The Merkhet

Motion and Time of Class 7

An oldest known astronomical instrument by Egyptian was the sundial known as 'merkhet' . It was developed around 600 BC and in this they uses a pair of stripped , a string with a weight as a plumb line to obtain a true vertical line, as shown in the picture. The other object is the rib of a palm leaf, stripped of its fronds and split at one end, making a thin slit for a sight.


Two merkhets were used to establish a direction in North-South by lining them up one behind the other with the Pole Star. Viewing the plumb lines through the sight made sure the two merkhets and the sight were in the same straight line with the Pole Star. This allowed for the measurement of night-time events with a water clock when certain stars crossed the vertical plumb line (a 'transit line'), and these events could then be recorded by 'night-time lines' drawn on a sundial.

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