1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Dark v Light

  1. Jan 18, 2008 #1
    Let " d" equal the speed of dark
    d = SQRT( e/m ) + 1

    I am at a loss can anyone help me !
  2. jcsd
  3. Jan 18, 2008 #2
    Please someone help !! its for a challenge Samssin
  4. Jan 18, 2008 #3
    There's really no such thing as the "speed of dark", light is actually something, and the speed of light is the speed of that something. Dark is the lack of light.

    The speed of light can be given as c=1/sqrt(e*u) where e and u are the permitivity and permeability of a vacuum(I forget which is which)and that's the only thing that looks similar to your equation
  5. Jan 18, 2008 #4

    Shooting Star

    User Avatar
    Homework Helper

    We are more than at a loss, we are zonked or something to that effect. :bugeye:

    Who is Samssin? :confused: Please answer asap.

    (Let the speed of darkness be 'd'.)

    Suppose a region was lit by a light source. Then you switch off the light. The envelope of darkness then would proceed at the speed of light, from the has-been light source. We may call this the speed of darkness, for which slightly contradicting but well meaning formulas had been given by you two.

    Hence, c=d.

  6. Jan 20, 2008 #5
    Hi me again, totally lost can anyone help ?

    what's that experiment when they slowed down light?
  7. Jan 20, 2008 #6
    samsam, can you tell us where all this is coming from? Who is asking you about the "speed of dark"?

    As for light being slowed down, light will always travel through any medium at a speed somewhat less than its speed in vacuum. That's not a specific experiment, it's just an outcome of the way light propagates through media.

    Perhaps you're referring to the recent experiments where light was effectively brought to a stand-still and stored for a short while before being released again? That's due to something called Quantum Entanglement, and cannot be explained by simple expressions from Classical Electrodynamics, such as what you seemed to be offering in your original post (although I'm still not sure what that was ... :confused:)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook