How fast does light travel in 1 ft?

  1. Hello everyone,

    I was wondering if anyone could help solve my problem...

    ...How much time in seconds (or milleseconds) would light travel in 1ft? (assuming that it was traveling in a vacuum.)

    I spent 2 and a half hours yesterday trying to solve this problem, but without much luck. I remember back in school, I would know how to do this kind of stuff, but now...well, you know.

    If anyone knows the answer to this problem (and if possible, a formula), I would much apreciate it.
     
  2. jcsd
  3. speed = distance / time. Use google calculator. Welcome to PF.
     
  4. Gokul43201

    Gokul43201 11,141
    Staff Emeritus
    Science Advisor
    Gold Member

    How much time to cover 300,000,000 meters (that's about 1,000,000,000 ft)? So, how much time to cover 1 ft?
     

  5. Wow, I don't believe how I could forget something so simple.

    Thanks anyways for reminding me.
     
  6. robphy

    robphy 4,203
    Science Advisor
    Homework Helper
    Gold Member

    um... wait, gimme just a .... o:)
     
  7. ...and a teeny, tiny bit more. :tongue2:
     
  8. mgb_phys

    mgb_phys 8,952
    Science Advisor
    Homework Helper

    Light travels at 1 foot / atto-fortnight, everyone knows that.
     
  9. You are a nerd among nerds :rofl:
     
  10. mgb_phys

    mgb_phys 8,952
    Science Advisor
    Homework Helper

    No, a real nerd uses c = 1.8 terafurlongs per fortnight
     
  11. HallsofIvy

    HallsofIvy 40,241
    Staff Emeritus
    Science Advisor

    And watch them ponys run!
     
  12. Dick

    Dick 25,664
    Science Advisor
    Homework Helper

    Um, what's that in planck units?
     
  13. mgb_phys

    mgb_phys 8,952
    Science Advisor
    Homework Helper

    That would be a good homework question, what is planck's constant in the furlong/firkin/fortnight system.
     
  14. Dick

    Dick 25,664
    Science Advisor
    Homework Helper

    Mines a trick question. In planck units c=1, hbar=1 and G=1. Yours is harder. What's the mass unit in the firkin system? Stones, right?
     
  15. robphy

    robphy 4,203
    Science Advisor
    Homework Helper
    Gold Member

    Using dimensional analysis,
    h is in Joule-seconds or kg*(m/s)^2*s = kg*m^2/s

    Although http://en.wikipedia.org/wiki/FFF_System says that firkin is a mass,
    according to http://en.wikipedia.org/wiki/Firkin and google, firkin is a volume: http://www.google.com/search?q=firkin+in+m^3 .
    However, since it is used with water (whose density is about 1000 kg/m^3), we have an expression for the mass in kg of a firkin of water http://www.google.com/search?q=kg+in+firkin*(1000+kg/m^3)

    So, since google has a problem with numerical constants in the unit conversion,
    http://www.google.com/search?q=h/1000+in+(firkin)*(kg/m^3)*furlong^2/fortnight

    h / 1 000 = 4.8405995 × 10-34 (firkin * (kg / (m^3)) * (furlong^2)) / fortnight


    or
    h = 4.8405995 × 10^(-34) (firkin of water) * (furlong^2) / fortnight


    (FYI: http://www.google.com/search?q=c+in+furlongs+per+fortnight yields
    the speed of light = 1.8026175 × 10^12 furlongs per fortnight)
     
    Last edited: Aug 9, 2007
  16. mgb_phys

    mgb_phys 8,952
    Science Advisor
    Homework Helper

Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook