How many times has the earth turned (rotated) so far?
The earth rotates once a day. In a year, one year is 365 days, so the earth rotates 365 times.
So how long has it been since the earth was born in space? Considering the results of many studies, the answer is about 4.6 billion years. This means that we can multiply the 4.6 billion years by 365 revolutions per year as mentioned above.
365 x 4.6 billion = 1.679 trillion revolutions. This is a simple calculation, but it seems that the Earth's rotation is getting slower and slower compared to the beginning of the Earth's rotation. Therefore, the actual number of revolutions may be a little more.
The speed of the earth's rotation is said to have changed over time.1) The length of a day is 24 hours, which was determined based on the average length of a day for about 100 years in the 19th century. Around 1990, however, it took about 2 milliseconds (one millisecond is one thousandth of a second) longer than 24 hours for the earth to make one rotation.
So, is the Earth's rotation speed slowing down? Studies have shown that this is not necessarily the case. 2003 observations of the Earth's rotation showed that each rotation took about 1 millisecond longer than 24 hours, meaning that the Earth was spinning faster in 2003 than it did in 1990. In other words, the rotation was faster in 2003 than it was around 1990.
Thus, the speed of the earth's rotation changes over a long period of time. Therefore, scientists add a second, called a leap second, at the end of December 31 or June 30 to adjust the time deviation.
reference data
(1) National Astronomical Observatory of Japan, "Is the Length of the Day Changing?" : https: //www.nao.ac.jp/faq/a0404.html
