Theory of Astronomical Time Keeping
Until recently all the time units that appear natural to us are caused by astronomical phenomena:
- Earth's orbit around the Sun => the year, and the seasons,
- Moon's orbit around the Earth => the month,
- Earth's rotation and the succession of brightness and darkness => the day (and night).
High precision appears problematic:
- amibiguities arise in the exact definition of a rotation or revolution,
- some astronomical processes are uneven and irregular, such as the noncommensurability of year, month, and day,
- there are a multitude of time scales and calendars to solve the first two problems.
Some of these time scales are sidereal time, solar time, and universal time.
Read more about this topic: Theoretical Astronomy
Famous quotes containing the words theory, time and/or keeping:
“The things that will destroy America are prosperity-at-any- price, peace-at-any-price, safety-first instead of duty-first, the love of soft living, and the get-rich-quick theory of life.”
—Theodore Roosevelt (1858–1919)
“From the time the Englishman’s bones harden into bones at all, he makes his skeleton a flagstaff, and he early plants his feet like one who is to walk the world and the decks of all the seas.”
—Willa Cather (1876–1947)
“There is a great stir about colored men getting their rights, but not a word about colored women, and if colored men get their rights, and not colored women theirs, you see the colored men will be masters over the women, and it will be just as bad as it was before. So I’m for keeping the thing going while things are stirring; because if we wait till it is still, it will take a great while to get it going again.”
—Sojourner Truth (1797–1883)