Earthquakes in Japan make the day shorter

The day became a little shorter due to the impact of intense earthquakes in Japan yesterday.

Cars, trees and more were swept away by water in Sendai, Miyagi Prefecture, Japan after an 8.9-magnitude earthquake on March 11. Photo: AFP.

According to the AP , Richard Gross, a researcher at the US Aerospace Agency (NASA), calculated that the earthquake yesterday made the earth's rotation speed increase by 1.6 millionths of a second, meaning the time of one day decreased by 1.6 milliseconds.

After the 8.8-magnitude earthquake struck Chile on February 27, 2010, Gross also used a computer model to investigate its impact on the earth's rotation speed. He noticed that the earthquake caused the earth axis to move about 8 cm, making it 1.26 milliseconds a day.

Large earthquakes always shift large amounts of rock and change the distribution of matter on the planet. When the material distribution on the planet changes, its rotation speed also changes. Rotation speed determines the length of the day.

Scientists use figure skating athletes to illustrate. When the athlete collapses his hand close to his body, he will rotate faster. It is due to the fact that the action of shortening changes the body weight distribution and therefore also changes the athlete's rotation speed.

The seismic 9.1 on the Richter scale in 2004 created a tsunami in the Indian Ocean that lost 6.8 milliseconds every day.