EARTH SCIENCE geology, the environment, and the universe 2008 (28)

Beyond Earth Chapter 27 The Sun-Earth-Moon System BIG Idea The Sun, Earth, and the Moon form a dynamic system that influences all life on Earth Chapter 28 Our Solar System BIG Idea Using the laws of motion and gravitation, astronomers can understand the orbits and the properties of the planets and other objects in the solar system Chapter 29 Stars BIG Idea The life cycle of every star is determined by its mass, luminosity, magnitude, temperature, and composition Chapter 30 Galaxies and the Universe BIG Idea Observations of galaxy expansion, cosmic background radiation, and the Big Bang theory describe an expanding universe that is 13.7 billion years old 760 CAREERS IN EARTH SCIENCE Astronaut This astronaut is working in the space lab While in space, astronauts perform various experiments in the lab, as well as collecting data and samples from space Earth Science Visit glencoe.com to learn more about astronauts Write a help wanted ad to recruit astronauts for a mission to another planet To learn more about astronauts, visit glencoe.com Unit • Beyond Earth 761 NASA/JSC Digital Image Collection The Sun-Earth-Moon System UV image of the Sun BIG Idea The Sun, Earth, and the Moon form a dynamic system that influences all life on Earth 27.1 Tools of Astronomy MAIN Idea Radiation emitted or reflected by distant objects allows scientists to study the universe 27.2 The Moon MAIN Idea The Moon, Earth’s nearest neighbor in space, is unique among the moons in our solar system 27.3 The Sun-Earth-Moon System MAIN Idea Motions of the Sun-Earth-Moon system define Earth’s day, month, and year GeoFacts • The volume of the Sun equals 1.3 million Earths • Earth is × 106 km closer to the Sun in January than it is in July • Finding water on the Moon might make permanent lunar bases possible False-color X-ray image of the Sun 762 (t)NASA/JPL-Caltech/CORBIS, (b)NASA/Photo Researchers, Inc., (bkgd)Craig Aurness/CORBIS Start-Up Activities Phases of the Moon Make the following Foldable to help you learn about the major phases of the Moon LAUNCH Lab How can the Sun-Earth-Moon system be modeled? The Sun is about 109 times larger in diameter than Earth, and Earth is about 3.7 times larger in diameter than the Moon The distance between Earth and the Moon is 30 times Earth’s diameter The Sun is 390 times farther from Earth than is the Moon Procedure Read and complete the lab safety form Calculate the diameters of Earth and the Sun using a scale in which the Moon’s diameter is equal to cm Using this scale, calculate the distances between Earth and the Moon and Earth and the Sun Cut out paper circles to represent your scaled Earth and Moon, and place them at the scaled distance apart Analysis Compare the diameters of your cutout Earth and Moon to the distance between them Infer why your model does not have a scaled Sun placed at the scaled Sun distance Visit glencoe.com to study entire chapters online; explore • Interactive Time Lines • Interactive Figures • Interactive Tables animations: STEP Fold four sheets of paper in half from top to bottom On two sheets of paper, make 3-cm cuts along the fold toward the center on each side STEP STEP Cut a slit approximately 16 cm long along the fold line in the remaining two sheets of paper Slip the first two sheets through the slit in the second two sheets to make a 16-page booklet STEP FOLDABLES Use this Foldable with Section 27.3 Draw each major phase of the Moon in order on the bottom pages of your Foldable Indicate the positions of the Sun, the Moon, and Earth Include a sketch of how the Moon appears from Earth during that phase As you turn the pages of your completed book, you will see how the Moon appears to change shape and position Take notes on the top pages access Web Links for more information, projects, and activities; review content with the Interactive Tutor and take Self-Check Quizzes Chapter Section 27 •1The • XXXXXXXXXXXXXXXXXX Sun-Earth-Moon System 763 Section 7.1 Tools of Astronomy Objectives ◗ Define electromagnetic radiation ◗ Explain how telescopes work ◗ Describe how space exploration helps scientists learn about the universe MAIN Idea Radiation emitted or reflected by distant objects allows scientists to study the universe Real-World Reading Link Have you ever used a magnifying lens to read fine print? If so, you have used a tool that gathers and focuses light Scientists use telescopes to gather and focus light from distant objects Review Vocabulary refraction: occurs when a light ray changes direction as it passes from one material into another Radiation The radiation from distant bodies throughout the universe that scientists study is called electromagnetic radiation Electromagnetic radiation consists of electric and magnetic disturbances traveling through space as waves Electromagnetic radiation includes visible light, infrared and ultraviolet radiation, radio waves, microwaves, X rays, and gamma rays You might be familiar with some forms of electromagnetic radiation For example, overexposure to ultraviolet waves can cause sunburn, microwaves heat your food, and X rays help doctors diagnose and treat patients All types of electromagnetic radiation, arranged according to wavelength and frequency, form the electromagnetic spectrum, shown in Figure 27.1 New Vocabulary electromagnetic spectrum refracting telescope reflecting telescope interferometry Wavelength and frequency Electromagnetic radiation is classified by wavelength—the distance between peaks on a wave Notice in Figure 27.1 that red light has a longer wavelength than blue light, and radio waves have a much longer wavelength than gamma rays Electromagnetic radiation is also classified according to frequency, the number of waves or oscillations that pass a given point per second The visible light portion of the spectrum has frequencies ranging from red to violet, or 4.3 × 1014 to 7.5 × 1014 Hertz (Hz)—a unit equal to one cycle per second ■ Figure 27.1 The electromagnetic spectrum identifies the different radiation frequencies and wavelengths Increasing frequency, f (Hz) 102 104 106 Radio waves (low f, long ) AM 106 104 108 1010 1012 1014 Microwave FM TV 102 1016 Infrared 1018 Ultraviolet 1020 X rays 10 Decreasing wavelength, (m) 764 Chapter 27 • The Sun-Earth-Moon System (bl)George Diebold, (bc)Royalty-Free/CORBIS, (br)Michael Nichols/National Geographic Image Collection 10 Visible light 10 10 1024 Gamma rays (high f, short ) Radar 10 1022 10 10 12 10 14 (tl)NOAO/AURA/NSF, (tc)Roger Ressmeyer/CORBIS, (tr)Paul Shambroom/Photo Researchers, Inc Pinwheel galaxy Mayall 4-m telescope Mayall Observatory ■ Figure 27.2 This photo of the Pinwheel galaxy was taken by the Mayall 4-m telescope, shown with its observatory Frequency is related to wavelength by the mathematical relationship c = λf, where c is the speed of light (3.0 × 108 m/s), λ is the wavelength, and f is the frequency Note that all types of electromagnetic radiation travel at the speed of light in a vacuum Astronomers choose their tools based on the type of radiation they wish to study For example, to see stars forming in interstellar clouds, they use special telescopes that are sensitive to infrared wavelengths, and to view remnants of supernovas, they often use telescopes that are sensitive to UV, X-ray, and radio wavelengths Telescopes Objects in space emit radiation in all portions of the electromagnetic spectrum Telescopes, such as the one shown in Figure 27.2, give us the ability to observe wavelengths beyond what the human eye can detect In addition, a telescope collects more electromagnetic radiation from distant objects and focuses it so that an image of the object can be recorded The pupil of a typical human eye has a diameter of up to mm when it is adapted to darkness; a telescope’s opening, which is called its aperture, might be as large as 10 m in diameter Larger apertures can collect more electromagnetic radiation, making dim objects in the sky appear much brighter Careers In Earth Science Space Engineer Space engineers design and monitor probes used to explore space Engineers often design probes to collect information and samples from objects in the solar system They also study the data collected To learn more about Earth science careers, visit glencoe.com Reading Check Name two benefits of using a telescope Another way that telescopes surpass the human eye in collecting electromagnetic radiation is with the aid of cameras, or other imaging devices, to create time exposures The human eye responds to visible light within one-tenth of a second, so objects too dim to be perceived in that time cannot be seen Telescopes can collect light over periods of minutes or hours In this way telescopes can detect objects that are too faint for the human eye to see Also, astronomers can add specialized equipment A photo– meter, for example, measures the intensity of visible light and a spectrophotometer displays the different wavelengths of radiation To read about new telescopes scientists are using to study space, go to the National Geographic Expedition on page 934 Section • Tools of Astronomy 765 Refracting telescope Reflecting telescope Eyepiece lens Focal point Eyepiece lens Focal point Objective mirror Convex lens Flat mirror ■ Figure 27.3 Refracting telescopes use a lens to collect light Reflecting telescopes use a mirror to collect light Foca l leng th Refracting and reflecting telescopes Two different types of telescopes are used to focus visible light The first telescopes, invented around 1600, used lenses to bring visible light to a focus and are called refracting telescopes, or refractors The largest lens on such telescopes is called the objective lens In 1668, a new telescope that used mirrors to focus light was designed Telescopes that bring visible light to a focus with mirrors are called reflecting telescopes, or reflectors Figure 27.3 illustrates how simple refracting and reflecting telescopes work Telescope technology has changed over time, as shown in Figure 27.4 Although both refracting and reflecting telescopes are still in use today, the majority of telescopes are reflectors because mirrors can be made larger than lenses and can collect more light Reading Check Compare refracting and reflecting telescopes Most telescopes used for scientific study are located in observatories far from city lights, usually at high elevations where there is less atmosphere overhead to blur images Some of the best observatory sites in the world are located high atop mountains in the southwestern United States, along the peaks of the Andes mountain range in Chile, and on the summit of Mauna Kea, a volcano on the island of Hawaii ■ Figure 27.4 Development of Astronomy Humanity’s curiosity about the night sky was limited to Earth-bound explorations until the first probe was sent into space in 1957 38,000 B.C Cro-Magnon people sketch moon phases on tools made out of bones 766 1054 Chinese astronomers document the explosion of the supernova that creates the Crab nebula, believing it foretells the arrival of a wealthy visitor to the emperor 410 B.C The first prophecies based on the positions of the five visible planets, the Moon, and the Sun were written for individuals in Mesopotamia 4236 B.C After lunar and solar calendars predict agricultural seasons, Egyptians adopt a 365-day calendar based on the movement of the star Sirius Chapter 27 • The Sun-Earth-Moon System (bcr)Russell Croman/Photo Researchers, Inc., (br)Hemera Technologies/Alamy A.D 900s Arab astronomers greatly improve the accuracy of the Greek astrolabe — a tool for celestial navigation that determines time and location Telescopes using non-visible wavelengths For all telescopes, the goal is to bring as much electromagnetic radiation as possible into focus Infrared and ultraviolet radiation can be focused by mirrors in a way similar to that used for visible light X rays cannot be focused by normal mirrors, and thus special designs must be used Gamma rays cannot be focused, so telescopes designed to detect this type of radiation can determine only the direction from which the rays come A radio telescope collects the longer wavelengths of radio waves with a large dish antenna, which resembles a satellite TV dish The dish plays the same role as the primary mirror in a reflecting telescope by reflecting radio waves to a point above the dish There, a receiver converts the radio waves into electric signals that can be stored in a computer for analysis The data are converted into visual images by a computer The resolution of the images produced can be improved using a process called interferometry, which is a technique that uses the images from several telescopes to produce a single image By combining the images from several telescopes, astronomers can create a highly detailed image that has the same resolution of one large telescope with a dish diameter as large as the distance between the two telescopes One example of this is the moveable telescopes shown in Figure 27.5 Both radio and optical telescopes can be linked this way ■ Figure 27.5 The Very Large Array is situated near Socorro, New Mexico The dish antennae of this radio telescope are mounted on tracks so they can be moved to improve resolution Space-Based Astronomy Astronomers often send instruments into space to collect information because Earth’s atmosphere interferes with most radiation It blurs visual images and absorbs infrared and ultraviolet radiation, X rays, and gamma rays Space-based telescopes allow astronomers to study radiation that would be blurred by our atmosphere American, European, Soviet, Russian, and Japanese space programs have launched many space-based observatories to collect data 1860s The invention of spectroscopy suggests that the celestial bodies are composed of some of the same elements that make up Earth’s atmosphere 1957 Russia launches the first two satellites into orbit around Earth, marking the beginning of space exploration 2004 A Mars rover discovers rock formations and sulfate salts indicating that the planet once had flowing water 1969 The U.S astronauts 1608 The telescope is invented allowing astronomers to discover planets, such as Uranus and Neptune, moons, and stars that are invisible to the naked eye become the first humans to walk on the Moon Interactive Time Line To learn more about these discoveries and others, visit glencoe.com Section • Tools of Astronomy 767 (tr)Roger Ressmeyer/CORBIS, (bl)Gustavo Tomsich/CORBIS, (bc)Science Museum/SSPL/The Image Works Spacecraft In addition to making observations from above Earth’s atmosphere, spacecraft can be sent directly to the bodies being observed Robotic probes are spacecraft that can make close-up observations and sometimes land to collect information directly Probes are practical only for objects within our solar system, because other stars are too far away In 2005, the Cassini spacecraft arrived at Saturn, where it went into orbit for a detailed look at its moons and rings; the Mars Reconnaissance Orbiter reached Mars in 2006 and began orbiting the red planet to use its high-resolution cameras to search for places where life might have evolved; and New Horizons was launched in 2006, on its way to Pluto and the region beyond New Horizons is armed with visible, infrared, and ultraviolet cameras, as well as equipment to measure magnetic fields Figure 27.6 The Hubble Space Telescope has been used to observe a comet crashing into Jupiter as well as to detect the farthest known galaxy ■ Table 27.1 Name Orbiting Telescopes Launch Wavelengths Studies Host Chandra 1999 X ray wide ranging NASA Newton 1999 X ray wide ranging, black holes ESA MAP 2001 microwave early universe NASA Integral 2002 X ray, gamma ray wide ranging, neutron stars ESA, Russia, NASA CHIPSat 2003 X ray interstellar plasma NASA Galex 2003 UV survey JPL, NASA MOST 2003 visible observe stars Canada Spitzer 2003 IR wide range NASA Swift 2004 X ray, UV, visible back holes NASA Suzaku 2005 X ray star-forming regions Japan Akari 2006 IR survey Japan 768 Chapter 27 • The Sun-Earth-Moon System NASA Hubble Space Telescope Orbiting Earth every 97 minutes, one of the best-known space-based observatories—the Hubble Space Telescope (HST)—shown in Figure 27.6, was launched in 1990 HST was designed to obtain sharp visible-light images without atmospheric interference, and also to make observations in infrared and ultraviolet wavelengths The James Webb Space Telescope is planned for 2013 It will only observe in the infrared range and is not a replacement for HST Some other space-based telescopes that observe in wavelengths that are blocked by Earth’s atmosphere are shown in Table 27.1 NASA/Photo Researchers, Inc Human spaceflight Before humans can safely explore space, scientists must learn about the effects of space, such as weightlessness and radiation The most recent human studies have been accomplished with the space shuttle program, which began in 1981 Shuttles are used to place and service satellites, such as the HST and the Chandra X-ray Telescope The space shuttle provides an environment for scientists to study the effects of weightlessness on humans, plants, the growth of crystals, and other phenomena However, because shuttle missions last a maximum of just 17 days, long-term effects must be studied in space stations A multicountry space station called the International Space Station, shown in Figure 27.7, is the ideal environment for studying the effects of space on humans Crews have lived aboard the International Space Station since 2000 The crew members conduct many different experiments in this weightless environment Spinoff technology Space-exploration programs not only benefit astronomers and space exploration, but they also benefit society Many technologies that were originally developed for use in space programs are now used by people throughout the world Did you know that the technology for the space shuttle’s fuel pumps led to the development of pumps used in artificial hearts? Or that the Apollo program that put humans on the Moon led to the development of cordless tools? In fact, more than 1400 different NASA technologies have been passed on to commercial industries for common use; these are called spinoffs Section 7.1 Figure 27.7 This view of the International Space Station was taken from the Space Shuttle Discovery The Caspian Sea is visible in the background Review What types of studies can be carried out in the space station? ■ Assessment Section Summary Understand Main Ideas ◗ Telescopes collect and focus electromagnetic radiation emitted or reflected from distant objects ◗ Electromagnetic radiation is classified by wavelength and frequency Report on how interferometry affects the images that are produced by telescopes ◗ The two main types of optical telescopes are refractors and reflectors Think Critically ◗ Space-based astronomy includes the study of orbiting telescopes, satellites, and probes ◗ Technology originally developed to explore space is now used by people on Earth MAIN Idea Explain how electromagnetic radiation helps scientists study the universe Distinguish between refracting and reflecting telescopes and how they work Examine the reasons why astronomers send telescopes and probes into space Assess the benefits of technology spinoffs to society Consider the advantages and disadvantages of using robotic probes to study distant objects in space MATH in Earth Science Calculate the wavelength of radiation with a frequency of 1012 Hz [Hint: Use the equation c = λf ] Self-Check Quiz glencoe.com Section • Tools of Astronomy 769 (cw from top)Jason Ware/Photo Researchers, Inc., (1)John Chumack/Photo Researchers, Inc., (3, 5, 7)John W Bova/Photo Researchers, Inc., (4)John Sanford/Photo Researchers, Inc., (6)Frank Zullo/Photo Researchers, Inc., (bl)Chris Cook/Photo Researchers, Inc., (br)Eyebyte/Alamy Visualizing the Phases of the Moon Figure 27.18 One-half of the Moon is always illuminated by the Sun’s light, but the entire lighted half is visible from Earth only at full moon The rest of the time you see portions of the lighted half These portions are called lunar phases View from Earth first quarter View from Earth waxing gibbous View from Earth waxing crescent Moon View from Earth full moon View from Earth new moon Light from the Sun View from Earth waning gibbous View from Earth waning crescent View from Earth third quarter Sometimes a dim image of the full moon is seen along with a crescent This is caused by Earth’s reflected light on the Moon’s surface It is often referred to as “the new moon with the old moon in its arms.” Because of the variations in the plane of the Moon’s orbit, the phases might appear different—either tipped, or misshapen To explore more about lunar phases, visit glencoe.com Section • The Sun-Earth-Moon System 779 Synchronous rotation You might have noticed that the surface features of the Moon always look the same As the Moon orbits Earth, the same side faces Earth at all times This is because the Moon rotates with a period equal to its orbital period, in other words, the Moon spins exactly once each time it goes around Earth This is no coincidence Scientists theorize that Earth’s gravity slowed the Moon’s original spin until the Moon reached synchronous rotation, the state at which its orbital and rotational periods are equal Lunar Motions The length of time it takes for the Moon to go through a complete cycle of phases, for example—from one new moon to the next—is called a lunar month The length of a lunar month is about 29.5 days This is longer than the 27.3 days it takes for one revolution, or orbit, around Earth, as illustrated in Figure 27.19 The Moon also rises and sets 50 minutes later each day because the Moon moves 13° in its orbit over a 24-hour period, and Earth has to turn an additional 13° for the Moon to rise A Earth New moon One complete lunar revolution (27.3 days) later B Sunlight C Earth One lunar month (29.5 days) later Additional distance the moon travels to the new moon phase Figure 27.19 As the Moon moves from A, where it is in the new moon phase as seen from Earth, to B, it completes one revolution but is now in the waning crescent phase as seen from Earth It must travel for 2.2 days to return to the new moon phase The Moon rotates as it revolves, keeping the same side facing Earth, as shown in the inset ■ 780 Chapter 27 • The Sun-Earth-Moon System Sun Moon Moon Earth Sun Earth Sun Tidal bulge large Tidal bulge large ■ Figure 27.20 Alignment of the Sun and the Moon produces the spring tides shown on the left Neap tides, shown on the right, occur when the Sun and the Moon are at right angles Tides One effect the Moon has on Earth is causing ocean tides The Moon’s gravity pulls on Earth along an imaginary line connecting Earth and the Moon, and this creates bulges of ocean water on both the near and far sides of Earth Earth’s rotation also contributes to the formation of tides, as you learned in Chapter 15 As Earth rotates, these bulges remain aligned with the Moon, so that a person at a shoreline on Earth’s surface would observe that the ocean level rises and falls every 12 hours Spring and neap tides The Sun’s gravitational pull also affects tides, but the Sun’s influence is half that of the Moon’s because the Sun is farther away However, when the Sun and the Moon are aligned along the same direction, their effects are combined, and tides are higher than normal These tides, called spring tides, are especially high when the Moon is nearest Earth and Earth is nearest the Sun in their slightly elliptical orbits When the Moon is at a right angle to the Sun-Earth line, the result is lower-than-normal tides, called neap tides The Sun and the Moon alignments during spring and neap tides are shown in Figure 27.20 ■ Figure 27.21 The stages of a total solar eclipse are seen in this multiple-exposure photograph Explain why the Moon seems to cross the Sun at an angle rather than directly right to left Solar Eclipses A solar eclipse occurs when the Moon passes directly between the Sun and Earth and blocks the Sun from view Although the Sun is much larger than the Moon, it is far enough away that they appear to be the same size when viewed from Earth When the Moon perfectly blocks the Sun’s disk, only the dim, outer gaseous layers of the Sun are visible This spectacular sight, shown in Figure 27.21, is called a total solar eclipse A partial solar eclipse is seen when the Moon blocks only a portion of the Sun’s disk Section • The Sun-Earth-Moon System 781 George Post/Science Photo Library/Photo Researchers Figure 27.22 During a solar eclipse, the Moon passes between Earth and the Sun Those on Earth within the darkest part of the Moon’s shadow (umbra) see a total eclipse Those within the lighter part, or penumbral shadow, see only a partial eclipse ■ Umbra Sun Moon Earth Interactive Figure To see an animation of an eclipse, visit glencoe.com Penumbra How solar eclipses occur Each object in the solar system creates a shadow as it blocks the path of the Sun’s light This shadow is totally dark directly behind the object and has a cone shape During a solar eclipse, the Moon casts a shadow on Earth as it passes between the Sun and Earth This shadow consists of two regions, as illustrated in Figure 27.22 The inner, cone-shaped portion, which blocks the direct sunlight, is called the umbra People who witness an eclipse from within the umbra shadow see a total solar eclipse That means they see the Moon completely cover the face of the Sun The outer portion of this shadow, where some of the Sun’s light still reaches, is called the penumbra People in the region of the penumbra shadow see a partial solar eclipse, where a part of the Sun’s disk is blocked by the Moon Typically, the umbral shadow is never wider than 270 km, so a total solar eclipse is visible from a very small portion of Earth, whereas a partial solar eclipse is visible from a much larger portion PROBLEM-SOLVING Lab Interpret Scientific Illustrations How can you predict how a solar eclipse will look to an observer at various positions? The diagram below shows the Moon eclipsing the Sun The Sun will appear differently to observers located at Points A through E Analysis Observe the points in relation to the posi- Think Critically Draw how the solar eclipse would appear to an observer at each labeled point Design a data table to display your drawings Classify the type of solar eclipse represented in each of your drawings tion of the Moon’s umbra and penumbra A Moon Sun 782 Chapter 27 • The Sun-Earth-Moon System B E C D Plane of Earth’s orbit Plane of the Moon’s orbit New Sun New Full 5º Full Unfavorable for eclipse Favorable for eclipse Figure 27.23 Eclipses can take place only when Earth, the Moon, and the Sun are perfectly aligned This can happen only when the Moon’s orbital plane and ecliptic plane intersect along the Sun-Earth line, as shown in diagram on the right In the left diagram, this does not happen, and the Moon’s shadow misses Earth ■ Effects of tilted orbits You might wonder why a solar eclipse does not occur every month when the Moon passes between the Sun and Earth during the new moon phase This does not happen because the Moon’s orbit is tilted 5° relative to the ecliptic plane Normally, the Moon passes above or below the Sun as seen from Earth, so no solar eclipse takes place Only when the Moon crosses the ecliptic plane is it possible for the proper alignment for a solar eclipse to occur, but even that does not guarantee a solar eclipse The plane of the Moon’s orbit also rotates slowly around Earth, and a solar eclipse occurs only when the intersection of the Moon and the ecliptic plane is in a line with the Sun and Earth, as Figure 27.23 illustrates Reading Check Determine why a total solar eclipse does not occur every month Annular eclipses Not only does the Moon move above and below the plane of Earth and the Sun, but the Moon’s distance from Earth increases and decreases as the Moon moves in its elliptical orbit around Earth The closest point in the Moon’s orbit to Earth is called perigee, and the farthest point is called apogee When the Moon is near apogee, it appears smaller from Earth, and thus will not completely block the disk of the Sun during an eclipse This is called an annular eclipse because, as Figure 27.24 shows, a ring of the Sun, called the annulus, appears around the dark Moon Earth’s orbit also has a perigee and apogee When Earth is nearest the Sun and the Moon is at apogee from Earth, the Moon would not block the Sun entirely The opposite is true for Earth at apogee to the Sun and the Moon at perigee to Earth ■ Figure 27.24 An annular eclipse takes place when the Moon is too far away for its umbral shadow to reach Earth A ring, or annulus, is left uncovered Predict Would annular eclipses occur if the Moon’s orbit were a perfect circle? Section • The Sun-Earth-Moon System 783 Fred Espenak/Photo Researchers, Inc Dennis di Cicco Penumbra Umbra Sun Moon Earth Figure 27.25 When the Moon is completely within Earth’s umbra, a total lunar eclipse takes place, as shown in the diagram The darkened Moon often has a reddish color, as shown in the photo, because Earth’s atmosphere bends and scatters the Sun’s light ■ Lunar Eclipses A lunar eclipse occurs when the Moon passes through Earth’s shadow As illustrated in Figure 27.25, this can happen only at the time of a full moon when the Moon is on the opposite side of Earth from the Sun The shadow of Earth has umbral and penumbral portions, just as the Moon’s shadow does A total lunar eclipse occurs when the entire Moon is within Earth’s umbra This lasts for approximately two hours During a total lunar eclipse, the Moon is faintly visible, as shown in Figure 27.25, because sunlight that has passed near Earth has been filtered and refracted by Earth’s atmosphere This light can give the eclipsed Moon a reddish color as Earth’s atmosphere bends the red light into the umbra, much like a lens Like solar eclipses, lunar eclipses not occur every full moon because the Moon in its orbit usually passes above or below the Sun as seen from Earth Section 7.3 Assessment Section Summary Understand Main Ideas ◗ Earth’s rotation defines one day, and Earth’s revolution around the Sun defines one year ◗ Seasons are caused by the tilt of Earth’s spin axis relative to the ecliptic plane Diagram the waxing and waning phases of the Moon ◗ The gravitational attraction of both the Sun and the Moon causes tides ◗ The Moon’s phases result from our view of its lighted side as it orbits Earth ◗ Solar and lunar eclipses occur when the Sun’s light is blocked 784 Chapter 27 • The Sun-Earth-Moon System MAIN Idea State one proof that Earth rotates, one proof Earth rotates in 24 hours, and make one observation that proves it revolves around the Sun in one year Compare solar and lunar eclipses, including the positions of the Sun, Earth, and Moon Analyze why the Moon has a greater effect on Earth’s tides than the Sun, even though the Sun is more massive Think Critically Relate what you have learned about lunar phases to how Earth would appear to an observer on the Moon Diagram the positions of the Sun, Earth, and the Moon and draw how Earth would appear in several positions to explain your answer MATH in Earth Science Consider what would happen if Earth’s axis were tilted 45º At what latitudes would the Sun be directly overhead on the solstices and the equinoxes? Self-Check Quiz glencoe.com eXpeditions! ON SITE: Living in Space n orbiting space shuttle and everyAthing aboard it, including the astronauts, are falling continuously around Earth The result is apparent weightlessness — they experience microgravity conditions Performing everyday tasks, such as sleeping and exercising, is challenging in microgravity What would it be like to float in space? Disorientation Some astronauts experience space sickness during the first few days in microgravity This happens because the brain is confused by the mismatched visual, sensory, and pressure messages that it receives To help their bodies prepare for microgravity, astronauts train in special airplanes where they experience short periods of free-fall weightlessness Once sensory systems have adjusted to microgravity, space sickness subsides Sleeping How would you sleep without gravity to keep you in bed? Astronauts on the orbiting space shuttle and the International Space Station spend about eight hours a day sleeping Although astronauts can sleep in any orientation they prefer, they must be anchored to something — a wall, a seat, or a bed This prevents them from floating and bumping into other things while they sleep, which might harm them as well as other astronauts and equipment Figure 1: These astronauts are working in microgravity Notice the footholds and handholds they use to stay in place Exercising In orbit, exercising is particularly important to the overall health of astronauts On Earth, muscles work against the force of gravity to move, maintain balance, and support our bodies In microgravity, muscles are underused and begin to atrophy, or lose tone and mass Supporting the weight of the body on Earth is one of the functions of bones Scientists know that gravity is important in the process of bone maintenance and formation In microgravity, bone formation is disrupted and bones lose important minerals Without proper amounts of these minerals, bones become weaker and the risk of fracture increases Astronauts exercise each day while in space while strapped to exercise equipment nce Earth Scie to interre going a u o y se ed from Suppo as return h Interview o h w t at stronau le Write view an a aper artic sp ow h w t e u n o a b ions a st e space for u q w ody and intervie human b e least five th ts c e Be sure vity aff day tasks ry microgra e v s e f o stronaut’ letion out the a b the comp a t s u n o io b ore a e quest o learn m T to includ s e c n e experi com personal it glencoe is v l, e v a space tr National Geographic Expeditions 785 NASA MAPPING: DETERMINE RELATIVE AGES OF LUNAR FEATURES Background: Recall from Chapter 21 that an intru- Analyze and Conclude sion or a fault can cut across an older geologic feature This principle of crosscutting relationships is also used to determine the relative ages of surface features on the Moon By observing which features cut across others, you can infer which features are older and which are younger Summarize the problems you had in identifying and choosing the ages of the features Select Based on information from all the photos, what features are usually the oldest? The youngest? Explain whether scientists could use this process to determine the exact age difference between two overlapping craters Why or why not? Identify the relative-age dating that scientists use to analyze craters on Earth Evaluate If the small crater in Photo 2, labeled A, is 44 km across, what is the scale for that photo? At that scale, what is the size of the large crater labeled F? Judge Which would be older, a crater that had rays crossing it, or the crater that caused the rays? Explain Estimate If the crater labeled A in Photo is 17 km across, how long is the chain of craters in the photo? Infer What might have caused the chain of craters in Photo 1? Question: How can you use images of the Moon to interpret relative ages of lunar features? Materials paper metric ruler Procedure Read and complete the lab safety form Review the information about the history of the Moon and the lunar surface starting on page 772 Observe Photo and identify the older of the craters in the crater Pairs A-D and C-B using the principle of crosscutting relationships Observe Photo Identify and list the features in order of their relative ages Observe Photo Identify the mare, rille, and craters Then list the features in order of their relative ages Observe Photo Identify the features using your knowledge of crosscutting relationships and lunar history Then list the features in order of their relative ages Earth Science Guidebook Using what you learned in this lab, prepare a guidebook that contains instructions for identifying and determining relative ages of lunar features For more information on lunar features, visit glencoe.com 786 GeoLab D A C B A D F E C B C A D B B D C E A GeoLab 787 NASA Download quizzes, key terms, and flash cards from glencoe.com BIG Idea The Sun, Earth, and the Moon form a dynamic system that influences all life on Earth Vocabulary Key Concepts Section 27.1 Tools of Astronomy • • • • electromagnetic spectrum (p 764) interferometry (p 767) reflecting telescope (p 766) refracting telescope (p 766) MAIN Idea • • • • • Radiation emitted or reflected by distant objects allows scientists to study the universe Telescopes collect and focus electromagnetic radiation emitted or reflected from distant objects Electromagnetic radiation is classified by wavelength and frequency The two main types of optical telescopes are refractors and reflectors Space-based astronomy includes the study of orbiting telescopes, satellites, and probes Technology originally developed to explore space is now used by people on Earth Section 27.2 The Moon • • • • • • • • albedo (p 771) ejecta (p 771) highland (p 771) impact crater (p 771) mare (p 771) ray (p 771) regolith (p 772) rille (p 771) MAIN Idea The Moon, Earth’s nearest neighbor in space, is unique among the moons in our solar system • Astronomers have gathered information about the Moon using telescopes, space probes, and astronaut exploration • Like Earth’s crust, the Moon’s crust is composed mostly of silicates • Surface features on the Moon include highlands, maria, ejecta, rays, and rilles It is heavily cratered • The Moon probably formed about 4.5 bya in a collision between Earth and a Mars-size object Section 27.3 The Sun-Earth-Moon System • • • • • • • • apogee (p 783) ecliptic plane (p 776) equinox (p 777) lunar eclipse (p 784) perigee (p 783) solar eclipse (p 781) solstice (p 777) synchronous rotation (p 780) MAIN Idea • • • • • 788 Chapter 27 • Study Guide Motions of the Sun-Earth-Moon system define Earth’s day, month, and year Earth’s rotation defines one day, and Earth’s revolution around the Sun defines one year Seasons are caused by the tilt of Earth’s spin axis relative to the ecliptic plane The gravitational attraction of both the Sun and the Moon causes tides The Moon’s phases result from our view of its lighted side as it orbits Earth Solar and lunar eclipses occur when the Sun’s light is blocked Vocabulary PuzzleMaker glencoe.com Vocabulary PuzzleMaker biologygmh.com Vocabulary Review Use the diagram below to answer Questions 11 and 12 Fill in the blanks with the correct vocabulary term from the Study Guide Linking telescopes to improve the detail in the images obtained is called Sun A technology originally developed for space exploration but now used in everyday life is known as a(n) A(n) can take place only when the Moon is in the new moon phase Each of the following sentences is false Make each sentence true by replacing the italicized words with vocabulary terms from the Study Guide The Moon’s perigee is the amount of sunlight that its surface reflects The far side of the Moon has many more maria than the near side Interferometry explains why the same side of the Moon is always visible from Earth Match each description below with the correct vocabulary term from the Study Guide a device that uses a mirror to collect light from distant objects the point in the Moon’s orbit when it is farthest from Earth loose, ground-up rock, such as the layer covering much of the surface of the Moon Understand Key Concepts 10 Which is the highest point in the sky that the Sun reaches on a given day? A ecliptic B solstice C tropic D zenith Chapter Test glencoe.com 11 In the diagram above, which season is it in the northern hemisphere? A autumn B spring C summer D winter 12 When Earth is in the position shown in the diagram, at which place on Earth is the Sun most likely to be directly overhead? A Arctic Circle B equator C Tropic of Cancer D Tropic of Capricorn 13 Which type of electromagnetic radiation has a longer wavelength than visible light? A gamma ray B X ray C radio wave D ultraviolet ray 14 Which geographic feature on the Moon is the oldest? A craters B highlands C maria D regolith 15 What is the mineral composition of most moon rocks? A basalts containing water B feldspar with high iron content C sedimentary breccias D silicates Chapter 27 • Assessment 789 Use the diagram below to answer Questions 16 and 17 20 Distinguish between rays and rilles, including where they are found and how they are formed on the Moon A 21 Summarize the ways in which Earth’s Moon is unusual among all the moons in the solar system B D 22 Assess the advantages of human missions compared with using robotic spacecraft to explore space C 16 Which area of the Moon is physically molten? A core B lower mantle C upper mantle D crust Think Critically Use the illustration below to answer Question 23 17 Which area of the Moon is probably solid iron? A core B lower mantle C upper mantle D crust Constructed Response 18 Describe the advantages of placing telescopes in space Use the illustration below to answer Question 19 23 Draw a diagram similar to the one above to illustrate ocean tides that are not neap or spring 24 Infer Why are lunar breccias not sedimentary like most breccias found on Earth? 25 Contrast the geological history of maria with that of the highlands 26 Consider What would seasons be like if Earth were not tilted on its axis? 27 Draw a diagram showing the altitude of the Sun at summer solstice viewed from a position of 40° north latitude 19 Identify What part of the lunar surface is most likely shown in this photograph? 790 Chapter 27 • Assessment PhotoDisc 28 Infer Would ocean tides exist if Earth had no moon? If so, describe what they would be like Chapter Test glencoe.com Use the illustration below to answer Questions 29 and 30 Additional Assessment 35 Light from the Sun Moon Earth Science Imagine that you are the science officer on a scouting mission from another planet You just observed the impact that formed Earth’s Moon Write a report describing the event Earth Document–Based Questions Earth 29 List the types of shadows as well as the types of eclipses that will be seen by an observer on the unlit side of Earth 30 Infer the view of the Sun from the Moon in each of the situations above 31 Appraise Based on what you know about how maria formed, where would you expect to find the highest concentration of iron? 32 Compare and Contrast the Moon’s interior structure in Figure 27.11 with Earth’s interior structure in Figure 1.3 Concept Mapping 33 Create a concept map using the following terms: Moon, albedo, Earth, phases, impact theory, highlands, maria, rilles, craters, rays, breccia, and regolith Refer to the Skillbuilder Handbook for more information Challenge Question 34 Describe the interrelationship between the Sun, Earth, and the Moon regarding tides and eclipses Chapter Test glencoe.com Bone loss in the lower extremities and spine is a serious problem for astronauts who spend long periods in microgravity The data below shows the percent loss of bone mineral per month from 13 crew members of the International Space Station Bone-Density Decrease in Astronauts Percent change in density Light from the Sun Moon Data obtained from: T Lang, et al 2004 Cortical and trabecular bone mineral loss from the spine and hip in long-duration spaceflight Journal of Bone and Mineral Research 19 (6) 2.5 2.0 1.5 1.0 0.5 0.0 Spongy Compact Spine bone Average Spongy Compact Hip bone 36 Evaluate which body area showed the highest overall rate of bone loss 37 Compare bone loss of the two types of bone in the hip Which has the highest rate of loss? By how much? Cumulative Review 38 What is the source of CFCs and how CFCs cause ozone depletion? (Chapter 26) 39 What are the most common minerals in granite? In basalt? (Chapter 5) Chapter 27 • Assessment 791 Standardized Test Practice Multiple Choice Which is not considered a renewable resource? A brick B stone C copper D wood What is debris from an impact that falls back to the surface of the Moon called? A rilles C ejecta B maria D albedo Use the illustrations below to answer Questions to Use the geologic cross section below to answer Questions and Map of Brownsville County Forest Urban area Shale Sandstone Volcanic ash Limestone Fault Assuming the rock layers shown are in the same orientation that they were deposited, which layer is the oldest? A shale B sandstone C volcanic ash D limestone Which layer would be most helpful in determining the absolute age of these rocks? A shale B sandstone C volcanic ash D limestone Which fossil fuel was originally known as rock oil? A petroleum B natural gas C coal D oil shale In which process does the weight of a subducting plate help pull the trailing lithosphere into a subduction zone? A slab pull B ridge pull C slab push D ridge push 792 Chapter 27 • Assessment Rural area Farm Which area of Brownsville is most likely to have problems with flooding during heavy rains? A I C III B II D IV If Brownsville County decided to clear area I in order to expand area III, Brownsville might develop problems with topsoil erosion and pesticide pollution What might be one way to minimize harmful effects? A deforestation B clear-cutting C monoculture D selective logging What will happen if the size of Brownsville’s human population reaches the carrying capacity for its environment? A There will be more births than deaths B The death rate will increase and the birth rate will increase C The population will reach equilibrium D The death rate will increase and the birth rate will decrease 10 The Marianas Islands in the Pacific Ocean were formed by volcanic action Which is a TRUE statement? A There are glaciers near the Marianas Islands B Tectonic plates collide near the Marianas Islands C The Marianas Islands are larger than most islands D The Marianas Islands are uninhabited Standardized Test Practice glencoe.com Reading for Comprehension Short Answer Use the diagram below to answer Questions 11 to 13 Space Observatories Present time Why put observatories in space? Most telescopes are on the ground where you can deploy a heavier telescope and fix it more easily The trouble is that earthbound telescopes must look through the Earth’s atmosphere which blocks out a broad range of the electromagnetic spectrum, allowing a narrow band of visible light to reach the surface Telescopes that explore the universe using light beyond the visible spectrum, such as those onboard the CHANDRA X-Ray Observatory need to be carried above the absorbing atmosphere The Earth’s atmosphere also blurs the light it lets through The blurring is caused by varying density and continual motion of air By orbiting above Earth’s atmosphere, the Hubble Space Telescope gets clearer images an s tile s Ma m ma ls Mesozoic ph ibi Re p Geologic time Bir d s Cenozoic Fis h Am Paleozoic 11 If a wider bar represents more species of that type of organism, explain the change in diversity of amphibians from their introduction to present time Article obtained from: Astronomy picture of the day Hubble Floats Free NASA November 24, 2002 (Online resource accessed October 17, 2006.) 17 What is a benefit of earthbound telescopes? A They can be larger and are more easily fixed B They are able to capture the entire electromagnetic spectrum C They can use larger mirrors D They can capture the visible light reaching Earth’s surface 12 What can be inferred about the conditions on Earth for living things from the Cenozoic Era to present time? 13 How might the idea that oceans developed before land be supported by looking at this diagram? 18 What can be inferred from this passage? A earthbound telescopes have no benefits for scientific study B Using telescopes outside the Earth’s atmosphere produces the clearest pictures C The Hubble Space Telescope needs to have larger mirrors to take better pictures D It is impossible to fix telescopes orbiting outside Earth’s atmosphere 14 How does passive solar heating differ from active solar heating? 15 Why is improving the energy efficiency of automobiles important? 16 What two major flaws did scientists of Wegener’s day cite as reasons to reject his hypothesis of continental drift? NEED EXTRA HELP? If You Missed Question Review Section 10 11 12 13 14 15 16 24.1 21.2 21.3 25.1 17.4 27.2 26.2 26.2 26.1 17.3 23.1 23.3 23.1 25.2 25.3 17.1 Standardized Test Practice glencoe.com Chapter 27 • Assessment 793 ... Calculate the diameters of Earth and the Sun using a scale in which the Moon’s diameter is equal to cm Using this scale, calculate the distances between Earth and the Moon and Earth and the Sun... perigee and apogee When Earth is nearest the Sun and the Moon is at apogee from Earth, the Moon would not block the Sun entirely The opposite is true for Earth at apogee to the Sun and the Moon... only does the Moon move above and below the plane of Earth and the Sun, but the Moon’s distance from Earth increases and decreases as the Moon moves in its elliptical orbit around Earth The closest