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Me and a friend were just chatting about the speed of life. Can someone tell me what would happen in the following thought experiment?
A beam of light gets fired down a tube, one light year long. It's fired so that it bounces off the sides of the tube millions of times before it reaches the end, so the light travels two light years.
How long does it take to reach the end of the tube? How fast is it going? What would these four different perpectives be; someone watching from the start of the tube, someone at the opposite end of the tube, a theoretical person travelling at the speed of light alongside the tube, and a person travelling with the light beam?
Any answers enormously appreciated.
Cheers!
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jugglia wrote:
... How long does it take to reach the end of the tube? How fast is it going?
It depends on the total length of the path followed by the light beam, plus any miniscule delays introduced by the process of reflection (i.e., absorbtion and re-emission by the atoms in the sides of the tube) at each "bounce."
What would these four different perpectives be; someone watching from the start of the tube, someone at the opposite end of the tube,
The same.
... a theoretical person travelling at the speed of light alongside the tube, and a person travelling with the light beam?
The question is analogous to asking "How many angels can stand on the head of a pin?" It really doesn't make sense. When you ask questions regarding velocities, you need to refer to specific inertial reference frames. Light never "stands still," which is another way of saying that there are no inertial reference frames in which light is at rest. So it's meaningless to ask what a person "traveling at the speed of light" or "traveling with the light beam" would "see" because you haven't specified—you can't specify—a meaningful inertial reference frame for that person.
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