Featured Image Credits: Purple Mountain Observatory (紫金山天文台), 中国科普网.

The modern history of China since 1840 had been a history marked by invasions. In 1931, Japan started a partial invasion in China and occupied Manchuria. The local invasion escalated into a total war in 1937 when Japanese started to invade the rest of the Chinese territory, making the largest battlefield in Asia in World War II. The Chinese people, despite in a great disadvantage of military power against the invaders, resisted hard and relentlessly for 11 years, and finally in 1945 triumphed over their enemies.

In 1934, on some newspaper, apart from news about the appalling atrocities spread by the Japanese army across Manchuria, in the field of science, an astonishing announcement was made by the Nanjing Purple Mountain Observatory that, on 21^st September 1941 there would be a total solar eclipse occurring within China, of which the totality zone would be around 4000 kilometres long, crossing 8 provinces in total. It would be the first total solar eclipse in China in about 400 years ever since the previous one in Ming dynasty in 1542. This announcement was later confirmed by the Greenwich Observatory in the UK. In addition, it was also confirmed that there would also be a prior total eclipse in 1936, of which the totality zone would mainly cross USSR and Japan.

Considering the rare nature of such phenomenon and following the world’s science trend of proving Einstein’s relativity through total solar eclipse observations, Chinese scientists and astronomers took this opportunity very seriously. They constituted the ChinaSolar Eclipse Observation Committee (CSEOC) in the same year of the announcement, the responsibility of which was mainly to organise eclipse observation expeditions and administrate all the affairs related to that. As the modern approach of solar eclipse observation had been unprecedented for Chinese people at the time, in order to accumulate relevant experience and communicate observation technique with foreign competent astronomers, in 1936 the committee sent one expedition to USSR and another to Japan as eclipse observation practice drills in preparation of the 1941 total eclipse observation in China. While the latter produced fruitful astronomical results, the observation in the USSR was greatly affected by the bad weather condition on the day of eclipse and returned without success.

On 16^th March 1939, the preparation of the 1941 eclipse expedition was officially initiated. At the time, a total solar eclipse was a global event that would attract keen observers from all over the world. However, in 1941 it was distinct, as World War II was spreading enormous tension to the world, and the Japanese were expanding their invasion in China and across the Pacific. The turbulent global context forced observers from other countries to cancel their plans to visit China. English astronomerD. H. Sadler expressed his hope that Japanese, Chinese and Russian astronomers could somehow conduct observations of the eclipse, in the absence of astronomers from other countries. The responsibility to observe and record the 1941 total eclipse in China was then left to the Chinese astronomers only.

The astronomical apparatuses constitute a vital part of an eclipse observation. The committee ordered an advanced horizontal camera from the Fecker company in the US in 1939, however, it never reached to the expedition team due to the Japanese air raids on its arrival in Hong Kong in July 1941. This disappointing news left the team with no choice but to make do with the existing instrument in China, which in retrospect limited their capacity for performing more advanced astronomical tasks on the observation site.

In a CSEOC conference on 5th March 1941, eventually two expedition teams were formed: a northwestern expedition team will observe at Lintao, Gansu, and a southeastern expedition team would observe in Chong’an, Fujian. The committee reckoned the northwestern observation of higher significance, and appointed Dr. Yuzhe Zhang, the then director of the Institute of Astronomy at the Academia Sinica, to be the captain of the northwestern expedition team. In addition, the committee requested the Central Radio Station of China to provide time announcements at the northwestern observation site near the period of the solar eclipse. Also, they asked Ministry of Education to refer their request to the Aeronautics Commission, arranging an aircraft at each observation location in preparation of potential aerial observation to minimise any potential weather impact on the day of eclipse. This request was proposed and insisted by Dr. Zhang, as he participated in the expedition to USSR in 1936, which as aforementioned turned out to be unsuccessful under bad weather conditions. However, this was extremely difficult to fulfil at the time, as aircrafts and aviation fuel were highly scarce resources in China of utmost military importance, with only 65 air crafts available in total in the Chinese air force in 1941.

There was an interesting story regarding the determination of the northwestern observation point. A senior astronomer, Dr. Qingsong Yu, collected meteorological data and recommended Tianshui, Gansu to be the observation point. However, the committee had their problem with name of the city, which literally means “water from heaven”, as they believed this was exactly any eclipse observer would avoid! As a result, they chose Lintao which shared a promising meteorological data.

China’s economics had experienced a significant inflation since 1937 when Japanese started the total invasion. By 1941, a round trip between the observatory in Kunming and the observation point in Lintao, only the cost of transportation alone amounted to a whopping 80000 yuan, not to mention the expenses for food, accommodation, porters, and so on. Looking back at 1936, with a meagre budget of 3000 yuan, the committee were able to send two expedition teams overseas. It’s truly incomparable. Fortunately, considering the significance of this eclipse event, the Academia Sinica eventually managed to provide a full financial support that the existing budget for eclipse observations could be supplemented whenever it fell short. The committee also requested assistance from the Gansu Oil Mining Bureau under the Resource Committee for free transportation between Chongqing and Lanzhou.

The appointed captain of the northwestern expedition team, Dr. Zhang, from the depths of his heart, was truthfully determined upon the success of the observation: “An eclipse obscured by clouds is not something unusual in the field of astronomy. Professors of astronomy like professor F. J. M. Stratton from the Cambridge University in England have undertaken distant expeditions seven times, each time bringing a large number of instruments to observe eclipses, only to be foiled by persistent rain on six occasions. However, many of the public are unaware of this. Since we have already started cultivating this endeavour, we must diligently reap the rewards. …… During the most difficult period of the nationwide resistance against the Japanese invasion, we are grateful for the opportunity to study the eclipse under such circumstances. Both the government and the Academia Sinica have shown great concern and provided full assistance and convenience regarding the eclipse observation, including funding and transportation. Given the current state of war, many foreign astronomers were unable to come for the observation. Therefore, the responsibility for this eclipse observation falls on us.” In the earlier life of Zhang, he studied abroad in the US and obtained his PhD degree in astronomy at the Chicago University in 1929. He abandoned the better-material and peaceful life in America and returned to war-time China in the same year. He then devoted himself to the development of astronomy in China. Zhang was considered a true patriot, and he was well respected in China for this reason.

On 30^th June 1941, the north-western expedition team of 8, led by captain Dr. Yuzhe Zhang, departed from Kunming, Yunnan, and started a journey to Lintao, Gansu, of 43 days and 3200 kilometres. They traveled the first 150 kilometres by train to reach Qujing, however, for the rest of the journey, they had to switch to trucks because the railway system after Qujing was sabotaged by Japanese invaders to restrain transportation. The expedition team loaded boxes of equipment onto the truck and covered them with tarps and luggage so that the eclipse chasers could sit or rest on top of them along the journey.

The path of the expedition travelled was not paved with roses, but rather with the wreckage of cars and trucks strewn chaotically – either overturned by the roadside, or fallen into steep abysses, shattered into pieces. Most of the damaged vehicles were further eroded by rainy weather. There were also a few accidents occurring on the very day they passed by, with fresh bloodstains on the ground serving as a chilling warning. The main reason behind these frequent accidents lied in the narrow roads, steep slopes, and a continuous series of sharp bends that exacerbated the danger. In addition to these transportive difficulties, they were always under the shadow of Japanese bombers, physically when not mentally. For numerous times, they had to leave the truck and observatory instruments, and hide under some cover at once on hearing of some siren which indicated approaching aerial attacks. When the expedition team approached the outskirts of Chongqing, 27 Japanese bombers glided past overhead, dropping one bomb so close to their truck that the explosion caused the truck to be covered in a layer of dirt. Fortunately, the team and instruments survived all these dangers intact.

When the expedition team arrived in county Baocheng, their truck broke down. Fortunately, they obtained strong support from the director of the Baocheng Charcoal Vehicle Factory, Shaoquan Yan, and others from the Northwest Highway Bureau. Yan instructed the workers in the vehicle factory to regard the repair of the truck as their utmost priority. The captain of the team, Zhang, played some educative films about solar eclipse and lectured the workers the significance of the upcoming total eclipse to the nation. This inspired a strong sense of patriotism within those workers, so they worked day and night to make hurried repairs to the truck, and eventually fixed it 13 days ahead of the schedule.

Along the journey, the expedition team endured various hardships, such as the scorching sun on the Qinghai-Tibet Plateau and the torrential rain in the upper reaches of the Yangtze River, but they were also fortunate to witness boundless beauty. The team were very grateful for the opportunity to embark on this eclipse observation, so to them a little physical discomfort was nothing to complain about, especially when they thought about their brave compatriots on various frontlines – their situation was truly perilous.

At Lintao, the expedition team were joint with other team members who departed from Chongqing and Chengdu and carried the rest of the filming equipment required in the observation. Some of these team members encountered challenges in their travels and were unable to make it in time to Lintao via usual transportation such as trucks. After numerous efforts of communicating the difficulty with the central government and the military, the government instructed the air force based in Lanzhou to offer two aircrafts to transport these team members and the equipment. Finally, they made it to Lintao on the very day before the total eclipse.

The government also agreed to provide a plane at disposal for the expedition team in Lintao, as per their request earlier for the aerial observation of the eclipse. In addition, the military sent a legion of artillery to near Lintao on the night before the eclipse and had 20 attacker planes standing by at the Lanzhou airport, to protect the observation from interventions of Japanese bombers. Moreover, the director of the Central Radio Station of China, Jian Feng, who was also a keen amateur astronomer, also arrived in Lintao and set up the time announcing system and broadcasting system in time. The expedition team were thrilled by the enormous support they received and were greatly heartened to perform a successful observation.

After consulting with the local government and certain field surveys, the expedition team eventually chose the observation site to be the Taishan Temple on a hill about one mile east of Lintao county. This was under the consideration to protect the observation from Japanese air raids, as the densely populated urban areas were evidently their favoured targets. This cautious decision appeared to be wise: during their time in Lintao, Japanese bombers paid visits to Lintao on three or four occasions.

While the expedition team were busy making sound preparations for the observation, they still made time to organise several lectures on solar eclipses for the public in Lintao. These lectures were under the purposes to inform the local people of the soon occurrence of the total eclipse, impart the scientific knowledge on eclipses, inspiring the public’s interests in astronomy, and erase the “heaven dog devouring the Sun” superstition inherited from ancient times.

On the morning of the eclipse day (21^st September 1941), while the expedition team spent the past night sleeplessly worrying about the thick clouds in the sky, news from Chongqing reached to them that an enemy air-squadron was approaching Lintao. The team were unsure whether they were just out on a leisurely flight to admire the spectacular sight of the total solar eclipse, or were specifically intending to force the team into shelters, thereby sabotaging the rare opportunity for observation. It was a relief to the team that the latter was eventually not the case.

Near the occurrence of the total eclipse, the thick clouds gradually dissipated. The clear sky greatly heartened the team as they felt a successful observation was within their reach. Around 9:30 AM, the eclipse was finally occurring! The observation site was full of silent excitement as every team member was carefully fulfilling their tasks.

Due to the limited equipment as aforementioned, the observation tasks of the expedition team only included:

1. Photographs taken every ten minutes from the initial contact until the fourth contact.
2. Capturing the flash spectrum at the edge of the sun.
3. Comparing the sky brightness during totality with the sky brightness under moonlight.
4. Taking photos of many crescent-shaped solar images under the shade of trees.

A member of the observation team, Zungui Chen, was responsible for the first task. He stated in his posthumous manuscript: “The eclipse lasted a total of two hours and fifty minutes, with the initial contact beginning at 9:30 AM, and the final contact occurring at 12:20 PM. My task was the same as during my previous observation in Japan, tracking the sun with instruments throughout the solar eclipse and taking a photograph every ten minutes.” The result was a series of eighteen images of the sun, starting from the initial contact, forming a hook shape, gradually becoming thinner, passing through totality, and then gradually recovering. Only during the third photograph, there happened to be floating clouds that temporarily obscured the brilliance of the sun, making this image appear unusually dim on the film. However, the nearby cloud shadows were clearly visible.

Near the occurrence of the eclipse, on the aircraft provided by the military, Yongxiang Qu, a student of the Jinling University and a member of the expedition team, made the first aerial solar eclipse observation in humankind history. He personally recalled the scene of filming the eclipse in Lintao years after the expedition: “I filmed it on a plane. I was young back then, and they let me go up because the older ones couldn’t. I said it was okay, let me try. So, I got on the plane, placed my camera on top of it, and once it was secured in the machine gun position, I started shooting.”

The Director of the Central Radio Station of China, Jian Feng, personally conducted a live broadcast on the scene, in which he served as both an engineer and a broadcaster. Early on the morning of the eclipse day, he led the laborers to set up a dedicated line from Taishan Temple to the telegraph office at Lintao. Through telephones, He transmitted the observation updates in both Chinese and English to Lanzhou, then broadcasted it via radio to Chongqing, and finally to the rest of the world. Three broadcasts in total were made at different phases of the eclipse: first contact broadcast at 9:30-9:40 AM; second contact to third contact broadcast at 10:40-11:00 AM; fourth contact broadcast at 12-12:20 AM. A member of the observation team, Hang Li, and a reporter from Central newspaper participated in the broadcast reporting the observation conditions. This was China’s first ever radio broadcast facing the globe.

The Director of the Central Radio Station of China, Jian Feng, personally conducted a live broadcast on the scene, in which he served as both an engineer and a broadcaster. Early on the morning of the eclipse day, he led the laborers to set up a dedicated line from Taishan Temple to the telegraph office at Lintao. Through telephones, He transmitted the observation updates in both Chinese and English to Lanzhou, then broadcasted it via radio to Chongqing, and finally to the rest of the world. Three broadcasts in total were made at different phases of the eclipse: first contact broadcast at 9:30-9:40 AM; second contact to third contact broadcast at 10:40-11:00 AM; fourth contact broadcast at 12-12:20 AM. A member of the observation team, Hang Li, and a reporter from Central newspaper participated in the broadcast reporting the observation conditions. This was China’s first ever radio broadcast facing the globe.

In this observation, more than 170 valuable astronomical data were captured, along with over 200 photographs and 20 rolls of colorful film. Especially noteworthy were the photos and film footage of the total solar eclipse, which, once developed, provided evidence confirming Einstein’s theory of general relativity to be accurate. The observation at Lintao was considered a total success.

Apart from the exciting success of the professional observation, thanks to the lectures given by the expedition team earlier, the general public at Lintao also shared a lot of passion in witnessing this spectacular astronomical event. Some people made drawings and composed poems to depict this special occasion, while the rest were just quietly enjoying the moment. Probably the only creature who did not have a good time was a rabbit who was captured. The poor rabbit, not understanding astronomy, mistook the total solar eclipse for nighttime and started moving around outside its burrow, exposing itself to the “hungry” people around.

The other expedition team, namely the southeastern team at Chong’an, Fujiang, faced two challenges: they had only limited manpower, equipment and support, and unfortunately, they encountered bad weather during the eclipse’s occurrence. It was not considered a successful observation as they could not fulfil most of their anticipated tasks, but they did manage to measure and record the geomagnetic changes during the total eclipse.

The solar eclipse expedition had a significant educational impact on the local people at Lintao, as the observation remained undisturbed by any fanfare or disruptions during the whole process (By old Chinese myths, people need to make a lot of noises to scare the “heaven dog” of eating the Sun or the Moon). On their return to the observatory in Kunming, they organised over twenty lectures on solar eclipses and astronomy for the public when they passed by larger cities such as Lanzhou, Chongqing, etc. They also collected many photos and drawings about solar eclipses, which were exhibited in several exhibitions they made. These lectures and exhibitions garnered a substantial number of participants and illuminated widespread interest in astronomical subjects among the public. It was in a retrospective review in the same year, the expedition team captain Dr. Zhang mentioned his hope that, even if this expedition did not yield significant scientific results, it still had accomplished something for the cause of astronomy.

The 1941 total solar eclipse expedition attracted great attention on the national scale, as a large number of newspaper and magazines across China all posted articles regarding the 1941 total solar eclipse, science education on solar eclipses, how to safely observe solar eclipses, stories of the expedition to Lintao, perspectives on observation process and results, description of Lintao on the eclipse day, etc. The Central Daily at the time evaluated this total solar eclipse observation as the first organised observation conducted on Chinese territory, at a time when the Chinese nation was suffering great foreign aggression. Its significance far exceeded the realm of “astronomy.”