sand clocks were used by our ancestors to know about
Answers
Answer:
Sand clocks were used by our ancestors to know about time.
Explanation:
An sandglass 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 flow of a substance from the upper bulb to the lower one.
Answer:
Time keeping is always calibrated against a reference. Originally the reference would be the sun at noon each day. That is a good 24 hour reference. From there you can divide into smaller intervals or if your device measures 24 h you can simply calibrate it against that.
In your example of a sandglass, you would put in the approximate amount of sand and then wait 24 hours. If there is sand left in the top you would pour that out and seal the glass. If the sand looked to be running out early you would add more as required. And the seal the glass.
Once you have a known good hour or minute glass you can use it to calibrate other similar glasses. Because the throat of the blown glass shell may vary slightly, the amount of sand can be initially approximated, but if you cared about accuracy, you would adjust the amount to match a reference glass.