The solar system is consisted of of the Sun, the planets that orbit the Sun, their satellites, dwarf planets and many, many tiny objects, like asteroids and comets. All of these objects move and we deserve to see this movements. We notice the sunlight rises in the eastern sky in the morning and sets in the western sky in the evening. Us observe different stars in the sky at various times that the year. When ancient people made these observations, castle imagined the the sky was actually relocating while the planet stood still. In 1543, Nicolaus Copernicus (Figure 24.21) suggest a radically various idea: the Earth and also the other planets make regular revolutions about the Sun. He additionally suggested the the earth rotates when a day on its axis. Copernicus’ idea slowly got acceptance and also today we base our check out of motions in the solar mechanism on his work. We also now know that every little thing in the universe is moving.

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Figure 24.21: Nicholas Copernicus.

In this lesson you will certainly learn about how the activities of the Earth, Moon, and also Sun affect different phenomena top top Earth, including day and night, the seasons, tides, and also phases the the Moon.

Lesson Objectives

Describe exactly how Earth’s movements affect seasons and also cause day and night.Explain solar and lunar eclipses.Describe the phases of the Moon and also explain why castle occur.Explain how movements that the Earth and also Moon affect Earth’s tides.

Positions and Movements

Earlier we disputed Earth’s rotation and also revolution. The earth rotates once on that is axis around every 24 hours. If you to be to look at at earth from the north Pole, it would be rotate counterclockwise. As the planet rotates, observers on planet see the sunlight moving throughout the sky from east to west v the beginning of each new day. We regularly say that the sun is “rising” or “setting”, however actually that is the Earth’s rotation that offers us the perception of the Sun climbing up or setting over the horizon. As soon as we look in ~ the Moon or the stars in ~ night, they likewise seem to increase in the east and collection in the west. Earth’s rotation is additionally responsible for this. As earth turns, the Moon and also stars readjust position in our sky.

Earth’s Day and also Night

Another result of Earth’s rotation is the we have a bicycle of daylight and also darkness around every 24 hours. This is dubbed a day. As planet rotates, the side of earth facing the sun experiences daylight, and also the opposite side (facing far from the Sun) experiences darkness or nighttime. Due to the fact that the earth completes one rotation in around 24 hours, this is the time it bring away to finish one day-night cycle. Together the planet rotates, various places on planet experience sunset and sunrise in ~ a different time. As you relocate towards the poles, summer and also winter days have different quantities of daylight hrs in a day. For example, in the north hemisphere, we start summer ~ above June 21. At this point, the Earth’s phibìc Pole is pointed straight toward the Sun. Therefore, locations north that the equator experience much longer days and shorter nights since the northern half of the earth is pointed toward the Sun. Due to the fact that the southern half of the earth is pointed far from the sunlight at that point, they have actually the opposite effect—longer nights and shorter days.

For people in the north hemisphere, winter starts on December 21. In ~ this point, that is Earth’s south Pole the is tilted toward the Sun, and so there are much shorter days and also longer nights for those who room north the the equator.

Earth’s Seasons

It is a common misconception the summer is warm and also winter is cold due to the fact that the sunlight is closer to planet in the summer and also farther far from it throughout the winter. Remember that periods are caused by the 23.5 degree tilt that Earth’s axis of rotation and Earth’s yearly transformation around the sun (Figure 24.22). This results in one component of the earth being much more directly exposed to rays indigenous the sunlight than the other part. The component tilted away from the sun experiences a cool season, if the part tilted towards the sun experiences a warmth season. Seasons adjust as the Earth proceeds its revolution, causing the hemisphere tilted far from or towards the sun to change accordingly. Once it is winter in the northern hemisphere, that is summer in the southern hemisphere, and vice versa.


Figure 24.22: The Earth’s tilt top top its axis leads to one hemisphere encountering the Sun an ext than the various other hemisphere and also gives rise to seasons.

NORTHERN HEMISPHERE SUMMERThe north Pole is tilted towards the Sun and also the Sun’s light ray strike the north Hemisphere an ext directly in summer. At the summer solstice, June 21 or 22, the Sun’s rays hit the earth most straight along the Tropic the Cancer (23.5 degrees N); the is, the angle of incidence of the sun’s rays there is zero (the edge of incidence is the deviation in the edge of one incoming ray from straight on). Once it is summer solstice in the north Hemisphere, that is winter solstice in the southern Hemisphere.

NORTHERN HEMISPHERE WINTERWinter solstice for the northern Hemisphere wake up on December 21 or 22. The tilt the Earth’s axis points far from the Sun. Irradiate from the sunlight is spread out out end a bigger area, so the area isn’t heated as much. Through fewer daylight hours in winter, there is additionally less time for the sunlight to warmth the area. As soon as it is winter in the northern Hemisphere, that is summer in the southerly Hemisphere.

EQUINOXHalfway between the 2 solstices, the Sun’s rays shine most straight at the equator, referred to as an “equinox.” The daylight and also nighttime hours are precisely equal on one equinox. The autumnal equinox wake up on September 22 or 23 and also the vernal or feather equinox wake up March 21 or 22 in the north Hemisphere.


A solar eclipse occurs when the new moon passes directly in between the Earth and also the sunlight (Figure 24.23). This casts a shadow on the Earth and blocks our see of the Sun. A full solar eclipse occurs as soon as the Moon’s shadow completely blocks the sun (Figure 24.24). As soon as only a section of the sunlight is the end of view, it is dubbed a partial solar eclipse. Solar eclipses are rare occasions that usually only last a couple of minutes. The is because the Moon’s shadow just covers a very small area on Earth and Earth is transforming very rapidly. As the sunlight is spanned by the moon’s shadow, it will actually acquire cooler outside. Bird may begin to sing, and also stars will come to be visible in the sky. During a solar eclipse, the corona and also solar prominences deserve to be seen.

Figure 24.23: A solar eclipse.


A Lunar Eclipse

lunar eclipse occurs as soon as the complete moon moves with the shadow of the planet (Figure 24.25). This have the right to only take place when the earth is between the Moon and also the Sun and also all three room lined up in the very same plane, called the ecliptic. The ecliptic is the airplane of Earth’s orbit around the Sun. The Earth’s shadow has two unique parts: the umbra and the penumbra. The umbra is the inner, cone shaped component of the shadow, in which every one of the light has been blocked. The outer part of Earth’s zero is the penumbra where only part of the irradiate is blocked. In the penumbra, the irradiate is dimmed but not completely absent. A complete lunar eclipse occurs as soon as the Moon travels completely in Earth’s umbra. During a partial lunar eclipse, just a portion of the Moon enters earth’s umbra. A penumbral eclipse happens once the Moon passes through Earth’s penumbra. The Earth’s shadow is rather large, for this reason a lunar eclipse lasts for hours and also can be seen by anyone v a view of the Moon at the moment of the eclipse.

Partial lunar eclipses happen at least twice a year, yet total lunar eclipses are less common. The next full lunar eclipse will occur December 21, 2010. The moon glows with a dull red coloring during a total lunar eclipse.

The Phases of the Moon

The Moon does no produce any kind of light the its own—it only reflects light from the Sun. As the Moon moves roughly the Earth, we see various parts the the near side the the Moon illuminated by the Sun. This reasons the transforms in the shape of the Moon that we notice on a constant basis, called the phases the the Moon. Together the Moon revolves approximately Earth, the illuminated part of the near side that the Moon will readjust from completely lit to totally dark and back again.

A full moon is the lunar phase seen once the totality of the Moon’s lit side is dealing with Earth. This step happens when planet is between the Moon and also the Sun. About one mainly later, the Moon start the quarter-moon phase. In ~ this point, the Moon shows up as a half-circle, since only fifty percent of the Moon’s lit surface ar is clearly shows from Earth. Once the Moon moves in between Earth and the Sun, the next facing earth is completely dark. This is called the brand-new moon phase, and we do not generally see the Moon at this point. Sometimes you deserve to just barely make out the rundown of the new moon in the sky. This is due to the fact that some sunlight mirrors off the Earth and hits the moon. Before and also after the quarter-moon phases space the gibbous and crescent phases. During the gibbous moon phase, the moon is an ext than fifty percent lit however not full. During the crescent moon phase, the moon is much less than fifty percent lit and is checked out as just a sliver or crescent shape. That takes around 29.5 days because that the Moon to revolve around Earth and also go with all the phases (Figure 24.26).

The Tides

Tides are the constant rising and also falling the Earth’s surface ar water in response to gravitational attraction native the Moon and Sun. The Moon’s gravity causes the oceans to bulge the end in the direction that the Moon. In various other words, the Moon’s heaviness is pulling upwards on Earth’s water, developing a high tide. ~ above the other side the the Earth, over there is an additional high birds area, developed where the Moon’s traction is weakest. As the earth rotates top top its axis, the locations directly in line with the Moon will endure high tides. Each location on planet experiences transforms in the elevation of the water transparent the day together it changes from high birds to short tide. There are two high tides and also two low tides each tidal day. Figure 24.27 and also Figure 24.28 will aid you far better understand just how tides work.

The first picture mirrors what is referred to as a spring tide. Confusingly, this tide has nothing to carry out with the season “Spring”, but way that the birds waters seem to spring forth. Throughout a spring tide, the Sun and also Moon space in line. This wake up at both the brand-new moon and the full moon. The Sun’s gravity pulls on Earth’s water, while the Moon’s gravity pulls ~ above the water in the same places. The high tide created by sun adds to the high tide produced by the Moon. So spring tides have higher than common high tides. This water is displayed on the photo as the gray bulges top top opposite political parties of the Earth. An alert that perpendicular to the gray areas, the water is at a reasonably low level. The locations where the water is being pulled out endure high tides, if the areas perpendicular come them suffer low tides. Since the planet is rotating top top its axis, the high-low birds cycle moves approximately the globe in a 24-hour period.

The 2nd picture reflects a neap tide. A neap tide occurs once the Earth and Sun space in line yet the Moon is perpendicular come the Earth. This happens as soon as the moon is at first or last quarter moon phase. In this case, the pull of gravity from the Sun partially cancels out the pull of heaviness from the Moon, and also the tides are much less pronounced. Neap tides develop less too much tides than the common tides. This is because the high tide produced by the sun adds to the low birds area the the Moon and vice versa. For this reason high tide is no as high and also low tide is no as low as it usually could be.

Lesson Summary

As the earth rotates top top its axis and revolves around the Sun, several different effects space produced.When the brand-new moon comes in between the Earth and the sun along the ecliptic, a solar eclipse is produced.When the planet comes in between the complete moon and also the sunlight along the ecliptic, a lunar eclipse occurs.Observing the Moon native Earth, we view a sequence of phases together the side facing us walk from totally darkened to completely illuminated and earlier again once every 29.5 days.Also as the Moon orbits Earth, the produces tides aligned v the gravitational pull of the Moon.The Sun likewise produces a smaller sized solar tide. Once the solar and also lunar birds align, at brand-new and full moons, we experience greater than common tidal ranges, called spring tides.At an initial and last quarter moons, the solar tide and also lunar birds interfere v each other, producing lower than normal tidal ranges referred to as neap tides.

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Review Questions

The world is separated into time zones, therefore that any type of given hour the the job in one time zone occurs at a different time in other time zones. For example, new York City is in one time zone and also Los Angeles is in an additional time zone. Once it is 8 am in new York City, that is just 5 to be in Los Angeles. Define how Earth’s motions cause this difference in times.Explain how Earth’s tilt top top its axis account for seasons on Earth.Explain exactly how the location of the Earth, Moon, and also Sun vary throughout a solar eclipse and a lunar eclipse.Draw a snapshot that shows exactly how the Earth, Moon, and Sun space lined up throughout the new moon phase.Why room neap tides less excessive than feather tides?


crescentPhase the the moon once it is less than half full but still contempt lit.gibbousPhase that the moon as soon as it is an ext than fifty percent lit however not totally full.lunar eclipseAn eclipse that occurs once the Moon moves through the zero of the Earth and is clogged from view.neap tideType that tide occasion when the Sun and Earth room in line and also the Moon is perpendicular come the Earth.penumbraOuter component of shadow the remains partly lit throughout an eclipseOccurs when moon overcome directly in between the Earth and Sun; the Moon’s shadow block the sun from view.spring tideAn excessive tide occasion that happens when the Earth, Moon, and the Sun space aligned; happens at complete and new moon phases.tideThe regular rising and also falling that Earth’s surface ar waters twice a tidal day as a result of the Moon’s and also Sun’s gravitational attraction.umbraInner cone shaped part of a shadow as soon as all light is blocked during an eclipse.

Points to Consider

Why don’t eclipses happen every solitary month in ~ the full and new moons?The earth Mars has a tilt the is very similar to Earth’s. What does this develop on Mars?Venus comes in between the Earth and the Sun. Why don’t we see an eclipse once this happens?