A Monarch's Calculation
King Mongkut of Siam, also known as Rama IV, was a monarch with a deep personal interest in Western science, particularly astronomy. He was largely self-taught, studying English, Latin, science, and mathematics with the help of foreign missionaries and texts like John Herschel's "Outlines of Astronomy". This passion set him apart from many of his contemporaries. The king put his skills to the ultimate test by calculating, two years in advance, that a total solar eclipse would occur on August 18, 1868. His detailed computations predicted the path of totality would cross over a small village named Waghor.
King Mongkut's prediction for the duration of totality at Waghor was 6 minutes and 46 seconds. To verify his findings and demonstrate Siam's scientific abilities on an international stage, he invited a group of European dignitaries and scientists to observe the event with him. Among the guests were a team of French astronomers and Sir Harry Ord, the British Governor of the Straits Settlements. The French team's own calculations differed slightly from the king's, predicting a duration about two seconds shorter.
The Eclipse at Waghor
To host his guests, King Mongkut ordered the construction of a large, temporary observatory and guest pavilions in the malarial jungles of Waghor. On August 18, 1868, the international assembly watched as the moon began to obscure the sun. The eclipse occurred exactly as the king had predicted. Totality lasted for the duration he had calculated, proving his figures were more accurate than those of the professional French astronomers, who graciously acknowledged his precision. The event was a personal triumph for the monarch and a sign of Siam's engagement with modern science.
The victory came at a great cost. During the expedition to the swampy Waghor area, both King Mongkut and his son, Prince Chulalongkorn, contracted malaria. While the prince recovered, the king's health failed. King Mongkut died on October 1, 1868, just weeks after demonstrating his scientific capabilities. For his contributions and his ultimate sacrifice, he is honored today as the "Father of Thai Science," and August 18th is celebrated as Thailand's National Science Day. The site of his observatory is now part of a science and technology park dedicated to his memory.