(New Scientist) Three times in the last decade Earth’s spin has missed a beat. These seemingly random blips cause days to temporarily stretch and shrink. They have emerged from the clearest ever view of how long a day is.

Earth’s spin fluctuates as the oceans and the atmosphere push and tug on the planet’s spin But these small daily variations hide longer-term patterns, some well known, some not.

Richard Holme of the University of Liverpool, UK, looked at 50 years of GPS and astronomical data to see how day length varied during that time. The analysis threw up a well-known cycle due to slow changes at the Earth’s core, which lengthen days by a few milliseconds over roughly a decade, then shrink them down again.

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