July 9 Was the Shortest Day This Year as Earth's Spinning Faster

Something weird is happing to our planet and it's making its rotation faster. In the coming weeks, Earth will spin a bit faster than usual, making some days slightly shorter this year. On July 9, July 22, and August 5, the Moon's position will influence Earth's rotation, shaving off 1.3 to 1.51 milliseconds from the standard 24-hour day, according to Live Science.

A typical day on Earth lasts about 86,400 seconds, or 24 hours. However, Earth's rotation isn't perfectly consistent. It's affected by factors like the gravitational pull of the Moon and Sun, the planet's magnetic field and shifts in Earth's mass caused by natural events or human activities.

Historically, Earth's rotation has been slowing down over millions of years. Around 1 to 2 billion years ago, a day lasted just 19 hours because the Moon was much closer to Earth, exerting a stronger gravitational pull. As the Moon drifted farther away, days gradually became longer. However, recent years have shown a surprising trend.

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In 2020, scientists noticed Earth spinning faster than it had since the 1970s. The shortest day ever recorded was on July 5 last year when the day was 1.66 milliseconds shorter than usual. The Moon plays a big role in these changes. When it's positioned farther from Earth's equator on certain days, it can speed up the planet's spin, much like a spinning top moves faster when its axis shifts.

Other factors, like melting ice and groundwater movement due to climate change, also affect Earth's rotation. Even natural events like earthquakes or seasonal changes can tweak the length of a day. For example, the 2011 earthquake in Japan shortened the day by 1.8 microseconds. Seasonal changes also have an impact. Richard Holme, a geophysicist at the University of Liverpool, explained to Live Science - "There is more land in the northern hemisphere than the south. In northern summer, the trees get leaves, which means that mass is moved from the ground to above the ground, further away from the Earth's spin axis." This shift in mass affects Earth's rotation, similar to how an ice skater spins faster with their arms tucked in and slower with arms outstretched.

As Holme noted, when Earth's mass moves away from its core in summer, "its rate of rotation must decrease, so the length of the day increases." While these changes are in milliseconds or microseconds, they show how dynamic our planet is.

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