How is twin paradox resolved in case of no/zero acceleration?

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Discussion Overview

The discussion revolves around the twin paradox in the context of special relativity, specifically addressing scenarios where one twin travels at a constant velocity without any acceleration or deceleration. Participants explore how the paradox is perceived and resolved when the twins do not meet or experience any changes in velocity.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that without acceleration or deceleration, the twin paradox does not exist, as there is no meeting point to compare ages.
  • Others argue that the lack of a meeting point means that the twins cannot definitively compare their ages, leading to a different interpretation of the paradox.
  • A participant suggests a three-clock model to illustrate the scenario, where clocks moving at constant speeds can be compared without acceleration, yet still yield results consistent with time dilation.
  • Some participants express confusion over the triplet paradox, questioning why it is considered paradoxical when it appears to simplify the twin paradox by removing the acceleration phase.
  • There is a discussion about the implications of removing the acceleration phase and whether it alters the essence of the twin paradox, with some asserting that it does not retain the paradoxical nature of the original scenario.
  • One participant mentions that the non-accelerated scenario could be viewed as a limit where acceleration approaches infinity, suggesting that the paradox remains relevant even in this context.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether the paradox is resolved in the absence of acceleration. Multiple competing views remain regarding the implications of constant velocity and the necessity of acceleration for the paradox to hold.

Contextual Notes

Some participants highlight that the discussion hinges on the definitions of simultaneity and the conditions under which time dilation is observed. The lack of a meeting point complicates the comparison of ages, and the assumptions about the observers' frames of reference are crucial to the arguments presented.

  • #121
DaleSpam said:
If A kills B while they are distant

this can only happen if something is sent from A to B and the max speed it can be sent is speed of light. when accounted for that and transition to B's frame of reference all paradoxes/confusion disappears?

however if we were to take a case where A can kill B instantaneously from a distant:

would it work? i mean would the whole thing won't integrate into the theory of relativity. won't we have "mismatches" that cannot be explained?
 
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  • #122
San K said:
this can only happen if something is sent from A to B and the max speed it can be sent is speed of light. when accounted for that and transition to B's frame of reference all paradoxes/confusion disappears?
Yes.

San K said:
if we were to take a case where A can kill B instantaneously from a distant:

would it work? i mean would the whole thing won't integrate into the theory of relativity. won't we have "mismatches" that cannot be explained?
If you make an unphysical assumption you will get unphysical conclusions.
 
  • #123
DaleSpam said:
25 and 12.5

How you got these numbers?
 
  • #124
A and B are perpetually inertial twins separated at age 0, correct? B is 25 when he dies in all frames. Therefore, since in A's frame A is 50 when B dies the time dilation factor is 2. 25/2 is 12.5 so A is 12.5 years old in B's frame when B dies.
 
  • #125
tiny-tim said:
they don't disagree on their age, they disagree on their rate of ageing

(they don't disagree on their age because they can't make measurements at what they both agree is at the same time)


Well don't they disagree on both?

1. rate of aging
and
2. age

because for 2, so just need to bring them both into same frame of reference and compare.

they can make measurements by bringing them (stationary and moving twin) into the same frame of reference at a particular point in time.

both are correct and it depends upon who is brought into the frame of reference of who, or more generally, what frame of reference are they finally compared in?

i.e. whether the stationary Earth is accelerated to match the speed of the spaceship

or the spaceship is slowed down to (a stand-still) to match the speed of the spaceship

or some other common/same frame of reference
 
  • #126
San K said:
Well don't they disagree on …
2. age

No!
… it depends upon who is brought into the frame of reference of who …

exactly! … so what are they disagreeing on? :confused:
 
  • #127
tiny-tim said:
No!


exactly! … so what are they disagreeing on? :confused:

when they are in same frame of reference there is no disagreement.


however when they are in different frames of reference (speed) then

isn't there disagreement on both

1. rate of aging
2. age

however it certainly gets resolved when the bought on same frame of reference

for example there are twins A and B.

A says B is older, B says A is older

now both are correct, however if only one of them (A or B) is brought to the other's frame of reference...then in hindsight, we can say...who was correct...

i.e. we can make either of A or B to be correct, in a sense, depends upon who moves ...assuming...only one of them is allowed to "move" (back into others frame of reference)
 
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  • #128
San K said:
for example there are twins A and B.

A says B is older, B says A is older

now both are correct

yes
… , however if only one of them (A or B) is brought to the other's frame of reference...then in hindsight, we can say...who was correct...

no!

they were both correct …

you just said so yourself!​
 
  • #129
tiny-tim said:
yes


no!

they were both correct …

you just said so yourself!​

they both are correct, when far...i.e. different frame of reference.

however when brought into same frame of reference...depending upon who was moved (taking a simple case) ...one of them will be older than other...
 
  • #130
San K said:
they both are correct, when far...i.e. different frame of reference.

however when brought into same frame of reference...depending upon who was moved (taking a simple case) ...one of them will be older than other...

Yes, but they were still both correct …

where is the paradox? :confused:​
 
  • #131
San K said:
when they are in same frame of reference there is no disagreement.

In classical physics as well as in SR, they are always in the same reference system; as a matter of fact, they are always in an infinite number of reference systems.

Is that clear to you so that it's just a matter of formulation, or are you perhaps not familiar with the definitions of classical mechanics?

[...] i.e. we can make either of A or B to be correct, in a sense, depends upon who moves ...assuming...only one of them is allowed to "move" (back into others frame of reference)
Whatever inertial reference system you choose, the prediction will be the same.
For example:

1. As determined with a system in which the "stay-at-home" is always in rest (approximately):
- Nearly all the time the traveler's clock appears to be slowed down due to speed.

2. As determined with a system in which the traveler is in rest during the first leg:
- Nearly all the time the stay-at-home's clock appears to be slowed down due to motion.
- during the second leg the traveler appears to move much faster than the stay-at-home, and his clock appears to be much more slowed down.

Calculation shows - as it ought to be - that the results of both descriptions are the same.

Harald
 
  • #132
San K said:
Twin paradox where twins do not meet

Is resolved by the fact that:

Both are in different frames of reference and not comparable.
Both are correct if they say the other aged faster because they both are right in their frame of reference/point of view.
No!

Special relativity uses the same concept of a reference frame as does Newtonian mechanics. Reference frames extend to infinity. An object can be described from the perspective of any frame of reference, but the object isn't "in" anyone of those frames (to the exclusion of others).

As far as the resolution of the paradox, what paradox? There is only an apparent paradox that results from the erroneous thinking that because A sees himself as being older than B then B must necessarily see herself as being younger than A. There is no paradox here; there is only erroneous thinking.
 

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