The Earth is accelerating; The length of the day must change



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GOES-East satellite view of Earth from January 15, 2021. Scientists say the Earth is spinning faster than ever on its axis.  Image: NOAA
GOES-East satellite view of Earth from January 15, 2021. Scientists say the Earth is spinning faster than ever on its axis. Image: NOAA

Scientists have noticed that the Earth is accelerating; it’s going so much faster now that they want to change the length of a day. A day on Earth is known as 24 hours or 1,440 minutes or 86,400 seconds; it is the time it takes for the Earth to rotate once on its axis, creating daylight for areas facing the sun and night for those away from it. But don’t throw away your watches and calendars yet; the difference in speed is only seconds, although even seconds can have a big impact on things on and beyond Earth.

In general, the speed of the Earth’s rotation has slowed down over time. De-acceleration has also changed over time; Earth’s molten core, fluid atmosphere, and liquid oceans, combined with gravitational influences from nearby bodies such as the Moon, can help slow the slowing of Earth’s rotation. Precision atomic clocks, space systems, and high-tech computer systems require sophisticated and highly accurate time measurements. The International Earth Rotation and Reference Systems Service (IERS) is monitoring this slowdown and adding “leap seconds” to official Coordinated Universal Time (UTC) which is the gold standard for timekeeping and timing on the planet. . The UTC time standard, widely used for international timekeeping and as a benchmark for civil time in most countries, uses precise atomic time. The addition of “leap seconds” adjusts these atomic clocks to keep the right time in sync with the speed of the Earth.

Since the 1970s, a total of 27 leap seconds have been added to the official time to deal with the slowing of the Earth’s rotation. The last leap of a second was added on New Years Eve in 2016. However, that suddenly changed in 2020.

On July 19, 2020, the actual day on Earth was 1.4602 milliseconds shorter than a full 24 hours, making it the shortest day on record. Since then, the short day record has been broken a total of 28 times. Now, in 2021, the days are turning faster, almost 0.5 milliseconds less than a full 24 hours.

Peter Whibberley, principal investigator in the Time and Frequency group at the National Physics Laboratory, told The Telegraph: “It is certainly true that the Earth is spinning faster now than at any time in the past 50 years … a Negative leap second will be needed if the rate of Earth’s rotation increases further, but it is too early to tell if this is likely to happen.

A negative leap second would have the opposite effect of a leap second; rather than adding a second when needed, one would simply be deleted. A negative leap second has never been used before.

Whibberley added: “There are also international discussions about the future of leap seconds, and it is also possible that the need for a negative leap second will push the decision to end leap seconds for good.”

The time difference is insignificant on the surface for humans, but very significant for human activity. Scientists say it would take another 100 years of this acceleration to be noticeable where you could “see” Earth speeding up and time moving faster. But for the technology humans depend on, these changes could be extremely problematic. For example, communication and navigation systems based on modern satellite technology depend on the consistency of time with the usual positions of the Sun, Moon and stars. But if these systems are turned off for even a few milliseconds, they can fail, rendering the tools used by humans broken.

As scientists struggle to understand why this time lag is occurring and how to prevent systems from crashing because of it, one thing is certain: 2021 is likely to become the shortest year on record due to the speed at which the Earth rotates.

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