot
    Aug 1, 2017 at 7:37
  • $\begingroup$ @Mołot Immediate option is more interesting as man will have to operate in zero-g conditions and not just walk out of the pool while there is still some gravity. $\endgroup$ Aug 1, 2017 at 7:43
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    $\begingroup$ You should note that if you don't have a "swimming nose clip", you will at first have some water in your nose. At this point you either panic and waterboard yourself. Or breathout some air by the nose and use a hand to clip it. Now you theories about your surviving. $\endgroup$ Aug 1, 2017 at 12:40
  • $\begingroup$ @DragandDrop Huh? I can swim underwater, rightside up and and upside down without water going up my nose. Either I'm automatically exhaling really slowly, or water doesn't want to go up my nose no matter which way gravity faces; in either case, why would zero gravity change this? $\endgroup$
    – Yakk
    Aug 1, 2017 at 15:27

5 Answers 5


Surface tension will try to keep the water together, but it will retain (of course!) all of its inertia, so several things will happen:

  • The large mass of water (like that on a swimming pool will break up due to inertia locally (think: "ripples") overcoming the force due to surface tension.
  • Each mass will stick to any "wettable" surface it encounters.
  • The swimmer can give a hard stroke to get rid of the large mass of water he is swimming into and sail straight towards the ceiling.
  • His action will produce large ripples in the pool and a large number of smaller masses will detach and start floating around.
  • Masses touching each other will try to merge, but this will produce waves on the surface and smaller masses may be expelled.
  • The swimmer has a chance to use the environment strategically to propel himself through the door before the swimming pool is filled by so many "water bubbles" it may become difficult to breathe.
  • At equilibrium (after all kinetic energy is "consumed" by friction) water will cover any wettable body (including the swimmer) it can reach and stick to it.
  • 2
    $\begingroup$ The important thing to recognize (which this answer does) is that surface tension is very small when compared to inertia. If you calculate the pressure difference between the inside and outside of a large droplet of water (e.g., the one in the linked question), it's basically negligible . In addition, keep in mind that while it's more convenient to shake water off your hands on earth by shaking in the direction of gravity, it's also quite simple to shake droplets off in any other direction (ever flicked water at someone?), and this same motion will clear the water in a free fall environment. $\endgroup$
    – Aliden
    Aug 1, 2017 at 12:44

Removing gravity will remove the buoyancy on the poor swimmer. The surface tension of water will make it flow all around him/her and also inside his/her nose and lungs.

Basically the swimmer will be sucked into the mass of water by the surface tension, and according to his/her apnea skills he/she can survive up to few minutes before drowning if he/she doesn't manage to reach a solid grip and exit the bubble.

Moving inside a bubble is doable (basically it is just underwater swimming), the issue is breaking the water film to get out of it, as there will be no gravity assisting the effort (insect drinking from water droplets have to hold firmly on a surface to not be sucked into the droplet, same would apply here). In the scene you link the swimmer would not be able to poke her head out of the bubble and breath as she does there.

See this video for reference of what happens when you squeeze a wet cloth on ISS.

After the first moments the water will then start to expand by wetting all wettable surfaces. If the swimmer has managed to exit the bubble he/she better run for the exit and have it sealed. Else a thin film of water is going to cover the entire ship interiors, with easily imaginable consequences on electronic and mechanical devices.

  • 1
    $\begingroup$ Could you explain why you can't move inside a bubble of water in zero-g, please. $\endgroup$ Aug 1, 2017 at 7:46
  • $\begingroup$ @DenisKulagin, I expanded my explanation $\endgroup$
    – L.Dutch
    Aug 1, 2017 at 8:03
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    $\begingroup$ Do you have a source for the surface tension being too high to break through? Humans have much more inertia than insects so I would expect that it should at least be possible to break through with the head, if not the whole body. -- Several answers in response to this question seem to indicate that suface tension would be very weak. $\endgroup$ Aug 1, 2017 at 8:35
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    $\begingroup$ @L.Dutch: inertia is there. if you violently shake your head (or hands) water will flow away. in the (very nice!) video you linked the astronaut was veru careful to move slowly and without jerks for exactly this reason, othewise water would have started floating around in spherical bubbles (some of them were produced and he was quite fast to catch them again); after all surface tension forces are not that strong. $\endgroup$
    – ZioByte
    Aug 1, 2017 at 9:34
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    $\begingroup$ @L.Dutch, I guess we can all just speculate here, but I would assume that vigorously shaking your head, and repeatedly swishing over your face with your hands (which you freed of water before by waving them around as fast as you can) should be pretty enough (compare dogs shaking dry after a bath). If there are any real experimental facts surrounding all of this anywhere, that would be great to link. Else, most of the comments are a little to "fact-heavy" for my taste, when we're all just extrapolating what we think to know. $\endgroup$
    – AnoE
    Aug 1, 2017 at 11:30

One should theoretically be able to swim in water within a zero-g environment, seeing as how the fish involved in the Medaka study aboard the ISS were able to swim without gravity. The swimmer can still push the water in order to propel themselves in a zero-g environment, just like they would if they were swimming in an environment with gravity.

(link to video of fish swimming http://iss.jaxa.jp/library/video/medaka_suisoutounyuujinoyousu.html)

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    $\begingroup$ This is not a complete answer, because it doesn't resolve the question about surface tension, but I think it is a useful answer because it gives actual experimental evidence regarding the question about propulsion. $\endgroup$
    – David K
    Aug 1, 2017 at 10:23

(Clearly none of you have passed your starfleet pool safety training course, so you will not be allowed in the pool and therefore will not die) Although the death and mayhem described by others provides a better story here is what will happen.

(Starfleet of course will have rules, regulations, and advanced safety gear.) (Protocol demands at least triple (3 levels) redundancy for every system.)

Emergency teleports will activate and beam the people to safety.

If you have a ship that advanced the safety computers are going to be hay we are going to loose gravity, start draining the pools NOW! They will need pumps to suck it out, but drains all sides of the pool meaning whatever direction the water goes in those drains will open.

The pools will have independent gravity field generates for this very emergency. In the Star Trek world you be trained and it would be in your safety procedures guide padd(manual).

There will be redundant sensors all over the pool to detect a massive increase in pressure on any side of the pool. Once detected, drains will open up and allow all the water to be evacuated. The drains, of course, will have safety measures like grates and etc to prevent people from being sucked in.

In the end a bunch of people, who were once swimming will be on the bottom or against a side of the pool wondering what happened. Sure accidents are possible, and some will get injured. Every once and a while someone will die. Most likely the medical staff will be able to evacuate the water from the people lungs and CPR them.

Addenum: We will probably have rebreathers that can suck the oxygen from the water and/or people will have to carry small tanks of oxygen to provide enough air to survive a full evacuation of water plus a safety margin.

There will be safety drills just like we have fire,tornado, or etc. Which will prepare people for this very type of thing. You will have to pass ## (whatever is approved by regulation of starfleet command) of drills with trained life guards before you can go in alone.


If you switch off an artificial gravity field on a swimming pool without changing the speed or orientation of the ship the changes are going to be slow to build up and might afford time to escape, probably not though. The first thing is that the water is going to suck the swimmer in if they're not already below water, no gravity, no buoyancy. Secondly the water is going to start to flow out around the room across any surface it comes in contact with. Both these effects are due to the liquid surface tension. If a swimmer can stay conscious while the water flows out to coat the inside of the room and the room has sufficient surface area then the swimmer may be able to then use a wall to get enough leverage to escape the pull of the water and affect an escape.

Unless you slow it very very gradually switching off spin gravity on a pool will result in water going everywhere as it maintains its momentum while the ship stops moving around it, anyone caught up in that is likely going to get pummeled to death long before they drown. This agitated mass of water is going to spray droplets off into the room for a long time and it's going to keep moving until air resistance and surface friction strip in of all it's kinetic energy, it's going to be like being in a washing machine on spray-rinse. There is however a possible advantage to a lucky swimmer who doesn't get killed early in that the very chaos of the event means that they're less likely to be stuck in any single significant volume of water; they won't need to hold their breath all the time just be ready to dodge the large droplets on their way to the door.

Both scenarios are complicated by the fact that the water will not all stay together. The artificial gravity situation will see blobs and bubbles of water separate from the main mass of liquid and move independently around the room until they stick to something, unless the water is perfectly and completely at rest when the gravity goes down, and even then the swimmer breaking free will liberate a lot of droplets. A spin gravity shutdown is likely to impart so much relative velocity to the water that it turns into a chaotic foam of such bubbles for a short interval before they shed enough momentum to start sticking instead of splashing when they hit.

Once the water settles on to the walls, if it's still reasonably deep, the surface tension will make wading around the walls somewhat comparable to walking under gravity in that you'll stick to the surface instead of bouncing off into the room, if you're careful anyway. It will however require considerable strength to open any doors coated in water and considerable momentum to punch through the curtain of water that initially covers the door. Also you'll want to shut the door fast once you're out because the water is going to want to spread itself across every surface in the ship to a uniform depth.

  • $\begingroup$ Wouldn't the filter suck some of it away? $\endgroup$
    – DCook
    Aug 1, 2017 at 12:45
  • $\begingroup$ @DCook Possibly but 1. a filter is designed to circulate water so if it does suck some away it will also put it back again and 2. the water will be just as tenacious about soaking the filter motor as everything else it can come in contact with so it's not likely to keep running that long unless it has an absolutely perfect seal. $\endgroup$
    – Ash
    Aug 1, 2017 at 13:07
  • $\begingroup$ Starfleet safety protocols, mean independent sensors would detect this situation and the pump would divert the water into tanks. $\endgroup$
    – cybernard
    Aug 1, 2017 at 13:11
  • $\begingroup$ @cybernard I thought this was tagged for reality-check, what is the word Starfleet even doing here. $\endgroup$
    – Ash
    Aug 1, 2017 at 16:04
  • $\begingroup$ @Ash Any sufficiently advance society with space faring ships will have an organization to manage every aspect of it. Especially safety. I could have just said NASA, but that would just be boring. I put in their for fun, and because <organization name here> is to much typing every time. $\endgroup$
    – cybernard
    Aug 1, 2017 at 16:09

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