Time Dilation Explained: Feynman Lectures 15-4

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Discussion Overview

The discussion revolves around the concept of time dilation as presented in Feynman's Lectures, specifically addressing the apparent paradox of how a moving clock can both slow down and show more elapsed time to an outside observer. Participants explore the implications of this phenomenon within the framework of special relativity.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Meta-discussion

Main Points Raised

  • Some participants question the clarity of the wording in the Feynman Lectures regarding time dilation, suggesting it leads to confusion about how time is perceived by moving and stationary observers.
  • One participant asserts that a moving clock shows less time elapsed to an outside observer, which is interpreted as "running slow."
  • Another participant clarifies that when the clock in the spaceship records 1 second, the outside observer's clock shows a time dilation factor of ##1 / \sqrt{1 - u^2 / c^2}## seconds.
  • Some participants express frustration with the confusing nature of materials on special relativity and consider alternative texts, such as AP French's book, for clearer explanations.
  • There is a suggestion that Taylor & Wheeler's "Spacetime Physics" might be a better introductory resource, although opinions on AP French's book vary, with some noting its old-fashioned approach and limited coverage of modern geometric views of spacetime.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the clarity of the Feynman Lectures or the best resources for understanding time dilation, indicating multiple competing views on the effectiveness of different educational materials.

Contextual Notes

Some participants note that the Feynman Lectures may not be specialized for teaching special relativity, which could contribute to the confusion experienced by readers.

Who May Find This Useful

This discussion may be useful for students and educators interested in the nuances of time dilation, those seeking clarification on special relativity concepts, and individuals looking for recommended resources on the topic.

Jazzyrohan
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Feynman Lectures 15-4 Transformation of time first para
http://www.feynmanlectures.caltech.edu/I_15.html
How is it possible that the moving clock slows down and also shows more time elapsed to the man outside?
 
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@Jazzyrohan I don't know where all the HTML cruft in the first paragraph your post is coming form, but it makes it unreadable.

However, the last sentence is readable and can be answered without even having to read the rest of your post:

Jazzyrohan said:
How is it possible that the moving clock slows down and also shows more time elapsed to the man outside?

It shows less time elapsed to the man outside. That is what "running slow" means.
 
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All I see is a pair of broken image tags. You are aware that the Feynman lectures are available online? What diagram/equation/section/whatever are you talking about?
 
Ibix said:
All I see is a pair of broken image tags. You are aware that the Feynman lectures are available online? What diagram/equation/section/whatever are you talking about?
Please do take a look now.
 
PeterDonis said:
@Jazzyrohan I don't know where all the HTML cruft in the first paragraph your post is coming form, but it makes it unreadable.

However, the last sentence is readable and can be answered without even having to read the rest of your post:
It shows less time elapsed to the man outside. That is what "running slow" means.
Please do take a look now.
 
Jazzyrohan said:
Please do take a look now.
That agrees with what Peter said. The "outside" observer's watch measures more ticks (by a factor of ##1/\sqrt{1-u^2tc^2}##) because the "moving" observer's watch ticks slow.
 
Jazzyrohan said:
Please do take a look now.

The wording is confusing. The last sentence should read: "That is, when the clock in the spaceship records 1 second elapsed, as seen by the man in the ship, the clock carried by the man outside shows ##1 / \sqrt{1 - u^2 / c^2}## second to the man outside."
 
PeterDonis said:
The wording is confusing. The last sentence should read: "That is, when the clock in the spaceship records 1 second elapsed, as seen by the man in the ship, the clock carried by the man outside shows ##1 / \sqrt{1 - u^2 / c^2}## second to the man outside."
Why is it that every material I am reading on Special Relativity is consisting of confusing wordings? I am stuck on understanding time dilation due to this.I am thinking of reading Special Relativity by AP French now.Will that be a good choice?
 
Jazzyrohan said:
Why is it that every material I am reading on Special Relativity is consisting of confusing wordings?

What material have you read? The Feynman Lectures are generally good, but that's not to say they're perfect, and they are not specialized for teaching SR.

Jazzyrohan said:
I am thinking of reading Special Relativity by AP French now.Will that be a good choice?

Unfortunately I have not read that book so I can't comment on it. My usual suggestion is Taylor & Wheeler's Spacetime Physics.
 
  • #10
French's book is very good but old-fashioned. He discusses experimental evidence at length and covers a lot of ground (including Terrell rotation if I remember correctly). Old-fashioned because he uses relativistic mass and he doesn't spend much time on the geometric view of spacetime (four-vectors are covered but only briefly toward the end I think).

I second Taylor & Wheeler as an introduction.
 

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