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Transcript
Earth and space Unit 6E.1: Earth and Space Movement of the Earth and Moon • Sun, moon, and Earth. • The movement of the Earth. • The phases of the Moon and eclipses Science skills: • Observing By the end of this unit you should know: • Sun and stars are sources of light and the sun is the source of heat too. • The moon orbiting the sun causes the Phases of moon. • The causes of tides. • What causes the solar eclipse? • What causes the lunar eclipse? • The effect of Earth orbiting the sun. 127 Grade 6, Unit 6E.1: Earth and space Earth and space 6.13.1, 6.13.2, 6.13.3 The Sun –Earth –Moon system There are nine planets moving around the sun, the Earth is one of them. The sun and the nine planets make up the solar system. The Sun: The sun warms the Earth. Without the sun the temperature of the earth would be several hundred degrees below zero. If we did not have the sun, nothing would be alive on the Earth. The sun is the source of light and heat that living things need. The sun is a star; stars are made up of gases only. It is much too hot for solids or liquids to exist there. If something is hot enough, it will “glow”. 128 Grade 6, Unit 6E.1: Earth and space Earth and space “Star light” is the light given out by very hot gases that make up the stars. The sun is the source of our daylight. The sun is a star; it is a huge ball of fire that may reach 6000°C. Why do we see the sun more brightly than other stars? --------------------------------------------------- Solar flare A flare is defined as a sudden, rapid, and intense variation in brightness. A solar flare occurs when magnetic energy that has 2T 2T built up in the solar atmosphere is suddenly released. 2T 2T 129 Grade 6, Unit 6E.1: Earth and space Earth and space The moon: The moon is Earth's only natural satellite. 2T 2T U U The moon is a cold, dry place whose surface is filled with craters, rocks and dust. The moon has no atmosphere. Recent lunar missions indicate that there might be some frozen ice at the poles. 2T 2T If you were standing on the moon, the sky would always appear dark, even during the daytime. Also, from any spot on the moon (except on the far side of the moon where you cannot see the Earth), the Earth would always be in the same place in the 2T 2T sky. The face of the Earth changes because the Earth rotates, displaying various continents. Suppose you were on the moon. What would Earth look like in the sky? ----------------------------- 130 Grade 6, Unit 6E.1: Earth and space Earth and space Where does the moon’s light come from? The moon’s light comes from reflected light from the Sun. The sun is a source of light it will shine the rays of light on the moon. Since the moon is like a dull mirror it is illuminated by the light that comes from the sun. The moon which is an illuminated object will then reflect the light to our eyes. The moon is an illuminated object that reflects the light that shines from the sun. During the day time we can’t see the moon because the light that shines from the sun is much stronger than the light reflected from the moon. The Earth, the Moon and the Sun have a spherical shape. Out of the Earth, moon and U U sun, the sun is by size the biggest, the Earth is the next biggest and the moon is the smallest. The diameter of the Earth is about U U 12000 km. 131 Grade 6, Unit 6E.1: Earth and space Earth and space Sun, Earth and Moon system The average distance from the earth to the sun is 149,597,890 km. This distance was not known until recently and it is called the astronomical unit. The distances of the other planets to the sun are usually measured in astronomical units. The average distance from the earth to the moon is 149,597,870 km. Project: Create a display of photographs of the Sun, the Earth and the Moon system. In your design • Make very approximate scale models of the Sun, the Earth and the Moon. • Include information about their size, climate, and what the surface is like etc. 132 Grade 6, Unit 6E.1: Earth and space Earth and space Key Ideas: • The Sun is a source of light and heat, without the sun there will be no life. • Earth sun and moon are spherical objects. • The Sun is much bigger, and then the Earth, and the moon is the smallest. • The Moon orbits the Earth and this cause the phases of the moon. Key words: • Illuminated object • Lunar month • Spherical • Moon phases • Lunar month Do you know that? The word 'sphere' comes from the Greek word spherical, which means ball. Key questions: Q1: What would be easier to do on the moon than the Earth? _______________________________________________ Q2: What would happen if Earth moved closer to the Sun? _______________________________________________ 133 Grade 6, Unit 6E.1: Earth and space Earth and space 6.13.7,6.13.8 The movement of the Earth Day and night: Notice in the following picture, the part of Earth facing the sun is lighted. This part of the earth has daytime. The part of the earth away from the sun that is not lighted has night time. The spinning of the Earth on its axis takes 24 hours; as a result we get day and night. 134 Grade 6, Unit 6E.1: Earth and space Earth and space Seasons Different parts of our planet get different amounts of sun light. The more direct sunlight a place gets the warmer it is. Sun light strikes the equator straight most of the time, so it’s hottest there. The equator is an imaginary line that circles Earth half way between the two poles. 135 Grade 6, Unit 6E.1: Earth and space Earth and space Scientists learn things by observing the sun; they have figured out that the sun’s changing path shows something about Earth’s motion. The earth orbits the sun. U U It takes Earth a year to complete one orbit around the sun. Look at the picture below. Do you notice anything strange about the axis? It is tilted! U U Having a tilted axis means that Earth is tilted a little to one side as it orbits the sun. 136 Grade 6, Unit 6E.1: Earth and space Earth and space The tilting of the earth's axis causes one part of the earth to be closer to the sun. The part of the earth that is closer has summer. The tilt of the Earth’s axis and its orbiting around the sun causes the seasons. In summer: Because your part of the Earth (hemisphere) is tilted toward U the sun, the sun appears highest in the sky. In summer, the sun’s path is the longest. Because it is a long pathway, there are more day light 137 Grade 6, Unit 6E.1: Earth and space Earth and space In winter: U During winter, your part of the earth (hemisphere) is far from the sun, the sun appears lower in the sky, this results in the day light hours becoming less in winter. U U U U U U In winter the sun’s path way is shorter because the sun is lower in the sky, there are less daylight hours. Ancient people used their observations on the sun, earth and moon to know the date, they created a system that we call the calendar. A Calendar, is a system of measuring time for the needs of civil life, by dividing time into days, weeks, months, and years. A day is the average time required for one rotation of the Earth on its axis. 138 Grade 6, Unit 6E.1: Earth and space Earth and space Calendar divisions are based on the movements of the Earth and the regular appearances of the Sun and the Moon. The measurement of a year is based on one revolution of the Earth around the Sun and is called a solar year. A solar year contains 365 days, 5 hours. The number of days required for the Moon to circle the Earth is 29.5 days. This measurement, called the lunar month, resulted in a lunar year of 354 days, 11 days shorter than a solar year. The earliest calendars based on lunar months eventually failed to agree with the seasons. A month occasionally had to be intercalated or added, to reconcile lunar months with the solar U U year. In modern calendars, however, the number of days in a month in a solar year is not based on the phases of the Moon. The length of the months is approximately one-twelfth of a year (28 to 31 days) and is adjusted to fit the 12 months into a solar year. 139 Grade 6, Unit 6E.1: Earth and space Earth and space A calendar that makes periodic adjustments of this kind is a solar calendar. U U Examples of Calendars: Modern calendar Six years after the death of the Prophet Muhammad ﺻﻠﻰ ﷲ ﻋﻠﻴﻪ ﻭ ﺳﻠﻢ, Islam’s second caliph ‘Umar ﺭﺿﻲ ﷲ ﻋﻨﻪrecognized the necessity of a calendar to govern the affairs of the Muslims. This was first of all a practical matter. Correspondence with military and civilian officials in the newly conquered lands had to be dated. A solar year is not based on the phases of the Moon. The length of the months is approximately one-twelfth of a year (28 to 31 days) and is adjusted to fit the 12 months into a solar year. 140 Grade 6, Unit 6E.1: Earth and space Earth and space A solar calendar is a calendar whose dates indicate the position of the earth on its revolution around the sun. Project: Design a calendar of your own depending on the solar years, and label it with the months that represent the seasons in Qatar. Key words: • Seasons • Tilted • Equator • North pole • South pole Do you know that? The ancient Egyptians were the first to replace the lunar calendar with a calendar based on the solar year. Key Ideas: ▫ Movement of Earth around the sun causes seasons and it takes the earth a year to orbit the sun. ▫ The sun is higher in the sky during summer. ▫ How hot or cold a place is depends on the angle of sun light. 141 Grade 6, Unit 6E.1: Earth and space Earth and space Key questions: 1. Why is it warmer in the equator than it is in the North Pole and South Pole? ------------------------------2. How does the tilt of Earth’s axis help cause the seasons? -------------------------------------------. 3- a. Suppose you are planning a trip to the South Pole. What month would you choose to visit there? Explain ---------------------------------------------------. 3- b. Give reasons for your choice: - ---------------------------------------------------------------. 4. The diagram shows the Earth in four positions during its orbit around the Sun. a. Which position is summer in Qatar? Draw an arrow to the position. Explain why it is hotter during the day in summer than in winter. ------------------------------------------------------------------------------------------------------------------------------------------------- 142 Grade 6, Unit 6E.1: Earth and space Earth and space 6.13.4,6.13.6 The phases of the Moon and eclipses Phases of the moon The sun earth and moon are in orbit, the moon orbits the earth and the earth orbits the sun. The moon orbits the Earth; it takes about 28 days for one complete orbit. The 28 days make up the lunar month. The movement of the moon around the earth causes the phases of the moon. People have used the phases of moon to tell the dates. Muslims use the phases of the moon to know when Ramadan, Eid and Hajj begin 143 Grade 6, Unit 6E.1: Earth and space Earth and space The orbit of the moon around the Earth takes a lunar month; as a result we see the different phases of the moon. The phases of the moon are shown by these diagrams. They show what the moon would look like when seen from Earth. Full Moon Waning Gibbous Moon Last Quarter Moon Waning Crescent Moon New Moon Waxing Crescent Moon First Quarter Moon Waxing Gibbous Moon Full Moon (again) 144 Grade 6, Unit 6E.1: Earth and space Earth and space Key questions: Q1: Draw (4) phases of the moon till day 14 of the lunar month: Q2: What is the moon’s phase when it appears closest to the sun? ___________________________________________ Q5: Circle the right answer for the following: 1. When only a small part of the moon is visible, the moon may be in its: a. first-quarter phase b. waning-crescent phase c. new moon phase d. last-quarter phase . 2. Because the moon rotates once for each revolution around the Earth, a. you see some phases more than others. b. a different side of the moon faces Earth each day. c. you never see the far side of the moon. d. the far side of the moon is visible only during the full moon phase. 145 Grade 6, Unit 6E.1: Earth and space Earth and space Eclipses: Lunar Eclipse The moon is an illuminated object that reflects the light that shines from the sun. The moon orbits the Earth. Most of the time, the moon does not move into the Earth’s shadow, but sometimes it does. When the moon is in the shadow of the Earth, the sunlight is blocked by the earth and does not reach the moon. When the Moon moves into the Earth’s shadow we have a Lunar Eclipse. 146 Grade 6, Unit 6E.1: Earth and space Earth and space The lunar eclipse happens more often than the solar eclipse since there is more chance for the moon to be in the shadow of the earth. The Earth is much bigger than the moon thus Earth has a much bigger shadow. During the lunar eclipse, hardly any sunlight reaches the moon. The moon becomes very dim. Comparison between solar eclipse and lunar eclipse: A lunar eclipse lasts much longer than a solar eclipse. This is because the Earth’s shadow is very wide where the moon passes. The moon takes a long time to pass through. Lunar eclipse can be seen from more areas of the Earth than a solar eclipse. From start to finish, a lunar eclipse lasts from three to four hours and sometimes longer. During a solar eclipse, the moon’s shadow covers only a small part of the Earth. A solar eclipse can be seen only in a small part of the Earth. 147 Grade 6, Unit 6E.1: Earth and space Earth and space During a lunar eclipse, the entire moon is in shadow. It can be seen from any part of the Earth that is having night at the time of the eclipse. Solar Eclipse How often have you noticed your own shadow following you? You have seen shadows of trees, buildings, and fences. You can see a shadow right now!! Just hold your hand close to the paper. What do you see? What is a shadow? A shadow is an area of darkness. It forms when an object blocks the light. 148 Grade 6, Unit 6E.1: Earth and space Earth and space A shadow is made when objects block the light. The Earth and moon are no exceptions. The Earth and moon block the sun’s light. They cast huge cone-shaped shadows deep into space. As the moon orbits the Earth, the Earth sometimes moves behind the moon .The moon will block the light, a part of the Earth will be in the moon’s shadow. For the people at that part of the Earth the moon Eclipses or blocks out the sun light. A solar eclipse takes place when the sun, moon and Earth are in straight or almost straight line with the moon between the sun and the Earth. 149 Grade 6, Unit 6E.1: Earth and space Earth and space The eclipsed area becomes dark. For a short period of time it looks like it is night time. A solar eclipse does not last long – no longer than a few minutes in any one place. Comparison between Solar Eclipse and Lunar Eclipse: U Solar Eclipse Lunar Eclipse The moon shadow covers only a small part of the Earth. The moon shadow covers large part of the Earth. It takes a short time to complete. It takes (3-4) hours or longer to complete. Can be seen from limited areas of Earth. Can be seen from different areas of Earth. 150 Grade 6, Unit 6E.1: Earth and space Earth and space Key words: • • • • • • Eclipse Orbit Rotation Phase Umbra Penumbra Do you know that? The Earth, lit by the Sun, casts a long, conical shadow in space. At any point within that cone the light of the Sun is wholly obscured. Surrounding this shadow cone, called the umbra, the area of partial shadow is called the penumbra. Key Ideas: • A Lunar eclipse happens when the moon moves into the Earth’s shadow. • Lunar eclipses occur more often than solar eclipses and last longer. • This is because the Earth is much bigger than the moon. Project: Lunar Eclipses 1. When did the last lunar eclipse happen in Qatar? ----------------2. How long did it take? ------------3. Where else was it visible from earth? --------------------------------------------3. When will the next one occur? ----------------- 151 Grade 6, Unit 6E.1: Earth and space Earth and space Key questions: Q1: Write true or false: a. _______ during lunar eclipse, the moon is in the Earth’s shadow. b. _______The moon reflects the sun’s light. c. _______ The phases of the moon always take the same number of days. d. _______ Solar eclipses must occur during New Moon phase. Q2: Find the answer for the following questions: 1. A lunar eclipse takes place only during one moon phase. Which phase is it? ______________________________________ 2. The lunar eclipse lasts much longer than a solar eclipse? _________________________________________ Q3: Which of the following describes an eclipse of the Moon? A. The Moon passes between the Earth and the Sun. B. The Sun is not illuminating the side of the Moon facing the Earth. C. The shadow of the Moon passes across the surface of the Earth. D. The shadow of the Earth passes across the surface of the Moon 152 Grade 6, Unit 6E.1: Earth and space Earth and space Key question: Figure (A) shows a solar Eclipse. Study it and answer the questions: Q1: Match the letter on the picture with the words: -----1. Sun -----2.Earth -----3. Moon -----4. Moons orbit -----5. Total eclipse ---6. Partial eclipse The shadow has a dark middle part, and a lighter outer part. 5. What do we call the darker middle part? ---------6. What do we call the lighter outer part? ----------Q2: Draw diagram on your note book that represents a solar eclipse. 153 Grade 6, Unit 6E.1: Earth and space Earth and space 6.13.5 T ides Have you ever spent a day at the beach? If you have, then you know that the water of the ocean does not stay at one level. At certain times of the day the water is higher than at other times. The water level rises and falls at regular time periods. Tides are the regular rise and fall of ocean’s level. High Tide Low Tide There are two major types of tides: 1. High tides 2. Low tides 154 Grade 6, Unit 6E.1: Earth and space Earth and space Tides do not change suddenly. High tide moves in slowly, then after the water reaches its highest point, it moves out slowly. A low tide is followed by a high tide, which is followed by a low tide, which is followed by another high tide. Most sea shores have four tides every day, two high tides and two low tides. A change of tide takes about 6 hours and 12 minutes. What causes tides? The sun, earth and moon are in orbit. Tides are caused by the pull of gravity by both the moon and the sun on the earth. The moon is more important in causing tides because it is closer to the Earth. The moon pulls on the Earth with greater force than the sun. The moon pulls upon the Earth’s land and water. The pull has hardly any effect upon the land. The rock, part of earth does not move easily. But water is different, water moves very easily, it flows. 155 Grade 6, Unit 6E.1: Earth and space Earth and space The pull bulges the water on the part of the Earth that is facing the moon. This part of the Earth has high tide. There is a high tide on the opposite side of the Earth the side facing away from the moon as well. The Earth is always rotating. As it turns different parts face the moon, this causes the tides to keep changing. The sun also has an effect on tides. Its effect is less than the moon. This is because the sun is so far away. Its pull upon the Earth is very weak. 156 Grade 6, Unit 6E.1: Earth and space Earth and space When the moon and the sun are pulling in the same direction we get higher tides. Key words • Tides • Pull of Gravity • Neap tide • Spring tide Project: Go to the seashore and mark the level of the water. On the next day at the same time, go and observe the level of the water. Record your observations. Do this for several days if you can. Key ideas: • Tides are the regular fall and rise of ocean’s water. • The average change of tides takes 6 hours and 12 minutes but has different lengths in different places. • Tides are caused by the pull of gravity by both moon and sun. The highest tides occur at Full Moon and New Moon. 157 Grade 6, Unit 6E.1: Earth and space Earth and space Key questions: 1. Which one is more important in producing tides? The moon or sun? ______________________ Why? ____________________________________ 2. Look at the following diagram, and answer the questions below: 1. Which side of the Earth is facing the moon? ________ 2. Which sides of the Earth are having high tide? _____ 3. Which sides of the Earth are having low tides? _____ 3. If gravity is always pulling towards the moon, what causes the bulge on the opposite side of the earth? -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 158 Grade 6, Unit 6E.1: Earth and space