Comment As the author of the New Scientist story... (Score 2, Interesting) 429
...that was partly responsible for this whole mini media frenzy, I just wanted to add a couple things. First off, the media coverage has been (I suppose not surprisingly) all about reporting Guenter Nimtz's sensational claims without hearing from the other side. The other side, in this case, is definitely the mainstream point of view... and Aephraim Steinberg at the Univ. of Toronto makes a very compelling counter-argument. The train analogy he uses is helpful.
But if you want to get more geeky, you don't even need to use any quantum mechanics or even relativity to explain what Nimtz is observing. You can also explain it using good old classical physics. What Steinberg is saying is that the microwave, which is a packet of some finite size, gets slightly delayed as it hits the edge of the prism. There's a component of the wavefront that continues propagating into the gap past the reflective surface. (Technically, this is called the wavefront's "evanescent mode" -- meaning it has a wavelength measured in imaginary numbers... so there's no physical wave in this region of space.) And if there's a small gap separating the two prisms, the wavefront returns to the physical world, with a real wavelength again, back inside the second prism. That's what quantum physics would call "photon tunneling." The seemingly faster-than-light transmission speed is just the consequence of the wavefront's being slowed down at the boundary between prism and air. So the sum-total of time the wavefront spent in transit seems faster-than-light when you only look at one portion of its overall trip. But other portions of its trip (i.e. at that boundary between prism and air) were being slowed down.
Of course to explain this in all its gory detail -- and I've kind of done a butcher job here -- requires a lot more words than we had room for in this piece. So the train analogy had to do.
The other thing, to get even more geeky -- and extra-credit is definitely awarded to anyone who picked this up in the story -- there is no such thing as 33 cm microwaves. (Wavelength too long.) That's a typo. It's 33 mm.
Consider this a big ol' nerdy D'OH!
But if you want to get more geeky, you don't even need to use any quantum mechanics or even relativity to explain what Nimtz is observing. You can also explain it using good old classical physics. What Steinberg is saying is that the microwave, which is a packet of some finite size, gets slightly delayed as it hits the edge of the prism. There's a component of the wavefront that continues propagating into the gap past the reflective surface. (Technically, this is called the wavefront's "evanescent mode" -- meaning it has a wavelength measured in imaginary numbers... so there's no physical wave in this region of space.) And if there's a small gap separating the two prisms, the wavefront returns to the physical world, with a real wavelength again, back inside the second prism. That's what quantum physics would call "photon tunneling." The seemingly faster-than-light transmission speed is just the consequence of the wavefront's being slowed down at the boundary between prism and air. So the sum-total of time the wavefront spent in transit seems faster-than-light when you only look at one portion of its overall trip. But other portions of its trip (i.e. at that boundary between prism and air) were being slowed down.
Of course to explain this in all its gory detail -- and I've kind of done a butcher job here -- requires a lot more words than we had room for in this piece. So the train analogy had to do.
The other thing, to get even more geeky -- and extra-credit is definitely awarded to anyone who picked this up in the story -- there is no such thing as 33 cm microwaves. (Wavelength too long.) That's a typo. It's 33 mm.
Consider this a big ol' nerdy D'OH!
