Photo of the Day

Periodic wobbles in Earth’s core change the length of a day every 5.9 years, according to a study published today (July 10) in the journal Nature.

Teasing out this subtle cycle, which subtracts and adds mere milliseconds to each day, also revealed a match between abrupt changes in the length of day and Earth’s magnetic field. During these short-lived lurches in the magnetic field intensity, events called geomagnetic jerks, Earth’s day also shifts by 0.1 millisecond, the researchers report. Since 1969, scientists have detected 10 geomagnetic jerks lasting less than a year.