An example of moving towards a light source

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Discussion Overview

The discussion revolves around the effects of relativistic motion on the perception of time and light, specifically examining a scenario where an observer moves towards a light source (a clock) at speeds close to the speed of light. Participants explore concepts such as time dilation and the Doppler effect in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes a scenario where Einstein drives towards a clock and questions whether he would perceive events as accelerated due to his motion towards the light source.
  • Another participant introduces the Doppler effect, suggesting that the perceived rate of the clock's ticking would change based on the observer's direction of motion, independent of time dilation.
  • A follow-up question is posed regarding whether extreme speeds could alter the perceived color of traffic lights, indicating curiosity about the implications of relativistic speeds on visual perception.
  • Responses indicate that at high speeds, the color of a traffic light could indeed appear to change, referencing a hypothetical scenario from a relativity textbook.
  • Humor is introduced regarding the consequences of ignoring traffic lights while speeding, highlighting the playful nature of the discussion.

Areas of Agreement / Disagreement

Participants express varying views on the implications of relativistic motion, particularly concerning the Doppler effect and time dilation. The discussion remains unresolved regarding the specific perceptions of time and color at high speeds.

Contextual Notes

There are limitations in the assumptions made about the effects of relativistic speeds on visual perception and the relationship between the Doppler effect and time dilation that are not fully explored.

atomqwerty
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Hi,

I've a question that I'll illustrate by presenting the following example:

Let's imagine Einstein in a car that's moving away from a clock. This clock 'send' a light beam with the information 'It's 12 o'clock'. If the velocity of this car is close to c, I understand that Einstein will be driving beside the light beam, therefore beside the information, always seeing that the time is 12 o'clock, no changes. But, and this is my question, if Einstein drives towards the clock (close to c, too), will he see the events accelerated on the reference system of the clock (-earth)? why? I mean, einstein's only moving to the light: the only thing that he'll notice is that the information of '12 o'clock' will arrive earlier to his eyes...

Thanks
 
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Hi atomqwerty, welcome to PF!

What you're describing is the http://en.wikipedia.org/wiki/Doppler_effect" . You see the clock faster or slower, depending on direction.
Only after you correct for the light travel times, you conclude that the clock ticks slower from your perspective. This is time dilation, and independent of direction.
 
Last edited by a moderator:
Thank you, Ich :)
You mentioned the Doppler effect and if that effect only implies a change of the wavelength that comes from a source of light (em field) or sound, would you see, for example, that the red color of a traffic light has turned into a green light if you'd drive at a huge speed?
 
would you see, for example, that the red color of a traffic light has turned into a green light if you'd drive at a huge speed?
Yes.
Actually, that was an exercise in my relativity textbook in school. The driver got away without a ticket, IIRC.
 
Ich said:
Yes.
The driver got away without a ticket
.(for ignoring lights) but got a huge one for speeding
 
thecritic said:
.(for ignoring lights) but got a huge one for speeding

Hahaha! :D
 

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