Hold off on the Funeral for Special Relativity

Harvard physicist LuboÅ¡ Motl throws some cold water on recent claims to have broken the speed of light.  He argues:

Two years ago or so, Robert Helling
explained what these experiments are all about. As far as I can say,
there is nothing new about Nimtz's findings or observations and not
much interesting about them either. He's been doing the very same
things for decades.

He builds a setup in which the maximum
of a wave moves faster than light (although you need amplifiers to find
where the maximum is at the end). That's of course possible. In fact,
it's very easy. You can make such things with normal classical
electromagnetic waves as long as you have a layer of material where
they exponentially drop. In analogy with Schrödinger's equation, you
may realize that tunneling can be very fast.

microscopically, no signal or information is moving superluminally and
nothing is violated about special relativity whatsoever because all
these waves perfectly satisfy Maxwell's equations where the speed of
light is safely bounded. Nimtz must know that, I think, so his behavior
seems dishonest to me.


  1. Barbara Meyer:

    I'm a loyal fan, but huh??? Love, Mom

  2. dearieme:

    Dishonest? He's just made to be a proponent of Goebbels Warning, then.

  3. TCO:

    Watch out for Lumos. He banned me. Oh...string theory is poopoo. It's not physics. It's doodling. Not even wrong!

  4. Bill Nettles:

    So basically, Nimtz has measured a

  5. Bill Nettles:

    So basically, Nimtz has measured a

  6. Bill Nettles:

    Let me try this again! So basically Nimtz measured a phase velocity , not a group velocity (which is what carries the information). Then why isn't Neall deGrasse Tyson (journalists' physicist de jour screaming about this?

  7. Wulf:

    This type of thing pops into the news pretty regularly, because journalists hear that something is moving faster than light and they wet themselves. I don't know if this is due to science reporters who only took intro physics courses in college, or perhaps science reporters who are trying to be sensational - or heck, as one of my professors suggested, perhaps they think readers really understand the difference between phase velocity and group velocity. Most physicists seem to make that mistake, so why not science reporters?

    Bottom line, whenever you read that something went faster than light in a laboratory, they're actually messing around with phase velocity.