In 1936 van Stockum solved the Einstein equations for the gravitational field of a rapidly rotating infinite cylinder. It is shown that such a field violates causality, in the sense that it allows a closed timelike line to connect any two events in spacetime. This suggests that a finite rotating cylinder would also act as a time machine.
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森林浴
Shinrin-Yoku

The growing interest in environmental stress has been accompanied by a rapid accumulation of evidence indicating that environment can elicit substantial stress in people living in urban environments [1]. Furthermore, it is broadly conceived that the natural environment can enhance human health [2]. There have been several questionnaire studies on the psychological effects of forest environments. A previous study found an enhancement of positive emotions among subjects who were shown pictures of natural environments [3–6]. Moreover, other studies have also found that forest environments improve the psychological wellbeing of people [7–12].
Continue reading “L’âge des cavernes”

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Continue reading “Roaring 40”

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Continue reading “La Vague, 1870”