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anotherpaulgyesterday at 11:23 PM1 replyview on HN

The Earth is generally expected to spin more slowly over time, due to tidal friction. But it has been spinning faster and faster since the 1960s. As shown in the figure in the wikipedia article [0].

I have read numerous explanations, but haven't found a really authoritative discussion.

[0] https://en.wikipedia.org/wiki/Leap_second#Rationale


Replies

pinkmuffinereyesterday at 11:55 PM

Wow that's really interesting. A great quote form the article:

> In 2021, it was reported that Earth was spinning faster in 2020 and experienced the 28 shortest days since 1960, each of which lasted less than 86399.999 seconds.[24] This caused engineers worldwide to discuss a negative leap second and other possible timekeeping measures, some of which could eliminate leap seconds.[25] The shortest day ever recorded was 29 June 2022, at 1.59 milliseconds less than 24 hours.[26] In a 2024 paper published in Nature, Duncan Agnew of the Scripps Institution of Oceanography projects that the water from increasing ice cap melting will migrate to the equator and thus cause the rate of rotation to slow down again.[26]