Do I arrive before a light-speed train if I jump off the front?

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Discussion Overview

The discussion revolves around a thought experiment involving a person jumping off a train traveling at or near the speed of light and whether they would arrive at a destination (planet B) before the train. The scope includes conceptual understanding of relativity and the implications of traveling at light speed.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether they would arrive at planet B first if they jump off a train traveling at light speed, expressing confusion about the implications of such a scenario.
  • Another participant suggests that if the train is traveling near the speed of light, the jumper would arrive before the train, but still slower than light, highlighting the relativistic velocity addition formula.
  • It is asserted by a different participant that traveling on a train at the speed of light is fundamentally impossible, indicating that the scenario is nonsensical within the framework of relativity.
  • Another participant emphasizes that even if one could jump off a train at light speed, they would not reach planet B before light does, due to the increase in mass and the barrier posed by the speed of light.
  • A later reply acknowledges the nonsensical nature of the scenario but appreciates the responses provided, indicating a desire for clarification rather than resolution.

Areas of Agreement / Disagreement

Participants generally agree that the scenario of traveling at the speed of light is nonsensical, but there are differing views on the implications of jumping off a train traveling near light speed, leading to unresolved questions about the outcomes.

Contextual Notes

The discussion includes assumptions about relativistic physics and the limitations of jumping off a train at light speed, which are not fully resolved. The implications of mass increase and velocity addition are also mentioned but not explored in detail.

Sweep
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I'm having a lot of trouble wrapping my mind around this... It seems there are some similar questions in this forum, but I can't tell if the answers can apply to my question... I'm sorry if this is an extra post:

I am traveling in a vacuum, on a train, at the speed of light, from planet A to planet B. I go to the front of the train, get outside, and jump forward/propel myself toward planet B. Do I arrive at planet B first?

I understand, that I am not going faster than the speed of light relative to the train, but relative to an observer on planet B, who arrives first? If I arrive first, does that mean I traveled from planet A to planet B faster than light?

Thanks in advance.

-Sweep
 
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Sweep said:
I am traveling in a vacuum, on a train, at the speed of light, from planet A to planet B. I go to the front of the train, get outside, and jump forward/propel myself toward planet B. Do I arrive at planet B first?

If the train is traveling near the speed of light, then yes, you get there first. (Relative to the planets you'd be traveling faster than the train, but still less than the speed of light no matter how hard you jumped.)

If the train is traveling at the speed of light, then you're describing something that's fundamentally impossible and nonsensical in the context of relativity.
 
You cannot go on a train at the speed of light.

Let's say you were on a train at c - 1 m/s relative to Earth and you jumped off the train at 10 m/s relative to the train. Then you would arrive before the train, but after light from your jump. According to the relativistic velocity addition formula you would be traveling at c - 0.99999993 m/s relative to earth.

EDIT: like wle said.
 
No you will not. Speed of light is a barrier. If you somehow increase your kinetic energy, your mass will increase instead of your velocity. So even if you jump off from the train traveling at speed of light, light will surely reach planet B before you because of your increase in moment of inertia due to increase in your mass.
 
Thank you all for the quick responses! Really appreciated. I understand it's nonsensical to think that you can be in a train in space traveling at the speed of light, but wasn't really sure of a better way to explain the answer I was looking for. Thanks for looking past that and providing great answers.
 

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