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Catching up to light

  1. Jul 11, 2003 #1
    did you ever think that since light speed is absolute,and nothing no matter how fast you go can't catch up to light.that if your in a ship traveling at any speed,the electrons in all the elctrical systems are traveling at close to light,so you traveling with light not trying to catch up to it.
     
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  3. Jul 11, 2003 #2

    Integral

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    Since electrons are massive particles they do not travel at anywhere near the speed of light under normal conditions.

    How ever you will not observe the lights of your near light speed ship to behave in anything other then a normal manner.
     
  4. Jul 11, 2003 #3

    Ivan Seeking

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    The speed of electrons in a wire is about 1m/s. The signal in a wire travels at about 1/2 light speed. This signal is really the information that a potential [voltage] exists across the circuit. One can imagine this signals travels much like sound waves in the air. Sound travels at 800 ft/second, but the individual air molecules are not moving as such. They just transfer the information.
     
  5. Jul 13, 2003 #4
    Re: Re: catching up to light

    Ivan Seeking,

    Taking this analogy of sound, are you saying that a radio tower transmitting say FM radio broadcast is not sending anything? It simply generates radiation which induces a wave in the particles that are pre-existing? I'm just trying to understand, not argue :)

    Thanks.
     
  6. Jul 13, 2003 #5

    Ivan Seeking

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    Re: Re: Re: catching up to light

    No. I meant this as an analogy to the signal speed for electricity in a wire. I was comparing the speed of an individual electron, even though such a thing can't really be referenced, to the speed of the signal that travels through the wire. For example, if we are talking on the telephone, the information that comes out as my voice travels through the wires between us at about 1/2C. However, classically, or by taking an average velocity, the electrons in those wires are barely moving by comparison.

    For a radio wave, not electricity, there is no classical medium that transmits the energy; that the wave travels through. Be they radio waves, microwaves, infrared, visible light, X-Rays, or gamma rays [are all examples of Electromagnetic Waves (EM)], they are self propagating and need no media through which to transfer. This idea died with the old Ether Theory of Light. Maxwell's equations show us how an EM wave propagates, and two guys named Michelson and Morley showed us that there is no Ether "transferring" the light - which the light travels through.
     
  7. Jul 13, 2003 #6
    Again about radio:

    So when a radio wave eminates from say a radio tower particles actually "fly through the air" at a certain wavelength/frequency rather than energy causing existing matter to modulate? This would lead to the fact that radio broadcasts cause both particle and wave activity? And what are these particles called, electrons?

    As an example, if we send a message to a Mars rover the radiation then eminates out of a transmitter will travel the distance to Mars roughly at the speed of light? Lets say that the first particle that is sent out of the transmitter is an eletron, will that EXACT electron reach the receiver sitting on the planet of Mars?
     
    Last edited by a moderator: Jul 13, 2003
  8. Jul 13, 2003 #7

    Ivan Seeking

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    Yes. You are approaching to proper point of confusion.



    No. These are photons. And a photon is really a name for the things that ARE an electromagnetic wave. These things can act like either waves or particles.

    With the understanding that we are talking about photons and not electrons, and assuming that the photons do not collide with interplanetary material between here and there, then roughly, yes. However, it is best to imagine a wave front made of many photons. If we start to talk about a particular photon we can quickly get into trouble; this gets heavily into Quantum Mechanics and we should avoid this for your sake and mine.
     
  9. Jul 13, 2003 #8
    Ok got ya.. Thanks for your reply!

    Wow, you obviously know a lot about this. I guess we get in trouble when we try to discern waves and particles.

    Got confused with electrons/photons. I know the "basic" definition from entry level college physics of what photons and electrons are. But as I dig deeper you cant simply describe an electron as a little sphere rotating around the nucleus of an atom with a definite size and mass.
     
  10. Jul 13, 2003 #9

    Ivan Seeking

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    It is a never ending road. If you happen to spot the end you just land in a big traffic circle.

    If you get into really deep questions like, what is a measurement, you will find no less than a dozen major competing theories; each with its own ration of certitude. It can get really confusing; especially since half of these guys don't seem to know about the other half.
     
  11. Jul 14, 2003 #10
    Now thats something I've never contemplated... What is measurement?? Seems like a simple question. Could you elaborate or post some links?
     
  12. Jul 14, 2003 #11

    Ivan Seeking

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    Oh you're going to be sorry you asked this one!

    http://plato.stanford.edu/entries/qt-measurement/

    I suggest that you read through this and get as much from it as you can. Take your time. Look up definitions when possible; and ignore the math when it gets over your head...which should be about step one. This starts to get into some heady stuff. But if you take your time the flavor should still come through. Feel free to ask questions if you want, but they could get over my head pretty quickly. See also the related links at the bottom of the page.


    You may also wish to read this related discussion. This discussion exemplifies the essence of how bothersome this question can be.

    https://www.physicsforums.com/showthread.php?s=&threadid=2971&perpage=15&pagenumber=1
     
    Last edited: Jul 14, 2003
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