Understanding the Twin Paradox: Breaking the Symmetry in Time Dilation

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Discussion Overview

The discussion revolves around the Twin Paradox in the context of special relativity, specifically addressing the implications of time dilation and the symmetry of time experienced by two observers moving relative to each other. Participants explore the conceptual challenges and nuances of the paradox, including the roles of acceleration and simultaneity.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants express confusion about why one hour for a traveling observer corresponds to a vastly different time on Earth, questioning the symmetry of time dilation.
  • Others argue that the effect is symmetric: each observer sees the other's clock as running slow, which is a fundamental aspect of relativity.
  • A participant highlights the Twin Paradox specifically, questioning why only one twin ages differently despite both experiencing time dilation.
  • It is noted that the symmetry is broken due to the acceleration of one twin during the turnaround, which is a critical factor in understanding the paradox.
  • Participants mention the need to consider length contraction and the relativity of simultaneity alongside time dilation to fully grasp the situation.

Areas of Agreement / Disagreement

Participants generally agree that the time dilation effect is symmetric from the perspective of both observers, but there is disagreement regarding the implications of acceleration and how it affects the aging of the twins in the Twin Paradox.

Contextual Notes

The discussion highlights limitations in understanding due to the complexity of the concepts involved, including the need for a comprehensive grasp of length contraction and simultaneity, which are not fully resolved in the conversation.

gsingh2011
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So what I've heard so far is that if you're in a spaceship and you're moving at a speed close to the speed of light relative to the Earth then what seems like 1 hour for you could be something like 1 million years for people on earth. This made sense to me until I realized you're moving relative to the earth, so if you saw a clock on the Earth it would be moving slower for you. So why does one hour in the spaceship take 1 million years on Earth and not one hour on Earth take a million years on the spaceship? If they're relative to each other both make sense...
 
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gsingh2011 said:
So what I've heard so far is that if you're in a spaceship and you're moving at a speed close to the speed of light relative to the Earth then what seems like 1 hour for you could be something like 1 million years for people on earth.
OK.
This made sense to me until I realized you're moving relative to the earth, so if you saw a clock on the Earth it would be moving slower for you.
Right!
So why does one hour in the spaceship take 1 million years on Earth and not one hour on Earth take a million years on the spaceship?
But it does! According to spaceship observers, Earth clocks run slow; according to Earth observers, spaceship clocks run slow.
If they're relative to each other both make sense...
Correct! The effect is completely symmetric.

(Note that to fully understand this, you'll need to consider length contraction and the relativity of simultaneity as well as time dilation. These three effects work together.)
 
The reason this didn't make sense to me is because I was thinking of the twin paradox, and I was wondering why only one twin got older. If both clocks were moving slow relative to each other, then why does only one get older? Is this due to the length contractions and simultaneity parts that I am missing? I don't see how...
 
gsingh2011 said:
The reason this didn't make sense to me is because I was thinking of the twin paradox, and I was wondering why only one twin got older. If both clocks were moving slow relative to each other, then why does only one get older? Is this due to the length contractions and simultaneity parts that I am missing? I don't see how...
In the case of the twin paradox, the symmetry is broken: One of the twins must turn around and thus accelerate, while the stay-at-home twin never accelerates.

Please do a search on "twin paradox" and you'll find many detailed discussions.
 

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