GEOGRAPHY 101 Front PageEARTH AS A PLANET
MATERIALS NEEDED FOR CLASS:
Daily Lesson Plans. H.K.C--Take roll and announcements. TEXT: Essential of Physical Geography: 6th Edition, Robert E. Gabler, Robert J. Sager, Daniel L. Wise, and James Peterson. Saunders College Publishing, Harcourt Brace College Publishers 1999. Rand McNally GOODE's WORLD ATLASGENERAL OUTLINE
III. Earth as a Planet
A. To recall the Solar System and Beyond.
B. To depict the relationship between the Earth and the Sun.
C. To describe the Size and Shape of the Earth and Special Note remember the
plane of Inclination
D. To describe the March of the Seasons.
E. To recount important lines of parallel--Arctic Circle and Antarctic Circle, The
Tropics of Cancer and Capricorn
F. To describe the use of Analemma on a Globe.
G. To describe how Insolation and and Seasons are related.THE MATERIAL IN THIS OUTLINE COVERS PAGES 70--89 BUT THERE IS MATERIAL NOT IN YOUR BOOK--KNOW IT--KNOW IT--KNOW IT
ANTICIPATORY SET How does the Earth Move? What is Earth's place in the Solar System and beyond? What are the Annual March of the Seasons? What is the Earth --Sun relationship ? >What are the important lines of Parallel? What is the Size and Shape of the Earth? What is the connection between Insolation and the Seasons?
BEHAVIORAL OBJECTIVES
To define galaxy and light year. To recall the difference between the gas planet and the terrestrial planets To recollect Eratosthenes. To trace the Big Bang. To describe the force of gravity To identify BCE To identify the Solar System and Earth's place in it. To recount the size and shape of the Earth To compare a perfect sphere and oblate spheroid. To identify the Planets and to compare and contrast the difference between the gas giants and the terrestrial planets. To identify the Arctic Circle, Antarctic Circle, the Tropic of Cancer and Capricorn. To describe the movement of the Earth. To define perihelion and aphelion To investigate different views on the shape of the Earth To recognize the relationship between Insolation and the Seasons. To portray the plane of the Ecliptic Inclination and parallelism To explain the shape of the Analemma To identify the variations of insolation with latitude. To contrast solstice and equinox. INSTRUCTIONAL INPUT
Content Methods:Lecture and Classroom discussionI SOLAR SYSTEM AND BEYOND
A. Outside of the lights of a city on a cloudless summer night part of the Milky Way Galaxy, a flattened disk-shaped cloud of stars, can be seen and our sun is only a very small light in the cosmos. A galaxy can be called an immense island of billions of stars in the absolute blackness and vast distances of intergalactic space. There are billions of galaxies. (What is the nearness galaxy to the Milky Way?) (Take a look at Figure 3.1 on p.72.)
THE BIG BANG
B. Most astronomers, but not all, believe that the universe began 15 billion years ago with a great blast called the "Big Bang," with the mass scattering at great speeds. Since distances in space are so huge it is practical to use the distance light travels in one year as measure of distance called a light year. Light travels at 186,000 miles per second--the speed limit of the universe. The distances involved and the immense size of the universe is mind boggling and comparisons sometimes work, but such comparisons make me feel very small and insignificance. The nearest star other than the sun is 4.3 light-years away and the nearest galaxy is 75,000 light years away. (What is the name of the nearest star not counting the sun?)
THE SOLAR SYSTEM
C. A solar system is a star with all the heavenly bodies associated with that particular star, due to the star's overwhelming gravitational influence and mass. The Sun is the center of our Solar system which consists of nine planets revolving around it. The planets revolve around the sun and are held in place by gravitational attraction (centripetal force) and follow more or less an elliptical orbit. It is a balance between gravity and centrifugal force. With the exception of Pluto the other planets are nearly in the same plane. (Take a look at Figure 3.2 on p. 73.)
D. There are 61 moons, or satellites, revolving around the planets. There are more than 50,000 asteroids, (a small planet usually smaller than 500 miles across) mostly rock and/or metal most but some quite large and could strike the Earth. I wonder if that could make a good Science Fiction movie? (Asteroids sometimes are credited with the extinction of what life form?) There are also many comets, which are more or less giant snowballs, and there are millions of meteors . (small stone like objects) Sometimes they are called shooting stars and can make impressive displays at certain times of the year. When meteors strike the Earth and survive they are called meteorites. (What was recently discovered in a meteorites?)
OUR SUN IS A YELLOW DWARF STAR
E. The energy created by the sun is a nuclear reaction created in the interior of the Sun. The sun is made up of superheated gases under high pressure, the hydrogen is converted into helium by nuclear fusion. Our sun is a yellow dwarf star and is of no particular importance to the universe. It is about an average-sized star. But very important to life on Earth.
THE PLANETS
F. The four inner planets of Mercury, Venus, Earth, and Mars are small and more or less rocks, (That does explain the title of a current TV program) and are called terrestrial planets. (Take a look at Figure 3.3 on p. 74.) The four outer planets, the planets, Jupiter, Saturn, Uranus, and Neptune are much larger, and are made mostly of hydrogen. They may be planets which almost became suns and are called giant planets or gas giants. (Take a look at Figure 3.4 on p. 75.) Pluto does not seem to fit into either pattern and may have been a moon of one of the giant planets.
G. There is another concept I want you to know about and that is Gravitation. It is the attractive force one body has for another. The greater mass or amount of matter a body has the greater the gravitation pull it will exert on other bodies. If you want something simpler gravity is the invisible glue which holds the universe together.(What English physicist formulated the Laws of Gravity?)
II THE SIZE AND SHAPE OF THE EARTH
ERATOSTHENES
A. The Greeks did usually accept the world on face value, but tried to prove their theories. One such Greek was Eratosthenes, who was the director of the Library at Alexandria around 200 B.C.E.. The Library at Alexandria, was more than just a library, it was part university, health club, and research center. A rough comparison might be the Library of Congress, the Smithsonian, and a dash of Harvard and Yale added to the mix. By using measuring the length of the shadow at two different places in Egypt, on the longest day of the year, the summer Solstice, he plotted the circumference of the Earth and was only a few hundred miles off the actual circumference. (What does B.C.E mean?- Why is a better term than B. C. or A. D.)
B. Even in the late Middle Ages, or early Renaissance, most educated people in Europe at the time knew the world was a sphere, after all it was the most perfect form, and since God created a perfect world it most be a sphere as well. The only problem no one knew the size of the sphere. Columbus was wrong, the earth was much bigger than he thought--about 25 per cent larger.
C. Sometimes things are so obvious, they might need just a reminding. The spherical nature of the planet influences the extent and time of sunlight. Remember the poles and the the equator. Differences in in temperatures move the currents of water and air. The curvature of the Earth is why New York City is in a different time zone than Denver. Connected with the time zones is the global grid system.
THE TRUE SHAPE OF THE EARTH
D. Although the Earth is practically a sphere. It is a little more elliptical or an oblate spheroid or ellipsoid of rotation than a true sphere. The difference is about. 0.3 percent or about 26.70 miles, with the area around the equator being just a little fatter, it bulges just a little, and the poles are a little flat. However, the variations can affect navigation, mapping and distance. The space program using satellites has conformed these variations by the differences between the gravitation attraction at the poles and at the equator. Even if a person took the highest point on the Earth, Mount Everest, and the lowest, the Marina Trench, those differences are very minor on a planetary scale, but on a human scale, they are very large.
III MOVEMENTS OF EARTH
OVERVIEW:
There are two movements of the Earth from a geographic view point. The first is the movement from day to night called rotation. The second is the yearly cycle called revolution. The results of these movements is the length of day and a major influence on the march of the seasons. Depending on the location on the Earth the speed or rotation is different. Speeds are faster at the equator and decrease towards the poles. (Take a look at Figure 3.7 on p. 79.) Of course we feel no sense of motion.
THE EARTH'S ROTATION ON ITS AXIS--LOOK AT THE NEXT SEVERAL POINTS
A. The Earth spins east to west on it's axis, the imaginary line running from the North Pole to the South Pole. The Earth's rotation on its axis has a steady speed making a complete turn in regard to the sun in twenty four hours. It does appear that the sun, moon, and the stars rise, in the east. This is an optical illusion because of the counterclockwise motion of the Earth--It is the Earth that moves, not the sun. (Take a look at Figure 3.6 on p. 78)
THE CORIOLIS EFFECT--TIDES
CIRCULATORY MOVEMENTSB. The rotation of the Earth influences the circulatory movements of the atmosphere and the world's oceans. This is called the Coriolis effect, and will be discussed in the chapters about wind, ocean currents and the atmosphere. The deflection is toward the right or in a clockwise direction in the Northern Hemisphere and toward the left or a counter clockwise direction in the Southern Hemisphere. Despite several good stories, the water in a sink does not move counter clockwise in the Southern Hemisphere. The rotation of the Earth brings different locations in the gravitational influence of the Moon and the Sun. The dry land is too solid to be moved, but the oceans are a different story. The water of the oceans are moved. The waters rise and fall in a predicable pattern called the tides.
THE DIURNAL PATTERN
C. The most notable pattern of the Earth's rotation is the diurnal pattern of day and night. Local Temperatures, humidity, and the movement of the wind changes with exposure to sun. Most life on this planet has adapted to the pattern of light and darkness. This is the major biorhythm or biological clock of most organisms on the planet and is called a Circadian rhythm. The great circle separating day from night is known as the circle of illumination. (What is it called when a person crosses time zones at high speed and has a sense of fatigue?)
REVOLUTION
D. The Earth makes one revolution around the sun each 365.242199 days which is called the tropical year, but for the most part a year is 365.25 days. However, since fractions are difficult a year is 365 days, except for every fourth year which is a leap year. Since the orbit of the Earth is an ellipse, (an ellipse is circular but not a perfect circle and more egg shaped) the distance varies..The nearest point is called the perihelion and the furthest point is called the aphelion. It seems to have little effect on the seasons. (Take a look at Figure 3.8 on p. 79 for a diagram on what an ellipse looks like.)
THE INCLINATION OF THE EARTH--THE TILT OF EARTH'S AXIS 23.5š
E. The Earth moves in its orbit around the sun in a constant plane. This plane is called the plane of the ecliptic. However, the plane of ecliptic, and the equatorial plane of the Earth, do not match because the Earth's rotation axis is not perpendicular to the ecliptic plane. The Earth is always tilted at an angle of 23.5š from the perpendicular and forms an angle of 66.5š to the ecliptic plane. Most of the time this inclination is not described in terms of the angle, but as being 23.5š from perpendicular. Like many things in this course a picture can do a better job than words.(Take a look at Figure 3.9 on p. 80.)
AXIAL PARALLELISM
F. In addition to the constant tilt of 23.5š the Earth's axis also has another constant called parallelism or polarity of the axis. The axis remains more or less pointed to the Polaris--the North Star. The combination of rotation, revolution, tilt, and parallelism is why there are differences in the concentration of sunlight from location to location and why there is more sunlight during certain parts of the year. This is the reason for the seasons in much of the Northern and the Southern Hemisphere.
SIDE BAR
IMPORTANT PARALLELSLines connecting all points of the same latitude are called parallel lines. I know you know about parallels but this list is important, especially the numbers. The list of parallel lines could be unlimited, there are seven which have significance to geography.
1. Equator, 0 š 5. Tropic of Capricorn, 23.5 š S 2. North Pole, 90 š N 6. Arctic Circle, 66.5 š N 3. South Pole, 90 š S 7. Antarctic Circle, 66.5 š S 4. Tropic of Cancer, 23.5 š N IV THE ANNUAL MARCH OF THE SEASONS
THE SOLSTICES
THE SUMMER SOLSTICE IN THE NORTHERN HEMISPHERE
THE WINTER SOLSTICE IN THE SOUTHERN HEMISPHEREA. Around June 21, (the date varies from year to year) the noon rays from the Sun are vertical or direct to the Tropic of Cancer, The circle of illumination reaches 23.5 š beyond the North Pole, and stops 23.5š S short of the South Pole as well. Those places north of 66.5 Nš, the Arctic Circle, remain in daylight for 24 hours. The points in the Southern Hemisphere 66.5 Sš are in 24 hours of darkness. This is the Summer Solstice in the Northern Hemisphere, but the Winter Solstice in the Southern Hemisphere. Near December 21 the roles are reversed and the Tropic of Capricorn receives the Sun's rays at noon strike that parallel perpendicularly. (Take a look at Figure 3.10 on p. 81.) (The direction of the sun rays is on pp. 82-3 of your book if you are confused I just combined them.)
EQUINOXES
B. So far, I've discussed the Summer and Winter seasons, just remember that when it is Summer in the Northern Hemisphere, it is winter in the Southern, but what about the Spring and Fall? Around March 20, the vernal, or spring equinox, in the Northern Hemisphere, and Autumnal equinox around September 22. The vertical rays of the Sun strike the equator and equal amounts of sunlight shine on the poles. Daylight and darkness are 12 hours long all over the Earth. The seasons are flip-fopped in the Southern Hemisphere. (What holiday falls after the first Sunday after, the vernal equinox, and the first full moon?)
CHANGES IN DAYLIGHT AND DARKNESS
C. From the Spring Equinox in the Northern Hemisphere to the Summer Solstice, Daylight increases in Colorado and means about 15 hours of Daylight. After the Summer Solstice daylight decreases until the Winter Solstice around December 21. (Take a look at Table 3.3 on p.85 and give me the approximate latitude for Denver.) The process is reversed in the Southern Hemisphere. (What holiday falls around the Winter Solstice in the Northern Hemisphere?)
TELLING TIME
D. All the great civilizations, Egypt, Mesopotamia, India, and China in the Old World, as well as the great civilizations like the Aztec and Mayan in the New World, all developed systems for telling time. All these civilizations developed calendars. In the last thirty or so years, other places like Stonehenge in England, and the Chaco Canyon in the Four Corners have been recognized as calendars. (Why is it important to tell time in agricultural societies, and to have calendars?)
ANALEMMA
E. There are some things which are right in front of your eyes, but have little significance until they are pointed out. One of these things is the analemma. On globes it is usually placed in the middle of the Pacific Ocean and looks a very badly drawn "figure 8" that shows the latitude at which the noon sun is directly over head. Simply, an Analemma is a scale to show the declination of the sun throughout the year. All that is needed is the day and looking at the chart. (If you wanted to get the angle very simple math is involved. It must be simple because I figured it out quickly.) (Take a look at Figure 3.12 on p. 84.)
V INSOLATION AND THE SEASONS
A. Insolation is the technical word for Solar Radiation, and is part of the electromagnetic spectrum (Take a look at Figure 4.5 on p. 99.) Insolation is short for incoming sol ar radiation. Essentially, all the energy comes from Solar Radiation, there are other sources but they are insignificant. The seasonal differences in temperature are due because of changes in insolation.
B. There are several factors for differences in insolation. On factor can be Atmospheric Obstruction. It is a technical term for cloud cover and the particulates in the atmosphere, but cloud cover is an iffy thing and is not a factor in the long run.
C. The reasons for differences in insolation are angle of sunlight and length of day. Both are linked to the tilt of 23.5š of the Earth and the parallelism of the planet. This is the reason for the seasons and why the polar regions are cold and the tropics are warm. The rest of the world falls somewhere in the middle.(Take a look at Figure 3.10 on p. 81 and Figure 3.11 on p. 83. Also compare Table 3.2 and 3.3 on p. 85.) Your book uses the analogy of cooking a roast with increased temperature or a longer time. The two factors with the Earth are the same: More direct (Intensity) sunlight, the sun shines longer (Duration), or both.
INTENSITY
D. Recall the Angle of Incidence and how different places on the Earth receive different amounts of sunlight during the course of the year and also consider the curvature of the Earth. The tropics, 23.5š N and 23.5š S the area between the Tropic of Cancer and Capricorn receive more solar radiation because the angle to the sun is almost at 90š which is a right angle. The area covered by the sun's rays is narrower and more intense. In the Middle Latitudes the Angle of Incidence is more oblique, around 40š and the surface enlarged so that and the solar radiation is less intense. Near the poles the Angle of Incidence is only about 10š and the area is spread over a much greater surface area. (Take a look at Figure 3.13 and Figure 3.13b on p. 86 and read the cutlines.)
DURATION
E. Another factor involved in solar radiation is the length of the day--Duration. This is not a factor near the equator because all the days are about the same, but at higher latitudes there are major differences in daylight hours. In short, it is hotter in summer and colder in winter in higher latitudes.
VI VARIATIONS OF INSOLATION WITH LATITUDE
A. There are many factors concerning insolation and one is the atmosphere, but for the moment we can ignore the atmospheric effect on insolation. At any location insolation begins at dawn and will increase until a locations obtains its maximum of insolation at solar noon. Insolation decreases after solar noon until finally when the sun sets it stops. (Solar noon is not necessarily the warmest part of the day, there are other factors, but they are in the next chapter.)
SIX ZONES OF INSOLATION AND TEMPERATURE
B. The amount of insolation shifts in most locations with the seasons. Geographers love to map patterns and locations and they have mapped the locations of the seasonal distribution of insolation. There are three patterns of insolation in each hemisphere. The patterns are the foundation for identifying six zones of insolation and temperature which circle the Earth. (Take a look at Figure 3.14 on p. 87 and read the cutline. Remember what I say about pictures.)
C. In the Northern Hemisphere the Tropic of Cancer 23.5š N and the Arctic Circle 66.5 š N act as dividing lines for three of these zones. The region between the equator and the Tropic of Cancer is called the North tropical zone. In this region, insolation is always high and the only way to tell the difference between winter and summer is by looking at the calender. The north midlatitude zone is an expansive area between the Tropic of Cancer and the Arctic Circle. Most people on this planet live in this zone. In midlatitude locations in the Northern Hemisphere, insolation is at its maximum during the June solstice, and is at its minimum during the December solstice. The Polar Zone, or Arctic zone, ranges from the Arctic Circle to the pole. Like midlatitude locations insolation is at its maximum during the June solstice.
D. Reversing directions a corresponding patter is followed in the Southern Hemisphere. There is the south tropical zone, the south midlatitude zone, most of this zone is ocean, and the south polar or Antarctic zone. The lines separating the different zones are the Tropic of Capricorn 23.5š S and the Antarctic Circle 66.5 š S. Amounts of maximum and minimum insolation are reversed from their northern counterparts.
CONNECTIONS
E. In spite of differences in insolation there are some observations which can be made. The total amount of annual insolation at the top of the atmosphere of a given latitude is constant from year to year. Insolation tends to decrease from the tropics to the poles, and the closer to the poles more extremes of temperature. The seasonal balance of insolation and the movement of the atmosphere determines the climate and vegetation, the temperature, precipitation, and the winds. Of course, these factors determine where animals and people can live .
GUIDED PRACTICE
Questions during the lecture.INDEPENDENT PRACTICE Readings at home What is the connection to Sunlight and the Seasons? Culmination Yes, I know you know this but I am laying a foundation for things to come. How does the Earth rate in cosmic scale and how is it very different? What type of orbit does the Earth sun follow ? Is the Earth a perfect sphere and who first measured it? How does rotation and revolution differ? What is the Plane of the Ecliptic, Inclination, and Parallelism? How are they connected to the Seasons? What are Solstices and Equinox and how are they connected to the Seasons? List the important lines of Parallel and their relationship with the Sun?