Sound traveling faster than light… and through PVC?

January 18, 2007

Apparently a few college professors, a high school teacher, and two high school kids managed to make sound travel faster than the speed of light.

… or something like that. You’ll have to read the article to get the full science-y details. I must say, I don’t 100% (or even like 20%) get this, but it gets put in the category of “just plain cool.”

Here’s a quote to assuage all you dead-set relativists out there:

“So it’s not the actual sound waves that exceed c, but the waves’ ‘group velocity,’ or the ‘length of the sample divided by the time taken for the peak of a pulse to traverse the sample.'”

Yeah. So, maybe not as cool as I thought. Or I might just not be getting it. Either way, enjoy!



One Response to “Sound traveling faster than light… and through PVC?”

  1. Davum said

    Yeah… this didn’t really seem promising from the beginning. I think I know what they’re talking about. Interference refers to two waves travelling through the same object. Waves in an object refer to vibration… imagine laying the pipe along the x-axis. If you scale up the effect of vibration, you would see that the atoms form a sort of sine wave when the object vibrates.

    Imagine two waves flowing through the pipe. In order to find the position of the atoms, you would add the two waves together. At a location where there are two peaks, this is called constructive interference, because the two peaks add together to make a larger peak. At a location where there is one positive peak and one negative peak, the resultant is zero, or some small non-zero number. This is called deconstructive interference because the two peaks cancel eachother.

    Now that you have no idea what relevance this has, I’ll put some relevance on it. What I think they’re saying is that there’s a peak… a constructive interference peak that travels across the pipe faster than the speed of light. The peak, however, isn’t an object or information and therefore it doesn’t violate the speed of light principle.

    The fact that the peak moves is actually an illusion created by the movement of two waves past eachother. Even though the peak can travel to the other side faster than the speed of light, it doesn’t mean that the information can be transmitted faster than the speed of light. I’m actually a little caught up on as to how to prove that, but I’m sure you’ll take my word for it, lol.

    I prefer to learn about those inversy particles that can’t travel slower than the speed of light. I didn’t look into those too much, but I sure would like to.

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