Trying to Understand Light in Motion: A Frustrating Puzzle

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    Light Motion Puzzle
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SUMMARY

The discussion centers on the relativistic effects of light reaching a passenger on a moving train from two different light sources. It establishes that the light from both sources can reach the passenger simultaneously if emitted in the passenger's rest frame, while in the ground's rest frame, the light reaches the passenger at different times due to the train's motion. Key concepts include four-velocity, Lorentz transformations, and the synchronization of events in different frames of reference. The mathematical framework involves equations for calculating the time elapsed for light to reach the sensors, emphasizing the importance of understanding the observer's frame.

PREREQUISITES
  • Understanding of special relativity principles, including time dilation and length contraction.
  • Familiarity with four-velocity and its components in Minkowski spacetime.
  • Knowledge of Lorentz transformations and their application in different reference frames.
  • Basic grasp of light cones and their significance in relativistic physics.
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  • Study the derivation and implications of Lorentz transformations in special relativity.
  • Explore the concept of simultaneity in different inertial frames and its effects on event timing.
  • Learn about the mathematical representation of four-velocity and its applications in relativistic scenarios.
  • Investigate the graphical representation of light cones and their role in understanding causality in spacetime.
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Students and enthusiasts of physics, particularly those studying special relativity, as well as educators looking for clear explanations of relativistic concepts and their implications in real-world scenarios.

  • #391


solarflare said:
this was posted to show the videos worldline
Once again, you have switched scenarios. This diagram is for the standard scenario in which the lightning strikes are simultaneous in the platform frame.

the strikes are along the X axis both at t = 0
Yes, in the platform frame.

as they occur on the train - they must be simultaneous
The fact that they occur 'on the train' is irrelevant. They are simultaneous in the platform frame, not the train frame.

the light then travels from the sources to the platform observer at t = 4
Sure, it takes time for the light to travel to the platform observer.

the lines also cross the t prime axis but the x prime line is not used to show where they cross on the t prime line
You should be able to draw in the lines to see where and when the events (the lightning strikes) happen in the train frame.
 
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  • #392


it is not irrelevant when the graph says they occur on the train simultaneously

and again the lines cross t prime from the source on the x-axis

if you want to say that t prime is relevant then the source of the lines that cross t prime must also be relevant
 
  • #393


This thread is obviously going nowhere (and very slowly at that). So it's time to shut it down.

Solarflare: All your questions have been answered several times over. Repeating the same thing isn't going to help. If you're serious, I suggest getting an intro book on relativity. (Or you can read Einstein's own words--see George's link.) Then you can go back and read through this thread again.

Thanks to everyone who contributed their time and effort to this thread.
 

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