Earth is expected to witness its shortest day on record this Wednesday, with more unusually short days predicted later this month on July 22 and again on August 5. Scientists say the phenomenon is caused by the Moon’s current position, which is making Earth spin slightly faster and cutting a fraction of time from each day.
According to a report by Live Science, the Moon’s influence will shorten these days by between 1.3 and 1.51 milliseconds compared to the usual length of a day.
Similar effects are expected on July 22 and August 5, as reported by the New York Post, citing figures from the International Earth Rotation and Reference Systems Service (IERS), the organisation responsible for global timekeeping.
Experts say that to adjust for this slight but important change in the planet’s rotation, the IERS will eventually need to add a “negative leap second” — a first-of-its-kind correction. This step is expected to take place in 2029.
Read | Astronomers receive powerful radio signal only 4,500 km away from Earth
Describing the situation, Duncan Agnew, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego, told NY Post: “This is an unprecedented situation and a big deal.”
He added: “It’s not a huge change in the Earth’s rotation that’s going to lead to some catastrophe or anything, but it is something notable.”
Read | Earth is rotating faster, and the effect could be ‘devastating’
What causes Earth’s spin to change?
A single day on Earth is defined by how long the planet takes to complete one full rotation, roughly 24 hours, or 86,400 seconds.
But this spinning speed can change due to several factors — including the pull of the Moon and Sun, changes in the Earth’s magnetic field, and the way the planet’s mass is distributed.
Over millions of years, Earth’s rotation has generally slowed down. Scientists believe that about 1 to 2 billion years ago, a full day lasted around 19 hours because the Moon was much closer to Earth, increasing the planet’s spin.
Also Read | Space mission Axiom 4: The universe can be a family one day
As the Moon gradually drifted away, its pull weakened, causing Earth’s rotation to slow and days to lengthen.
However, in recent years, this slowing trend has not been consistent. In 2020, scientists noticed the Earth spinning faster than at any time since detailed records began in the 1970s.
The fastest day so far was recorded on July 5, 2024, when the planet completed its rotation 1.66 milliseconds quicker than the standard 24 hours, according to timeanddate.com.
Why July 9, 22 and August 5 will be shorter
On these dates, the Moon will reach its farthest point from Earth’s equator. This slight shift changes how its gravity affects our planet’s spin.
Imagine Earth like a spinning top. If you push it at the edges, it spins faster than if you push it at the centre.
When the Moon is positioned closer to Earth’s poles instead of the equator, it alters the balance of forces acting on the planet. This leads to a slightly quicker spin, making the days fractionally shorter.