1. Joined
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    29 Oct '06 12:31
    Originally posted by drumset04
    it is physicily impossible to travle the speed of light.

    i think you mean theoretically impossible. Unless you're physically talking about the human body moving at the speed of light relative to everything else then yeah, you'd become a very fast puddle.
  2. Joined
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    29 Oct '06 12:49
    Originally posted by danandi1
    You nare able to see the light reflected of other objects as in a normal car as explained in my last post (if you do not understand special relativity the it can be confusing)
    I've been reading up on this to make sure, and special relatitvity relates to how an observer sees light being reflected back to him, regardless of his own velocity. The problem here is that there is no light being reflected back before the observer reaches the point from which reflection will take place..
  3. Joined
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    29 Oct '06 13:53
    Originally posted by Ian68
    I've been reading up on this to make sure, and special relatitvity relates to how an observer sees light being reflected back to him, regardless of his own velocity. The problem here is that there is no light being reflected back before the observer reaches the point from which reflection will take place..
    Your second statement contradicts the first. The observer in the car observes the light to travel at 'the speed of light' relative to himself regardless of his own velosity. As far as he is concerned the photons from his headlights travel away from the car at the same speed as if the car was stationary.
  4. Standard memberTheMaster37
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    29 Oct '06 14:14
    Originally posted by danandi1
    Your second statement contradicts the first. The observer in the car observes the light to travel at 'the speed of light' relative to himself regardless of his own velosity. As far as he is concerned the photons from his headlights travel away from the car at the same speed as if the car was stationary.
    I've always thought physicians went wrong there.

    If the photons of the headlight would indeed go at the speed of light relative to the driver then the photons would travel at twice the speed of light relative to a observer out of the car (standing still).

    If not, then the speed is a constant for wich c + c = c. This cannot be true (well except for c = infinite, wich isn't the case now).

    I passed special relativity theory with 90% right, but this bit never stopped confusing me.
  5. Joined
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    29 Oct '06 14:23
    Originally posted by danandi1
    Your second statement contradicts the first. The observer in the car observes the light to travel at 'the speed of light' relative to himself regardless of his own velosity. As far as he is concerned the photons from his headlights travel away from the car at the same speed as if the car was stationary.
    You can only see light waves which are travelling towards you. If you and the light source are together and travelling at the speed of light then light waves from that source are never travelling towards you because there is no time for them to be reflected back to you.
  6. Joined
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    29 Oct '06 14:32
    Originally posted by TheMaster37
    I've always thought physicians went wrong there.

    If the photons of the headlight would indeed go at the speed of light relative to the driver then the photons would travel at twice the speed of light relative to a observer out of the car (standing still).

    If not, then the speed is a constant for wich c + c = c. This cannot be true (well except for ...[text shortened]...

    I passed special relativity theory with 90% right, but this bit never stopped confusing me.
    This is the very essence of spesial relativity, it contradicts clasical physics and, to some extent, logic. The explanation of this is fairly confusing. Basically the car and the photons are in different inertial frames and the time that has passed at any given moment need not be the same in each inertial frame. So after a certain time the car and the photons will have been travelling at the same speed but the photons may hve been travelling for twice as long, if that makes sence.

    note: i'm also studying spesial relativity as part of my physics course and i find it confusing and logic defying too - hopefully I also get
    90%!


    NOTE: physicians are doctors
    physicists study physics
  7. Joined
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    29 Oct '06 15:57
    Originally posted by AThousandYoung
    No, you CANNOT go the speed of light.
    Then how do u explain lightning?
  8. Joined
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    29 Oct '06 16:02
    Originally posted by ChessManCLoss
    Then how do u explain lightning?
    YOU cannot go at the speed of light

    LIGHT (photons) can go at the speed of light
  9. Joined
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    29 Oct '06 16:09
    Originally posted by Ian68
    You only see light if:

    a. you have a direct line of sight to the source, which in this case you don't.

    or

    b. you see the light reflecting off something else, which cannot happen for the reason I gave before.
    Imagine another car, also travelling at the speed of light, constantly just ahead of you. Light can reflect off that, which removes your objection.
  10. Joined
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    29 Oct '06 16:13
    Originally posted by TheMaster37
    I've always thought physicians went wrong there.

    If the photons of the headlight would indeed go at the speed of light relative to the driver then the photons would travel at twice the speed of light relative to a observer out of the car (standing still).

    If not, then the speed is a constant for wich c + c = c. This cannot be true (well except for ...[text shortened]...

    I passed special relativity theory with 90% right, but this bit never stopped confusing me.
    The problem here is you're assuming you can apply a Galilean transformation, in other words you can just add the speeds together. Which is what your intuition says you can do.

    But the whole point of special relativity is that you can't do this. Unfortunately the universe is a bit more complicated than that.
  11. Joined
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    29 Oct '06 16:16
    Originally posted by mtthw
    The problem here is you're assuming you can apply a Galilean transformation, in other words you can just add the speeds together. Which is what your intuition says you can do.

    But the whole point of special relativity is that you can't do this. Unfortunately the universe is a bit more complicated than that.
    Thankyou for saying what i am trying to say much more clearly
  12. Standard memberTheMaster37
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    29 Oct '06 19:411 edit
    My major is mathematics, defying logic is not easy :p

    Thanks for the clearup though (and the later posts as well). I wish you well with the exam. For me it was merely applying the correct formulas (and trying not to let your mind rebel against the theory).

    Originally posted by danandi1

    NOTE: physicians are doctors
    physicists study physics


    I am deeply ashamed. My english should have been good enough to be able to spot such a mistake...
  13. Joined
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    29 Oct '06 21:00
    danandi1 sounds like a physics professor. Until someone can prove Albert Einstein wrong, danandi1 answered the question in his/her first statement, no arguement.
  14. Joined
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    29 Oct '06 21:10
    Originally posted by vance554
    danandi1 sounds like a physics professor. Until someone can prove Albert Einstein wrong, danandi1 answered the question in his/her first statement, no arguement.
    Thanks I am 17, I started university a month ago and special relativity is part of my course, i found it facinating, by far the most interesting part so i made sure i understood the basics fully.
  15. Joined
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    30 Oct '06 01:04
    Originally posted by danandi1
    Thanks I am 17, I started university a month ago and special relativity is part of my course, i found it facinating, by far the most interesting part so i made sure i understood the basics fully.
    pretty advanced stuff for a 17 year old. Keep it up.
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