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High-Tech Channel Hitachi High-Tech GLOBAL

The length of a day is not the time it takes for the earth to rotate!?

Symbol: d / Base data: time. SI Combined units. 1 day = 86,400 sec.

Determined by calculating the average

86,400 seconds – that is the exact length of a day. Is this the amount of time it takes for the earth to rotate...? Actually, no it isn’t. There is the effect of orbital revolution, so it’s about 4 minutes longer than a single rotation of the earth on its own axis. The actual length of a day was decided by calculating the average based on observations of the sun’s movements.