How did humans make time?

As a domain expert in the history of timekeeping, I'm delighted to delve into the fascinating subject of how humans have made time. Timekeeping is a fundamental aspect of human civilization, with its roots stretching back to the earliest recorded history. The development of timekeeping devices and methods has been a continuous process, evolving from simple sundials to the complex atomic clocks we use today. Let's explore this journey in detail.

Step 1: Sundials and Shadows
The earliest known method of timekeeping was the use of sundials, which date back to ancient Egypt around 1500 BC. These devices were essentially a flat plate with a gnomon, or a vertical rod, that cast a shadow onto the plate as the sun moved across the sky. The position of the shadow indicated the time of day. However, sundials were limited by their dependence on sunlight and clear skies, which meant they were not reliable for nighttime or cloudy conditions.

Step 2: Water Clocks
To overcome the limitations of sundials, ancient civilizations developed water clocks, known as clepsydras. The first water clocks were simple containers with a small hole from which water would drip at a constant rate. The time was measured by the amount of water that had dripped from the container. Water clocks were used in many ancient cultures, including the Greeks, Chinese, and Indians, and they were a significant improvement over sundials as they could measure time in any weather conditions.

Step 3: Candle Clocks and Hourglasses
Another innovation in timekeeping was the candle clock, which used the consistent rate at which a candle burned to measure time. Similarly, hourglasses, which consist of two glass chambers filled with sand, allowed for the measurement of time by the rate at which the sand flowed from one chamber to the other. These devices were portable and did not require water, making them popular for navigation and timekeeping at sea.

Step 4: Mechanical Clocks
The invention of the mechanical clock in Europe during the Middle Ages marked a significant leap in timekeeping technology. These early mechanical clocks used a verge-and-foliot escapement mechanism to control the motion of the clock's hands. They were large, often found in church towers, and their primary purpose was to signal times for prayer and work.

Step 5: Pendulum Clocks
The introduction of the pendulum to mechanical clocks in the 17th century by Christiaan Huygens was a pivotal moment. The pendulum's regular swinging motion allowed for much greater accuracy in timekeeping. This innovation led to the development of clocks that could be used in homes and institutions, making precise timekeeping more accessible to the general public.

**Step 6: Marine Chronometers and Longitude**
The quest for accurate timekeeping at sea to determine longitude was a significant driving force in the development of timekeeping technology. The marine chronometer, a highly accurate timepiece designed to be used on ships, was developed in the 18th century by John Harrison. These chronometers were crucial for navigation and allowed sailors to determine their longitude with unprecedented accuracy.

Step 7: The Rise of Quartz Clocks
In the 20th century, the development of quartz clocks revolutionized timekeeping once again. Quartz clocks use the vibrations of a quartz crystal to regulate the clock's timekeeping element. They are highly accurate and require less maintenance than mechanical clocks, making them the standard for most consumer timekeeping devices.

Step 8: Atomic Clocks and the Modern Era
The most accurate timekeeping devices in the world today are atomic clocks. These clocks use the oscillations of atoms, typically cesium or hydrogen, to keep time. Atomic clocks are so precise that they are used to define the international unit of time, the second. They are essential for scientific research, telecommunications, and GPS technology.

**Horology: The Study of Timekeeping Devices**
Throughout history, the invention and refinement of timekeeping devices have been a significant part of human progress. Horology, the study of these devices, is a rich field that encompasses engineering, physics, and history. It is through the lens of horology that we can appreciate the ingenuity and creativity that has gone into making time.

A large variety of devices have been invented to measure time. The study of these devices is called horology. An Egyptian device that dates to c.1500 BC, similar in shape to a bent T-square, measured the passage of time from the shadow cast by its crossbar on a nonlinear rule.