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History of Time: Difference between revisions
→Calendars: adding to Greeks
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== Calendars == | == Calendars == | ||
* | * measurement of time based upon social need by measuring heavenly bodies | ||
=== Paleolithic calendars=== | === Paleolithic calendars=== | ||
*** 13,000 BC cave painting depicting cycles of the moon | *** 13,000 BC cave painting depicting cycles of the moon | ||
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** based on star Sirius (they recognized some planets) | ** based on star Sirius (they recognized some planets) | ||
** 1st of the year = day of the Nile flooding | ** 1st of the year = day of the Nile flooding | ||
** 360 days x 12 months x 10 days | ** 360 days x 12 months x @ 10 days | ||
** 12 month solar year | ** 12 month solar year | ||
** adopted by the Romans, used by Copernicus | ** adopted by the Romans, used by Copernicus | ||
=== Greek Calendar=== | === Greek Calendar=== | ||
* Hipparchus: | |||
** Greek astronomy | ** applied Greek astronomy (sun, moon, stars, planets and their motions) and mathematics | ||
** | *** earlier Greek astronomers and mathematicians, such as Eudoxus of Cnidus, established these concepts | ||
*** earth not an exact sphere | *** that the solar year was 365.24 days was already understood by them | ||
*** | *** Hipparchus measured the year more exactly to 365.24667 days or 365 days, 5 hours, 55 minutes, 12 seconds | ||
** he also identified the "procession of the equinoxes" | |||
*** = he understood that earth is not an exact sphere | |||
*** and that the earth changes its rotation angle slightly, estimating it at 1 degree change per century | |||
*** thus he identified the difference between: | |||
**** "solar" or "tropical" year = the time for the earth to rotate around the sun as measured by equinoxes or solstices (i.e. in relation to the sun) | |||
**** "sidereal" year = the time for the earth to rotate around the sun as measured against the stars, which is impacted by the "procession of the equinoxes" | |||
=== Roman calendar === | === Roman calendar === | ||
* 10 lunar months: from Spring moon in March to late December... 300 days | * 10 lunar months: from Spring moon in March to late December... 300 days | ||
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** but this system caused confusion | ** but this system caused confusion | ||
** so it was adjusted by Julius Caesar, Caesar Augustus, and others to bring regularity | ** so it was adjusted by Julius Caesar, Caesar Augustus, and others to bring regularity | ||
*** Augustus added | *** February was shortened to 28 days, with an additional day added every 4 years (29 days) | ||
**** the 29th day was called "Bissectus" | |||
*** Caesar Augustus added month names for Julius Caesar (July) and himself (August) thus using the calendar for propaganda and authority | |||
=== Gregorian calendar === | === Gregorian calendar === | ||
* 1582 | * 1582 | ||
== Clocks == | == Clocks == | ||