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![]() The Earth’s shadow has two distinct parts: the umbra and the penumbra. The ecliptic is the plane of Earth’s orbit around the Sun. This can only happen when the Earth is between the Moon and the Sun and all three are lined up in the same plane, called the ecliptic. A Lunar EclipseĪ lunar eclipse occurs when the full moon moves through the shadow of the Earth (Figure 24.25). The corona is the white region surrounding the Sun. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere.įigure 24.24: Photo of a total solar eclipse. With fewer daylight hours in winter, there is also less time for the Sun to warm the area. Light from the Sun is spread out over a larger area, so that area isn’t heated as much. The tilt of Earth’s axis points away from the Sun. Winter solstice for the Northern Hemisphere happens on December 21 or 22. When it is summer solstice in the Northern Hemisphere, it is winter solstice in the Southern Hemisphere. At the summer solstice, June 21 or 22, the Sun’s rays hit the Earth most directly along the Tropic of Cancer (23.5 degrees N) that is, the angle of incidence of the sun’s rays there is zero (the angle of incidence is the deviation in the angle of an incoming ray from straight on). The North Pole is tilted towards the Sun and the Sun’s rays strike the Northern Hemisphere more directly in summer. When it is winter in the Northern hemisphere, it is summer in the Southern hemisphere, and vice versa.įigure 24.22: The Earth’s tilt on its axis leads to one hemisphere facing the Sun more than the other hemisphere and gives rise to seasons. Seasons change as the Earth continues its revolution, causing the hemisphere tilted away from or towards the Sun to change accordingly. The part tilted away from the Sun experiences a cool season, while the part tilted toward the Sun experiences a warm season. This results in one part of the Earth being more directly exposed to rays from the Sun than the other part. Remember that seasons are caused by the 23.5 degree tilt of Earth’s axis of rotation and Earth’s yearly revolution around the Sun (Figure 24.22). It is a common misconception that summer is warm and winter is cold because the Sun is closer to Earth in the summer and farther away from it during the winter. At this point, it is Earth’s South Pole that is tilted toward the Sun, and so there are shorter days and longer nights for those who are north of the equator. Since the southern half of the Earth is pointed away from the Sun at that point, they have the opposite effect-longer nights and shorter days.įor people in the Northern hemisphere, winter begins on December 21. Therefore, areas north of the equator experience longer days and shorter nights because the northern half of the Earth is pointed toward the Sun. At this point, the Earth’s North Pole is pointed directly toward the Sun. ![]() For example, in the Northern hemisphere, we begin summer on June 21. As you move towards the poles, summer and winter days have different amounts of daylight hours in a day. As the Earth rotates, different places on Earth experience sunset and sunrise at a different time. Since the Earth completes one rotation in about 24 hours, this is the time it takes to complete one day-night cycle. ![]() As Earth rotates, the side of Earth facing the Sun experiences daylight, and the opposite side (facing away from the Sun) experiences darkness or nighttime. Earth’s Day and NightĪnother effect of Earth’s rotation is that we have a cycle of daylight and darkness approximately every 24 hours. As Earth turns, the Moon and stars change position in our sky. Earth’s rotation is also responsible for this. When we look at the Moon or the stars at night, they also seem to rise in the east and set in the west. We often say that the Sun is “rising” or “setting”, but actually it is the Earth’s rotation that gives us the perception of the Sun rising up or setting over the horizon. As the Earth rotates, observers on Earth see the Sun moving across the sky from east to west with the beginning of each new day. If you were to look at Earth from the North Pole, it would be spinning counterclockwise. The Earth rotates once on its axis about every 24 hours. Explain how movements of the Earth and Moon affect Earth’s tides.Įarlier we discussed Earth’s rotation and revolution.Describe the phases of the Moon and explain why they occur.Describe how Earth’s movements affect seasons and cause day and night.In this lesson you will learn about how the movements of the Earth, Moon, and Sun affect different phenomena on Earth, including day and night, the seasons, tides, and phases of the Moon. ![]()
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