Washington, April 4 : A new study has found that tiny shifts that are making our days longer by some milliseconds, may be due to electrical forces present deep under the Earth.
According to a report in National Geographic News, it has long been known that natural phenomena on Earth's surface, such as tides and winds, affect its rotation speed.
Now scientists are investigating how events in a mineral layer at the core-mantle boundary, 1,615 miles (2,600 kilometers) deep, similarly affect the planet's spin.
"The length of a day is changing due to the interaction between the mantle and the core in the very deep Earth," said study co-author Kei Hirose, a geoscientist at the Tokyo Institute of Technology in Japan.
"This is basically because the bottom of the mantle has very high electrical conductivity," he added.
For the study, Hirose and his colleagues simulated the physical properties of the deep mantle in their lab to learn more about how minerals in Earth's lower mantle behave.
They squeezed a mineral called post-perovskite between the points of two 0.2-carat diamonds under high pressure, after which, they heated it with a laser to 4,900 degrees Fahrenheit (3,000 degrees Kelvin).
Under these conditions, the mineral conducted electricity at high rates.
"This means that we have lots of electricity at the bottom of the mantle, which is coming from Earth's core," said Hirose.
"What this means is that the magnetic field in the core can grab onto, or lock into, the lowermost mantle," said Raymond Jeanloz, an Earth and planetary scientist at the University of California, Berkeley.
"And so, one of the influences that this can have is in altering the length of day, or the rotation rate of the Earth, depending on when and where the core is grabbing onto the mantle," he added.
According to Hirose, this interaction accounts for several milliseconds of increase in day length over the past 150 years.
"Such miniscule time periods might seem negligible, but they do matter," he said.