403 Quiz Review the Sun and the Earth-moon-sun System

The solar system is made upwards of the Sun, the planets that orbit the Sun, their satellites, dwarf planets and many, many small objects, like asteroids and comets. All of these objects move and we can see these movements. We observe the Sunday rises in the eastern heaven in the morning and sets in the western heaven in the evening. We discover dissimilar stars in the sky at dissimilar times of the year. When aboriginal people made these observations, they imagined that the heaven was actually moving while the Globe stood still. In 1543, Nicolaus Copernicus (Effigy 24.21) proposed a radically different idea: the Earth and the other planets make regular revolutions around the Dominicus. He also suggested that the World rotates once a twenty-four hours on its axis. Copernicus' idea slowly gained acceptance and today we base our view of motions in the solar system on his work. We as well now know that everything in the universe is moving.

Figure 24.21: Nicholas Copernicus.

In this lesson you volition learn most how the movements of the World, Moon, and Dominicus bear upon different phenomena on Earth, including mean solar day and night, the seasons, tides, and phases of the Moon.

Lesson Objectives

• Depict how Globe'due south movements impact seasons and cause day and night.
• Explain solar and lunar eclipses.
• Describe the phases of the Moon and explain why they occur.
• Explain how movements of the Earth and Moon affect Earth'southward tides.

Positions and Movements

Earlier nosotros discussed Earth'due south rotation and revolution. The World rotates one time on its axis about every 24 hours. If you were to wait at Globe from the North Pole, it would exist spinning counterclockwise. Equally the Earth rotates, observers on Earth encounter the Sun moving across the sky from eastward to west with the offset of each new 24-hour interval. We often say that the Sunday is "rising" or "setting", but really it is the Earth'southward rotation that gives us the perception of the Sunday ascent up or setting over the horizon. When we await at the Moon or the stars at night, they also seem to rising in the east and set up in the west. Earth's rotation is also responsible for this. As Earth turns, the Moon and stars alter position in our sky.

Earth'due south Day and Nighttime

Another effect of Earth'due south rotation is that we have a cycle of daylight and darkness approximately every 24 hours. This is chosen a day. Every bit Earth rotates, the side of Earth facing the Lord's day experiences daylight, and the opposite side (facing away from the Sun) experiences darkness or night. Since the Globe completes one rotation in about 24 hours, this is the time it takes to consummate ane day-nighttime bicycle. As the World rotates, different places on Earth experience sunset and sunrise at a different time. As you move towards the poles, summertime and wintertime days have different amounts of daylight hours in a twenty-four hour period. For example, in the Northern hemisphere, we begin summer on June 21. At this bespeak, the Earth's N Pole is pointed directly toward the Sun. Therefore, areas northward of the equator experience longer days and shorter nights considering the northern half of the Globe is pointed toward the Sun. Since the southern half of the Globe is pointed away from the Sun at that indicate, they accept the opposite outcome—longer nights and shorter days.

For people in the Northern hemisphere, winter begins on December 21. At this point, it is Earth's South Pole that is tilted toward the Sun, and then there are shorter days and longer nights for those who are northward of the equator.

World'southward Seasons

It is a common misconception that summer is warm and winter is cold because the Lord's day is closer to Earth in the summer and farther away from information technology during the wintertime. Remember that seasons are caused by the 23.five degree tilt of World's centrality of rotation and Globe's yearly revolution around the Sun (Effigy 24.22). This results in one part of the Globe existence more directly exposed to rays from the Sun than the other role. The part tilted away from the Sun experiences a cool flavor, while the part tilted toward the Sun experiences a warm season. Seasons modify as the World continues its revolution, causing the hemisphere tilted away from or towards the Sun to change accordingly. When information technology is wintertime in the Northern hemisphere, it is summer in the Southern hemisphere, and vice versa.

Figure 24.22: The Earth's tilt on its centrality leads to 1 hemisphere facing the Sun more than the other hemisphere and gives rise to seasons.

NORTHERN HEMISPHERE Summer
The North Pole is tilted towards the Lord's day and the Dominicus's rays strike the Northern Hemisphere more directly in summer. At the summer solstice, June 21 or 22, the Sun's rays hit the Globe about directly along the Tropic of Cancer (23.5 degrees N); that is, the bending of incidence of the sun's rays there is nil (the bending of incidence is the deviation in the angle of an incoming ray from directly on). When information technology is summer solstice in the Northern Hemisphere, it is wintertime solstice in the Southern Hemisphere.

NORTHERN HEMISPHERE Winter
Winter solstice for the Northern Hemisphere happens on December 21 or 22. The tilt of Earth's centrality points away from the Sun. Lite from the Lord's day is spread out over a larger surface area, so that surface area isn't heated as much. With fewer daylight hours in wintertime, there is likewise less time for the Sun to warm the area. When information technology is wintertime in the Northern Hemisphere, information technology is summertime in the Southern Hemisphere.

EQUINOX
Halfway between the two solstices, the Dominicus's rays smoothen most directly at the equator, called an "equinox." The daylight and nighttime hours are exactly equal on an equinox. The autumnal equinox happens on September 22 or 23 and the vernal or spring equinox happens March 21 or 22 in the Northern Hemisphere.

Solar Eclipses

Asolar eclipse occurs when the new moon passes directly between the Earth and the Sun (Figure 24.23). This casts a shadow on the Globe and blocks our view of the Lord's day. A total solar eclipse occurs when the Moon'southward shadow completely blocks the Lord's day (Figure 24.24). When only a portion of the Lord's day is out of view, information technology is called a partial solar eclipse. Solar eclipses are rare events that commonly only last a few minutes. That is because the Moon's shadow simply covers a very small area on Earth and Earth is turning very rapidly. As the Dominicus is covered by the moon'south shadow, information technology will really get cooler outside. Birds may brainstorm to sing, and stars will become visible in the sky. During a solar eclipse, the corona and solar prominences tin can be seen.

Figure 24.23: A solar eclipse.

Effigy 24.24: Photograph of a total solar eclipse. The corona is the white region surrounding the Sun.

A Lunar Eclipse

Alunar eclipse occurs when the full moon moves through the shadow of the Earth (Figure 24.25). This can only happen when the Globe is between the Moon and the Sun and all iii are lined upwards in the same plane, called the ecliptic. The ecliptic is the airplane of Earth's orbit around the Sunday. The Earth's shadow has ii distinct parts: the umbra and the penumbra. Theumbra is the inner, cone shaped role of the shadow, in which all of the light has been blocked. The outer role of Earth'south shadow is thepenumbra where merely part of the light is blocked. In the penumbra, the light is dimmed but not totally absent-minded. A total lunar eclipse occurs when the Moon travels completely in World'due south umbra. During a partial lunar eclipse, only a portion of the Moon enters World's umbra. A penumbral eclipse happens when the Moon passes through Earth's penumbra. The Earth's shadow is quite large, and so a lunar eclipse lasts for hours and tin be seen by anyone with a view of the Moon at the time of the eclipse.

Figure 24.25: The formation of a lunar eclipse.

Partial lunar eclipses occur at least twice a twelvemonth, but total lunar eclipses are less common. The next total lunar eclipse volition occur December 21, 2010. The moon glows with a ho-hum cherry-red coloring during a full lunar eclipse.

The Phases of the Moon

The Moon does non produce any light of its own—information technology but reflects low-cal from the Sun. As the Moon moves around the Globe, we see different parts of the almost side of the Moon illuminated by the Sun. This causes the changes in the shape of the Moon that we notice on a regular footing, called the phases of the Moon. As the Moon revolves around Earth, the illuminated portion of the near side of the Moon will change from fully lit to completely night and back again.

A full moon is the lunar phase seen when the whole of the Moon's lit side is facing World. This phase happens when Earth is between the Moon and the Sun. Virtually one week later on, the Moon enters the quarter-moon stage. At this point, the Moon appears as a half-circle, since only half of the Moon's lit surface is visible from Earth. When the Moon moves betwixt Earth and the Dominicus, the side facing Earth is completely dark. This is chosen the new moon stage, and nosotros do not usually see the Moon at this bespeak. Sometimes you can just barely make out the outline of the new moon in the heaven. This is because some sunlight reflects off the Earth and hits the moon. Before and after the quarter-moon phases are thegibbous andcrescent phases. During the gibbous moon stage, the moon is more than half lit just non total. During the crescent moon stage, the moon is less than one-half lit and is seen every bit only a sliver or crescent shape. It takes about 29.5 days for the Moon to revolve effectually Earth and go through all the phases (Figure 24.26).

Effigy 24.26: The phases of the Moon. Note that the Sunday would exist above the top of this pic, and thus, the Lord's day's rays would be directed downward.

The Tides

Tides are the regular rising and falling of Earth's surface h2o in response to gravitational allure from the Moon and Sun. The Moon'due south gravity causes the oceans to bulge out in the direction of the Moon. In other words, the Moon'south gravity is pulling upward on Earth'due south h2o, producing a loftier tide. On the other side of the Earth, at that place is some other high tide expanse, produced where the Moon's pull is weakest. Every bit the Earth rotates on its centrality, the areas directly in line with the Moon will experience high tides. Each place on Earth experiences changes in the peak of the water throughout the day every bit it changes from high tide to low tide. There are two loftier tides and two low tides each tidal solar day. Figure 24.27 and Figure 24.28 will assist you improve understand how tides work.

Effigy 24.27: A jump tide.

Figure 24.28: A neap tide.

The start picture shows what is called abound tide. Confusingly, this tide has nada to practise with the season "Spring", just ways that the tide waters seem to spring forth. During a spring tide, the Dominicus and Moon are in line. This happens at both the new moon and the total moon. The Lord's day's gravity pulls on World's h2o, while the Moon'south gravity pulls on the h2o in the aforementioned places. The high tide produced past Sun adds to the high tide produced past the Moon. So spring tides take higher than normal high tides. This water is shown on the picture as the gray bulges on opposite sides of the Earth. Notice that perpendicular to the grayness areas, the h2o is at a relatively low level. The places where the water is beingness pulled out experience high tides, while the areas perpendicular to them experience low tides. Since the Earth is rotating on its axis, the loftier-low tide wheel moves around the globe in a 24-hr menses.

The 2d moving-picture show shows aneap tide. A neap tide occurs when the World and Sun are in line but the Moon is perpendicular to the World. This happens when the moon is at first or last quarter moon stage. In this example, the pull of gravity from the Sun partially cancels out the pull of gravity from the Moon, and the tides are less pronounced. Neap tides produce less extreme tides than the normal tides. This is because the high tide produced past the Sun adds to the low tide area of the Moon and vice versa. So high tide is not every bit high and low tide is not equally depression as it normally might be.

Lesson Summary

• As the Earth rotates on its axis and revolves effectually the Sun, several unlike effects are produced.
• When the new moon comes betwixt the Earth and the Lord's day along the ecliptic, a solar eclipse is produced.
• When the Earth comes between the total moon and the Sun forth the ecliptic, a lunar eclipse occurs.
• Observing the Moon from Earth, we see a sequence of phases equally the side facing us goes from completely darkened to completely illuminated and back once again once every 29.5 days.
• Also as the Moon orbits Globe, it produces tides aligned with the gravitational pull of the Moon.
• The Sun also produces a smaller solar tide. When the solar and lunar tide align, at new and full moons, we experience higher than normal tidal ranges, called bound tides.
• At outset and last quarter moons, the solar tide and lunar tide interfere with each other, producing lower than normal tidal ranges called neap tides.

Review Questions

1. The world is divided into time zones, and so that any given hour of the mean solar day in one time zone occurs at a different time in other time zones. For example, New York City is in one fourth dimension zone and Los Angeles is in another time zone. When information technology is 8 am in New York City, it is merely five am in Los Angeles. Explain how World's motions cause this divergence in times.
2. Explicate how Globe's tilt on its axis accounts for seasons on Earth.
3. Explicate how the positions of the Earth, Moon, and Lord's day vary during a solar eclipse and a lunar eclipse.
4. Draw a picture that shows how the Earth, Moon, and Sun are lined upwards during the new moon phase.
5. Why are neap tides less extreme than spring tides?

Vocabulary

crescent

Phase of the moon when it is less than half full but still slightly lit.

gibbous

Stage of the moon when information technology is more than half lit but not completely full.

lunar eclipse

An eclipse that occurs when the Moon moves through the shadow of the Earth and is blocked from view.

neap tide

Type of tide event when the Sunday and Earth are in line and the Moon is perpendicular to the Earth.

penumbra

Outer part of shadow that remains partially lit during an eclipse.

solar eclipse

Occurs when moon passes straight between the Earth and Sun; the Moon's shadow blocks the Sun from view.

spring tide

An extreme tide event that happens when the World, Moon, and the Lord's day are aligned; happens at full and new moon phases.

tide

The regular rising and falling of Earth's surface waters twice a tidal day as a consequence of the Moon's and Sunday's gravitational attraction.

umbra

Inner cone shaped part of a shadow when all light is blocked during an eclipse.

Points to Consider

• Why don't eclipses occur every single month at the full and new moons?
• The planet Mars has a tilt that is very similar to Earth's. What does this produce on Mars?
• Venus comes between the Earth and the Sun. Why don't nosotros see an eclipse when this happens?

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Source: https://courses.lumenlearning.com/earthscience/chapter/the-sun-and-the-earth-moon-system/

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