Built on Facts

The Speed of Light Rock

I spent a few hours on the interstate this weekend, and I heard a Kid Rock song on the radio called “All Summer Long”. If your tastes are anything like mine you’d probably rather not hear it. The song describes Kid’s life as an 18-year-old, when “it was summertime in northern Michigan”. Basically he does several irresponsible things in the chorus, topping the list off with the assertion that these things were done while “singing Sweet Home Alabama all summer long”.

Come on, Kid. You were closer to thirteen-letter-expletive Quebec than you were to Alabama. Your lyrical choice lacks a certain… authenticity. When I was 18, I lived in Baton Rouge, Louisiana. We were probably a third the distance to Alabama but we never felt the need to import some other state’s song. If anything we felt sorry for those poor people with the singular misfortune to live in a state containing both Auburn and the Crimson Tide. (kidding!)

Sadly, physics can’t stop weird bits of culture traveling the miles between Alabama and the mind of an impressionable young rocker. But it does limit the speed of movement to the speed of light.

Normally this limit of influences traveling between points isn’t terribly significant in daily life. Conscious human perception is hard pressed to detect processes which happen on timescales much under a few dozen milliseconds, and even in one millisecond light manages to travel quite a long way. 186 miles, or 300 kilometers if you prefer.

On the other hand, the processor in your computer is probably flipping along a few billion times per second. A 3 GHz processor executes each clock cycle in an average of 0.3 nanoseconds, and light doesn’t get very far in that time even by human standards. It travels about 4 inches. The inside of a CPU is a lot smaller than that, but you can see how real-time communication between (say) the RAM and the processor is already precluded by fundamental physics.

Even nanoseconds are pretty long by physics standards. Chemical reactions can occur on timescales of a few hundred femtoseconds. In one femtosecond light travels roughly the width of a few thousand atoms. Therefore the process of two molecules snapping together to form a single molecules usually takes a lot longer than it does for light to carry information from one side of the molecule to the other. But physicists have been only comparatively recently able to directly produce light on such short timescales in order to “look” at those reactions in progress using techniques like pump-probe spectroscopy.

But that’s virtually slow motion compared to events in particle physics. The lifetime of the W and Z bosons are on the order of 10-25 seconds. In that time, light travels only about a 10th the diameter of a proton. Anything that occurs so quickly can’t possibly take place over a larger distance. As a result, those particles pretty much blow themselves apart as soon as they know they exist.

We’ll probably someday be able to study even shorter timescales. The record for short light pulses is constantly shrinking, and the LHC could very possibly generate particles with lifetimes shorter than the W and Z bosons.

Preventing questionable music is unfortunately somewhat beyond our present capabilities. But we’re working on it.


  1. #1 Uncle Al
    August 5, 2008

    Signal speed in a conductor is lightspeed divided by the square root of the surrounding dielectric constant. In fiberoptic it is lightspeed divided by refractive index. Serious computation bleeds whenever data travels, even to RAM. Find and plug holes with Valgrind,


    Wincrap is hopeless, especially Vista. Valgrind optimizes Linux. Our number cruncher runs 40% faster in Linux than WincrapXP in the same iron. Redmond’s hairball on the hard drive is ignored by Knoppix Live! booted from DvD. Wincrap or Linux, dump the results to a flash drive. 40% is big when this requires three months 24/7 in an AMD FX-55. Locking a value in cache memory gave us a 1% speed boost. 92 days is 2200 hrs. 1% is a lot.

  2. #2 Jonathan Vos Post
    August 5, 2008

    It’s like Las Vegas. What happens in a 10th the diameter of a proton stays in a 10th the diameter of a proton.

  3. #3 Odysseus
    August 5, 2008

    Yep, even the Atlantic can’t stop that music. Kid Rock has been in the charts here in Europe for weeks, virtually preventing me from listening to the radio longer than an hour or so.

  4. #4 Michael
    August 6, 2008

    come on, in comparison, Kid Rock is “nice easy Rock music”. And I kinda like the fact that he’s this really disrespectful-to-anyone persona, which, originally, is what being a Rocker should be all about.

  5. #5 MathMike
    August 6, 2008

    To be a Rocker you need to have a ‘disrespectful-to-anyone persona‘ and talent.
    Having only half the equation leaves you as a half-a**ed rocker.

  6. #6 Michael Heath
    August 6, 2008

    As someone who was raised and still lives in Northern Michigan and graduated from H.S. in ’78, I have some authority on this matter.

    Where I grew up (Mancelona, a mere 15 miles from where Kid Rock has an annual summer concert), southern rock, especially Lynyrd Skynyrd as well as outlaw country, e.g., Waylon Jennings, Marshall Tucker, and The Outlaws, were huge up here during the late-70’s/early-80’s. In fact, I am in possession of one of the aprox. 18,000 Street Survivor albums, LP, with flames on the cover.

    While Seger was certainly our poet/hero and Uncle Ted our party-hearty rocker, southern rock fit perfectly into the lifestyle (think Skoal, trucks, guns, hunting, hiking, camping, etc.). Lynyrd songs like Simple Man, Gimme Three Steps, and All I Can Do Is Write About It, all rang true.

    The Doobie Brothers played up here three years in a row to huge crowds and Marshall Tucker drew thousands even though they were a warm-up band for others.

    Kid Rock’s song All Summer Long rings clear and true and it’s sadly ironic that this song is published this year given the recent murders on the Menominee River last week which makes the case that we aren’t protected from the insanity we read about happening in other places but rarely here and which contrasts so sharply from the innocence and joy found in “All Summer Long”.

  7. #7 badgergrrl
    August 6, 2008

    “To be a Rocker you need to be an ass. Having only half the equation leaves you as a half-a**ed rocker.”

    FixeD that for you. :)

  8. #8 MathMike
    August 6, 2008

    “To be a Rocker you need to be an ass. Having only half the equation leaves you as a half-a**ed rocker.”

    FixeD that for you. :)

    Aw, thanks for getting my back, side badgergrrl.

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