The working principle of hourglass is to measure the time by the time it takes for a glass ball filled with sand to flow into the bottom glass ball through a narrow tube from above. Once all the sand flows to the glass ball at the bottom, the hourglass can measure the time backwards.

The hourglass is also called the sand clock, and its working principle is basically the same as another timing tool in ancient China. Leakage is timed according to the amount of water flowing from one pot to another, while hourglass is timed according to the amount of sand leaking from one container to another.

History:

It is said that the hourglass was invented by Alexander in the third century. They sometimes carry it with them, just like the watches that people carry with them today. Presumably, the compass was invented as a tool for night navigation in the12nd century.

The irrefutable discovery dates back to14th century. The earliest hourglass is a written record of Humblot Renzetti's fable, 1338, a suitable government mural. At the same time, the hourglass is mentioned, which appears in the list of ship shops.

The earliest existing record is 1345 sales receipt of Thomas Stesham, a clerk on the British ship "Shangri-La George".