The sundial and water clocks are probably the oldest instruments whose function was to tell time. As long-ago as 4,000 BC, we were using gravity and water to measure time.
Inflow Timekeepers - The ghati
These timekeepers measure time by how long it takes for water to fill a container.
In India, the standard water clock was a 'ghati' that measured time in 24 minute intervals - 60 of which together made up a 21st century 24-hour day.
The ghati was half a coconut shell with a hole drilled to just the right size in it. When floated in a tank of water, the shell would slowly take on water till it sank.
The size of the hole and the coconut half-shell were such that it took 24 minutes for the shell to sink.
The ghati was in use for over 5,000 years all over the ancient world.
Outflow Timekeepers - The Klepsydra
These time keepers measure time by long it takes for water to empty a container of fixed volume.
The jar at the higher elevation is filled to a fixed height. Water flows out of the hole at the bottom into another jar.
The klepsydra was made in the conical shape (a wide top and a narrow bottom) so that it would also be used to measure the passage of time. The conical shape ensured that the pressure at the bottom of the jar (that pushed out the water) remained constant as the water level dropped - A greater amount of water would flow out when the jar was filled, so that the surface level of the water in the jar would drop at a steady rate.
Water, a most abundant substance on the planet, also has a vast abundance of uses.
Inflow Timekeepers - The ghati
 |
| A Coconut Shell with a hole Source - sciencephoto.com |
In India, the standard water clock was a 'ghati' that measured time in 24 minute intervals - 60 of which together made up a 21st century 24-hour day.
The ghati was half a coconut shell with a hole drilled to just the right size in it. When floated in a tank of water, the shell would slowly take on water till it sank.
The size of the hole and the coconut half-shell were such that it took 24 minutes for the shell to sink.
The ghati was in use for over 5,000 years all over the ancient world.
Outflow Timekeepers - The Klepsydra
 |
| A Klepsydra Source - depthome.brooklyn.cuny.edu |
The jar at the higher elevation is filled to a fixed height. Water flows out of the hole at the bottom into another jar.
The klepsydra was made in the conical shape (a wide top and a narrow bottom) so that it would also be used to measure the passage of time. The conical shape ensured that the pressure at the bottom of the jar (that pushed out the water) remained constant as the water level dropped - A greater amount of water would flow out when the jar was filled, so that the surface level of the water in the jar would drop at a steady rate.
Water, a most abundant substance on the planet, also has a vast abundance of uses.
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