Beyond the Boundaries of Time and Space – Astrobites

Astronomy, one of the oldest science subjects, represents the intrinsic curiosity and the shared intelligence of mankind. One of the most common phrases used by academic papers in Astronomy and Astrophysics is that we need more data and will know more with better equipment in the future. Undoubtedly, more advanced telescopes and deeper detections will uncover a whole perspective of the universe.

While we are grateful for the technology we have today and look forward to an even brighter future, we should also appreciate and feel amazed by the glorious contributions our ancestors made to science thousands of years ago without any better equipment. More importantly, those ancient records and findings still hold a deep impact on modern science.

Although the system of modern astronomy in the western world is believed to be built on Greek findings, the earliest recorded discoveries of astronomical objects of all humans originated in the eastern world, the oriental land of Ancient China.

For example, some of the most popular objects among ancient sky observers were comets.As early as 168 B.C., Chinese ancestors did a fabulous illustration of comet observations. Out of many scrolls discovered in 1973 from the Mawangdui Silk Texts, one specifically describes astronomical and meteorological phenomena, including 29 drawings of comets with different morphologies (Figure 1). Scientists estimate that, in order to produce such a figure, those anonymous observers might have kept a full record of ~100 comets. If our ancestors saw comets with naked eyes as frequently as us nowadays, the observations may take ~1000 years and several generations of consistent documentation!

Although our ancestors didnt understand the physical nature of astronomical objects as well as we do now, their astonishing records are significantly meaningful to modern astronomy.

Although many comets follow periodical trajectories, they lose a small part of their compositions each time they reach close to the sun. Therefore, the dynamics and morphology of comets change over time. No. 29 in Figure 1 is a schematic illustration of an active comet. In this case, the active comet ejects so much gas and dust that it starts whirling on its axis, which is extremely rare nowadays. Moreover, in 648 A.D., at the beginning of Tang dynasty in China (or Byzantine era in Rome), some observers already studied the relation between the tail of the comet and its location to the sun in the Book of Jin. After 900 years, the same relation was also discovered by European astronomers.

Up till now, historians have found evidence of amazing astronomical observations carried in all ancient civilizations. What makes ancient China stand out is not just the early timing but also the scientific accuracy.

The New Book of Tang, a work of official history covering the entire Tang dynasty, records comprehensive activities of the well-known comet Halley from March 22, to April 28 in the year of 837 A.D.. During this period, the writing documents the observed time, location, length, shape and change of Halley every day until it disappeared. Although comet Halley was visible to the entire world at that time, historical records in other regions of the world are much more general, serving for a more poetic goal than scientific. In fact, the first scientific documentation in Europe as complete as the one in the New Book of Tang only occurred in 1456.

Another important parameter in scientific studies is time. Since ancient Chinese used both lunisolar and sexagesimal calendars, the dates of astronomical events are very precise. Moreover, historians also use the evolution of Chinese characters and languages to further confirm the time of the discovered tablets, scrolls, papers etc. Therefore, it is surprisingly accurate to convert the dates of 29 observations on Halley across 2200 years from different Chinese dynasties, to the modern calendar we use now.

Thanks to these detailed ancient records with precise dates, astronomers were able to revise the trajectory of Halley in 1982 after combining all previous observations dated back to 240 B.C.. They concluded that the period of Halley is not a constant but floating between 76 and 79 years.

Other than comets, ancient Chinese have made countless significant scientific contributions to modern astronomy:

The earliest record of a supernova explosion in 185 A.D. (Han dynasty of China) supports the recent X-ray observational results on supernova remnant RCW 86 in 2006;

The thorough sky maps (Figure 2) made in 320 A.D. (Jin dynasty of China) led to an early estimate of axial precession without any modern equipment;

Six different theories had emerged independently in China to probe the structure of the Universe, including Xuan Ye Shuo proposed before 648 A.D.. This theory suggests that stars and the Milky Way are made of gas and floating in the endless universe, which is surprisingly close to what modern astronomy suggests!

The exploration of astronomy has been deeply embedded in Chinese culture and history. , the word for universe in Chinese, means space and time. The theoretical support of this definition first appeared in 1907 as Albert Einstein developed the concept of general relativity. However, the word itself was invented before 200 B.C.. Ever since, it has reminded humans that the story of the universe has no boundaries in time or space.

The life expectancy of humans can be ignored compared to the vastness of the universe. However, looking back in history, the curiosity for the universe from various minds always remains the same beyond the boundaries of time and space. With sincere affection, we are just humans that look up into the same starry sky with numerous wonders regardless of time, location, country, or any other difference. Meanwhile, every inch of the starlight embraces us all equally.

Thanks to all the valuable ancient documents, we can now take a glance at the same sky our ancestors looked up to. Those diligent and rigorous scientists in the early days of human civilization made unimaginable contributions to the history of astronomy. They composed a lore of time, marking the glory of human intelligence and devotion like the brightest star.

Reference: 4000 ans Dastronomi Chinoise by Jean-Marc Bonnet-Bidaud

Edited by Gloria Fonseca Alvarez

Featured image credit: Pixabay

About Wei Vivyan YanI am a PhD candidate at Dartmouth College, where I study AGNs and their host galaxies. My research focuses on origin and evolution of AGN obscuration. Before then, I did my undergraduate at University of Science and Technology of China. Outside of astronomy, I am currently writing my first fiction novel. I also enjoy traveling and outdoor activities.

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Beyond the Boundaries of Time and Space - Astrobites