The Earth, however, is not so precise. Our planet is a large, wobbly, sticky sphere rotating around the Sun at a staggering speed of 107,000 kilometers per hour. Thus, the planet's rotation does not adhere strictly to a 24-hour time interval.
Many fluctuations in the duration of Earth's days have well-known causes. However, on scales ranging from decades to millennia, scientists have observed slight variations in the length of the day that are a bit more challenging to pinpoint.
Now, a team of geophysicists from the Swiss Federal Institute of Technology Zurich believes they have found the answer in the molten iron core of the Earth, where tiny changes affect the planet's rotation.
There are several different fluctuations that influence the change in the length of the Earth's day. One of these is about 1.72 milliseconds per century, caused by the Moon and slow oscillations of the Earth's crust where it was once weighed down by ancient ice. Changes in water volumes can also affect the Earth's rotation as mass shifts beneath its surface, much like the volumes of ice.
On decadal scales, fluctuations of 2 to 3 milliseconds are associated with large-scale flows in the Earth's liquid core.