Speed of light pulse if you have a velocity of c

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Homework Help Overview

The discussion revolves around the behavior of a light pulse emitted in an inertial frame while an observer moves away from it at the speed of light, c. The original poster questions whether the light pulse will reach them and what velocity they would measure for it, given their initial distance of 10 meters from the pulse.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the implications of moving at the speed of light and question the logic behind the original poster's assumption that the light pulse would reach them. They discuss the invariance of the speed of light and the nature of reference frames.

Discussion Status

The discussion is active, with participants providing insights into the nature of light and reference frames. Some express confusion about the original scenario, while others clarify that the speed of light remains constant relative to all observers, regardless of their motion.

Contextual Notes

There is a notable emphasis on the impossibility of traveling at the speed of light for massive objects, which is a key assumption under discussion. The original poster's framing of the problem raises questions about the validity of their scenario.

ed2288
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Homework Statement



A light pulse is emitted in an inertial frame. You are moving at a constant velocity of c AWAY from the pulse, and initially 10m away from the pulse. Will the pulse reach you, and what velocity will you measure for c?



Homework Equations





The Attempt at a Solution



Well I know that c is invariant in inertial frames so I'm going to say yes the pulse will reach me and it'll be traveling at velocity c, but surely this is the most illogical answer ever? My classical brain wants to say, No the pulse will not reach me and will remain 10m away. Any thoughts? Thanks
 
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Who wrote this?? :confused:
ed2288 said:
A light pulse is emitted in an inertial frame.

This makes no sense.

Nothing happens in a frame.

A frame is what you observe things from. The same thing can be observed from every possible frame (both inertial and non-inertial). This light pulse, however it was created, can be observed in every possible frame.
You are moving at a constant velocity of c AWAY from the pulse, and initially 10m away from the pulse.

This is the opposite of making no sense. This is so inevtiable true that it contains no information at all. Your speed will always be c relative to light. And if you're moving away from the light, then it's moving away from you.
 
But how is it possible for the light pulse to catch up to you if you're 10m ahead of it and both traveling a c?
 
Just to clarify, by light pulse, I mean for example a bulb is switched on and off sending out a sphere of light.
 
ed2288 said:
Just to clarify, by light pulse, I mean for example a bulb is switched on and off sending out a sphere of light.
ed2288 said:
But how is it possible for the light pulse to catch up to you if you're 10m ahead of it and both traveling a c?

You can't travel at c relative to the bulb.

The light travels at c relative to everyone. It inevitably travels at c relative to you, and you inevitably travel at c relative to it, even if you're just standing there.

Assuming the bulb emits light in only one direction, it will either miss you or hit you, and it will only hit you if you're in the way! :rolleyes:
 

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