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Wednesday, 28th January 2009

Xi He and Shou Shi (Time Service)

On the third day of the Chinese New Year, the last day of the holidays, all was quiet in the grounds of the Hong Kong Observatory (HKO). I picked up by chance the ancient Chinese book Shang Shu which had been lying idle on the book rack for quite some time. Flipping through the pages, I came to the chapter Yao Dian. It says that the first thing Emperor Yao did on achieving stability in his empire was to appoint Xi He to study the sun, the moon and the stars so as to be able to "show people the time" (jing shou ren shi in Putonghua). The officials were to determine the four seasons by means of astronomical observations, so as to help people time agricultural activities. Yao Dian also makes reference to how birds and animals behave following the seasons. Ancient people knew very early that climate and the living world were closely related.

According to researchers, Xi He is the collective name of two tribes. To me, they are the ancient predecessors of the HKO. To HKO people, they are the equivalent of Lu Ban to carpenters and other building artisans. Not too many people are aware that the most important job of HKO when it was established in 1883 was in fact the determination of Hong Kong's local time based on astronomical observations and the dissemination of this information to ships in the harbour by means of the "time ball" (see figure below). In English, this is known as "time service"; in Chinese, the service is called shou shi, a name most probably having its root in the phrase jing shou ren shi in Yao Dian mentioned above.

The main task of the first director of HKO in the early years was observing stars through a telescope at night. He liked to label himself as the Government Astronomer in spite of repeated instructions from the Governor not to do so. Owing to the importance of astronomy in our early work and probably reflecting also the stubbornness of the first director, the Chinese name of the HKO (which is still in use today) was rendered Xianggang Tianwen Tai, which means "Hong Kong Astronomical Station" in literal translation. A direct translation of "Hong Kong Observatory" should have been Xianggang Guanxiang Tai, where Guanxiang means "observing phenomena".

Although more than a century has passed, astronomy and time service remain a part of HKO's work. While we no longer observe stars, we do compute the times of sunrise, sunset, moon rise, moon set, solar and lunar eclipses as well as other interesting astronomical phenomena. We also post monthly star maps on our website. While we no longer drop the time ball, we do broadcast the 6-pip time signal over the radio. The time of the Standard Clock is also available to the public via the internet. You are welcome to visit the following link :



More than three thousand years have elapsed since the writing of Shang Shu. Science and technology have been changing incessantly. However, one thing has not changed, that is, human beings and indeed all living things still have to synchronize their pace of life with the march of the seasons. Also, apart from superficial differences in technical detail, the Hong Kong Observatory is still performing the same function as Xi He.

CY Lam




The time ball was dropped at a fixed time everyday from the top of the mast on the time ball tower.  The first time ball tower was built on the southern side of the knoll accommodating the old marine police headquarters.  The tower is still in good shape, located near the Cultural Centre.

The time ball was dropped at a fixed time everyday from the top of the mast on the time ball tower. The first time ball tower was built on the southern side of the knoll accommodating the old marine police headquarters. The tower is still in good shape, located near the Cultural Centre.



Last revision date: <17 Jan 2013>