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Astronomy, Chapter 1 Learning Target #1 Explain the motion of the sun, the moon, the earth and stars in the sky with the use of models a) Identify factors that determine the strength of the force of gravity between two objects b) Identify factors that combine to keep the moon and Earth in orbit c) Explain and identify what causes the cycle of seasons d) Explain and identify what causes day and night to occur on Earth e) Explain how the calculation of a year and a month show stability in our system so that we can make predictions Why is Earth and other planets in our solar system formed in a spherical shape? Gravity attracted particles toward its center while it was in a liquid or gaseous state What is gravity? It is a force that attracts all objects toward each other What influences the amount of gravity of an object? The larger the object, the larger its gravitational pull will be How is the force of gravity measured? Measured in units called Newtons What two factors does the strength of the force of gravity between two objects depend on? 1) The mass of the objects 2) The distance between the objects What is mass? a) Amount of matter in an object b) Mass and Weight are NOT the same Who was the first person to answer the question of what keeps the Earth and Moon in orbit? Isaac Newton a) Newton realized that there must be a force acting between Earth and the moon that kept the moon in orbit b) Newton was the first person to realize that gravity occurs everywhere What keeps the Earth and Moon in orbit? Newton’s law of universal gravitation Every object in the universe attracts every other object What factors keep the Moon and Earth in orbit? Combination of Gravity and Inertia What is gravity in relation to the moon and Earth? Earth exerts a gravitational force on the moon, large enough to keep it in orbit. The moon also exerts a gravitational force on Earth. What is inertia in relation to the moon and Earth? Tendency of an object to resist a change in motion Most places outside the tropics and polar regions have four distinct seasons: winter, spring, summer, and autumn But, there are great differences in temperature from place to place Why does Earth have seasons? Its axis is tilted It revolves around the sun What would have to different for Earth not to have any seasons? Earth’s axis would have to be straight up and down relative to its orbit What causes temperatures in the summer to be higher than temperatures in the winter? More of the Sun’s rays directly hit a particular region on Earth during the summer than during the winter. The figure above shows the Earth at two different positions in its orbit around the sun. If Texas is in the Northern Hemisphere which is the top half of the Earth, which position corresponds to summer and which position corresponds to winter? A is winter because it is tilted away from the sun B is summer because it is tilted toward the sun What are characteristics of Earth’s tilted axis? a) Earth’s axis is always tilted at an angle of 23.5 degrees from the vertical b) As Earth revolves around the sun, the north end of its axis it tilted away from the sun for part of the year and toward the sun for part of the year c) Summer and winter are caused by Earth’s tilt as it revolves around the sun. d) Seasons are NOT caused by changes in Earth’s distance from the sun. Earth is actually farthest from the sun when it is summer in the Northern Hemisphere e) Daytime is longer than nighttime during the summer than during the winter. f) Certain regions on Earth can experience non-stop daylight for six months of the year g) The Northern and Southern hemispheres experience opposite seasons How does Earth move? Two ways a) Rotation b) Revolution What is a rotation? The spinning of Earth on its’ axis What is an axis? An imaginary line that passes through Earth’s center and the North and South Poles. What are unique characteristics about Earth’s rotation? Earths rotates eastward, making the sun appear to move westward It takes about 24 hours to rotate once which makes 1 day = 24 hours What unit of time on Earth is based on the rotation of the Earth? Day What is a revolution? The movement of one object around another. What is a year? Once complete revolution of Earth around the sun is called a year. a) Earth follows a path (orbit) as it revolves around the sun b) Earth’s orbit is NOT circular, it is a slightly elongated circle or ellipse What causes day and night to occur on Earth? The spinning of Earth on its axis, called rotation, causes you to experience day and night Earth spins in a counterclockwise motion How does the calculation of a year, a day, or month show stability in our system? It shows that patterns are in place so that scientists can make predictions about type of things to expect during a year, a day, or a month Patterns show us what is going to reoccur Learning Target #2 Identify the parts of our solar system (planets, moons, asteroids) and show the gravitational relationship they have with our system How does gravity affect our solar system? Kepler's three laws of planetary motion describe the orbits of objects about the Sun. The Law of Ellipses, The Equal-Areas Law, and The Harmonic Law The force of gravity or the gravitational pull is what enables movement in the solar system. The gravity of the sun tries to pull objects to it, although they keep moving away. Gravity plays a crucial role over the entire history of our Solar System, from its very beginnings as a condensation inside a Giant Molecular Cloud (GMC) right up to the present day. Gravity is very weak but acts over very large length scales even across the universe. The large scale of interaction between bodies is the key to understanding gravity over all things large in the universe. The gravitational pull of the Sun keeps the planets in orbit around it. What is the solar system composed of? Sun, planets, asteroids, comets, and other objects in orbit around the Sun. What is the sun? It is a star located in the center of the solar system It is the largest object in our solar system It is an enormous ball of gas that produces energy by fusing hydrogen into helium in its core More than 99% of all matter in the solar system is contained in the sun The energy produced by the Sun comes from nuclear fusion reactions from the Sun’s core. The gravitational pull of the Sun keeps the planets in orbit around it. The largest object in our solar system It is so hot that the huge amount of hydrogen is undergoing a constant star-wide nuclear reaction, like in a hydrogen bomb. Even though it is constantly exploding in a nuclear reaction, the Sun and other stars are so large and have so much matter in them that it will take billions of years for the explosion to use all the "fuel" in the star. How are planets in our solar system classified? Inner or Outer planets Which planets are inner planets and why? Mercury, Venus, Earth, and Mars, also known as terrestrial planets They are similar in size to Earth and are made up mainly of rock These planets have orbits that lie inside the orbit of the asteroid belt Which planets are outer planets and why? Jupiter, Saturn, Uranus, Neptune They are all gaseous giant planets with thick atmospheres They are made up of light elements such as hydrogen and helium These planets have orbits that lie outside the orbit of the asteroid belt What is the order of planets in relation to the Sun? Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune Which planet is closest to the Sun? Mercury Which planet is the 5th largest? Earth Which planet is the 3rd closest to the Sun? Earth Why is Venus referred to as Earth’s twin? Only because of their similar sizes and masses How many moons does each planet have? Mercury &Venus = 0 Earth = 1 Mars = 2 Jupiter = 62 Saturn = 33 Uranus = 27 Neptune = 13 Which planets only have 1 moon? Earth Which planet has the largest number of moons? Jupiter Which planet is known for a large storm that appears as a giant red spot on its surface? Jupiter Which planet is the only one known to have liquid water? Earth What objects revolve around the sun? Comets Meteoroids Asteroids Planets Pluto used to be considered a planet, but with new evidence it has been reclassified. What is Pluto labeled as now by scientists? Dwarf planet Which of the objects that revolve around the sun is considered the largest? Planets What are asteroids? Small, rocky objects that mostly lie in a belt located between the orbits of Mars and Jupiter The asteroid belt is used as dividing line that separates the inner and outer planets Asteroids vary greatly in size and are mostly made up of stone, iron and nickel Smaller than planets, but larger than meteoroids What are meteoroids? Sand to boulder-sized particles of debris in the Solar System A mass of rock in space They are classified as stony, stony iron, & iron They become visibly bright when they enter Earth’s atmosphere What are comets? Made mainly of rocky particles and water ices As their orbits approach the sun, parts of comets vaporize and form tails Almost all of the solar systems comets are located in the Kuiper Belt (beyond Neptune) and the Oort Cloud (beyond what used to be known as the planet Pluto) Are usually smaller than planets, moons, & asteroids Made mostly of dust particles, frozen water, and frozen gas Learning Target #3 Explain the phases of the moon a) Identify the moon’s cycle in relationship to a month on Earth (full moon, new moon) using diagrams b) Explain how many days it takes for a moon to go through one cycle …such as how long it would take for a new moon or full moon to occur during the next cycle c) Compare/contrast a solar and lunar eclipse d) Identify factors that create tides e) Explain different types of tides that occur on Earth What causes of the phases of the moon? The changing relative positions of the moon, Earth, and sun Why is a day and a year on the moon the same length? The moon rotates once on its axis in the same amount of times as it revolves around Earth. Also, the same side of the moon always faces Earth The length of the moon’s day is shorter than the 29.5 days between consecutive full moons What is the relationship of the Earth and the Moon? The moon orbits the Earth Why does the moon not produce light? Does not produce light, it reflects light from the sun What are the phases of the moon? a) The different shapes of the moon you see from Earth (changes in Moon’s visibility) b) The whole (entire) set of phases that a moon goes through represents one complete revolution around Earth c) The phase of the moon we see depends on how much of the sunlit side of the moon faces Earth What is each phase of the moon? a) New Moon The side with sunlight faces away from Earth making it appear completely dark (no light anywhere) 29.5 days after the last new moon, the cycle is complete, and a new moon begins Moon is on same side of Earth as the Sun b) Waxing Crescent Moon (the light is growing) c) First Quarter Moon (the light is growing) d) Waxing Gibbous Moon (the light is growing) d) Full Moon (happens about once every month) e) Waning Gibbous Moon (the light is shrinking) f) Third Quarter Moon (the light is shrinking) e) Waning Crescent Moon (the light is shrinking) Position at a full moon of Earth, moon, and sun Position at a new moon of Earth, moon, and sun The full moon doesn't occur on the same day of every month because the moon takes 29½ days, and not specifically a month, to orbit the Earth. (As a result of this, you get to witness two full moons in a single calendar month every three years.) On the day of the full moon, it is at its best appearing very bright and full from the planet. On a new moon day, on the other hand, it appears as if there is no moon in the sky, unless you use a telescope to get a glimpse of it. What is an eclipse? When an object in space comes between the sun and a third object, it casts a shadow on that object What are two types of eclipses? 1. Solar 2. Lunar What is a solar eclipse? It occurs when the moon (new moon) passes directly between the Earth and the sun, blocking sunlight from Earth. What are characteristics of a total solar eclipse? The very darkest part of the moon’s shadow is called the umbra which is cone-shaped. From any point in the umbra, light from the sun is completely blocked by the moon. The moon’s umbra is long enough so that its point can reach a small part of Earth’s surface. What are characteristics of a partial solar eclipse? The moon cast a shadow called the penumbra. Part of the sun is visible from Earth. It is not safe to look directly at the sun because the extremely bright part of the sun remains visible What is a lunar eclipse? Occurs at a full moon when Earth is directly between the moon and the sun Earth blocks sunlight from reaching the moon Why does a lunar eclipse happen only during a full moon? The moon is closest to Earth’s shadow at that time What is a total lunar eclipse? Earth’s shadow has an umbra and a penumbra. When the moon is in Earth’s umbra, you see a total lunar eclipse (Sun – Earth – Moon) What is a partial lunar eclipse? This occurs when the moon passes partly into the umbra of Earth’s shadow. What is a tide? The rise and fall of ocean water that occurs every 12.5 hours or so. The water rises for about 6 hours, then falls for about 6 hours, in a regular cycle What causes tides? Differences in how much the moon’s gravity pulls on different parts of Earth along with some pull from the Sun Describe the relationship of the moon and Earth during the high and low tide? Two bulges of water form, one on the side of the Earth closest to the Moon and one on the opposite side of Earth. The reason two bulges form is because the Moon’s gravity pulls harder on parts of Earth closer to the Moon than on parts farther away. What is a spring tide? These combined forces produce a tide with the greatest difference between consecutive low and high tide. (high tide and low tide are at its lowest) When does a spring tide occur? a) This occurs because of the gravity of the sun and the moon pulling in the same direction b) This occurs twice a month, at a new moon, and at a full moon What is a neap tide? A tide with the least difference between consecutive low and high tides a) The sun’s pull is at right angles to the moon’s pull. b) Happens during a quarter moon c) Medium sized tides that occur across Earth’s surface When does a neap tide occur? d) This happens during the moons first quarter and during the third quarter phase Which phase of the moon produces highest tides? Full Moon Which phase of the moon produces the least variation in tides? First Quarter Moon