Astronomy has always been a topic of interest to me; I decided to pursue a degree in physics with a concentration in astrophysics to further explore the clockwork behind the celestial mechanics I viewed in the night sky. I am especially fascinated by how astronomy influenced the daily life of ancient civilizations. I was intrigued to investigate if and how astronomy may have influenced the lives of ancient Japanese civilizations in the form of examining the influence the stars had in the design and manufacture of everyday devices and artwork. It was difficult to locate architectural and artistic examples of astronomy in Japanese art, but I was able to find several stunning examples of Japanese Sun worship and technological devices with links to astronomy through celestial motions. Each one of these examples leaves me in awe of the prowess of Japanese craftsmanship and attention to detail.
Daisen-ryo Kofun (Tomb of Emperor Nintoku)
The Daisen-ryo Kofun (c. 395- 427) is the largest example of an early Japanese-style tomb measuring 540 yards, but close to 900 yards when its triple moats are included and spanning 458 acres . The sheer size and scope of this tomb showcased the skill of Japanese architects and technology at the time. This tomb consists of a circular mound and a rectangular one in the shape of a keyhole. This mausoleum was built in the Kofun period, a period named specifically after these early mounds, for the emperor Nintoku to reside in after death. The keyhole shape of this burial site suggests that the emperor residing in it could unlock the door to the afterlife and live in the presence of the kami, the gods . The shape could also be representative of the sun rising over a horizon as the rectangular portion of the tomb raised until the skyline was continuous and unbroken. This symbolism is implied as the Japanese people worshiped the Sun goddess, Amaterasu Ōmikami, they believed she had the ability to purify the souls of the deceased so they could be reborn in the next life . Evidently, these keyhole-shaped tombs were reserved for the tombs of emperors. The Kofun tombs were constructed to be oriented toward the rising sun at the winter solstice. We infer this is so that the dead could be protected by the Sun goddess on the darkest day of the year. Moats surround these burial tombs so that the tomb was protected from all sides from theft. People visiting to pay their respects to the deceased could not visit the inside of the tombs; they could only walk around the tomb on the “green belt” pathway planted between the moats. These burial tombs are very lavish and ostentatious when compared to Western burial techniques such as purchasing headstones to commemorate a deceased person. Hence, it is evident that the Japanese people believed in kami and life after death as they designed mausoleums dedicated to aiding the soul in its journey through the afterlife and toward rebirth.
The Circular Mirror (3rd century BCE) of the Kofun period contains what appears to be a symbol of the Sun. This mirror is made of bronze, a valuable material associated with the ruling class. This mirror contains a symbol reminiscent of the Sun and the cardinal and ordinal directions. Bronze mirrors are typically placed within the burial mounds of emperors. They are said to be fountains of life as the Sun goddess was born from a mirror. The presence of the mirror serves as a plea to purify the soul of the deceased from the squalor of death so they can be reborn. The amount of detail and precision used to create details on this mirror shows the prowess of Japanese metalworkers.
The Reverse Compass and the Pocket Sundial
The reverse sun compass was a navigational tool introduced to the Japanese by the Chinese, Portuguese, or Dutch. These bronze devices were owned by the upper class and used for navigation during commercial trade. During the Tokugawa period, merchant boats needed to navigate the sea to travel across the Japanese archipelago to trade goods. They would rely on terrestrial landmarks during the day and the positions of the stars at night to navigate the seas. These methods could not be used when conditions were not favorable. When the skies were cloudy and the stars and landmarks were hard to see, Tokugawa sailors were left to sail blind until seeing conditions improved. In these situations, the reverse compass, the yami hari or “darkness needle”, was employed to guide the soldiers on their voyage . The reverse compass was also a desirable tool for Japanese mariners who could not control their ships during typhoons. The compass could be used to note which direction a ship was going so that sailors could determine where their ship was being taken during these strong storms. As its name implies, the reverse compass used a very unconventional system to denote the cardinal directions, East and West. This unusual way of representing the cardinal directions proved to be useful as the needle would represent the actual direction one was going instead of being fixed on the north when pointing to say the East and appearing as if it is heading in the Northwest direction instead of the Northeast direction [See Figure 1 below].
The Tokugawa Japanese reverse compasses displayed directions in terms of the twelve animal signs derived from Chinese cosmology. The twelve animal signs – Rat (11), Ox (12), Tiger (1), Rabbit (2), Dragon (3), Snake (4), Horse (5), Sheep (6), Monkey (7), Rooster (8), Dog (9), Boar (10) – were imported to Japan from China in the eighth century and created from the twelve lunar months and correspond to the twelve hours and twelve directions (30-degree intervals). Typically, the compass was read clockwise. The month of the winter solstice, the darkest month of the year, was associated with midnight and the north. The month of the summer solstice, the brightest month of the year, was associated with noon and the south. The vernal equinox was associated with dawn and the east while the autumnal equinox was associated with dusk and the west.
The pocket sundial was a tool attached to the reverse compass; this artifact was very useful to the Japanese people because it gave them a fairly accurate way of keeping time and direction with one device. The pocket sundial also contained the same twelve animal signs as the reverse compass, but this time, these signs represented the hours of the day. A small metal pole was placed in the middle of the sundial so that on a sunny day in a clear location its user could tell time based on which zodiac (1-12) the pole cast a shadow onto. This is yet another way in which the Sun goddess played an important role in the daily lives of the Japanese people.
Nonakado Stone Circle & Stonehenge
The Nonakado Stone Circle was a famous Late Jōmōn stone circle 42 meters in diameter and was used as a clock. It consists of one large, long upright at the center of a small stone circle. Longer stones radiate outward from the central, upright stone. These heavy stones were oftentimes carried 5 to 7 kilometers to their construction sight . This shows the skills of ancient Japanese architects as these large, heavy stones sometimes had to be carried up mountainsides through remote, dangerous terrain without the help of modern-day tools such as cranes and wheels. Stone circles were typically located on mountaintops where the stars could be seen away from residential areas where pit dwellings were found. Hence, it is thought that stone circles like the Nonakado Stone Circle were constructed as a gathering spot for rituals so that prehistoric people could orient themselves with the stars to keep time and perform social and religious rituals. After orienting themselves with the timekeeping stone circle, natives used circumstellar stars such as Polaris in the Big Dipper to tell time. The apparent rotation of the Big Dipper around Polaris was seen as a gigantic clock dial. The handle of the Big Dipper served as the hand of the clock. The skies around Polaris were then mentally divided into twelve sections corresponding to the twelve hours. Midnight was placed at the bottom, directly underneath the North Star which represented noon. The Big Dipper rotates counterclockwise, so ancients had to imagine the skies as a clock with the hours written in reverse order. This site is similar to that of the famous Stonehenge site in Salisbury Plain in Wiltshire, England. This configuration of rocks is thought to be an astronomical calendar developed by the ancient Britons to help keep time. There is no clear use of the stone circles and Stonehenge as no ancient records have been found indicating their usage . Nevertheless, it is evident that the prehistoric Japanese and British people employed remarkable architectural techniques to construct these awe-inspiring monuments.
In essence, it is clear that the Japanese people have always had a sense of appreciation and respect for celestial events as they worshiped celestial beings like the Sun goddess, Amaterasu Ōmikami, and looked to the stars to determine their temporal and spatial relationship with the natural world by using the sundial and reverse compasses to tell time and direction based on celestial occurrences. Thus, “Japan-ness” is seen in the way the Japanese regarded religion and spirituality as integral parts of their society, how they have been a technologically advanced society since early times, and how they have incorporated celestial happenings into their daily lives.
 “Secrets of the Stone Circles.” Heritage of Japan, November 18, 2015. https://heritageofjapan.wordpress.com/just-what-was-so-amazing-about-jomon-japan/ways-of-the-jomon-world-2/did-the-jomon-have-a-calendar/secrets-of-the-stone-circles/.
 Frumer, Yulia. “Japanese Reverse Compasses: Grounding Cognition in History and Society.” Science in Context 31, no. 2 (2018): 155–87. doi:10.1017/S0269889718000157.
 Kidder, J. Edward. Early Japanese Art; the Great Tombs and Treasures by J. Edward Kidder. Princeton, N.J,: Van Nostrand, 1964.
 Baratta, Norma Camilla, Giulio Magli, and Arianna Picotti. 2022. “The Orientation of the Kofun Tombs” Remote Sensing 14, no. 2: 377. https://doi.org/10.3390/rs14020377