On the afternoon of December 15, 2015, the famous celestial mechanics scientist Academician Sun Yisui was invited to the 48th session of SUSTC Lectures to give a lecture on the topic “from the Law of Universal Gravitation to Development of Astro-dynamics”. The lecture was chaired by SUSTC Vice President Tang Tao.
Professor, the famous celestial mechanics scientist, was elected as the Academician of the Chinese Academy of Sciences. As the Professor at Nanjing University, School of Astronomy and Space Science and Chief Scientist in the Program of Non-linear Science Issues in National Program on Key Basic Research Project (973 Program), Academician Sun Yisui used to work as the Dean of Nanjing University, College of Postgraduates. In 2010, the International Astronomical Union (IAU) named the No. 185640 asteroid as the Sun Yisui Asteroid.
Discovery of Law of Universal Gravitation-Newton standing on the shoulder of giant
Starting with the discovery of the Law of Universal Gravitation, Professor Sun Yisui, at first, pointed out that the formula in Kepler’s Third Law was just an approximate result, and the Law of Universal Gravitation was actually developed out of Kepler’s Law of Planets. As a matter of fact, 2 scientists had reached quite similar conclusions before Newton. Nevertheless, Newton’s Law of Universal Gravitation was exceptional in one key point. It used the calculus to figure out the movement of planets on the oval orbit, which perfectly matched the data made in the observations. The 2 scientists mentioned above could only explain the movement of planet on the oval orbit. “As a result, Newton actually stood on the giant’s shoulder”, said Professor Sun.
Scientific discoveries are both accidental and logical
After that, Professor Sun Yisun talked about the twists and turns experienced in the discovery of Neptune. He showed a graph comparing the actual orbit and presumed one of Neptune, pointing out it was accidental to discover the Neptune. However, he also said, “Sometimes, we can also find the logical elements in an accidental event. After all, opportunities are for those who are prepared. Even though this scientist didn’t find it, one in the future generations can also find it.”
Professor Sun Yisui also explained a few issues in the interest of students, such as the few famous astronomical telescopes in the world, landing of probes on Mars, probe to Saturn, Cassini-Huygens Spaceship, Three-body issue, Trojan asteroid cluster on the orbit of Jupiter, stellar dynamics and comet, etc. He also explained in detail the advanced technologies of using inter-stellar expressway to launch spacecrafts and design of deep-space probe orbit, etc.
Astro-dynamics for disaster prevention and future exploration
Professor Sun Yisui mentioned that, the near-Earth object in the Solar System might hit the Earth in more than 1 decade. “That means catastrophic for the Earth and no nation can be exempted from it”. For this, he explained in detail the damage caused by the cratering of asteroids against the Earth while showing pictures of meteorite craters. After that, he introduced the approach of active intervention made by asteroid tugboat, which can avoid the catastrophic collision between the asteroid and the Earth. According to him, Japan has started to use the technology.
Professor Sun also mentioned the expanded objects of astro-dynamics study. Major powers of space in the world are looking for planets suitable for human living. “Though our spacecraft has been very far from the Earth, our explorations are still in the Galaxy.”
Success is the result of curiosity and persistence
At the end of the lecture, Professor Sun Yisui introduced the space missions made by China in the past few decades to analyze the history of spacecrafts. “China has been working hard to catch up with the leading countries in space development in the world. And the gap has kept narrowing.”
He said, “We have to think very carefully about what success needs. I believe success needs curiosity and persistence. Just like Pigu, who made dull observations for decades. Kepler spent more than 10 years analyzing the data. It would be very difficult for them if they lived in modern days with colorful life. So to secure success, one has to have curiosity,without which there would be no interest. Without interest, one could not learn knowledge very well. Besides, persistence is also very important. Once you have started, keep doing well and probably you will reach success very soon. Though it might be difficult, we must be brave to take challenges because challenges and achievements exist together. Opportunities are for those who are prepared.”
After the lecture, Professor Sun had interactions with SUSTC students and answered each of the questions raised by them.
Contributed by Zhang Shanshan of SUSTC News Agency
