【Haichuan Teahouse】The Secret of Time Across Different Floors

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Do you know? On Earth, the lower the floor, the slower time passes. This is not some kind of mysticism; it is the effect of time dilation predicted by Einstein’s theory of general relativity: the stronger the gravity, the slower time passes. An article on the cover of Nature today demonstrates that even a difference of just one millimeter in height results in a different rate of time passage; this is the experiment that has verified general relativity at the smallest scale to date. This research comes from the team led by Jun Ye at the JILA Laboratory at the University of Colorado in the United States. He led a team in developing the most precise atomic clock in the world, showing that a difference in height of just one millimeter results in a time difference of about one quintillionth of a second; in other words, it takes around 300 billion years for there to be a difference of 1 second, which is consistent with the predictions of general relativity. This time difference caused by different gravitational fields is called gravitational redshift. Although it has been verified countless times, such high-precision detection has been achieved for the first time.