Casmir Force reversed

[Ender]

linka

Levitation has been elevated from being pure science fiction to science fact, according to a study reported today by physicists.

Beijing saleswoman demonstrates toy which levitates by magnetic force; Physicists have 'solved' mystery of levitation
In theory the discovery could be used to levitate a person

In earlier work the same team of theoretical physicists showed that invisibility cloaks are feasible.

Now, in another report that sounds like it comes out of the pages of a Harry Potter book, the University of St Andrews team has created an 'incredible levitation effects’ by engineering the force of nature which normally causes objects to stick together.

Professor Ulf Leonhardt and Dr Thomas Philbin, from the University of St Andrews in Scotland, have worked out a way of reversing this pheneomenon, known as the Casimir force, so that it repels instead of attracts.

Their discovery could ultimately lead to frictionless micro-machines with moving parts that levitate But they say that, in principle at least, the same effect could be used to levitate bigger objects too, even a person.

The Casimir force is a consequence of quantum mechanics, the theory that describes the world of atoms and subatomic particles that is not only the most successful theory of physics but also the most baffling.

The force is due to neither electrical charge or gravity, for example, but the fluctuations in all-pervasive energy fields in the intervening empty space between the objects and is one reason atoms stick together, also explaining a “dry glue” effect that enables a gecko to walk across a ceiling.

Now, using a special lens of a kind that has already been built, Prof Ulf Leonhardt and Dr Thomas Philbin report in the New Journal of Physics they can engineer the Casimir force to repel, rather than attact.

Because the Casimir force causes problems for nanotechnologists, who are trying to build electrical circuits and tiny mechanical devices on silicon chips, among other things, the team believes the feat could initially be used to stop tiny objects from sticking to each other.

Prof Leonhardt explained, “The Casimir force is the ultimate cause of friction in the nano-world, in particular in some microelectromechanical systems.

Such systems already play an important role - for example tiny mechanical devices which triggers a car airbag to inflate or those which power tiny 'lab on chip’ devices used for drugs testing or chemical analysis.

Micro or nano machines could run smoother and with less or no friction at all if one can manipulate the force.” Though it is possible to levitate objects as big as humans, scientists are a long way off developing the technology for such feats, said Dr Philbin.

The practicalities of designing the lens to do this are daunting but not impossible and levitation “could happen over quite a distance”.

Prof Leonhardt leads one of four teams - three of them in Britain - to have put forward a theory in a peer-reviewed journal to achieve invisibility by making light waves flow around an object - just as a river flows undisturbed around a smooth rock.

No details, but pretty cool. I'm sure they are exaggerating its power but still this could be useful.

[Darth Wong]

You have to take it with a grain of salt when they start off by saying that invisibility cloaks have been proven to be possible.

[The Duchess of Zeon]

Isn't this related to the expected results of Heim Theory and some other prior articles published on the subject from the UK and New Zealand, IIRC?

[Singular Intellect]

You have to take it with a grain of salt when they start off by saying that invisibility cloaks have been proven to be possible.

I thought that was stated in the context of being scientifically viable, if not necessarily practical, whereas bending light around an object makes it invisible since it neither reflects or stops light.

[Darth Wong]

You have to take it with a grain of salt when they start off by saying that invisibility cloaks have been proven to be possible.

I thought that was stated in the context of being scientifically viable, if not necessarily practical, whereas bending light around an object makes it invisible since it neither reflects or stops light.

To be more precise, the article used the word "feasible".

[CaptainZoidberg]

You have to take it with a grain of salt when they start off by saying that invisibility cloaks have been proven to be possible.

What's so far fetched about an invisibility cloak? It's not like it violates any physical laws to have sensors on one side of the suit tell the other side to change colors...

[Darth Wong]

You have to take it with a grain of salt when they start off by saying that invisibility cloaks have been proven to be possible.

What's so far fetched about an invisibility cloak? It's not like it violates any physical laws to have sensors on one side of the suit tell the other side to change colors...

Don't be stupid. That's camouflage, not invisibility.

[Gullible Jones]

The problem with a real invisibility cloak is that it would make you blind.

[CaptainZoidberg]

Don't be stupid. That's camouflage, not invisibility.

But if your camouflage was so good that no one could discern you from the object behind you, wouldn't you be "invisible"?

[Ender]

Don't be stupid. That's camouflage, not invisibility.

But if your camouflage was so good that no one could discern you from the object behind you, wouldn't you be "invisible"?

No. Swap to another wavelength and I can still see you.

[CaptainZoidberg]

Don't be stupid. That's camouflage, not invisibility.

But if your camouflage was so good that no one could discern you from the object behind you, wouldn't you be "invisible"?

No. Swap to another wavelength and I can still see you.

Oh, right. And I guess there'd be some big technical hurdles in trying to detect a large part of the spectrum and project it out the other side...

[Fingolfin_Noldor]

I believe there was some paper aboout negative refractive index that allows "cloaking" but it is incredibly wavelength specific. I'm not too familiar with the details of the paper however.

[Knife]

Oh, right. And I guess there'd be some big technical hurdles in trying to detect a large part of the spectrum and project it out the other side...

Yes, like HEAT. Project it out the other side and you get seen. Hold it all in and you get fried.

[Darth Wong]

The other obvious problem with the projected camo concept for invisibility is directionality. It depends on the observer looking at you from a certain angle, so that you can simulate what he should see behind you. But that really only works in one direction.

Therefore, you could theoretically pull this off if you know exactly where the observer is. But what if you don't? What if there are two observers, watching you from different angles? What if there's one observer, but he has (gasp!) two eyes and he's not that far away?

[CaptainZoidberg]

The other obvious problem with the projected camo concept for invisibility is directionality. It depends on the observer looking at you from a certain angle, so that you can simulate what he should see behind you. But that really only works in one direction.

Therefore, you could theoretically pull this off if you know exactly where the observer is. But what if you don't? What if there are two observers, watching you from different angles? What if there's one observer, but he has (gasp!) two eyes and he's not that far away?

Right, but what if the sensors and color displays were very, very small - and at each point on the suit there was a color and a display. That way the front side would display the back side, the back side would display the front side, the right side would display the left side, and so on.

I don't know where the problem is with heat. If the detectors on the suit take up most of the incoming light, convert it to energy, and the projectors send it back out as light, I don't see a big problem. Now of course some heat is going to pool up due to inefficiency.

[Darth Wong]

The other obvious problem with the projected camo concept for invisibility is directionality. It depends on the observer looking at you from a certain angle, so that you can simulate what he should see behind you. But that really only works in one direction.

Therefore, you could theoretically pull this off if you know exactly where the observer is. But what if you don't? What if there are two observers, watching you from different angles? What if there's one observer, but he has (gasp!) two eyes and he's not that far away?

Right, but what if the sensors and color displays were very, very small - and at each point on the suit there was a color and a display. That way the front side would display the back side, the back side would display the front side, the right side would display the left side, and so on.

You obviously didn't understand the objection. In order to know the "back side" for any given observer, you need to know the direction of his line of sight through you. Therefore, you need to know exactly where he is. And your camo would not work for a second observer because his line of sight would be different; your "back" side from his perspective is different from your "back" side from the first guy's perspective. Get it?

[CaptainZoidberg]

You obviously didn't understand the objection. In order to know the "back side" for any given observer, you need to know the direction of his line of sight through you. Therefore, you need to know exactly where he is. And your camo would not work for a second observer because his line of sight would be different; your "back" side from his perspective is different from your "back" side from the first guy's perspective. Get it?

Yeah, I realize that it would only work if you had one observer and knew their exact line of sight.

[starslayer]

Yes, they're exaggerating the Casimir Effect. It's quite tiny, and easily overwhelmed by pretty much any other possible interaction in macroscopic objects. Any levitation of a person that could be done using it would likely be completely impractical and useless, just like levitating someone through diamagnetism would be, but for different reasons.

Isn't this related to the expected results of Heim Theory and some other prior articles published on the subject from the UK and New Zealand, IIRC?

IF Wikipedia is correct on Heim's results and theory, no, they aren't related. It appears Heim was trying to unify quantum mechanics and GR; the Casimir effect is purely quantum mechanical.

[Starglider]

You obviously didn't understand the objection. In order to know the "back side" for any given observer, you need to know the direction of his line of sight through you.

The OP probably didn't understand your objection, but this problem is solvable in principle with sufficiently advanced sensors and displays. The relatively easy way to do this is to make each transceiver node a cluster of highly directional photodiodes and LEDs. Primitive versions of this have been in use for some time to make 3D displays that don't require polarisation or shutter glasses; the problem with those is that your effective resolution is divided by the number of distinct angles you want to generate a view for. However resolutions have been scaling steadily, as has the cheap massively parallel compute power you need to drive it. My guess is that we should be able to build something in a couple of decades that works reasonably well, omnidirectionally, as long as the observer is at least ten metres away and the camouflaged object is out of direct sunlight.

A truly holographic invisibility system would probably require optical phased arrays, which are possible in theory but would require very impressive nanotechnology to fabricate (particularly in bulk). There would still be the tricky waste heat issue, but in low-intensity warfare the enemy would likely not be constantly scanning with thermal imaging equipment (or even possess it).

[avatarxprime]

I believe there was some paper aboout negative refractive index that allows "cloaking" but it is incredibly wavelength specific. I'm not too familiar with the details of the paper however.

Yeah, they had created metamaterials that can make an object invisible in the infrared wavelength, but it only worked in two dimensions IIRC. Designing one that would work for visible light (and all the wavelengths there-in) and work in three dimensions would be quite a challenge.

[Fingolfin_Noldor]

Yeah, they had created metamaterials that can make an object invisible in the infrared wavelength, but it only worked in two dimensions IIRC. Designing one that would work for visible light (and all the wavelengths there-in) and work in three dimensions would be quite a challenge.

Yeah, it was very wavelength specific. It might well be impossible to get one that works in 3D given the nature of nonlinear materials. A lot of nonlinear materials are polarisation dependent and what not.

[CaptainChewbacca]

I'm really disappointed this article provides zero information on how they're reversing the effect. You'd think they would shout something like that from the rooftops. If it works, clear a space on the wall for your nobel prize.

Between this and synthetic petroleum, its an interesting week for science.