mean solar second

mean solar second

[′mēn ′sō·lər ′sek·ənd]
(astronomy)
A unit equal to 1/86,400 of a mean solar day.
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References in periodicals archive ?
In an era during which the Earth's rotation was the world's timekeeping reference, Maxwell remarkably suggested to Peter Guthrie Tait (a childhood friend) and William Thomson (later to be known as Lord Kelvin) that the "period of vibration of a piece of quartz crystal of specified shape and size and at a stated temperature" would be a better absolute standard of time than the mean solar second, but it would still depend "essentially on one particular piece of matter, and is therefore liable to all the accidents, etc.
The mean solar second was equal to 1/86 400 of the mean solar day.
Leap seconds are periodically added to UTC to keep it within [+ or -]0.9 s of UT1, an astronomical time scale based on the mean solar second. Adding a leap second to UTC stops atomic time for one second to allow astronomical time to catch up.