Earth Day, which falls on the 22nd of April each year, technically contains 86,400 seconds. Up until a few decades ago, this was always believed to be the case. However, our ability to measure time has improved so much that now, it’s no longer accurate. The site had to propose a new concept known as the second – a one-second adjustment that happens once in a while when the Earth’s rotation slows down enough to make time calculations on Earth no longer accurate. All of this is due to advancements in various measurements using distant objects like quasars, which are used for extremely accurate measurements of time. Modern satellites, including GPS satellites, directly rely on all of these calculations and adjustments. Recent observations and calculations have discovered some other mysteries in the process. For some reason, the length of the day on the planet has been increasing, and nobody has explained why this is happening.
The moon itself has always been slowing down the rotation of the planet. It’s been doing this for billions of years. Originally when the moon was created, a single rotation on the planet was approximately six hours long. But because of the moon’s pull on the planet and the Earth’s pull on the moon, Earth’s day changed from six hours to the 24-hour day we have today. Modern calculations suggest that the moon adds approximately 2.3 milliseconds every hundred years because of its gravitational influence on the planet. So this is a small process that doesn’t affect much in terms of scientific calculations or measurement of time on the planet.
Another process has been more influential and began approximately 20,000 years ago, at the end of the last glaciation. Approximately 20,000 years ago, the Earth started to speed up because the ice caps that melted in the last few thousand years reduced the overall surface pressure, forcing some of the mantle from within the planet to move toward the poles, redistributing the weight and slightly increasing the rotation speed. This shortens the day by approximately 0.6 milliseconds every hundred years.
Earthquakes also influence the rotation. For example, the 2011 earthquake in Japan likely sped up the rotation by about 1.8 microseconds. Tidal variations and various weather effects on the planet tend to redistribute water, which changes the rotation as well. While some of these variations have a very predictable period, at least 18.6 years in this case, there is a variation in milliseconds that can either speed up or slow down the rotation. A lot of different weather patterns can affect the motion of the atmosphere on the planet, which then affects how fast the planet spins. These atmospheric effects are even more dramatic on planets like Venus, where the atmosphere causes the planet to completely slow down. The rotation on Venus is in hundreds of days, not because the atmosphere is much thicker, but because of the effects of the atmosphere on the planet’s rotation.
Today, all of the time calculations involve the Quasar map that is used in combination with various radio telescopes to precisely calculate the Earth’s rotation and time. When used in combination with modern atomic clocks, it often allows us to precisely calculate by how much the rotation of the planet has changed. Turns out, June 29, 2022, was so far the shortest day on record, even though the opposite was happening in the last few years, where the days were getting a little bit longer. Nobody knows why this happened for sure. The most likely explanation is the sudden appearance of extreme weather effects in various locations on the planet. For example, South Korea experienced the heaviest rain ever, with 14 centimeters of rain every hour for at least a few hours.