How can floating limbs work?

Question

(I'm new here, so if I'm doing something wrong please let me know)

I have an idea for a world where most fauna (and potentially flora) have floating, disembodied limbs that hover in place. Think Rayman, but less uncanny. Instead of using muscles and blood to move their joints, they simply "pivot" their limbs around an axis and get around like that. That way it doesn't use as much energy as a complete limb, let them get through small spaces easier, and leave less area for a predator to grab onto, all while still getting the job done.

I just have no idea how this would work. At all. Ideally, the limbs shouldn't be magical, continue working if something gets in the empty space between the limb and the body, and let them move like regular Earthly creatures (running, jumping, flying if possible), but I'm not sure that leaves much left to work with. Is there any way floating limbs can work?

Answer 1

Higher dimensions

Your critters are 5D lifeforms (4 spatial + time) so they are all one organism and all connected normally - they just intersect our familiar 4D spacetime in such a way that they appear and interact with matter in four dimensions as though they have detached limbs that move freely.

Answer 2

For this tough question, I'm going to go crazy and say convergent symbiotic evolution.

It would work like this. Millions of years earlier on the planet, three separate species began working together. A tubular flying species with a hovering ability like hummingbirds, a sort of floating gas bag species that was highly intelligent, and precariously balanced hopping land creatures. They worked together so well that over a massive number of evolutions, they became so symbiotic as to be essentially a singular unit (an example in our own planet would be our cellular mitochondria, which all animals need to process energy the way they do, but still have separate DNA from us).

The land creatures would be the legs, the floating gas bag the torso and main intelligence, the long tube hummingbirds the arms. The creatures would have neural centers packed on the surface of their "junction points" so that the regular electromagnetic field generated by nerves could actually communicate across the short air gap between them (meaning they can't move that far away without becoming stupid).

Advantages to the arms and legs are that they gain the survivability of the giant brain in the torso. The advantage to the torso is that the arms bring it food (and later, tool use), and it can rest on the legs to see further and stay away from the planet's very mean ground insects (which one presumes the legs have a defense against).

The whole system works with a lot less energy underwater, but I got the impression you intended for land use.

There's obviously a few problems with this system, but it doesn't need magic or psionics, and presents the fun of writing for a truly alien species.

Answer 3

So: this really isn’t energy efficient, nor is it necessarily possible, but:

Flux pinning

There is an effect where a superconducting material placed in a magnetic field becomes ‘locked’. It will then not move (much) relative to the magnetic field. Not only that, but it can be used to exert force on the magnet (because conservation of energy and all that jazz). With a suitable array of magnets, muscles and superconducting nodes you could (hypothetically) float a limb some distance away from a body. Controlling fingers is hard, as is sensory feedback, but the control array would be so fearsomely complex that I’m sure evolution would have figured it out, likely with magnets and superconductors both in the shoulders and limbs.

Now: there are some big big problems. 1: To get any decent kind of mechanical leverage you need big magnetic fields. I’ve done this in a lab setting with some small magnets, and I could break the effect with a decent blow. You’ll need really powerful solid state magnets and suitably strong mounts (bones) to put them in.

2: Superconductors need to be cold. The highest temperature superconductor we know of (IIRC) is a funky sulphur based compound that exhibits the right kind of properties at somewhere around -40C and a cool couple of million atmospheres of pressure. This is obviously Not Conducive to inclusion in a living thing.

3: Controlling the limbs will be stupidly complicated and potentially impossible. Magnetic fields are finicky things. They loop. They whorl. They don’t like going through superconductors (which is why flux pinning works). I’m not altogether certain that the kind of non-trivial, moving, dynamically maintained system that I’m proposing is even possible, even if you have big magnets and room temperature superconductors.

But. If physics gives you whopping great magnets and room temperature superconductors, then make uncannily floating hands and blame it on evolution.

Answer 4

Magnets!

But here's the good part:

Each limb is a separate entity. They can't move unless they are paired together. Then once they find a pair (or group) they can modify their magnetic flux to create larger "creatures" that operate as one.

...is what I would have said if I didn't then read the comment from Joe.

Acoustic levitation then brought me to Optical Levitation.