Hourglass

Hourglass is a device used to measure the passage of time. It comprises two glass bulbs connected vertically by a narrow neck that allows a regulated trickle of material (historically sand) from the upper bulb to the lower one. Factors affecting the time interval measured include the amount of sand, the size of the sand particles, the size of the bulb, and the neck width.

History

The hourglass, also known as a sand clock or sandglass, dates back to the 14th century. It is one of the few reliable methods to measure time at sea. The hourglass was the ideal instrument for navigation during this period because it was not affected by the motion of the ship or changes in humidity.

Design and Function

The design of an hourglass is simple yet effective. The two bulbs of an hourglass are symmetric so that the hourglass will measure the same duration regardless of orientation. The material in the neck does not flow until the upper bulb is empty. Therefore, the hourglass continues to be accurate even if it is stopped and restarted.

Uses

Hourglasses have been used in a variety of contexts, from cooking and working to game playing and exercising. They are also used symbolically in art and culture to represent the passage of time.

See Also

• Timekeeping
• Clock
• Sandglass

References

Hourglass Resources
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