It's Thursday evening in the 21st century and I still don't have a jetpack. And now mice can hover. It's unfair.

September 10, 2009 5:39 PM

Somewhere on Earth, in a laboratory, a mouse is levitating. Science is awesome.
posted by ardgedee (63 comments total)

It appeared agitated and disoriented, seemingly trying to hold on to something.

They decided to mildly sedate the next mouse they levitated, which seemed content with floating.

The lesson: when sober, no fun. When stoned, super fun! Mice are much like us.
posted by ORthey at 5:41 PM on September 10 [13 favorites]

Are you thinking what I'm thinking, Pinky?
posted by rokusan at 5:44 PM on September 10 [15 favorites]

yeah baby
posted by fleetmouse at 5:44 PM on September 10 [2 favorites]

Is this how we do gravity in spacecraft? Everything would have to be made out of non-magnetic materials, could we do that?
posted by East Manitoba Regional Junior Kabaddi Champion '94 at 5:46 PM on September 10

They could do that, but it would take a monumental amount of electricity.
posted by dunkadunc at 5:49 PM on September 10

or well-insulated
posted by Jon_Evil at 5:49 PM on September 10

"It actually kicked around and started to spin, and without friction, it could spin faster and faster, and we think that made it even more disoriented,"

No shit, Sherlock.
posted by flapjax at midnite at 5:54 PM on September 10 [2 favorites]

They could do that, but it would take a monumental amount of electricity.

They use a superconductor. I don't know that it actually takes that much electricity to keep going.
posted by delmoi at 5:57 PM on September 10

Yeah, I would probably start freaking out too. Could this mean grav shafts? Sounds good to me.
posted by Askiba at 5:57 PM on September 10

Oh man, I would love to borrow this and install it around my kids' cribs. No gravity? They'd sleep like stones! And as a bonus I'd get to freak out my mother at the same time.

An explanation: my kids are twins -- a boy and a girl. The most common question we seem to get as parents are whether they're identical. I used to reply, "Well, they were until the gender reassignment surgery." Unfortunately that only seemed to confuse people.

Apparently, my twisted sense of humor is lost on the masses.

The second most common question we get is whether the kids have a telepathic link. "Do they feel what the other is thinking? Are they psychic? Have they done anything, you know.... unnatural?" The last person to ask us if we thought the kids were psychic happened to be my mother. In reply I snapped, "No, mom. But if I come into their room one morning and find 'em levitating four feet above their cribs, I'll be sure to call you immediately."

I wonder if NASA would let me borrow that equipment for a day. I'd even promise to tape her reaction and everything.
posted by zarq at 5:59 PM on September 10 [4 favorites]

water is magnetic?
posted by Avenger at 6:03 PM on September 10 [1 favorite]

I look forward to Friday night's live BBC special, in which he explains how he did it.
posted by jbickers at 6:06 PM on September 10 [2 favorites]

Can someone explain how this works? I didn't think there was enough "stuff" in a mouse to levitate it magnetically. i.e. ditto avenger
posted by R_Nebblesworth at 6:08 PM on September 10

Re: the physics. It exploits diamagnetism. A common diamagnetic material is water, which most living things are full of.
posted by jedicus at 6:11 PM on September 10

Water is diamagnetic. Diamagnetism and paramagnetism are much weaker than the ferromagnetism we're all most familiar with, but I think they occur in more materials.

Frog levitation on the same principle, plus informative linkery.
posted by hattifattener at 6:13 PM on September 10 [4 favorites]

Dang, I never heard of that before. FUCKING COOL
posted by R_Nebblesworth at 6:15 PM on September 10

Time to mount the frickin lasers. The shark is next.
posted by Hardcore Poser at 6:15 PM on September 10 [1 favorite]

I wouldn't make that mouse angry if I were you.
posted by mecran01 at 6:16 PM on September 10

"It actually kicked around and started to spin, and without friction, it could spin faster and faster, and we think that made it even more disoriented,"

No shit, Sherlock.
posted by flapjax at midnite


I know, right? Stupid mice-levitating scientists. Get a brain, morans!
posted by lazaruslong at 6:17 PM on September 10 [5 favorites]

such research with mice, being closer biologically to humans, could help in studies to counteract bone loss due to reduced gravity over long spans of time

Sure, it could do that, but I really doubt that it was the first idea the scientists had in mind.

My personal "what I would do with this technology": use this diamagnetism thing to create a forcefield umbrella. But that seems really tame now that I think about it; maybe I would just levitate beer for the hell of it.
posted by Think_Long at 6:19 PM on September 10 [1 favorite]

It's Thursday evening in the 21st century and I still don't have a jetpack. And now mice can hover. It's unfair.

This is no jetpack with the option flying around. It's keeping you above a certain patch of ground. Floating in a set location sounds like a lot of fun, but it won't get you to work, or let you zoom over tall buildings.
posted by filthy light thief at 6:21 PM on September 10

Are you thinking what I'm thinking, Pinky?

Yes Boss, but I don't think we can get the pink thong on a giraffe. Narf!
posted by johnj at 6:22 PM on September 10 [7 favorites]

They use a superconductor. I don't know that it actually takes that much electricity to keep going.

Does levitating something take energy? I guess not--there's a force, but not over a distance.
posted by DU at 6:24 PM on September 10

Also, levitating a person in this way would require a magnetic field of 40 tesla, which would consume about 1 GW, which is the power output of a entire medium sized power plant. There is one laboratory capable of producing such a field, but the magnet's bore is a mere 32mm, not nearly large enough to accommodate a person. Making a field of that strength large enough to levitate a person would be a pretty significant feat of engineering.
posted by jedicus at 6:29 PM on September 10

Wait 'till Tom hears about this.
posted by Brandon Blatcher at 6:35 PM on September 10

This story terrified my floating elephant.
posted by BitterOldPunk at 6:36 PM on September 10 [14 favorites]

Making a field of that strength large enough to levitate a person would be a pretty significant feat of engineering.

Killjoy. ;)
posted by zarq at 6:44 PM on September 10

Next thing you know we'll have to have levitating cats to catch the levitating mice.
posted by spitefulcrow at 6:47 PM on September 10 [2 favorites]

Do we finally get flying cars now?
posted by hypersloth at 6:54 PM on September 10

Does levitating something take energy? I guess not--there's a force, but not over a distance.

You have to have enough force to counter acceleration due to gravity.

For a 175 pound person, that would be approximately 778 newtons of force.
posted by empath at 6:56 PM on September 10

*grumble* It's actually, "Pinky, are you pondering what I'm pondering?"
posted by hippybear at 7:05 PM on September 10 [1 favorite]

*grumble* It's actually, "Pinky, are you pondering what I'm pondering?"

I think so, Brain. But where are you going to find a grouchy hippy bear at this hour?
posted by zarq at 7:09 PM on September 10 [5 favorites]

Actually how to convert from newton to energy, i dunno. If you just wanted to lift a 175 pound person 10 centimeters off the ground, that would take 77.8 joules of work. But that's assuming that you're lifting it up with a pulley, or something similar where you're not continually applying force to keep it up.
posted by empath at 7:12 PM on September 10

Damn, some of you people on Metafilter are fuckin' smart. It's really impressive, no lie.

I still think the scientist who said "we think" that spinning a mouse around in space faster and faster made it "even more disoriented" perhaps needs a trip to the Department of Obviousness for a refresher course.

/cut to character out of Hee-Haw, in his overalls, chewing on a straw and saying "these here scientists may be smart, but they ain't got no common sense."
posted by flapjax at midnite at 7:33 PM on September 10

I am all for my scientists not pretending that they know exactly what a mouse is thinking, even if it's a pretty good bet. It's exactly the right attitude to approach science with.
posted by ErWenn at 8:00 PM on September 10 [3 favorites]

OK, ErWenn, I hear that. Point taken.
posted by flapjax at midnite at 8:08 PM on September 10

I still think the scientist who said "we think" that spinning a mouse around in space faster and faster made it "even more disoriented" perhaps needs a trip to the Department of Obviousness for a refresher course.

/cut to character out of Hee-Haw, in his overalls, chewing on a straw and saying "these here scientists may be smart, but they ain't got no common sense."
posted by flapjax at midnite

I was just joshin' before, but I read it totally differently, I guess. I read it as typical scientific disregard for making absolute statements about unmeasured variables. That is, they cannot be 100% sure, without setting up a side experiment measuring some quantifiable level of "disoriented-ness", that it was the increased rotation that made the mice more disoriented. It seems self-evident, but only to us!

I love that scientists speak this way in the same manner that I love the way pro sports players always speak in platitudes.
posted by lazaruslong at 8:24 PM on September 10 [1 favorite]

Well damn. What ErWenn said.
posted by lazaruslong at 8:24 PM on September 10

Actually how to convert from newton to energy, i dunno. If you just wanted to lift a 175 pound person 10 centimeters off the ground, that would take 77.8 joules of work. But that's assuming that you're lifting it up with a pulley, or something similar where you're not continually applying force to keep it up.

Work (in the scientific sense) is a form of energy. They have the same units.

If you lift something with a pulley, you are continually applying force. If you are holding something by a rope and it is still, you are continually applying a constant force. This is why you'll eventually get tired if you stand up for a long time. Even though you aren't moving, gravity is applying a force equal to the mass of your body times the acceleration due to gravity (about 9.8 meters per second squared). To remain standing your body has to continually exert a force equal in magnitude but opposite in direction. We call this force our body weight.

Intuitively you might think that there's a hole in our definition of energy here. We're not moving over any distance, yet surely we must be using up energy to exert this force.

That's because there are other kinds of energy other than mechanical work. There can also be energy 'stored' in an object. Think of a spring. If you squeeze it together, you can feel it exert a force against your fingers. By squeezing the spring, you imparted it with something called potential energy. The spring wants to convert that potential energy into work by exerting a force to go back to its original length.

Physicists can correct the above, this is just from my understanding of classical mechanics.
posted by anifinder at 8:30 PM on September 10

I've been electrifying mice all day trying to reproduce this. Turns out you need a superconductor, not tinfoil.
posted by blue_beetle at 9:01 PM on September 10 [3 favorites]

spitefulcrow: This is the mouse, that worried the cat that killed the rat that ate the malt, that levitated in the house that Jack Built.
posted by Cold Lurkey at 9:03 PM on September 10 [1 favorite]

Diamagnetism and paramagnetism are much weaker than the ferromagnetism we're all most familiar with, but I think they occur in more materials.

If I remember correctly (and it's been a long time) diamagnetism is universal- everything is diamagnetic. But in some materials (the materials we conventionally consider "magnetic") diamagnetism is vastly overpowered* by ferromagnetism.

*overpowered isn't strictly the right word to use here, but it will do.

Regarding the energy we spend just standing up: Imagine the following. You've got a rope hanging from the ceiling right next to you. You grab the rope, pull yourself up a foot, and then drop. Your feet strike the ground and are warmed by the dissipating kinetic energy. Repeat this process thousands of times. You are clearly doing work to lift yourself, but the energy you put into this process just ends up as waste heat.

Now, while you do this you're being watched by gigantic aliens thousands of times larger than you, who see the world in slow motion. These aliens don't see you moving. Your average position appears to be constant. They can tell from the tension on the rope that you are exerting a net force, but they can't tell you're moving. They think you're exerting a force over zero distance, and therefore expend no energy, and are mystified as to why you should ever get tired as you appear to do.

When we look at someone pushing against a wall or some other futile force-but-no-distance kind of activity, we are those huge slow aliens, and we fail to see the fast microscopic back-and-forth struggles of tiny proteins that work inside our muscles; these proteins grip filaments and pull on them, but they lose their grip momentarily, and if the load on the muscle is too great, the filaments slip past the protein and the protein needs to grip and pull again and again just to stay in the same average position.
posted by Jpfed at 9:23 PM on September 10 [3 favorites]

Also, levitating a person in this way would require a magnetic field of 40 tesla, which would consume about 1 GW, which is the power output of a entire medium sized power plant. There is one laboratory capable of producing such a field, but the magnet's bore is a mere 32mm, not nearly large enough to accommodate a person. Making a field of that strength large enough to levitate a person would be a pretty significant feat of engineering.--jedicus

...and would be completely worth the effort!


I wonder about the whole force/work argument. If you can get a magnet to balance in the air above another magnet, it'll just sit there like that forever. There's no energy being exerted.
Of course, as jedicus mentions, an electromagnet is going to take a heck of a lot of energy.
posted by eye of newt at 9:30 PM on September 10

It's actually, "Pinky, are you pondering what I'm pondering?"

Yeah, I realized that a minute later, but the imaginary 10-second edit window had already closed.

Burned by the Write Once Web 2.0.
posted by rokusan at 9:41 PM on September 10 [2 favorites]

I'm pretty confident that the levitation itself takes no energy— it just takes energy to maintain that magnetic field using the technology we use today. If you had a permanent magnet with crazyhuge mmf, you could levitate stuff with it. (Or you could use a substance that's more diamagnetic than water, like graphite, and do it with easily-available supermagnets — see also billb's demonstration.).

The Nijmegen HFML Bitter coil takes 6 MW to run because it's plain-old non-superconductive copper. Presumably a superconducting magnet could produce that field with the only ongoing energy input being for the refrigeration. Anyone know what kinds of fields the LHC's coils maintain?
posted by hattifattener at 10:06 PM on September 10

So...a superconductor a few orders of magnitude large and we (us humans) can ride too? Sign me up.
posted by zardoz at 12:25 AM on September 11

How does one calculate the energy used by maintaining a force of X newtons for Y seconds, then? (Would that also be "what is the power required for a force of X newtons?")
posted by alasdair at 1:04 AM on September 11

There's a cat after it....
posted by Kronos_to_Earth at 1:23 AM on September 11

alasdair: 1 Watt is 1 Newton meter per second.
posted by floam at 3:03 AM on September 11

(and people often, when talking about Y units of time, talk about "watt-hours".)

But the simplest way to break it down is just to count joules.
posted by floam at 3:04 AM on September 11

alasdair: "How does one calculate the energy used by maintaining a force of X newtons for Y seconds, then? (Would that also be "what is the power required for a force of X newtons?")"

There's no relation. Think of a spring under tension. There's a force maintained, but there's no energy expended. Energy is only exchanged when things move (then you can measure the watt-meters, ie joules).

For a human, who gets tired from holding something, I suppose it depends on the biology of the muscles and such. I'd be interested in knowing if anyone has studied how many calories are used by a person simply holding a weight.
posted by alexei at 3:09 AM on September 11

You have to have enough force to counter acceleration due to gravity.

Do you? If you just tie a mouse to a rope it takes no energy to "levitate".
posted by DU at 4:34 AM on September 11

DU: Just because there's no energy source required, it doesn't mean there isn't a force. If we were to draw a free body diagram of something hanging on a string, we'd show a tension in the string.
posted by floam at 5:00 AM on September 11

Just imagine if they put this cat in an antigravity field.
posted by dunkadunc at 6:47 AM on September 11

Just because there's no energy source required, it doesn't mean there isn't a force

Right, but the person I was responding to was indicating that this DID mean it required energy. At least I assume that's what they meant by in turn quoting me. The lack of threading on MeFi is a real headache.
posted by DU at 6:51 AM on September 11

In an effort to provide a sort of peer review, I decided to duplicate blue_beetle's experiment, and I can confirm that tinfoil does not appear to be usable in the levitation of mice. However, if you model it properly, you can make cute little robot costumes for them out of it.

I remember back when they first floated the frog, when I saw the video I knew that we were living in The Future!
posted by quin at 7:55 AM on September 11

I don't quite understand how this would be quite the same as being in actual free-fall. Wouldn't the organs and bones of the creature in the magnetic field still be under the same amount of gravitational potential being near the surface of the earth, and thus the bone-loss and other effects of micro-gravity are not in effect? I thought the bone loss and other bad physiological things that happened to a body under micro-gravity were caused my there being no down, thus everything tends to settle towards the center of mass. I guess I could be wrong there, I dunno.

It just seems to me that instead of there being any micro-gravitational effects, this is simply making the creature in the field use the field as the "floor". You're still being accelerated downwards at 11 m/sec^2. It's just that the water in your body is being "pushed" away from the magnetic field by another force, strong enough to counter gravity. As soon as that field is removed, you are going to fall 11 m/sec^2 again. In microgravity, when the repelling force is removed, you wouldn't start to "fall" at 11 m/sec^2, but some other rate calculated by the distance from the large mass of the Earth, in relation to the mass. Or something.

My physics is rusty.
posted by daq at 10:34 AM on September 11

Why do I get the feeling that a magnetic field being so strong as to actually be able to repel you more strongly than the force of gravity... has to be doing something really bad to you somehow? What about the iron in the blood? Is that being affected by this? Why can I not shake the idea that there are unseen negative effects on living tissue having this done to it?

Maybe it's because the machine sounds vaguely like the one at the start of Primer?
posted by hippybear at 10:51 AM on September 11

alasdair: Simply applying a force doesn't need to take energy (i.e., it only takes energy if something else about the situation wastes energy, like the way animal muscles work, or the resistive losses in a huge electromagnet). Force times distance gives energy, however (usually called 'work' in that context but it's the same thing). So, for example, pushing a 1-ton weight 1 meter uphill takes a certain amount of energy. Put a chock under it which supplies enough force to keep it in place, but doesn't move it, and no energy is expended.

hippybear: It's actually kind of surprising to me also that there's no bad effect, but apprently there isn't. I think that's one of the things they're investigating with these experiments in the first place. As the researchers point out, really strong fields are also used in NMR scanners.

The iron in your blood isn't actually magnetic, because it's in the form of single atoms in hemoglobin. Ferromagnetism is an effect that happens when you have a bunch of iron atoms in a crystal. That is, it's a bulk effect. The reason for this is some wacky quantum-mechanical stuff which the Wikipedia article covers briefly.
posted by hattifattener at 2:54 PM on September 11

Yeah, I've been electrifying mice all day too. But what's this about levitation?

A superconducting magnet waterslide would be cool.

“I'd be interested in knowing if anyone has studied how many calories are used by a person simply holding a weight.”
You burn (or rather I burn at 275lbs) very roughly about 2 calories a minute just standing – holding body weight. But that’s mostly because the muscles involved are doing minimal work. Most of the mechanical force is borne by your skeletons and tendons which resist gravity through tension and load bearing stress on them so most of the metabolic energy expended is in upkeep (exchanging calcium to repair bone, etc.)
Just holding an additional weight is a different story – all depends on how you’re holding it. Whether the weight is being borne by muscular tension which would take more calories, or supported by the structural (skeletal) system in the body. If I do a curl and stop mid-motion that creates a whole different kind of stress on my biceps and arms than if I end the movement at the bottom and just hold it.
‘Work’ means something different in exercise physiology than it does in physics. You’re looking at the effect on the muscles rather than the caloric exchange for static physical output or force over distance.
I’d be an interesting study, but probably geared more towards holding a heavier weight. So you’d be measuring stress and muscle breakdown as well as increased metabolic rate and muscle recovery in situ. Dunno, lots of variables there. Just holding a weight is a fairly complex operation biologically.

That does relate to what daq is saying tho - there still would be a 'down' (far as my thinking carries me) since they're still technically in a gravity well, just being pushed back - as daq sez, but the gravity related stress impacts would be neutralized, so you would get to study how, say, the leg bones change over time without having to support weight constantly or take the (surprisingly large, on a human) impacts from walking.
posted by Smedleyman at 3:03 PM on September 11

(This is to say - although gravity isn't neutralized there are still aspects of physiology one can study such as the lack of, or greatly reduced, impact stress from gravity (for bones, muscles, etc) and the lack of mechanical tension and stress on the skeletal structure and tendons, etc. Spinning the mouse seems pretty counterproductive. I mean, centripetal force can cause the same kind of tensile stress that gravity can cause (almost dislocated my elbow once delivering a ridge hand). I'd think they'd have strain gauges (mercury/rubber) somewhere on the animal if they're doing the biomechanics thing. Article doesn't get right down to exactly what they're measuring other than talking generally about the effects of microgravity...which I don't know dick about)
posted by Smedleyman at 3:21 PM on September 11

alasdair: Simply applying a force doesn't need to take energy (i.e., it only takes energy if something else about the situation wastes energy, like the way animal muscles work, or the resistive losses in a huge electromagnet).

I guess the confusion is that the magnet requires x amount of energy to generate y amount of force, so it's easy to make the leap that it requires x amount of energy to levitate something.
posted by empath at 4:07 PM on September 11

daq: It just seems to me that instead of there being any micro-gravitational effects, this is simply making the creature in the field use the field as the "floor".

This would only be true if the field was only applying force to one small part of the mouse, such as the bottoms of its feet. If the force is being evenly applied across the body, then you don't get the same compression with the weight of everything above some random bone cell pushing down and the normal force of the cells below it pushing up. In the perfectly even levitation force situation, since each molecule has a magnetic force perfectly canceling the gravitational force, the molecules are not applying a significant force to each other, which is where the compression effects come from.

However, this perfect levitation force doesn't seem to be exactly the case. I believe the force is being exerted evenly on all the water in the body (please correct me if I've read that wrong). Not everything in the body is water, so the force that keeps all the non-water molecules supported is still being provided by other molecules in the body. Meta-however, the water in the body does seem to be very evenly placed throughout the body, some of it occurring in every cell. So any small speck of non-water completely surrounded by water really only has to deal with the compression induced by the weight of that one speck. Many of these specks are going to be individual molecules dissolved in a sea of water, in which case this compression is completely negligible. While I have no idea if there are large enough chunks of non-water in the body for compression to still have a noticeable effect, I suspect that the concerns of bone-upkeep have to do with more large-scale compression.

Note: while the compression I've referred to here is caused by forces, the forces on any individual molecule that doesn't move are always zero, regardless of whether this is due to small forces of gravity and magnetism being perfectly canceled out or large normal forces applied by contact with molecules above and below. But since a mouse is not a completely rigid thing, the molecules will move in response to gravity. In a simple example, the molecules in a fluid in some chamber (say the stomach, or the interior of a cell) will move somewhat downward, leaving more molecules near the bottom than at the top, possibly deforming the chamber. But there are also situations where relatively weak bonds between cells will break or bend. The mechanical work here is small because the distance moved is slight, but breaking these bonds expends energy in other ways.
posted by ErWenn at 7:37 AM on September 12