Four-Coeval Framework for Resolving the Twin Paradox

Abstract

Hyoungseok Koh*

This study presents a new solution to the twin paradox by distinguishing between the simultaneity of the Lorentz transformation and that of the inverse Lorentz transformation. The classical twin paradox poses a conflict with the principles of special relativity, which assume inertial systems: one twin remains on Earth while the other travels to a distant planet and returns. The paradox arises from comparing the simultaneity defined by the Lorentz transformation and that defined by the inverse Lorentz transformation. Therefore, it should be called the “ Four-Coeval Framework “. In this scenario, two coevals (i.e., simultaneous observers) are fixed on Earth and the distant planet, respectively, while the other two are aboard the front and rear rockets moving at the same constant speed. According to the Lorentz transformation, the coeval on the front rocket appears younger than the coeval on the planet. Conversely, applying the inverse Lorentz transformation, the coeval on Earth appears younger than the coeval on the rear rocket. This demonstrates the relativity of time. However, according to special relativity, the coevals on Earth and the distant planet can be pre-synchronized using light signals and rigid rulers, so their times are in agreement. Therefore, while the coeval on the front rocket appears younger than the planet coeval, the coeval on the rear rocket appears older than the Earth coeval. In summary, in the “Four-Coeval Framework”, both the relativity of time and absolute time coexist.

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