Khanh's Gallery

In the history of Vietnam, while there are many distinguished figures, the majority are found in the fields of politics, the military, and social sciences. Dang Lo appears in Vietnamese history as a brilliant star in the natural sciences.

Astronomer Dang Lo lived in the 14th century under the Tran Dynasty. He hailed from Mac Xa village, Chuong Duc district, Ung Thien province (modern-day Chuong My, Hanoi). Dang Lo served as a mandarin under three kings: Tran Minh Tong, Tran Hien Tong, and Tran Du Tong. From a young age, Dang Lo had a penchant for stargazing and observing the Sun, to the point of suffering severe eye damage from gazing directly at the Sun.

Upon growing up, Dang Lo studied at the Imperial Academy (Quoc Tu Giam), passed the Thai Hoc Sinh examination (equivalent to a Doctorate), and was appointed as the Investigation Commissioner (Liem Phong Su) for the two provinces of Dai Hoang and An Tiem (modern-day Ha Nam and Nam Dinh).

During the reign of King Tran Hien Tong, Dang Lo’s astronomical talent was recognized by the King and the court. Consequently, he was appointed Hau Nghi Lang Thai Su Cuc Lenh—essentially the Director of the Imperial Bureau of Astronomy (Kham Thien Giam), the agency responsible for astronomy during the Tran Dynasty.

During this period, Dang Lo invented an instrument used to observe and measure celestial phenomena called the “Lung Linh Nghi” (Lung Linh Instrument). This is considered the single most important invention in the field of astronomy in our country’s history. The Dai Viet Su Ky Toan Thu (Complete Annals of Dai Viet) assessed: “The Lung Linh Instrument examines celestial phenomena; in no instance was it incorrect.”

With his accumulated knowledge and research derived from the Lung Linh Nghi, Dang Lo compiled a new calendar system called the Hiep Ky Calendar (Hiep Ky Lich) and presented it to King Tran Hien Tong. This calendar was used to replace the Thu Thoi Calendar (Shoushi Calendar), a system our country had been using based on Chinese calendars.

In ancient times, our country inherently had its own calendar system, but it was lost. After the period of Northern domination, we were forced to temporarily use the Chinese calendar. However, the climates of the North (China) and the South (Vietnam) are inherently different, and the Chinese calendar of that period also had many inadequacies. This led to a discrepancy between the calendar and the actual weather cycles, causing difficulties for agricultural production. The application of the Hiep Ky Calendar—a new, more precise system—was a major step forward for the civilization of Dai Viet, greatly facilitating agriculture. This contribution by Dang Lo was immense.

Later, based on these studies, Tran Nguyen Dan wrote the book “Bach The Thong Khao” (Comprehensive Survey of a Hundred Generations), clearly recording astronomical events spanning many centuries up to the 14th century. Regrettably, when the Ho Dynasty lost the country, the books and records of Dang Lo and Tran Nguyen Dan were all looted or destroyed by the Ming invaders, causing their works to be lost to history. It was not until the Nguyen Dynasty that the Imperial Bureau of Astronomy recompiled the Hiep Ky Calendar, based on references to the calendar system of the Qing Dynasty.