GenreGenre Comprehension SkillComprehension Skill Text FeaturesText Features Science ContentScience Content NonfictionNonfiction SequenceSequence • Captions• Captions Day and Night SkyDay and Night Sky • Labels• Labels • Diagrams• Diagrams • Glossary• Glossary Scott Foresman Science 3.15Scott Foresman Science 3.15 ì<(sk$m)=bdifbh<ì<(sk$m)=bdifbh<ISBNISBN 0-328-13851-70-328-13851-7 +^-Ä-U-Ä-U+^-Ä-U-Ä-U
Vocabulary What did you learn? axis constellation 1. How do telescopes work? lunar eclipse phase 2. Why can’t we see the new moon? revolution rotation 3. Which star can be used to help star people find their way? Why? telescope 4. In this book you have read about manyby Sasha Griffin patterns. Write to explain how Earth’s movement around the Sun creates seasons. Use examples from the book. 5. Sequence Shadows are created Picture Credits when an object blocks sunlight. Every effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions. Describe how a shadow changes Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd). 1 Getty Images; 2 Brand X Pictures; 4 Brand X Pictures; 5 Brand X Pictures; 10 (TL) Brand X Pictures, (TR) Brooks between morning and evening. Kraft/Corbis; 11 (TR) Pedro Luz Cunha/Alamy Images; 12 (T, B, CL, CR) Getty Images; 13 Getty Images; 14 (TL, TR) Getty Images; 15 (TL, TR) Getty Images. Scott Foresman/Dorling Kindersley would also like to thank: 19 (CA) NASA/DK Images. Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson. ISBN: 0-328-13851-7 Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05
Daily Patterns Day and Night During the day there is light. At night it is Only half of Earth’s round surface faces the dark. This is a pattern that repeats all the time. Sun at any one time. The part facing the Sun is lit The causes of this pattern are the movement of by sunlight. The other half of Earth is dark since Earth and sunlight. it faces away from the Sun. The Sun and Earth To us, it looks like the Sun is moving across the sky. However, it is really Earth that is moving. The Sun is always in the sky. It is there during the day, at night, and in all kinds of weather. The Sun is a star. It is a round, glowing ball of hot gases. It gives light and heat to Earth. Earth is also round like the Sun, but much smaller. It does not make its own light. Earth needs light from the Sun. This photograph of Earth lit by the Sun was taken by Apollo astronauts from the surface of the Moon. 2 3
The Sun Suppose that Earth is a ball of clay, with Earth Axis a pencil running through its center from the top to the bottom. Spin the pencil. Then you can get an idea of how Earth spins around its axis. Earth’s axis is an imaginary line that runs through the planet. It passes through the North Pole and the South Pole. Earth spins around its tilted axis. It turns counterclockwise from west to east. It takes 24 hours for Earth to make one complete rotation, or spin around its axis. As it rotates, half of Earth is lit by the Sun. It is daytime for that part of Earth. The half of Earth that is facing away from the Sun is dark. Every part of Earth has day and night during this 24-hour rotation. Earth always rotates at the same speed. Because of this, the Sun seems to move in predictable patterns across the sky. Day Night The Sun shines on the part of Earth that faces it, giving daylight. 4 5
Noon The Sun seems to travel Sunrise across the sky. It is at its Sunset highest at noon. Changing Shadows As the Sun shines, it creates shadows on Early in the morning the Sun appears in the Earth. A shadow happens when light, such as east. Shadows at this time are long and stretch sunlight, shines on an object. The object blocks away from the Sun, toward the west. the light. Then a shadow appears on the surface Shadows grow shorter as the Sun seems to beneath or behind the object. The shadow is the move higher in the sky. By noon, the Sun appears part of the surface that is not getting light. at its highest. Then shadows are at their shortest. Shadows are the same shape as the objects As the Sun keeps moving toward the west, that stop the light. Unlike the objects, shadows shadows become longer once again. But now change length and direction. This is because they stretch east. This is the opposite direction shadows depend on where the Sun is in the sky. from the Sun. 6 7
Yearly Patterns During part of its trip around the Sun, the northern half of Earth tilts toward the Sun. Earth’s Movement When this happens, the northern half gets the While Earth spins on its axis, it also revolves most direct rays of sunlight. It is heated the around the Sun. One complete trip around most. It also has more hours of daylight than the Sun is called a revolution. It takes about darkness each day. one year, or 365 days, for Earth to make one At other times during Earth’s trip around the revolution. Sun, the southern half of Earth is tilted toward the Sun. Then this part of Earth gets more direct sunlight, heat, and hours of light. The four seasons of the year Spring Summer Winter When the northern When the northern part of Earth is tilted part of Earth is tilted toward the Sun, it is away from the Sun, summer there. it is winter there. Fall 8 9
Winter in Boston Summer in Brasilia Boston Boston is warmer at that time of year because it receives more sunlight. There are more hours of daylight than darkness each day. But in Brasilia it is colder, there is less sunlight, and there are Brasilia more hours of darkness in a day. We say it is summer in Boston and winter in Brasilia. Making Seasons As fall grows nearer, Boston receives less sunlight while Brasilia starts to receive more. Earth’s tilted axis and its movement around the The amounts of daylight and darkness each day Sun cause seasons. Temperatures and amounts of are almost equal in both cities. It is cooler than sunlight change in predictable ways throughout summer, but warmer than winter. the year. When Boston points away from the Sun, it Boston, Massachusetts, tilts toward the Sun in is winter. Temperatures are colder, and there are June. This is because it’s located on the northern fewer hours of daylight than darkness. When half of Earth. A city on the southern half, such as Brasilia points toward the Sun, it is summer. That Brasilia, Brazil, tilts away from the Sun. means more sunlight and warmer temperatures. 10 11
The Moon The Moon is about 384,000 kilometers (239,000 miles) away from Earth. That makes it Earth’s closest neighbor. Like Earth, the Moon rotates on its axis. The Moon also revolves around Earth. It takes about 29 days to make one rotation on its axis, and one revolution around Earth in relation to the Sun. Path of the Moon Earth At night, the Moon is the brightest natural object in the sky. The Moon does not make its own light. It reflects light from the Sun. We can see the Moon because sunlight shines on it and bounces off. The Moon is always in the sky, and we always see the same side of it. Sometimes we can see it during the day. But it is not as bright as it is at night. This is because the sunlight shining on Earth The Moon is brighter than the light that reflects off the Moon. 12 13
The Moon’s Phases After new moon First quarter Full moon Third quarter Sometimes the Moon looks like a bright During the phase called the new moon, we circle at night. Other times we can’t see it at cannot see the Moon at all. This is because the all. The look of the Moon follows a changing Moon is between Earth and the Sun. The dark pattern. This pattern repeats about every four half of the Moon is facing Earth. weeks. Each different way that the Moon looks As the Moon continues to revolve, we see a bit is called a phase. more of it each night. About two weeks after the Half of the Moon is always lighted by the new moon, we are able to see all of the lighted Sun. But we don’t always see the entire lighted part of the Moon. Now it looks like a circle. half. This is because of the way Earth and the This phase is called the full moon. For the next Moon move around each other and the Sun. two weeks we see less and less of the Moon until finally it is the new moon again. 14 15
A Lunar Eclipse A lunar eclipse happens when Earth moves between the Sun and the Moon. When Earth blocks the Sun’s light, it makes a shadow on the Moon. This shadow moves slowly over the Moon’s surface until it covers it completely. Then the shadow slowly moves off the Moon. A lunar eclipse is not a phase of the Moon and doesn’t happen as often. When Earth moves between the Sun and Star Patterns the Moon, it blocks the Sun’s light. The Moon is in Looking at Stars The Moon will appear Earth’s shadow. reddish in the part of When you look at the sky on a clear, dark night, Earth that has nighttime. you can see thousands of stars. Some of them are larger than the Sun. But they look small because they are so far away. Some stars are dimmer and The harder to see than others. This is because they are Earth Moon the farthest away. It is difficult for our eyes to see The Sun them. There are many stars that cannot be seen at all without special tools. 16 17
Galileo and the Telescope A telescope is a tool that makes faraway objects appear closer and easier to see. There are different kinds of telescopes. Most try to allow as much light as possible into the telescope. They are made with mirrors that reflect light and lenses that bend light. These telescopes make objects appear bigger or brighter. Galileo was a scientist who lived in Italy from 1564 to1642. He did not invent the telescope, but he is known for making one that could magnify objects by twenty times. With his telescope, Galileo discovered many new things in space. At that The Hubble Space Telescope fl oats in space. time, most people thought that the Sun revolved The Hubble Space Telescope around Earth. Galileo’s experiments and While most telescopes are meant to be used observations helped on Earth, the Hubble Space Telescope was built show that Earth for use in space. It is about 600 kilometers revolves around (375 miles) above Earth. It revolves around Earth the Sun. every ninety-seven minutes. Scientists receive pictures and information about space from the Galileo made important Hubble telescope. This has taught them lots about discoveries about space. faraway stars and planets in our solar system. 18 19
Constellations Cancer Scorpius Ursa Leo Major Long ago, people noticed that groups of stars One constellation is Ursa Major, which means made patterns in the sky. These patterns often Great Bear. We can see the Big Dipper in the looked like animals, people, or other things. They body and tail of the bear. The story the ancient gave names to these patterns and made up stories Greeks told about this constellation was that an about them. A group of stars that makes a pattern angry god turned a woman into a bear. Other is called a constellation. Today we still use many cultures told of a girl who turned herself into of the constellation names that people created a bear. Then she chased her sister and brothers. in ancient times. Different groups of people had To escape her, they all flew into the sky, where different names and stories for the constellations. they became the constellation of the Great Bear. Many of the names and stories came from legends. 20 21
North Star The stars in a constellation may look close together. But they are really very far apart. Because of this, they would not make the same pattern if you looked at them from space. Spring Summer Earth’s movement changes the patterns of stars. As Earth rotates on its axis, the stars appear to move across the sky. The constellations also change position as the seasons change. The constellations in the winter sky are different from those in the summer sky. Only the North Star does not appear to move. This is why people have used the North Star for Fall Winter hundreds of years to help them find their way. The sky has lots of patterns. Earth and the Moon are always following patterns as they move. Earth’s movements make it change from day to night and from season to season. We can learn a lot by studying these patterns and other objects in the sky, such as the Sun and stars. Year after year, Earth continues to follow some amazing patterns. The stars of the Big Dipper help people fi nd the North Star. 22 23
GlossaryVocabulary What did you learn? axis constellation 1. How do telescopes work? axislunar eclipse an imaginary line around which phase Earth spins 2. Why can’t we see the new moon? constellationrevolution a group of stars that make a rotation 3. Which star can be used to help pattern people find their way? Why? star lunar eclipsetelescope when Earth blocks the Sun’s light from shining on the Moon 4. In this book you have read about many phase the different ways the Moon looks patterns. Write to explain how revolution the movement of an object, such Earth’s movement around the as Earth, in one complete circle Sun creates seasons. Use examples around another object, such as from the book. the Sun 5. Sequence Shadows are created Picture Creditsrotation one complete turn around an axis when an object blocks sunlight. Every effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.star a large ball of glowing gases that Describe how a shadow changes Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd). 1 Getty Images; 2 Brand X Pictures; 4 Brand X Pictures; 5 Brand X Pictures; 10 (TL) Brand X Pictures, (TR) Brooksgives off light between morning and evening. Kraft/Corbis; 11 (TR) Pedro Luz Cunha/Alamy Images; 12 (T, B, CL, CR) Getty Images; 13 Getty Images; 14 (TL, TR) Getty Images; 15 (TL, TR) Getty Images. Scott Foresman/Dorling Kindersley would also like to thank: 19 (CA) NASA/DK Images.telescope a tool that magnifies objects that Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson.are far away ISBN: 0-328-13851-7 Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 0524
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