Some of what you say is correct, but you're missing a fairly vital point.
There are several versions of invisibility floating around, but the most promising one (proposed by Pendry, Smith and Schurig) and the only one, as far as I'm aware, to have actually been demonstrated, DOES NOT USE NEGATIVE INDEX MATERIALS! There seems to be a great deal of confusion on this point (not helped by the summary above).
The cloak and the negative refractive index are both made possible by the advent of metamaterials. However, this is all they have in common!
First of all, the idea you're attacking is definitely not liberalism. A more appropriate word would be socialism.
Secondly, it can be argued that poverty is always a relative concept. A reasonable definition of relative poverty could be, "Absence of the material needs to participate fully in accepted daily life". An increase in the number of people living in relative poverty is bad for everyone, rich and poor; it inevitably means an increase in unhappiness, resentment and despair. An increase in inequality is therefore a legitimate cause for concern.
I don't think you've RTFA. You certainly haven't read the paper.
At best, this would provide almost perfect camouflage. Bits of colour from the background would not show up on you; from whatever direction you look at it, you would see right through it. The light goes around the cloaked object, but there is no way for you to know that.
Of course, this only works over a restricted frequency range. In addition, since these metamaterials are usually based on resonant systems and are consequently strongly dispersive, there is some initial scattering while the resonance is established; very short pulses defeat the invisibility.
#1 The water thing is just an analogy, and is definitely not perfect, although it does convey the important point that the light flows around the cloaked object (never reaching it, or interacting with it in any way).
#2 The entire light field on the observer side appears EXACTLY as it would if the cloaked object were not there. In your example, the tree would not appear to be split -- it would just look like a tree.
Maybe they just got it backwards in the article. Perhaps they should have said that a change in the value of mu implies a change in the strong force (assuming that the change in the mass ratio is due to a corresponding change in the binding energy of the proton).
Obviously I haven't RTFA, but even a cursory glance through the summary reveals that this is not what has happened here. The claim is not that the value of the constant has been determined more accurately, but that it is not constant at all. The value itself has changed, not just the accuracy to which we are able to measure it.
Remembering things incredibly well doesn't imply high intelligence, or an ability to solve all the world's problems. After following your link, I carried on and read the article about S.V. Shereshevskii, who apparently had truly astounding recall -- he could remember speeches, complicated formulae, poems in a foreign language, and many other things, all very quickly and for years afterwards -- but an entirely ordinary level of intelligence.
His story is very interesting, and more than a little sad. After performing for years as a mnemonist, he became unable to distinguish between recent conversations and those which happened long ago -- but which he still recalled perfectly. Desperately trying to forget the never-ending lists of words, he wrote them down on paper which he then burned. He ended up in an asylum.
Maybe he believed that he could do it, but that things were taking too long. I think that this is when the temptation to fake results arises: when you're "certain" that the experiment can be done, and equally sure that you will be able to do it, but things aren't moving fast enough and you think that someone else might beat you to it.
A serious problem, even a fundamental flaw can seem to be nothing more than an annoying technical hitch -- and the pressure gets to you -- so you fake it.
One of the main reasons why people are so excited about these negative index materials is that you can beat the diffraction limit, ie. obtain sub-wavelength resolution. The problem is not the wavelength of light; the problem is making the necessary metamaterials. If you want to get 1nm resolution, the structure of the metamaterial needs to be on that scale... and that's hard.
Sub-wavelength resolution has already been achieved. The groups of Zhang (Berkeley) and Blaikie (Canterbury) obtained resolution of around 100nm using visible light. There's a Physics World article by a collaborator of ours which describes the work and has the references.
Photonic crystals are not the same as metamaterials. As you say, photonic crystals are periodic structures with a period close to the wavelength of light being used. Metamaterials, on the other hand, are not necessarily periodic, but have structure on a scale much smaller than the wavelength.
You can get negative refraction using a photonic crystal, but there are problems. I don't know whether genuine super-resolution can be achieved in this way. Super-resolution has been demonstrated for metamaterials, in particular the planar silver lens, which is nothing like a grating.
If the lens were "perfect", it wouldn't matter how far the object was from the lens. However, real lenses cannot be perfect, and the resolution worsens with distance.
The silver lens only works in the near field because the magnetic permeability is positive, ie. it is not a genuine negative index material. It relies on the fact that close to the object, the electric and magnetic fields are effectively decoupled; each field is important for only one type of polarisation. The lens only works for TM polarisation (where the electric field is important).
To get a negative refractive index requires both epsilon and mu to be negative. For a "superlens", the ideal value is -1 for both.
A metamaterial is structured on a scale much smaller than the wavelength. It can then be treated as an effective medium; in this approximation, the material parameters are just like the classical ones. The approximation breaks down if you look too closely -- at a length scale comparable with that of the structure -- just as it does for normal materials (where the scale of the structure corresponds to the distance between neighbouring atoms).
Yes, you can still build a magnifying lens out of a negative index material. However, a thin flat sheet of this material is already a "superlens"; it doesn't magnify, but produces (in theory at least) a perfect image, with no loss in resolution. Even the near-field (evanescent, exponentially-decaying) components are restored and focused.
Of course, in reality, the resolution is limited by absorption and the length-scale of the artificial structures.
Light doesn't go faster than c in these materials... see some of my other posts on this...
Snell's law doesn't give you any problems -- the angle of refraction is negative, ie. the light bends back on itself.
The point about the speed of light is more interesting. In negative index materials, the group and phase velocities are in opposite directions. Energy and information flow in the direction of the group velocity, which is always less than c.
Metals have negative dielectric permittivity, but positive magnetic permeability. Having both negative is completely new.
This is an element of truth in this. The group velocity and the phase velocity are in opposite directions. The group velocity (which determines the flow of energy, and the direction and speed of information transfer -- and photons) would point away from the boundary, while the phase velocity points towards the boundary.
It should also be noted that these negative index materials rely on resonant behaviour, and are consequently highly dispersive.
It's not quite the first time. Zhang's group in Berkeley published a paper in spring last year (Science 308, 534-537) describing experiments on the silver superlens, which works at optical frequencies. There have been other similar experiments since then.
Negative refraction is not found in nature, in the same way that cars are not found in nature. In this sense it is not "natural".
You want to insist on labelling all man-made creations as natural, because man is part of nature, but this seems unhelpful and rather pointless. In this case there it is obvious that "natural" means "not made by man".
How does a plasma cloud give you negative magnetic permeability? There would certainly be a regime of negative permittivity (just like in an ordinary metal), but I'm pretty sure the permeability would not be negative.
Please enlighten me if I'm wrong; if not, the parent post is incorrect.
With the present state of the art (in IT), I guess it would be possible to achieve a 100% democratic govt. But, as our elected representatives are probably not quite willing to have their jobs replaced by a couple of computers, I guess we will never get to that stage:-)
There is a more serious argument as to why true democracy would be a bad thing. The idea is that to achieve a deep understanding of the issues involved in managing a country takes a long time and a lot of effort, as well as some minimum level of intelligence. Most people do not have the time or the desire to obtain this level of understanding, so we employ elected representatives to do the job for us, trusting that they will make the right decisions. They are supposed to be more than just computers carrying out our wishes.
Whether many politicians actually obtain this level of understanding (or have the native wit required to do so) is a matter for debate...
I'm not sure that the history of the apostrophe is so clear-cut.
This article (PDF) suggests that the genitive ending was -es in Old English, and -ies or -ys in Middle English, and that the apostrophe was introduced as a replacement for omitted vowels.
However, he also describes an alternative view: that the apostrophe was originally used because of the mistaken assumption that the genitive ending was already a contraction of "his". Apparently even Shakespeare made this mistake...
cathartic: of, relating to, or producing catharsis. catharsis: a purification or purgation that brings about spiritual renewal or release from tension.
Slashdot Mirror
Some of what you say is correct, but you're missing a fairly vital point.
There are several versions of invisibility floating around, but the most promising one (proposed by Pendry, Smith and Schurig) and the only one, as far as I'm aware, to have actually been demonstrated, DOES NOT USE NEGATIVE INDEX MATERIALS! There seems to be a great deal of confusion on this point (not helped by the summary above).
The cloak and the negative refractive index are both made possible by the advent of metamaterials. However, this is all they have in common!
First of all, the idea you're attacking is definitely not liberalism. A more appropriate word would be socialism.
Secondly, it can be argued that poverty is always a relative concept. A reasonable definition of relative poverty could be, "Absence of the material needs to participate fully in accepted daily life". An increase in the number of people living in relative poverty is bad for everyone, rich and poor; it inevitably means an increase in unhappiness, resentment and despair. An increase in inequality is therefore a legitimate cause for concern.
At best, this would provide almost perfect camouflage. Bits of colour from the background would not show up on you; from whatever direction you look at it, you would see right through it. The light goes around the cloaked object, but there is no way for you to know that.
Of course, this only works over a restricted frequency range. In addition, since these metamaterials are usually based on resonant systems and are consequently strongly dispersive, there is some initial scattering while the resonance is established; very short pulses defeat the invisibility.
#2 The entire light field on the observer side appears EXACTLY as it would if the cloaked object were not there. In your example, the tree would not appear to be split -- it would just look like a tree.
Maybe they just got it backwards in the article. Perhaps they should have said that a change in the value of mu implies a change in the strong force (assuming that the change in the mass ratio is due to a corresponding change in the binding energy of the proton).
Obviously I haven't RTFA, but even a cursory glance through the summary reveals that this is not what has happened here. The claim is not that the value of the constant has been determined more accurately, but that it is not constant at all. The value itself has changed, not just the accuracy to which we are able to measure it.
His story is very interesting, and more than a little sad. After performing for years as a mnemonist, he became unable to distinguish between recent conversations and those which happened long ago -- but which he still recalled perfectly. Desperately trying to forget the never-ending lists of words, he wrote them down on paper which he then burned. He ended up in an asylum.
It doesn't sound like much fun to me.
Pretty easily.
Reason's crowning achievement will be to destroy religion; when reason, not faith, determines how we view the world, there will be no need for God.
A serious problem, even a fundamental flaw can seem to be nothing more than an annoying technical hitch -- and the pressure gets to you -- so you fake it.
All true, but I don't think a hypothetical ET wrote the article summary... but you never know.
Sub-wavelength resolution has already been achieved. The groups of Zhang (Berkeley) and Blaikie (Canterbury) obtained resolution of around 100nm using visible light. There's a Physics World article by a collaborator of ours which describes the work and has the references.
You can get negative refraction using a photonic crystal, but there are problems. I don't know whether genuine super-resolution can be achieved in this way. Super-resolution has been demonstrated for metamaterials, in particular the planar silver lens, which is nothing like a grating.
If the lens were "perfect", it wouldn't matter how far the object was from the lens. However, real lenses cannot be perfect, and the resolution worsens with distance.
The silver lens only works in the near field because the magnetic permeability is positive, ie. it is not a genuine negative index material. It relies on the fact that close to the object, the electric and magnetic fields are effectively decoupled; each field is important for only one type of polarisation. The lens only works for TM polarisation (where the electric field is important).
A metamaterial is structured on a scale much smaller than the wavelength. It can then be treated as an effective medium; in this approximation, the material parameters are just like the classical ones. The approximation breaks down if you look too closely -- at a length scale comparable with that of the structure -- just as it does for normal materials (where the scale of the structure corresponds to the distance between neighbouring atoms).
Of course, in reality, the resolution is limited by absorption and the length-scale of the artificial structures.
Light doesn't go faster than c in these materials... see some of my other posts on this...
The point about the speed of light is more interesting. In negative index materials, the group and phase velocities are in opposite directions. Energy and information flow in the direction of the group velocity, which is always less than c.
Metals have negative dielectric permittivity, but positive magnetic permeability. Having both negative is completely new.
It should also be noted that these negative index materials rely on resonant behaviour, and are consequently highly dispersive.
It's not quite the first time. Zhang's group in Berkeley published a paper in spring last year (Science 308, 534-537) describing experiments on the silver superlens, which works at optical frequencies. There have been other similar experiments since then.
You want to insist on labelling all man-made creations as natural, because man is part of nature, but this seems unhelpful and rather pointless. In this case there it is obvious that "natural" means "not made by man".
How does a plasma cloud give you negative magnetic permeability? There would certainly be a regime of negative permittivity (just like in an ordinary metal), but I'm pretty sure the permeability would not be negative.
Please enlighten me if I'm wrong; if not, the parent post is incorrect.
There is a more serious argument as to why true democracy would be a bad thing. The idea is that to achieve a deep understanding of the issues involved in managing a country takes a long time and a lot of effort, as well as some minimum level of intelligence. Most people do not have the time or the desire to obtain this level of understanding, so we employ elected representatives to do the job for us, trusting that they will make the right decisions. They are supposed to be more than just computers carrying out our wishes.
Whether many politicians actually obtain this level of understanding (or have the native wit required to do so) is a matter for debate...
Or even rhetorical.
This article (PDF) suggests that the genitive ending was -es in Old English, and -ies or -ys in Middle English, and that the apostrophe was introduced as a replacement for omitted vowels.
However, he also describes an alternative view: that the apostrophe was originally used because of the mistaken assumption that the genitive ending was already a contraction of "his". Apparently even Shakespeare made this mistake...
That still sounds exactly like sh*tting to me :-)