<text><span class="style10">ime (2 of 3)</span><span class="style7"></span><span class="style10">Calendars</span><span class="style7">The Earth takes </span><span class="style10">365.2422</span><span class="style7"> days to complete one orbit of the Sun, which makes planning a calendar rather difficult, as the extra </span><span class="style10">0.2422</span><span class="style7"> days per year have to be accounted for. The first person to attempt to do this was Julius Caesar (100-44 BC), who commissioned the astronomer Sosigenes to produce what became known as the </span><span class="style26">Julian calendar</span><span class="style7">. In order to compensate for the errors that had accumulated over previous years, Caesar decreed that the first year of his new calendar would be 445 days long. Thus 46 BC became known as `The Year of Confusion'. Julius Caesar also introduced the idea of </span><span class="style26">leap years</span><span class="style7"> to compensate for the extra 0.2422 days per year. However, the original Julian calendar had a leap year every third year - 0.0911 days or 2 hours 11 minutes too much.The calendar was further refined by the Emperor Augustus (63 BC-AD 14), who in 8 BC revised the frequency to one leap year every fourth year. This gives an `extra' 0.2500 days per year and reduces the error to 0.0078 days (i.e. 11 minutes) per year. By the 14th century, the extra 11 minutes per year had accumulated to a total error of 10 days. Pope Gregory XIII (1572-85) therefore introduced the </span><span class="style26">Gregorian calendar</span><span class="style7">, decreeing that 4 October 1582 should be followed by 15 October. He also decided that the century years would not be leap years, unless divisible by 400. Thus, for example, 1800 and 1900 were not leap years, but 2000 will be. The Gregorian calendar allows an extra 0.2425 days per year and is in error by just 0.0003 days per year. It will therefore be many centuries before the calendar will need to be revised again.When Britain and its colonies, long antagonistic to anything emanating from Rome, eventually adopted the Gregorian calendar in 1752, riots broke out with mobs chanting, `Give us back our eleven days!' Russia did not adopt the Gregorian calendar until after the 1917 Revolution, by which time there was a 13-day lag. This explains why the October Revolution (25 October 1917) is now commemorated in November (7 November).The Muslim calendar has either 354 or 355 days in a year. The Jewish calendar employs a year that varies from a minimum of 353 days to a maximum of 385 days. The Chinese used to have a calendar based on a 60-year cycle. Although it was banned in China in 1930, the Chinese calendar is still used in parts of Southeast Asia.</span></text>
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<text><span class="style10">idereal and solar days</span><span class="style7">. In traveling through distance A the Earth rotates once in relation to more distant stars, so completing one sidereal day (23 hours 56 minutes 4 seconds). To complete a mean solar day, with the Sun in the same position in the sky as it was 24 hours before, the Earth has to turn approximately 1 deg more, and in so doing travels the additional distance B.(Diagram not to scale.)</span></text>
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<text>ΓÇó THE UNIVERSE AND COSMOLOGYΓÇó THE SUN AND THE SOLAR SYSTEMΓÇó THE INNER PLANETSΓÇó QUANTUM THEORY AND RELATIVITYΓÇó THE REVOLUTIONARY CALENDAR</text>
