Revolution

  • Rotation and revolution are the two primary motions of the earth. The amount of heat received from the Sun also depends on these movements.
  • Rotation is the turning around of the earth on its own axis from west to east.
  • Revolution is the movement of earth around the Sun.
  • The time taken by the earth to complete one revolution is called a year and is 365 days approximately.
  • The path along which the earth travels round the Sun is called Orbit.
  • Perihelion is the time when the earth is closest to the Sun. This happens on January 3.
  • Aphelion is the time when the earth is farthest to the Sun. This happens on July 4.
  • The main effects of revolution are cycle of seasons, apparent migration of the Sun, and temperature zones.
  • Seasons are caused due to combined effect of revolution of the earth and the tilt of the earth’s axis.
  • Seasons of one hemisphere are opposite to that of the other hemisphere.
  • Earth on its elliptical orbit has some specific days.
  • On June 21st, rays of the Sun fall vertically over the Tropic of Cancer. This day is known as Summer Solstice. Northern Hemisphere has the longest day and shortest night on this day.
  • On December 22nd, rays of the Sun fall vertically over the Tropic of Capricorn. This day is known as Winter Solstice. Northern Hemisphere has the shortest day and longest night on this day.
  • On September 23rd, rays of the Sun fall vertically over the equator. This day is known as Autumnal Equinox. All the places have equal days and nights on this day.
  • On March 21st, rays of the Sun fall vertically over the equator. This day is known as Vernal Equinox. All the places have equal days and nights on this day.
  • It appears to us as if the Sun is moving. This is known as apparent migration of the Sun. However, the Sun does not move; it is the earth, which moves.
  • The earth has three temperature zones, depending on the amount of heat received. These are Torrid Zone, temperate zone and Frigid Zone.
  • Time is one of the most fundamental qualities of the physical world. The basis of measurement of time is the motion of the Sun across the sky.
  • Day is the average time taken by the earth to rotate once on its axis.
  • A month originally was the time taken by the moon to complete one revolution around the earth.
  • In modern calendars, a month consists of 30 or 31 days normally with the exception of February, which has 28 or 29 days.
  • There are various calendars, which are used in different parts of the world. Some of the major calendars are Julian Calendar, Gregorian Calendar, Hindu Calendar, Islamic Calendar, and Jewish Calendar

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