Today may feel like any other Tuesday but according to atomic clocks, August 5 could go down as one of the shortest days ever recorded- shaving approximately 1.34 milliseconds off the standard 24-hour
cycle. That sliver of time is imperceptible to humans as you won’t miss a moment of your morning coffee or evening commute but scientists are watching closely. These micro-adjustments in Earth’s rotation could have subtle yet significant effects on everything from GPS navigation to financial market timestamps- systems that rely on ultra-precise timekeeping.
What’s Causing Earth To Spin Faster?
Earth doesn’t rotate with perfect consistency. While we often think of a day as 86,400 seconds, the planet’s spin is affected by a number of geophysical and cosmic factors. The main suspect behind the current speed-up? The planet’s inner core. Recent research suggests the inner core- an iron-nickel ball suspended within the molten outer core- has been slowing down in its rotation relative to the mantle and crust. To conserve angular momentum (a fundamental principle in physics), the rest of the Earth spins a bit faster to compensate. Think of it like a figure skater pulling in their arms to spin more quickly. When one part of a system slows, another must speed up to keep the balance.
What Else Impacts Earth’s Rotation?
While the core plays a major role, Earth’s rotation is also influenced by external and surface-level forces including atmospheric winds, ocean currents, melting glaciers and even major earthquakes. Wind patterns in the upper atmosphere can subtly redistribute mass around the planet. The same is true for ocean currents and shifts in water levels. These movements- though mostly invisible to us- change the Earth’s moment of inertia, thereby tweaking its rotational speed. Even seismic events, like the massive earthquake that hit Japan in 2011, have been known to slightly shorten the length of a day.
Are Shorter Days Becoming More Common?
Yes and no. Historically, Earth’s rotation has been gradually slowing down, largely due to tidal friction caused by the Moon. Over millions of years, this drag has added hours to our days (a few billion years ago, a day on Earth lasted only 6 hours). However, in recent decades, scientists have observed a trend of temporary speed-ups. In 2020, Earth saw 28 of the shortest days on record. The previous record- 1.05 milliseconds shorter than 24 hours- was broken repeatedly.
In fact, the shortest day ever recorded occurred on July 5, 2024, when the Earth completed its rotation 1.66 milliseconds early. Just last month, on July 10, the planet came close again, finishing the day 1.37 milliseconds ahead of schedule. August 5 is now expected to follow closely behind.
Does This Affect Your Life?
Not directly but for scientists and engineers, every microsecond counts. Atomic clocks, which form the backbone of the world’s timekeeping infrastructure, are so accurate they can detect these minuscule changes. If the Earth continues to speed up, timekeepers might eventually need to introduce a “negative leap second”- subtracting a second from Coordinated Universal Time (UTC) to match Earth’s faster spin. This would be a historic first as modern life runs on precision timing. Satellites, internet services, financial transactions and navigation systems all require synchronisation with atomic time. Even tiny discrepancies can throw off location data, communication networks and algorithmic trading.
