The Seasons on Earth

The combined effect of the Earth's annual motion around the Sun and the tilt of its axis cause the seasons.

  • The length of time the Sun is above the horizon (daylight) changes. The path the Sun follows across the sky varies; the Sun's declination changes.

  • The noontime altitude of the Sun changes, causing the amount of concentration (area over which rays of sunlight are spread) of the sunlight to vary.

  • In summer, the Earth is tipped toward the Sun; in winter, away.

  • When it is summer in the northern hemisphere, it is winter in the southern.

  • The Sun's declination changes during the year too. Take a look at what happens in Ithaca.

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