Chapter 22outline
- 1. Chapter 22 Origin of Modern Astronomy
- 2. Early Astronomy Earth is just one of eight major planets and 3 dwarf planets that orbit our sun. Our sun is just one of perhaps 100 billion stars that make up our galaxy the Milky Way. The Milky Way is just one of billions of galaxies. Where does this knowledge come from??????????
- 3. Ancient Greeks ___________ is the science that studies the universe. Astronomy deals with the properties of objects in space and the laws under which the universe operates. “Golden Age” of early astronomy (600 B.C. – A.D. 150) was centered in ___________.
- 4. Greeks developed The basics of ___________ and ___________ Measured the distances of the sun and moon Aristotle determined that the Earth was round because it cast a round shadow on the moon. This theory was later abandoned. ___________ first to calculate the circumference of the Earth….. Describe his experiment and figure his mistakes.
- 5. Here is how he did it……….
- 6. 7.2 0 7.2 0
- 7. Then he calculated How much of a circle is ___________ ? ___________ The total distance was? 39,400 km. The actual distance is closer to 40,075 km.
- 8. Problems with the solution…… 1. 2. 3. 4.
- 9. ___________ developed star catalogue. He determined the locations of 850 stars, which de divided into six groups according to their brightness. He measured the length of the year to within minutes He developed a method of predicting the times of lunar eclipses to within a few hours.
- 10. ___________ Model ___________ centered solar system… outside the solar system the stars traveled within a hollow sphere called the celestial sphere.
- 11. ___________ Model ___________ centered Aristarchus (312 – 230 B.C.) first to believe in this model. This model was later proposed by Copernicus (1473 – 1543) and proved by his student Galileo. This model was not accepted originally.
- 12. Ptolemaic System An attempt to explain planetary movement referred to as ___________ . Retrograde motion is the ___________ of a planet. How is this possible?
- 13. ___________ : Concluded that Earth was a planet. He proposed a heliocentric solar system model.
- 14. v Built an observatory near Copenhagen. He developed and used several instruments made of stone to make calculations. Brahe made precise observations about Mars . Later in life he found and assistant by the name of Johannes Kepler.
- 15. ___________ Discovered three ___________. Astronomical unit – distance from the Earth to the sun or 150,000 kilometers
- 16. Three Laws of Planetary Motion All orbits are ___________ in shape An ___________ is an almost perfect circle
- 17. ___________ Law Each of these triangles are equal in area Can you understand the Earth travels faster as it gets closer to the sun and slower as it moves away from the sun?
- 18. ___________ Law This law ___________ ( its year) of any planet. The base unit of measure is the distance from the Earth to the sun which equals 1 astronomical unit or (approx. 150, 000,000 km.) Solar distances can be calculated when the periods of revolution (orbit) are known.
- 19. T 2 =d 3 Ex. Using Mars Mars revolution equals 1.88 years The square of this is 3.54 The cube root of this is 1.52 This means that Mars is 1.52 a.u. from the sun.
- 20. Using the formula another way… If you take the distance in a.u. and cube it. Then take the square root of that number, you will calculate the period of revolution of the orbiting body. Ex. Jupiter is approx. 5 a.u. from the sun # 3 then take square root 5 3 = 125 125 = 11.3 years
- 21. ___________ His most important contributions were his descriptions of the behavior of moving objects. 1609 Galileo heard of a Danish lens maker who had devised a system of lenses that could magnify objects. Without ever seeing a telescope Galileo constructed his own.
- 22. With the aid of his telescope Galileo discovered: 1. Four satellites orbiting Jupiter. Today these moons are called Galiliean moons. This discovery proved that objects were orbiting another body besides the Earth. 2. Planets are circular disks. It was believed they were only points of light. 3. Venus has phases just like the moon. 4. The moon’s surface was not smooth. 5. The sun had spots.
- 23. ___________ Scientists of the time wondered about two points: 1. What causes a moving object to continue to move. 2. What force keeps the bodies in space from traveling in a straight line out into space. Although others had theorized the existence of such a force, Newton was the first to formulate and test the law of universal gravitation.
- 24. According to Newton, every body in the universe attracts every other body with a force that is directly proportional to their masses and inversely proportional to the square of the distance between their centers of mass. Example: The gravitational force decreases with distance, so that two objects 3 kilometers apart have 32, or 9, times less gravitational attraction than if the same objects were 1 kilometer apart.
- 25. The greater the mass of the object, the greater is its gravitational force. (discuss the difference between mass and weight) ___________ being the total amount of matter an object contains. ___________ is the force of gravity upon an object.
- 26. Earth moves forward in its orbit about 30 kilometers per second. During the same second, the force of gravity pulls it towards the sun about 0.5 centimeters. Newton concluded that it is the combination of Earth’s forward motion and its “falling” motion that defines its orbit.
- 27. Newton’s laws of Gravity An ___________ (force) in motion will stay in motion until another ___________ (force) acts upon it. The larger the mass, means that it will have stronger gravity . (used to calculate escape velocities) For every action there is an ___________ & ___________ reaction
- 28. The Earth-Moon-Sun System Stonehenge……. Lets take a look
- 29. Motions of Earth The two main motions of Earth are ___________ (spin) and ___________ (orbit) .
- 30. Revolution is …….. is the motion of a body, such as a planet or moon, along a path around some point in space. Earth’s average speed is 107,000 kilometers per hour. Our average distance from the sun is 150,000,000 kilometers. However, all orbits are elliptical so….
- 31. Earth’s ___________ is when the Earth is closest to the sun about 147,000,000 kilometers. This occurs on January 3rd each year. Earth’s ___________ is when Earth is at is farthest point from the sun about 152,000,000 kilometers. This occurs on July 4th each year. Is this why we have seasons????????
- 32. The apparent annual path of the sun against the backdrop of the celestial sphere is called the ___________. The planets and moon travel along the same plane as Earth, so their paths on the ___________ lie near the ecliptic.
- 34. Earth’s axis …… is tilted on this plane ___________ to the ecliptic. This tilt creates ___________.
- 35. When the apparent position of the sun is plotted on the celestial sphere over a period of a year’s time, its path intersects the celestial equator at two points. These intersect points are spring (March 20 or 21) and fall (Sept. 22 or 23).
- 36. When the sun is 23.5 0 north of the equator….. ___________ occurs. When the sun is 23.5 0 south of the equator….. ___________ occurs.
- 37. Procession The Earth has another very slow motion called procession, which is a slight movement, over 26,000 years. The Earth’s axis traces a circle in space similar to the wobble of a spinning top.
- 38. At the present time the northern axis points to Polaris, which is referred to as the North Star. In the year 14,000 our northern axis will point to Vega, which will then become our north star. Then in the year 28,000 Polaris will again be our north star.
- 40. Rotation ……. Rotation results in day and night. It has become a standard of measuring time. Each rotation equals about 24 hours. Notice that it says about 24 hours!
- 41. ___________ is the time it takes for the Earth to make one complete rotation (360 degrees) with respect to a star other than our sun. A sidereal day is equal to ___________ hours ___________ minutes and ___________ seconds .
- 43. ___________ is good for determining time. Sidereal is used to determine the ___________ Earth is to be at the beginning of each season.
- 44. Earth-Sun Motion The Earth, sun, and the rest of the solar system travel through space at a speed of 20 kilometers per second towards the star, Vega. Our solar system also revolves around the galaxy. The trip takes 230 million years and travels at speeds approaching 250 kilometers per second.
- 45. Galaxies are also in motion. Earth is presently approaching the Great Galaxy in Andromeda.
- 46. Motions of the Earth-Moon System Average distance to the moon is 384,401 kilometers. ___________ (farthest point in its orbit) and ___________(closest point in its orbit). Lunar phases are a result of the motion of the moon and the sunlight that is reflected from its surface.
- 47. Lunar Motions The moon cycle of phases takes ___________ days . One orbit of the moon around the earth takes ___________ days One rotation on the moon takes ___________ days Something doesn’t seem to add up!!!!!!!!!!!!! What does this all mean????
- 48. If the orbit and rotation of the moon are the same (27.3 days), that means? ___________ Why then does it take the moon longer to go through its phases? It must “___________” to where the ___________ to be since the Earth is orbiting the sun.
- 49. Because the moon must catch up to the Earth each day, it rises 50 minutes later each night .
- 50. Phases of the Moon Phases result from the motion of the moon and the sunlight that is reflected. For the purposes of this class we will only use the following phases: ___________ - dark ___________ – lighted side grows larger ___________ ___________ – shadowed side grows larger
- 52. Eclipses Two types: ________ ________
- 54. ________ occur with new moon phase ________ occur with full moon . During a new-moon or full moon phase, the moon’s orbit must cross the plane of the ecliptic for an eclipse to occur. There are usually ________ that occur in two sets. One lunar and then a solar, then 6 months later another lunar and solar.
- 55. During any given year there are not more than ________ eclipses. Solar eclipses last about 7 minutes in any given area. The size of the shadow is approximately 275 kilometers wide or about the size of South Carolina. (FYI) The next total solar eclipse will occur August 21, 2017.
- 56. Earth’s Moon Moon characteristics: Size 3475 kms. Or about ________ that of Earth 6 Apollo missions landed on the moon between 1969 and 1972 Moon’s density is 3.3 which is less than the 5.5 of Earth rocks. Gravity is ________ of Earth
- 57. Lunar Surface No volcanism ________ – most craters were produced by the impact of rapidly moving debris. A meteoroid 3 meters in diameter can make a crater 150 meters wide. Larger craters like Kepler and Copernicus were formed with the impact of bodies 1 kilometer or more in diameter. ________ – debris splash marks near the crater.
- 62. ________ – or mountain peaks. The highest is near 8 kilometers in height or just 1 kilometer short of Mt. Everest.
- 63. ________ – (seas) name by Galileo Relatively dark smooth areas on the moon’s surface. Maria formed from ancient beds of basaltic lava, originated when asteroids punctured the lunar surface, letting magma bleed out. These lava flows are often 30 meters thick. Long channels called ________ are associated with maria. They may be the remains of ancient lava flows or lava tunnels then caved in.
- 65. ________ – lunar regolith, which is a soil like layer on the moon. It is composed of igneous rocks, glass beads, and fine lunar dust.
- 67. Lunar History Most accepted lunar formation model: The origin of the moon occurred when the solar system was forming, a body the size of Mars impacted the Earth. A portion of the liquefied material entered Earth’s orbit where it combined to form the moon.
- 68. Evidence 1. Ejected material would have been iron poor and so is the moon. 2. The ejected material would have stayed in orbit long enough to loose its water.
- 70. The moon evolved in three stages: The original crust meaning ________ maria basins rayed craters
- 71. Continued impact of meteoroids combined with radioactive decayed materials, generated enough heat to melt the moon’s outer shell and possibly the inner as well. The highland areas are estimated to be 4.5 billion years old.
- 72. The maria basins are younger than the highlands and in some places over lap some highland areas. The last features to form were the rayed craters. Most of the old craters are ray-less .