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What Causes the Seasons?. What about seasons? Why do we have them? Earth’s distance from the sun varies throughout the year – doesn’t that cause the seasons?

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Presentation on theme: "What Causes the Seasons?. What about seasons? Why do we have them? Earth’s distance from the sun varies throughout the year – doesn’t that cause the seasons?"— Presentation transcript:

1 What Causes the Seasons?

2 What about seasons? Why do we have them? Earth’s distance from the sun varies throughout the year – doesn’t that cause the seasons? Earth is closest to our Sun (91 million miles) in winter—January 3 Earth is farthest from our Sun (94 million miles) in summer –July 4

3 Tilt! Because of the tilt of Earth’s axis, the amount of solar radiation received by Northern and Southern Hemispheres changes seasonally Northern Hemisphere has summer when it tilts toward the sun, winter when it tilts away Southern Hemisphere has summer when it tilts toward the sun, winter when it tilts away

4 The earth is tilted

5 Earth’s axis is tilted – it always points in the same direction (Polaris, the North Star) as we orbit our Sun once a year This tilt causes the hemispheres to receive different amounts of sunlight throughout the year

6 Radiation is more intense near the equator compared to the poles. For this reason, it’s warmer near the equator than at the poles. North Pole Earth Equator South Pole

7 North Pole Earth When the north pole tilts toward the sun, it gets more radiation – more warmth during the summer SUMMER (Northern Hemisphere) South Pole WINTER (Southern Hemisphere) When the north pole tilts toward the sun, the south pole tilts away So when it’s summer in the north, it’s winter in the south Equator

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10 Planets that are tilted on an axis can experience seasons.

11 Equinoxes/Solstices Vernal Equinox – March 21/22 (1st day of spring) = amount of daylight and darkness Summer Solstice – June 21/22 (1st day of summer) longest daylight, shortest night Autumnal Equinox – Sept 22/23 (1 st day of fall) = daylight and darkness Winter Solstice – Dec 21/22 (1 st day of winter) shortest period of daylight, longest night

12 Seasons—a summary caused by the tilt of the earths axis As earth revolves around the sun its axis always points in the same direction Each hemisphere leans toward the sun during different parts of the orbit The seasons N and S of the equator are always opposite of each other The Earths Rotation Axis

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