Astronaut Nick Hague shares a photo of Earth from the International Space Station. (NASA/Nick Hague)
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The earth spun at its fastest speed on June 29, completing its shortest day and baffling scientists as to why this is happening.
The earth finished a spin 1.59 milliseconds earlier than the usual 24 hours on June 29 according to new measurements by the National Physical Laboratory in the UK. The rapid spin is in line with a trend observed in recent years. In 2020, earth registered its 28 shortest days since the 1960s when atomic clocks began to be used for accurate timekeeping. The shortest day in 2020 was recorded on July 19 when the earth completed its spin 1.47 milliseconds earlier.
Though the trend continued in 2021, the shortest day last year was still fractionally longer than the shortest day of 2020. But in 2022, earth began to spin faster, with June 29 being the shortest day in the era of atomic clocks. On July 26, earth almost beat this record as the day was shorter by 1.50 milliseconds.
A few years back, scientists believed that the earth’s spin was slowing down. The International Earth Rotation and Reference Systems Service (IERS) even added leap seconds to compensate for the slower rotation. It is only in the past few years that things have changed, with measurements showing the earth’s spin rate to be rising.
As to why this is happening, several theories have been put forward ranging from seismic activity to the motion of the earth’s inner molten core and melting of glaciers which lessens the weight at the poles, and more.
According to Leonid Zotov, the answer might lie in the “Chandler Wobble,” a term that refers to a change in the spin of the earth on its axis. It is thought to be largely the result of ocean bottom pressure fluctuations.
“The normal amplitude of the Chandler wobble is about three to four meters at Earth’s surface,” Dr. Zotov told Time and Date, the top ranking website for time and time zones. “But from 2017 to 2020 it disappeared.”
Software Issues
The faster rotation of the earth poses a challenge to software when it comes to timekeeping. After the IERS introduced the leap second, the Coordinated Universal Time (UTC) has been updated 27 times.
Until now, only positive leap seconds have been added. This increase in time would create “weird timestamps” in data storage that would corrupt data or crash programs, according to a July 25 blog post at Meta. Digital timestamps would look like “23:59:59 -> 23:59:60 -> 00:00:00.”
But “with the Earth’s rotation pattern changing, it’s very likely that we will get a negative leap second at some point in the future,” Meta said. As a result, the digital timestamps would look something like “23:59:58 -> 00:00:00.”
“The impact of a negative leap second has never been tested on a large scale; it could have a devastating effect on the software relying on timers or schedulers.”
The time change can negatively affect the functioning of GPS satellites, which use atomic clocks that do not account for earth’s changing spin. Smartphones, communication systems, and other devices that are synchronized with the Network Time Protocol (NTP) servers can also face issues.