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You are, of course, welcome to consult and make use of my pages at will. However, if you have found them useful in any appreciable way, please consider sending a small disbursement (even something as small as 1 Euro/Pound/Dollar/etc. would be received with appreciation).

B. Daugherty, 31 MH, Portsmouth PO5 3JG, Britain.

The Seasons

The Seasons are caused by the Earth's inclination - they are definitely not caused by the varying difference between the Earth and the Sun. For one thing, when the Earth is closest to the Sun is when we experience Winter in the Northern Hemisphere (at this time it is 3.3% closer to the Sun than in July).

Other planets having an inclination will likewise experience seasons, e.g. Mars which is inclined at 23° 59', almost the same as the Earth's.

Winter is experienced in a particular location when that particular location is 'tipped away' from the Sun, thus

  • There is a greater thickness of atmosphere for the Sun's radiation to 'fight through'. Earth is heated ultimately by the Sun's radiation hitting the ground and being re-radiated as Infra Red. High mountains might be closer to the Sun but they are undoubtedly colder - it is re-radiated heat from the ground that is responsible for the Earth's temperature.
  • Because of the Earth's inclination, less radiation would hit the Earth per unit area anyway
  • The Sun is in the sky for fewer hours per day

The increased length of daylight that we experience during Summer is a function of latitude. Considering the extremes:

  • At the equator, there will be little difference in daylight length during the course of the year
  • At the pole, daytime length will be longer than elsewhere and on midsummer day will amount to full 24 hours of daylight.

This scenario will be reversed during Winter, with the pole experiencing 24 hour nighttime on midwinter day (and Scandinavian countries only having a few hours of daylight each 24 hours).

The areas which will experience 24 hours daylight on Midsummmers Day and 24 hours nighttime on Midwinter Day are enclosed within the Arctic Circle and the Antarctic Circle. These circles are located at

90 - Earth's inclination

= 90 - 23.5

= 66.5 °

Length of seasons

  • Autumn 89 days
  • Winter 91 days
  • Spring 92 days
  • Summer 94 days

Perihelion 4 January

Aphelion 3 July

Crab Nebula

Big Red Spot on Jupiter