In January 2019, while watching a documentary about the formation of the Earth - Moon system, I started to contemplate on the mathematical equations governing the system. There were some scientific predictions made in the documentary which quite intrigued me to work on that problem and arrive at the same predictions. I also asked myself whether I could do all these by using only high school physics knowledge. The documentary pointed out that

- The Earth - Moon system was about 4 billion years old and the Moon was at a distance of a few tens of thousands of kilometers from the Earth in early times.
- The Earth was spinning (i.e rotating about its own axis) so fast that one full day would take only about 6 - 7 hours about 4 billion years ago.
- Due to tidal forces, the Moon has been slowing down the Earth’s spin motion.

Amazed by this documentary, I pondered the slowing of Earth’s spin problem over that night, without making any attempts to solve it till following morning … a great strategy I have adopted for years: “Think first, rushing into the solution later”. I would say, the most important phase of solving a science problem is the very first one where the problem is contemplated and comprehended, which involves lots of intense thinking … Then, I have put together this study for the benefit of all who are interested in understanding the Universe.

This study also demonstrates the power of basic physics knowledge to predict the PAST (i.e billions of years ago) and the FUTURE (i.e billions of years from today) of a dynamical system. I hope this study will also boost the motivation of students who would like to pursue their careers in one of the STEM (Science, Technology, Engineering, Math) fields.

# When Will the Earth Stop Spinning? (2nd Edition)

February 9, 2019