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 of, theory, time and/or keeping:
“If my theory of relativity is proven correct, Germany will claim me as a German and France will declare that I am a citizen of the world. Should my theory prove untrue, France will say that I am a German and Germany will declare that I am a Jew.”
—Albert Einstein (1879–1955)
“[Anarchism] is the philosophy of the sovereignty of the individual. It is the theory of social harmony. It is the great, surging, living truth that is reconstructing the world, and that will usher in the Dawn.”
—Emma Goldman (1869–1940)
“Play for young children is not recreation activity,... It is not leisure-time activity nor escape activity.... Play is thinking time for young children. It is language time. Problem-solving time. It is memory time, planning time, investigating time. It is organization-of-ideas time, when the young child uses his mind and body and his social skills and all his powers in response to the stimuli he has met.”
—James L. Hymes, Jr. (20th century)
“I have been searching history to see if really a woman has any precedent to claim the right to have her rights, and I am compelled to say that we men are not so much ahead of women after all, and the only way we have kept our reputation up is by keeping her down—and don’t you forget it!”
—George E. Foster, U.S. women’s magazine contributor. The Woman’s Magazine, pp. 38-41 (October 1886)