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# Chapter 22outline

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## Chapter 22outlinePresentation Transcript

• Chapter 22 Origin of Modern Astronomy
• 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??????????
• 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 ___________.
• 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.
• Here is how he did it……….
• 7.2 0 7.2 0
• 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.
• Problems with the solution……
• 1.
• 2.
• 3.
• 4.
• ___________ 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.
• ___________ Model
• ___________ centered solar system… outside the solar system the stars traveled within a hollow sphere called the celestial sphere.
• ___________ 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.
• Ptolemaic System
• An attempt to explain planetary movement referred to as ___________ .
• Retrograde motion is the ___________ of a planet.
• How is this possible?
• ___________ :
• Concluded that Earth was a planet.
• He proposed a heliocentric solar system model.
• 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.
• ___________
• Discovered three ___________.
• Astronomical unit – distance from the Earth to the sun or 150,000 kilometers
• Three Laws of Planetary Motion
• All orbits are ___________ in shape
• An ___________ is an almost perfect circle
• ___________ 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?
• ___________ 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.
• 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.
• 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
• ___________
• 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.
• 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.
• ___________
• 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.
• 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.
• 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.
• 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.
• 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
• The Earth-Moon-Sun System
• Stonehenge……. Lets take a look
• Motions of Earth
• The two main motions of Earth are ___________ (spin) and ___________ (orbit) .
• 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….
• 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????????
• 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.
•
• Earth’s axis ……
• is tilted on this plane ___________ to the ecliptic.
• This tilt creates ___________.
• 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).
• When the sun is 23.5 0 north of the equator…..
• ___________ occurs.
• When the sun is 23.5 0 south of the equator…..
• ___________ occurs.
• 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.
• 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.
•
• 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!
• ___________ 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 .
•
• ___________ is good for determining time.
• Sidereal is used to determine the ___________ Earth is to be at the beginning of each season.
• 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.
• Galaxies are also in motion.
• Earth is presently approaching the Great Galaxy in Andromeda.
• 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.
• 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????
• 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.
• Because the moon must catch up to the Earth each day, it rises 50 minutes later each night .
• 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
•
• Eclipses
• Two types:
• ________
• ________
•
• ________ 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.
• 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.
• 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
• 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.
•
•
•
• Rays with craters
• ________ – or mountain peaks.
• The highest is near 8 kilometers in height or just 1 kilometer short of Mt. Everest.
• ________ – (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.
•
• ________ – lunar regolith, which is a soil like layer on the moon. It is composed of igneous rocks, glass beads, and fine lunar dust.
•
• 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.
• 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.
•
• The moon evolved in three stages:
• The original crust meaning ________
• maria basins
• rayed craters
• 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.
• 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 .