The proposal is for an aquarium in the form of a horizontally mounted wheel, 3m or more in diameter, with a U-shaped transparent track forming the outer rim. It rotates rapidly enough to hold water in the channel by centripetal force as it spins around its central axle.

It is filled by pumping water through the central hub and out through one of the radial arms, by which time the water will have aquired sufficient momentum to stay in the channel.

The fish can be introduced by just tipping them into the water once the whole affair is spinning.

The fish will be unaware that their environment is rotating rapidly and will behave as if they were in a static tank, but with "down" at right-angles to Earth's gravity. To the observer, they will be orbiting rather fast.

The whole assemby is mounted on a central column above a large pond. If the power fails, the water and the fish will simply fall down into the pond.
-- 8th of 7, May 23 2008

Centrifugal Force http://www.xkcd.com/123/
at xkcd webcomic [baconbrain, May 23 2008]

Centrifugal fishtank Centrifugal_20fishtank
! [phoenix, May 23 2008]

Orbital Guppies orbital_20guppies
Quite the reverse of this idea but I like them both. [gnomethang, May 23 2008]

I was trying hard to think of an Earthbound application for this. One could use such a tank to simulate deepwater conditions and house critters that only like it deep. I understand why these deepwater creatures do not like to come rapidly up from the deep to the shallow, because of the popping, but I am not entirely sure that an aquarium of them must be under high pressure. But if it does, this is clearly how to do it.
-- bungston, May 23 2008


I like the idea. I feel like there will be a tendancy for the water to slow down so it may be necessary to have some fins attached to make sure the water maintains it's speed. Glass is pretty smooth.

I was wondering how fast this would have to spin to keep the water from falling out. In order to make the fish feel 'down' at a right angle from that of gravity you would have to put them under a force significantly stronger than that of normal gravity. This may not be a health concern for the fish since they float(ish) and water isn't very compressible.

If they are spinning too fast you won't be able to see them very well so you may want to consider having them feel 'gravity' at an angle more like 50 degrees or so off down. At any rate there will have to be a compromise between spinning too fast and having a more 'normal' orientation... unless you just want to spin them really fast. I used these (') half quotation marks too much.
-- Flipmastacash, May 23 2008


Also catching the dead floaters will be more fun than with the old-fashioned boring tanks.
-- Flipmastacash, May 23 2008


I think the [Flipmasta] is correct - 90 degrees will be impossible. Not because of the fish (which can deal with much pressure) but because of the load on the glass. If you actually wanted a vertical surface on the water the load would be infinite, which is beyond the capacity of most glass.

It would be very cool though. I'd suggest a chandelier-type version with internal lighting.
-- wagster, May 23 2008


You could never get to "down" at right-angles to Earth's gravity, without orbiting infinitely fast.

You could put the wheel upright, on a horizontal axis, like a waterwheel, and have something pretty amazing.

You could also look up the meaning of "centripetal force", and avoid another long discussion about all that. Because what this thing is depending on is inertia acting centrifugally, often called "centrifugal force".

//The fish will be unaware that their environment is rotating rapidly//

Oh, yes, they will be aware, every time they turn their little heads.

The water's surface will be a section of a paraboloid. You could build a cylindrical tank, spin it rapidly, and get the same thing, with a center for access.
-- baconbrain, May 23 2008


//You could build a cylindrical tank... center for access//

or a place to jump across to the other side.
-- FlyingToaster, May 23 2008


But by the time you got there, the other side would be where you were.
-- baconbrain, May 23 2008


It sounds like an "Anti-Orbital Guppies"
Cool!
-- gnomethang, May 23 2008


// Because what this thing is depending on is inertia acting centrifugally, often called "centrifugal force". //

Yes, yes, no, yes ....
-- 8th of 7, May 23 2008


I believe that another good way to avoid a long discussion about centripetal force [bacon] is to not start one :)

...but since it has already been started I would like to escalate it by adding my two cents. "Centrifugal force" is not a force at all. It is just the tendancy for things to not change direction when centripetal force is exerted on it. I don't see how you can say that [8th]'s use of the term is incorrect because it is the centripetal force that is holding the water in the channel instead of letting it continue moving in a straight line.

I like the cylinder idea.

//The water's surface will be a section of a paraboloid// what's the significance of this?
-- Flipmastacash, May 23 2008


It means that, if you install enough lights and then stand in the middle, you will combust.
-- MaxwellBuchanan, May 23 2008


I like this, generally, even if it were only at 45'. Fish are so enormously boring, something needs to be done.

But, see Jupiter. Or, if you are in a museum or in the SF airport, see the spheres with liquid in them. Spin them around an the liquid isn't all spinning at the same rate. It begins to form striations.

I do believe, in a rounded centripital/centrifugal force fishtank, there would be constant disturbance in the water. The disturbance would affect the fish very much.

If the 'bottom' of the fishtank were flat (such as a car tire), this would still not work due to the infinite amount of rotating fastly required to reach the 90' change (although offhand I think not quite an infinite amount of rotation is required for 89'). So to appease the anti-infinitely fast rotators, if the fishtank bottom were angled dynamically* to the speed of the rotation, there would be less disturbance, and the guppies would be less distracted during lovemaking.

*I don't see how this could be done
-- mylodon, May 24 2008


Do I get a centripetal chair to enjoy the orbit fish?
-- Amos Kito, May 24 2008


Do I get a centripetal house to enjoy my centripetal chair?
-- mylodon, May 25 2008


When the house spins, the furniture will follow.
-- Amos Kito, May 25 2008



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