Time is a crucial factor with a significant impact on human life. This article aims to share how we measure time and the earliest clocks created by humanity.
How Humanity Has Measured Time
Humans have sought ways to track time since ancient times, but history does not record when this practice began. However, there is evidence that our ancestors established primitive calendars by observing the sunrise, sunset, and the position of the sun in the sky. For example, they recorded the horizon points where the sun rose and set each day, helping them recognize changes in the day and seasons over time. Throughout the year, these positions gradually change:
- Near the summer solstice, the sun rises and sets at the farthest points to the north.
- Near the winter solstice, the sun rises and sets at the farthest points to the south.
Additionally, they tracked the sun’s altitude through shadows or used angles based on the sun’s path. At noon each day, the sun reaches its highest point in the sky, and this height changes throughout the year:
- In summer, the sun reaches a higher point, indicating longer days and warmer weather.
- In winter, the sun is much lower, resulting in shorter days and colder weather.
The oldest sundial base found in Egypt.
The earliest recorded clock dates back to Egypt around 1500 BC, later optimized by the Greeks and Romans. They used a vertical stick placed on a semicircular base, divided into 12 fan-shaped sections. The stick’s shadow on the base indicated the time of day. The number 12 was chosen to divide time mainly due to their understanding of time and celestial movements or its sacred meaning in religion.
The Egyptians and ancient peoples also tracked the sun’s path based on the length of shadows throughout the day. Shadows were longer in the morning and evening when the sun was lower in the sky, and shortest at noon, when the sun was at its highest. By combining this with a scale measuring shadow length, these sundials could determine time based on shadow length at that moment, rather than the position of the shadow on a horizontal plane.
Roman sundial in Pompeii.
The Romans also had their first sundial around 260 BC, which had a significant impact on their lives. Plautus, a Roman playwright, lamented that before clocks, he counted time by his stomach when mealtime approached. But “damn” those who created clocks that measured every second, as he could only eat when the clock struck noon.
Water Clocks
As humanity succeeded in establishing time-measuring tools, our ancestors continued to optimize and develop alternative methods. Water clocks were another innovation developed by the Egyptians and Babylonians about 3,500 years ago. The earliest water clocks (clepsydra) consisted of a stone vessel with a small hole at the bottom, allowing water to drip out at a steady rate, with the passage of time indicated by the water level in the vessel. Another method used by the Egyptians involved water flowing into a reservoir marked with indices to display the gradual passage of time.
Egyptian clepsydra water clock with water flowing into the bottom part to indicate time.
Besides the Egyptians, the Chinese also invented water clocks, with historical accounts mentioning a figure named the Yellow Emperor, who is both historical and legendary, around 2717 to 2599 BC.
The first recorded water clock in China dates back to approximately 1046-771 BC during the Western Zhou Dynasty. This early form of water clock was called “louke” – a leaking water vessel. Its mechanism operated similarly to the Egyptian clepsydra, typically consisting of a container with a small hole, allowing water to drip in or out at a steady rate. The water level was used to measure time, with 100 equal units representing time intervals from midnight today to midnight the next day.
Later, during the Han Dynasty (202 BC – 220 AD), water clocks became more sophisticated, incorporating multiple containers and sometimes intricate designs to improve accuracy. Over time, these clocks evolved significantly and became important tools for astronomy and timekeeping in ancient China. By the early 8th century AD, during the Tang Dynasty, monks developed a more complex mechanical water clock. In this design, water flowed steadily into a wheel, causing it to rotate at a constant speed. The wheel’s rotation was then used to drive other mechanical parts of the clock, such as gears and levers, ensuring accurate time measurement. This design was a breakthrough compared to earlier water clocks, which only measured time based on rising or falling water levels.
The water clock of Su Song with improvements and a complex gear system.
In 1194 AD, under the Song Dynasty in China, an official and scholar named Su Song improved previous water clock designs. He developed an extremely advanced clock standing 12 meters tall. This clock represented a significant advancement in timekeeping and operated similarly to mechanical clocks with complex gear mechanisms, which would later be invented in Europe about 200 years later. Su Song’s work was a major milestone in both timekeeping and mechanical design, showcasing the advancement and complexity of Chinese technology during this period.
Standard Time and Seasonal Time Operating in Parallel
In modern times, an hour always has a fixed length of 60 minutes, regardless of day or night, summer or winter. The definition of a fixed hour of 60 minutes actually originates from ancient Babylonian astronomy around 2000 BC, when the Babylonians used a sexagesimal (base-60) counting system. They divided a day into 24 equal parts (hours), each hour into 60 minutes, and each minute into 60 seconds. However, this concept was not immediately standardized worldwide.
Clock of the Babylonians.
Additionally, in ancient times, the way people measured time was more flexible and varied depending on culture. Some ancient civilizations divided the day according to a different type of hour: They used a system in which both day and night were divided into 12 parts. This is similar to our concept of 12 hours of day and 12 hours of night.
However, there was a significant difference: the length of these hours varied throughout the year, depending on the season. Therefore, the length of each “hour” during the day or night was not fixed as it is today. These “seasonal hours” would expand or shorten based on the amount of daylight. For example, in summer, when days are long, daytime hours would be longer, and nighttime hours would be shorter. Conversely, in winter, nighttime hours would be longer, and daytime hours would be shorter.
This time measurement system was used in areas where the length of the day changed throughout the year, almost everywhere except near the equator, where day and night are nearly balanced year-round. This approach to timekeeping means that the length of an hour is very flexible and changes with the seasons.
The Transition to Mechanical Clocks: A New Era of Time Measurement
The advent of mechanical clocks marked a significant advancement in timekeeping technology. Unlike water clocks or sundials, which rely on the flow of water or sunlight, mechanical clocks operate based on a system of gears, weights, and complex escapements. This innovation brought greater accuracy and officially ushered in the era of fixed hours, significantly impacting daily life. Communities could adjust their activities more effectively according to a structured and unified time system.
Mechanical clocks became an integral part of European history.
Before the advent of mechanical clocks, fixed time systems and seasonal timekeeping coexisted until the 14th and 15th centuries in Europe. In Japan, seasonal timekeeping continued to be used until the 19th century. However, the increasing popularity of Christianity, combined with the spread of mechanical clocks from Europe to other regions, made this type of clock more widespread. Large clocks placed in town squares became symbols, ensuring that everyone followed the same schedule. These early mechanical clocks laid the foundation for modern watchmaking and paved the way for more accurate timekeeping devices such as pendulum clocks.
The global development of these clocks contributed to the standardization of fixed time in the 19th century, especially as commerce, travel, and international communication demanded a consistent time system. This was further formalized at the International Meridian Conference in 1884, when time zones were established and the concept of standard time was unified globally.
Since then, humanity has become increasingly intertwined with time management, and these tools have played an essential role in human life, including the formation of highly accurate financial transaction systems and GPS technology.
