Is the Twin Paradox Real or Just Apparent in Relativity?

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Discussion Overview

The discussion revolves around the Twin Paradox in the context of relativity, exploring concepts such as time dilation, the nature of mass in relation to velocity, and the implications of these phenomena on aging and physical properties. Participants seek clarification on whether the effects described by relativity are real or merely apparent, and they delve into the complexities of these relativistic effects.

Discussion Character

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

Main Points Raised

  • Some participants assert that the different passage of time is real, with every observer agreeing on the elapsed time when they reunite, indicating that aging and time-dependent processes reflect this reality.
  • Others argue that the concept of mass increase is frame-dependent and suggest that inertial mass remains constant, with the perceived effects being a result of relative motion rather than a change in fundamental properties.
  • There is a contention regarding whether anything physically shrinks in length; some participants suggest that length contraction is merely an appearance from a moving frame rather than a physical change.
  • One participant questions the nature of aging in the Twin Paradox, noting that both twins perceive each other as aging slower during their respective journeys, yet one twin returns younger, leading to confusion about the reality of time dilation.
  • Another participant discusses the implications of a photon’s mass, stating that it has no mass and cannot accelerate, while also addressing the interaction of light with matter as a factor in its perceived speed in different media.
  • One participant emphasizes the equivalence of both twins during the initial leg of the journey, arguing that both can make measurements that confirm the other is aging more slowly, which they assert is a real effect rather than an illusion.

Areas of Agreement / Disagreement

Participants express differing views on whether the effects of time dilation and mass increase are real or merely apparent. While some agree on the reality of time dilation, others challenge the interpretation of mass and length contraction, leading to an unresolved discussion with multiple competing perspectives.

Contextual Notes

Participants highlight the complexity of relativity and the nuances involved in understanding the implications of time dilation, mass, and length contraction. There are references to specific conditions under which these effects are observed, but no consensus is reached on the interpretations presented.

  • #61
ananthu said:
My confusion has only increased now.

If each looks young to the other, then it means no body has actually aged.

In special relativity, whenever the twins AREN'T co-located, they generally will NOT agree about the correspondence between their current ages, nor about their respective current rates of ageing. And neither of them is "the one who is ACTUALLY correct" ... they are EACH correct: each of their conclusions is CORRECT and REAL, in the sense that each of their conclusions agrees with each of their own elementary measurements and first-principle calculations. This is true no matter WHAT either of them is doing ... whether or not either of them is inertial or accelerating.

[...]
When they approach each other should not the opposite happen, i.e., the clock in the reference frame of A who is actually returning should appear to go fast with respect to that of B and similarly the clock of B should appear faster to A?

Here, I think you are being confused by different meanings and usages of the term "appear". If one of the twins sees a TV image of the other twin (perhaps holding a sign giving her age), then when the twins are approaching each other, the age reported on the sign will be changing faster than the observer's age. That rate of ageing IS appropriately referred to as the "apparent ageing" of the other twin. But it obviously is NOT the true rate of ageing of the other twin, according to the observer. The age reported on the sign is the other twin's age at the instant the image was TRANSMITTED. The observer must determine how much the other twin aged while the message was in transit, and use that additional ageing to calculate the age of the other twin at the instant that the message was RECEIVED. The result of that calculation is the correct current age of the other twin, according to the observing twin. Some people mistakenly call this latter result "the apparent age" of the other twin, but that is very misleading terminology, and should not be used. That (properly) computed result is as real as real can be.

Mike Fontenot
 
Last edited:

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