"Looking up at the sky" through time and space: the past and present of the planetarium

The winning works of the 2023 "China Science Popularization Star Creation Competition"

Author: Lu Qi

Whenever night falls, countless stars will blink and look at us quietly. We look up curiously. Under normal time, you may feel that all the stars are still. Only when we speed up time can you see them moving slowly. Occasionally, there are satellites and meteors across the sky. If you can see a meteor, you must be very lucky.

Ancient and modern understanding of the starry sky

Zhang Heng, a famous Han Dynasty scientist, wrote in his "Commentary on the Hun Tian Yi": "The Hun Tian Yi is like an egg, the celestial body is round like a bullet, and the earth is like the yolk of the rooster, isolated inside. The sky is big and the earth is small. There is water inside and outside the sky, and the sky covers the earth like a shell covers the yolk... The north and south ends are called the North and South Poles." He believed that the sky covers the earth, the sky is like an eggshell, and the earth is like an egg yolk floating in the middle. The relative position of the eggshell and the yolk is used to illustrate the relationship between heaven and earth, and the North and South Poles are the center of the celestial body's rotation. "Records of the Grand Historian: Book of Celestial Officials" records that "the Dipper is the emperor's chariot, moving in the center, and controlling the four directions." The ancients believed that the North Pole was the center of the sky, and all the stars revolved around the North Star. Now we know that the stars are not moving, but the earth under our feet is rotating. During the day we see the sun rise in the east and set in the west, and at night we see the stars and the moon also rise in the east and set in the west. This phenomenon is called diurnal apparent motion in astronomy. Because of the rotation of the earth, the stars move, and the world we live in has day and night, and only then we have the concept of "a day". In addition to its rotation, our earth also revolves around the sun. The earth revolves around the sun once a year. As the earth revolves, the position of the sun on the ecliptic will change, moving about 1 degree a day. This phenomenon is called annual apparent motion in astronomy.

Ancient Chinese astronomical instruments

Long before the invention of the telescope, the ancients observed the sky with their naked eyes and recorded the celestial bodies seen in the night sky. They invented various mechanical devices to demonstrate the movement of celestial bodies. Among them, the more famous ones are the armillary sphere, the artificial celestial instrument and the water-powered astronomical observatory. The armillary sphere is an instrument used in ancient times to demonstrate the movement of celestial bodies on the celestial sphere. It draws celestial bodies such as the sun, the moon, the twenty-eight constellations, as well as the equator and the ecliptic on a spherical surface, so that people can understand the celestial phenomena at any time. It is similar to the modern celestial globe. The difference between the armillary sphere and the armillary sphere is that the armillary sphere is mainly used to show the changes in celestial phenomena, while the armillary sphere is mainly an observation instrument used to measure the ecliptic and equatorial coordinates of celestial bodies.

Schematic diagram of the fake sky instrument

Su Song and Han Gonglian of the Song Dynasty jointly developed an instrument that allows people to enter the celestial sphere to observe the stars - the artificial celestial instrument, which enabled the ancients to understand the movement of stars in the sky more intuitively. The sphere of the artificial celestial instrument is made of bamboo strips, and small holes are drilled on the sphere according to the position and size of the stars. The base of the sphere is a square wooden cabinet, which is half hidden in the cabinet and half out of the cabinet. When people enter the sphere, they can see dots of light like stars in the night sky. The Water-powered Astronomical Clock, known as the "earliest astronomical clock in the world", is an astronomical clock built in the Northern Song Dynasty that integrates timekeeping, astronomical observation, and star-phenomenon demonstration. It was designed by Han Gonglian and others and built by Su Song in the seventh year of Yuanyou. The platform is a wooden frame structure, about 12 meters high, and the base is about 7 meters long and wide. It is narrow at the top and wide at the bottom, and is divided into three layers. The top layer is the armillary sphere, which is used to observe the starry sky. The top plate of the platform can be uncovered during observation. The middle layer is the armillary sphere, which is used to display the stars. The bottom layer is the power device and the timing and time-telling mechanism, which is connected to the armillary sphere and the armillary sphere through a gear transmission system, so that each layer of the device is linked together and runs synchronously with the celestial body. It not only reflects the superb mechanical manufacturing skills of ancient China, but also reflects the eternal spirit of exploration of the laws of the universe by Chinese civilization. "

Linglong Instrument Reproduction

Following Su Song and Han Gonglian, the Linglong Instrument created by Yuan Dynasty astronomer Guo Shoujing was similar to the artificial celestial instrument, both of which were instruments used to demonstrate celestial phenomena. The traditional method of observing the celestial body from the outside was changed to an artificial celestial structure of observing the stars from the inside. The original instrument has been lost. Yang Huan in the early Yuan Dynasty recorded in the Linglong Instrument Inscription: "All kinds of instruments have their own uses. The most practical instrument is the Linglong Instrument. It has more than 100,000 points, and the longitude and latitude are evenly distributed. It is the same body as the sky, and it is in harmony with the rules. The whole body is empty and bright, and it is revealed inside and outside. There are countless mysterious phenomena. The stars have a sequence, and the distance to the pole has a degree. People can see through it and understand it with their eyes." The Beijing Planetarium commissioned the Suzhou Ancient Astronomical Timing Instrument Research Institute to restore the Linglong Instrument, which is now placed in the Beijing Ancient Observatory. In 1913, Americans made an enterable spherical celestial phenomenon demonstration device called the Atwood Sphere. The sphere is 17 feet in diameter and has 692 holes on its surface, which can simulate the stars in the night sky when light is allowed to pass through. The original is still preserved as a collection in the Adler Planetarium in Chicago, USA, and is open to visitors for viewing and experience.

Atwood Ball

The Birth of the Modern Planetarium

In astronomy, the English name for planetarium is Planetarium. The English names for planetarium and planetarium are also Planetarium. A planetarium is a hemispherical dome building used for astronomical demonstrations. It is a place for people to understand and know the starry sky and is the core of a traditional planetarium. Planetariums have always been the iconic exhibit of planetariums, which can realistically reproduce the starry sky seen on the earth and simulate the apparent motion of celestial bodies. People call facilities and places that perform artificial starry skies planetariums. Initially, planetariums only appeared in the form of planetariums, so European and American countries usually use the same word to represent both.

The idea of ​​authentically reproducing the details of the starry sky came from Oscar von Miller, the founder of the Deutsches Museum in Munich. In 1913, Oscar von Miller sought to develop a demonstration device for the Deutsches Museum that could realistically display the positions and movements of stars, planets, the sun and the moon. So, Director Oscar von Miller consulted Carl Zeiss in Jena about making such a device, and Zeiss accepted this special order. The development work was interrupted by the First World War. In 1919, Zeiss's chief engineer, Bauersfeld, proposed a design concept based on an optical-mechanical projection planetarium. He and his team set about deepening the details and finally putting it into reality.

Sketch of the design of the first optical planetarium

On October 21, 1923, in Munich, Germany, Carl Zeiss Jena presented the world's first optical planetarium developed for the Deutsches Museum. This was the first public demonstration of an artificial starry sky. After a few weeks of trial operation in Munich, the planetarium was transported back to the factory for improvement and perfection. For further development and testing, Zeiss built a temporary dome with a diameter of 16 meters on the roof of the factory. On July 22, 1924, the Zeiss planetarium performed a starry sky show in front of a large audience for the first time. From July to September 1924, starry sky demonstrations were held almost every day. In this short period of time, more than 30,000 visitors experienced the artificial starry sky created by optical projection for the first time. Based on the experience feedback of visitors, the optical planetarium was subsequently improved and its functions were expanded. On May 7, 1925, the planetarium was officially opened to the public in the planetarium of the Deutsches Museum, marking the birth of the modern planetarium. The planetarium is 10 meters in diameter, with a Zeiss I planetarium installed in the center. It can project 4,500 stars, the Milky Way and the names of constellations, but it can only show the local starry sky in Munich.

Zeiss Planetarium I

In reviewing the birth and development of planetariums, we have to mention the planetariums made in China and their role in the Chinese planetarium industry. The development of planetariums in my country began in the 1950s. Beijing Institute of Technology (now Beijing Institute of Technology) independently developed the first prototype of a domestic planetarium in three months, referring to the German Carl Zeiss planetarium. After that, the school cooperated with Beijing Planetarium, Beijing Optical Instrument Factory, and Beijing Power Control Equipment Factory to develop a large planetarium with Chinese characteristics. From 1976 to 2007, this planetarium operated continuously for 30 years in Beijing Planetarium, and it could show the 24 solar terms on the ecliptic and the three enclosures and 28 constellations reflecting the Chinese star culture. However, due to various reasons, the later research and development of the project failed to keep up. In the following decades, domestic planetariums did not continue to innovate and improve in terms of performance or technology. In 2008, the Beijing Planetarium completed its renovation, and the planetarium was upgraded to a digital projection system and a Zeiss optical planetarium. After its retirement, this domestically-made planetarium was displayed as a collection in the permanent exhibition hall.

Domestic large planetarium

The Development and Inheritance of the Planetarium

Over the past century, science and technology have developed rapidly, and planetariums have also triggered a series of revolutions with the changes of the times. In 1983, the American company E-World Computer launched a digital astronomical system, which completely abandoned the traditional optical projection mode and used computer technology to create a digital planetarium with computer graphics. Today, the combination of optical planetariums and digital astronomical systems has become the main astronomical demonstration method in modern large-scale planetariums.

Theme poster to celebrate the 100th anniversary of the Planetarium

Looking back at history, the most classic exhibit in a planetarium is the planetarium. As a long-standing astronomical display device, the planetarium was first invented by Carl Zeiss of Germany in 1923. In 1925, the planetarium of the Deutsches Museum demonstrated the artificial starry sky to the public for the first time. From 1923 to 2023, the planetarium and the planetarium have experienced a hundred years of development and inheritance. Today, the planetarium has integrated the characteristics of optical projection and digital astronomical systems, and can realistically display the starry sky seen at any time and place. Demonstrate the basic apparent motion of celestial bodies, including diurnal and annual apparent motion; the apparent motion of the sun, moon and major planets; show the influence of precession; realistically display the Milky Way, the Large and Small Magellanic Clouds, famous deep-sky objects, variable stars and visual binaries; realistically display the changes in moon phases and celestial phenomena such as lunar eclipses, perigee full moons, meteor showers, etc.; can also project panoramic images of urban landscapes, natural scenery, etc., including twilight shadows, auroras, zodiacal light and atmospheric effects that simulate urban light pollution; display the lines, patterns and Chinese names of the 88 constellations throughout the sky, as well as the lines, patterns and Chinese names of ancient Chinese constellations; display the basic astronomical coordinate system (equator, horizon, ecliptic and its scale values, etc.).

When was the last time you saw a starry night sky? The starry sky can bring a sense of peace and happiness to people. It is the starting point of human curiosity and exploration. However, with the development of society, air pollution and light pollution have made it difficult for urban residents to see the starry night sky. The original intention of the planetarium to establish a planetarium is to use special optical and digital projection technology to realistically simulate the natural starry sky, so that the audience can calm their minds under the pure starry sky and have a reverence and thinking about the universe.