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Time Dilation different depending on cause?

  1. Apr 11, 2004 #1
    My question concerns gravitational time dilation and time time dilation due to motion. If an outside observer views a person falling into a black hole to stand still when the person falling into the event horizon due to time standing still at the horizon, then why don't particle physicists view particles they accelerate to slow down...as they speed them up. I know that the half-life of particles is increased when they accelerate them, but why don't they view the motion of the particles to slow down as well. The same would qualify for light wouldn't it? Light experiences 100 percent time dilation, meaning that no time passes for light, but if it experiences time dilation, then why do we see it moving? Shouldn't it appear stationary like the man falling into the event horizon? The same question applies for accelerated particles.
  2. jcsd
  3. Apr 11, 2004 #2
    Consider the photon with which you measure either the black hole infalling particle or the particle accelerated in the laboratory. In the former case, we observe a particle that must pass through the black hole gravitational field, time dilating near the point of "freezing". The latter situation involves photons passing through the reference frame of the laboratory, itself at rest relative to us. The acceleration of these particles may be the same at v~0 or v~c; acceleration is absolute, whereas in general velocity is not.
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