How does an hourglass measure time?

Answer 1

By using carefully calculated amounts of sand.

The hourglass is sometimes referred to as a sand clock or a sandglass. Like other timepieces, it needs to be carefully calibrated. The hourglass maker must test the instrument and fine tune it to measure the correct length of time.

There are many factors that contribute to the ability of an hourglass to accurately measure time. The type and quality of sand is key. It must have a rate of flow that does not fluctuate. Sand that is too coarse will wear away the glass, eventually making the neck too large. Most important is the ratio of the neck (the hole, or tube) width to the diameter of the sand particles.

Here are the other factors that affect the accuracy of an hourglass:

The amount or volume of sand used
The size and angle of the glass bulbs
The quality of the sand or granular material. It must be fine, dry and consistently formed so it can flow smoothly. (Some substances used in the past were fine grain sand, powdered eggshells, and powdered marble.)
The width of the neck
A tight seal so no moisture can get into the chambers. Moisture can add weight to the sand or clog up the neck.
A flat and level surface on which to rest the hourglass
We still use the hourglass to keep track of time. Just think of its many uses for cooking and for playing games!

Answer 2

An hourglass, also known as a sandglass or sand timer, is a device for the measurement of time. It consists of two glass bulbs placed one above the other which are connected by a narrow tube. One of the bulbs is usually filled with fine sand which flows through the narrow tube into the bottom bulb at a given rate. Once all the sand has run to the bottom bulb, the device is inverted in order to measure another time period.

Factors affecting the amount of time that the hourglass measures include: the volume of sand, the size and angle of the bulbs, the width of the neck, and the type and quality of the sand. Alternatives to sand that have been used are powdered eggshell and powdered marble. It is still in use, but typically only ornamentally or when a relatively approximate measurement of time is needed (for example in cooking or board games). For cooking and games the time period will be only a few minutes (for cooking eggs, a three minute timer is typical, hence the nickname eggtimer for three minute hourglasses). Today, hourglass collecting has become a niche but avid hobby for some, with elaborate or antique hourglasses commanding huge prices.

Answer 3

When the sand runs out. TIME'S UP!!!

Answer 4

the sand falls at a certain speed....that speed then makes the time.