As the earth is continuously rotating and revolving, the portion of the earth that is exposed to sun changes. Earth’s axis makes an angle of 62.5 degrees with its orbital plane – the plane formed by earth’s orbit.

Effects of Earth’s Revolution

It takes 365¼ days (one year) to revolve around the sun. We consider a year as consisting of 365 days only and ignore six hours for the sake of convenience.

Image taken from NCERT Class 6

• Summer Solstice

• On 21st June, the Northern Hemisphere is tilted towards the sun. 
• The rays of the sun fall directly on the Tropic of Cancer. As a result, these areas receive more heat. The areas near the poles receive less heat as the rays of the sun are slanting. 
• Continuous daylight in The North Pole – The North Pole is inclined towards the sun and the places beyond the Arctic Circle experience continuous daylight for about six months. 
• Since a large portion of the Northern Hemisphere is getting light from the sun, it is summer in the regions north of the equator. 
• The longest day and the shortest night at these places occur on 21st June. 
• At this time in the Southern Hemisphere all these conditions are reversed. It is winter season there. The nights are longer than the days. 
• This position of the earth is called the Summer Solstice.

• Winter Solstice
  • 22nd december, the sun rays fall straight on the Tropic of Capricon
  • The South Pole is tilted towards the Sun
  • As the sun’s rays fall vertically at the Tropic of Capricorn (23½° S), a larger portion of the Southern Hemisphere gets light. Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights. 
  • The reverse happens in the Northern Hemisphere. 
  • This position of the earth is called the Winter Solstice.

• Equinox
  • When the length of the day and the length of the night is exactly same
  • On 21st March and 23rd September
  • Direct rays of the sun fall on the equator. 
  • At this position, neither of the poles is tilted towards the sun; so, the whole earth experiences equal days and equal nights. This is called an equinox. 
  • On 23rd September, it is autumn season in the Northern Hemisphere and spring season in the Southern Hemisphere. The opposite is the case on 21st March.

Effects of Earth’s Rotation

• Circle of Illumination
  • The circle that divides day from night on the globe is called the Circle of Illumination. 
  • This circle does not coincide with the axis

• Rotation – Earthday
  • The Earth rotates once around its axis in 24 hrs, this daily motion of the earth is called as earthday

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