Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How do we know the speed of light exists ?

  1. Aug 7, 2011 #1
    How do we know the speed of light "exists"?

    If we "know" that it can't be reached, how do we know it exists? Like I am looking at this from a math view.

    So okay, "infinity" is not a number, it is a concept. It took me about a year of convincing to settle it down.

    So is the speed of light the same thing? Not a number, but a concept? How do know this certain number 3 * 10^8 is not possible? Because I am just loooking at this as a number and the book tells me this is impossible.
     
  2. jcsd
  3. Aug 7, 2011 #2
    Re: How do we know the speed of light "exists"?

    All light is electromagnetic radiation. It is derived by [tex]{1/\sqrt{\beta_0\epsilon_0}}[/tex] where [tex]{\beta_0}[/tex] is the magnetic permitivity in a vacuum and [tex]{\epsilon_0}[/tex] is the electrical permitivity in a vacuum. This is the direct cause of Maxwell's equations.

    Is light like infinity? I don't have that much exposure to the concept of infinity, but I would have to say no. Light is more like a number, than a concept in my opinion.
     
  4. Aug 7, 2011 #3

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: How do we know the speed of light "exists"?

    Unlike infinity, the speed of light is large but finite and can be measured experimentally.
     
  5. Aug 7, 2011 #4
  6. Aug 7, 2011 #5

    Pengwuino

    User Avatar
    Gold Member

    Re: How do we know the speed of light "exists"?

    What do you mean how do we know the speed of light exists? We measure it. What exactly is the issue?

    You're confusing massive and massless particles. Massless particles (photons) always travel at 'c' and we observe them always traveling at that speed. Massive particles never reach 'c' and we've never observed them reaching 'c'.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: How do we know the speed of light exists ?
Loading...