Is a day on Earth always exactly 24 hours long? At first glance, it may seem so, but scientifically, the speed of Earth’s rotation is constantly undergoing slight changes, due to which the length of a day can vary at the level of milliseconds.
According to recent research, Earth sometimes rotates slightly faster on its axis than usual, as a result of which the length of a day can be a few milliseconds shorter than 24 hours.
Why does Earth’s speed change?
According to scientists, several factors affect the speed of Earth’s rotation. These include movements within Earth’s interior, changes in the distribution of mass caused by melting ice, and global environmental factors such as El Niño.
The extremely hot liquid metal present in Earth’s outer core is constantly moving. As a result of this movement, Earth’s rotation can speed up or slow down slightly.
The ‘hidden gear’ inside Earth
According to University of Alberta geologist Matthew Dumberry, the gravitational relationship between the rotation of Earth’s inner core and irregularities present in the mantle can cause slight changes in the speed of Earth’s rotation.
In research published in the renowned scientific journal Nature, scientists identified a gravitational mechanism inside Earth that they compared to a kind of “hidden gear.”
According to the research, Earth’s inner core does not rotate at exactly the same speed as the rest of the planet. Because of this difference, the inner core interacts gravitationally with certain irregularities in the mass present in the mantle, which can affect Earth’s overall rotation.
Data from 1964 to 2019
Researchers used data obtained from earthquakes during the period from 1964 to 2019 and scientific models related to the movement of liquid metal inside Earth to examine this gravitational interaction. The research found that the interaction between the inner core and the mantle can play an important role in understanding slight changes in Earth’s rotation.
Will leap seconds have to be removed?
According to physicist Judah Levine of the National Institute of Standards and Technology, Earth’s rotation currently appears to be relatively faster. For this reason, in the future, there may be a need to reduce a leap second in order to keep time synchronized with Earth’s rotation. Experts say such a change may potentially be required around 2029.
In the past, leap seconds have been added to keep time accurate due to the slowing of Earth’s rotation. However, if Earth’s rotation speeds up, there may be a need to remove a leap second for the first time.
According to scientists, the interaction between the inner core and mantle is not the only reason for changes in the length of a day. Earth’s atmosphere, oceans, ice reserves, and other geographical factors also affect this process.
Thus, although a 24-hour day is certainly a fixed measure in our everyday lives, in reality, Earth’s rotation is a continuously dynamic process in which even extremely small changes can affect the calculation of time.