If you were traveling in a spaceship that had a velocity JUST under light speed

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Discussion Overview

The discussion revolves around the scenario of a person running forward in a spaceship traveling just under the speed of light. Participants explore the implications of relativistic effects such as time dilation and velocity addition from different frames of reference.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions what would happen to a sprinter running forward in a spaceship moving at a velocity just under light speed, particularly regarding time and length effects.
  • Another participant references the addition of velocities formula to clarify that the sprinter would not be seen as moving at light speed by an outside observer.
  • It is suggested that due to time dilation, an outside observer would perceive the sprinter as moving very slowly, ensuring that the combined speed remains below the speed of light.
  • A participant inquires about the sprinter's perspective, asking whether they would perceive their running speed as normal or slowed.
  • It is noted that the sprinter would not be able to tell if the spaceship was moving without external visual cues, drawing a parallel to the experience of passengers in an airplane.

Areas of Agreement / Disagreement

Participants generally agree on the relativistic effects involved, but there are nuances regarding the perceptions of speed and motion from different frames of reference that remain open for further exploration.

Contextual Notes

The discussion does not resolve the complexities of relativistic effects and how they interact with human perception and reference frames.

CombustionMan
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If you were in a spaceship that was going JUST under light speed & you ran forward...

If you were in a spaceship that was traveling JUST under light speed & you ran forward towards the front of the
Spaceship, what would happen? I'm talking literally JUST under c, like 0.999999999999999999999..
...999c.
Since it's impossible for someone to be moving at light speed, and he would be to an outside observer, what would happen with time/length to prevent that from happening? There's already heavy time dilation on the occupants of the ship so I was wondering what would happen to the sprinter
 
Last edited:
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Hi CombustionMan! :smile:
CombustionMan said:
Since it's impossible for someone to be moving at light speed, and he would be to an outside observer …

No, he wouldn't … see http://en.wikipedia.org/wiki/Addition_of_Velocities_Formula" :wink:
 
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Because of the time-dilation that an outside observer sees, he would see the sprinter as running very very very very slowly...such that the sprinter's speed (relative to the rocket) plus the speed of the rocket (relative to the outside observer) in the outside frame is still less than c.
 


Ok, makes sense. So from the runners point of view would he appear to be running normally or slowed
 


He wouldn't be able to tell whether his ship was moving at all, without "looking outside" through the windows or whatever. Just like when you're flying in an airplane you don't notice that you're moving except when you look out the window or your plane hits an air pocket or something.
 

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