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Our Solar System Day and Night Phases of the Moon Planets Georgia Performance Standards S4E2 Students will model the position and motion of the earth in the solar system and will explain the role of relative position and motion in determine sequence of the phases of the moon. a. Explain the day/night cycle of the earth using a model. b. Explain the sequence of the phases of the moon. c. Demonstrate the revolution of the earth around the sun and the earth’s tilt to explain the seasonal changes. d. Demonstrate the relative size and order from the sun of the planets in the solar system. Essential Questions • Why are different phases of the Moon observed throughout the month? What is the sequence of those phases? • What are the relative sizes of the planets in our solar system? • What is the relative order of the planets from the Sun on our Solar System? • While you are enjoying breakfast in Georgia, night is falling in places half way around the world. • How can this be so? CYCLE OF NIGHT AND DAY • The cycle of night and day occurs because the Earth rotates. • To ROTATE means to turn on an axis. • An AXIS is an imaginary line through the center of an object. The Earth’s axis passes through the North and South poles. • Remember that the Earth is a sphere. Only one half of the Earth receives light and heat from the Sun at any given time. • The other half of the Earth is dark, and it is nighttime there. • Since the Earth rotates, the half that receives light and the half that is dark changes positions throughout the rotation of the Earth. • As the day goes on, the Sun appears to move across the sky. • THE SUN IS NOT MOVING. Instead, Earth is rotating, causing the Sun to look like it is moving. • As the Earth turns, the position of the Sun in the sky changes, This causes the angle at which sunlight strikes your part of the Earth. • The changing angle of sunlight causes shadows to change throughout the day. • When the Sun is low in the sky, shadows are long. When the Sun is high in the sky, shadows are short. • Long ago, in ancient times, people used the positions and lengths of shadows to tell the time of day. • Sundials can be used to tell the time of day. Earth’s Moon • The Earth’s moon is a sphere made up of rock. • It revolves around Earth every 27 ½ Earth days. • The moon does not make its own light. “Moonlight” is really sunlight reflecting from the Moon’s surface. MOON • The rocky surface of the Moon is covered with mountains, flat plains, and craters. • A CRATER is a bowl shaped dent that is caused by an object from space striking the surface of a planet or moon. • There is no air or liquid water on the Moon, which means there are NO LIVING things. • Daytime temperatures are much hotter on the Moon than on Earth and nighttime temperatures are much colder. MOON • The Moon’s diameter (distance around) is only about one-fourth of the Earth’s diameter. • The Moon is smaller than the Earth so its gravity is weaker than the Earth’s gravity. Because of this, things weigh less on the Moon than they do on the Earth. The same side of the moon always faces the Earth. If the same side of the moon always faces the Earth, why does the moon appear to change shape? As the moon revolves around the Earth, the near side receives different amounts of sunlight. Phases of the moon • The moon’s shape appears to change from a crescent to a half circle, to a whole circle, and back again. • The changes are caused by the way sunlight strikes the Moon as it revolves around the Earth. NEW MOON • At one point during the moon’s revolution around the Earth, it receives NO sunlight and cannot be seen. Crescent Moon • As the moon revolves around the Earth, a small part of the near side becomes sunlit and can now be seen from the Earth. Quarter Moon • When the moon has revolved one quarter of its orbit around the Earth, half of the Moon’s near side can be seen from Earth. Full Moon • When the moon has revolved half way around the Earth, the Moon’s entire near side is sunlit and can be seen from Earth. WAXING MOON • After a new moon (when the moon is not sunlit and you cannot see it), an increasing amount of the Moon’s near side is sunlit. WANING MOON After a full moon (when the near side of the moon is completely sunlit and you can see it), a decreasing amount of the near side is sunlit. Seasonal Changes • As the Earth orbits the Sun, the tilt of the axis causes the seasons to change. REVOLVE • Remember that is takes one year for the Earth to revolve around the Sun. • REVOLVE means to move in a path around another object. • The orbit is in the shape of an ellipse. An ELLISPE is a circle that is flattened and slightly stretched out. SEASONS The four parts of the year---spring, summer, fall, and winter. In June, the Earth’s Northern Hemisphere (where you live), is tilted toward the Sun. It receives strong, direct sunlight, so it is summer here. In December, the Earth tilts away from the Sun. It receives weak, indirect sunlight and it is winter here. • Remember that the EQUATER is an imaginary line the circles the Earth halfway between the North and South Poles. • It divides the Earth into NORTHERN and SOUTHERN halves, called hemispheres. Length of Day and Night • The length of day and night changes throughout the year. This is caused by the tilt of the Earth on its axis. • Because the Earth is tilted towards the Sun in the summer, there are more daylight hours and fewer hours of darkness. • In December, when the Earth is tilted away from the Sun on its axis, there are more hours of darkness than daylight hours. The shorter amount of sunlight is what helps make winter colder than summer. The Inner Planets • Mercury, Venus, EARTH, and Mars are called the INNER PLANETS. • These planets get a lot of heat and light because they are close to the Sun. • The inner planets are small and are made up of solid rock materials. There surfaces have mountains and craters. Inner Planets Mercury Venus Earth Mars Mercury • Is the closest planet to the Sun. It is very hot during the day and very cold at night. Venus • Is the second planet from the Sun. It is covered by thick clouds of gas. The clouds trap the heat and make the planet very hot. Earth • Is the third planet from the Sun. It is the only planet known to support life. Earth has an atmosphere. Mars • Is the fourth planet from the Sun. The surface of Mars has many craters, mountains, and volcanoes. Mars has the largest volcano ever discovered in the solar system. THE OUTER PLANETS • Jupiter, Saturn, Uranus, and Neptune are called the outer planets. They are cold and dark because they are far from the Sun. They are large, made of gases, and have many moons. Each also has a system of rings. • Pluto was once known as the ninth planet. In 2006, astronomers classified it as a dwarf planet. Pluto is smaller than any planet. It is made of rocks and frozen gases. It has no rings and only one moon. Jupiter • Is the fifth planet from the Sun and is the largest planet. The Great Red Spot is a large storm. Saturn • Is the sixth planet from the Sun. It has beautiful rings made of dust, ice, and rocks. Uranus • Is the seventh planet from the Sun. Unlike any other planet, Uranus spins on its side. Neptune • Is the eighth planet from the Sun. Methane in its atmosphere gives Neptune its blue color. Pluto • Is now called a dwarf planet. It is smaller than the planets, and very far from the Sun. Planets in Motion • As it orbits the Sun, each planet spins like a top. Earth’s day, one full spin, is 24 hours long. Some planets spin more quickly than Earth, while others spin more slowly. Jupiter spins around about every 10 hours. Venus takes 243 Earth days to spin just once. • The farther a planet is from the Sun, the longer it takes to orbit. The time it takes to complete one trip around the Sun is called a YEAR. • Earth’s year is about 365 days long. Mercury makes a complete orbit in just 88 days. Neptune takes about 165 Earth years to complete its orbit around the Sun. • For thousands of years, people have been observing the Sun, the Moon, and other objects in the sky. • Scientists did not learn how these objects move until a few hundred years ago. • Why do you think they took so long? Essential Questions • Why are different phases of the Moon observed throughout the month? What is the sequence of those phases? • What are the relative sizes of the planets in our solar system? • What is the relative order of the planets from the Sun on our Solar System?