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Home , Antarctic Circle, Arctic Circle, Equator, Imaginary line, International Date Line, Latitude

Where in the World….

THE GLOBE

Since the of the ancient , people knew the was round. In 150 BCE the Greek geometer Crates of Mallus built a world globe ten feet in diameter. Thus for , we have known the shape of Earth, but most people visualize it only as the small, flat area that surrounds them. Contrary to popular legend, Columbus did not envision a flat world, nor did he prove the world was round by sailing to the .

LONGITUDE AND

Although a globe is round, with no beginning or end, there are two main reference lines from which all distances and are calculated. One is the running east and around the middle of the globe, dividing it into two equal hemispheres. The other is the , an running from pole to pole and cutting through , a section of , England. Both of these lines are 0° and the globe numbering system starts at the point where they intersect.

Locate the equator and on the globe.

All lines running east and west, parallel to the equator, are called LATITUDE LINES. They are sometimes referred to as parallels because they are parallel to each other. Latitude lines are shown at intervals and of the equator.

What are the intervals (in degrees) for lines of latitude on your globe? 15o

Look at New Orleans on your globe and you will find it located at 30°. Since it is north of the equator, we say it is 30° north latitude, or 30o N.

The lines running north and south from pole to pole are called LINES, or sometimes referred to as meridians. Longitude lines are numbered along the equator on your globe at intervals east and west of the prime meridian at Greenwich., England.

What are the intervals (in degrees) for lines of longitude on your globe? 15o

Again using New Orleans as an example, we find it located at 90°, or 90° west of 0° longitude. Thus, New Orleans is located at 30o N latitude and 90o W longitude.

Find the longitude and latitude of the following cities:

Longitude Latitude Boston, MA 71o W 42o N , 150o E 34o S , 140o E 35o N , 37o E 55o N , Iraq 44o E 32o N EARTH’S AXIS Imagine that you are the watching the earth revolving about its axis once a . Looking down from the , which direction does the earth spin, clockwise or counter-clockwise? How did you determine this? (Hint: Which coast of the experiences first?)

Looking down from the North Pole the Earth spins counter-clockwise

The East Coast of the US receives before the West Coast

Where in the World 1 Notice that the earth’s axis is not perpendicular with the of the table. The axis is tilted in the same direction throughout a ; however, as the Earth orbits the Sun, the hemisphere (north or south of the equator) that is tilted away from the Sun will gradually come to be tilted towards the Sun, and vice versa. This effect is the main cause of the changing . Whichever hemisphere is currently tilted toward the Sun experiences more of sunlight each day, and the sunlight at midday also strikes the ground at an nearer the vertical and thus delivers more heat.

A protractor has been fitted with a string and so that the weight will always 90 hang vertically regardless of the tilt of the protractor. When the straight-edge of 0 the protractor is aligned along the earth’s axis the tilt of the earth can be estimated.

What is the tilt of the earth’s axis (in degrees)? 23o

LINES OF LATITUDE: THE EQUATOR AND THE

The equator is where the sun is directly overhead at on the two . For locations in the , the VERNAL occurs on the first day of around March 21, and the AUTUMNAL EQUINOX that occurs on the first day of around September 21. All locations on the earth, regardless of being in the northern or or at the equator or at the poles, experience 12 hours of and 12 hours of darkness making them equal in length.

In addition to the equator, the Tropic of , and the are two other significant lines of latitude that lie north or south of the equator.

What are their lines of latitude? 23o N Tropic of Capricorn 23o S

How do these lines of latitude correspond with the tilt of the earth’s axis that you estimated earlier?

The tilt of the Earth’s axis is equal to the (North or South of the Equator)

The tropics are the two lines where the sun is directly overhead at noon on the two , near 21 and 21.

 The sun is directly overhead at noon on the Tropic of Cancer on . This is the beginning of in the Northern Hemisphere and the beginning of in the Southern Hemisphere.

 The sun is directly overhead at noon on the Tropic of Capricorn on . This is the beginning of winter in the Northern Hemisphere and the beginning of summer in the Southern Hemisphere.

For locations in the southern hemisphere, what is the for the summer ? December 21

The ? June 21

For locations in the southern hemisphere, what is the date for the vernal equinox? September 21

The autumnal equinox? March 21

The area bounded by the Tropic of Cancer on the north and Tropic of Capricorn on the south is known as the "TROPICS." This area does not experience seasons because the sun is always high in the sky. Only higher latitudes, north of the Tropic of Cancer and south of the Tropic of Capricorn, experience significant seasonal variation in .

Where in the World 2 THE POLES

The North and South Poles represent the maximum distance either north or south from the equator. At a distance from the poles lie the CIRCLE and CIRCLE. Similar to the tropics and the equator these are lines of latitude. What is the latitude of the and ?

Arctic Circle 67o N Antarctic Circle 67o S

How do these lines of latitude correspond with the tilt of the earth’s axis that you estimated earlier?

The Arctic/Antarctic Circles are located 23o from the North/South Poles

The Arctic Circle marks the southern extremity of the polar day (24 sunlit day) of the in June and the polar (24 hour sunless night) of the winter solstice in December. Within the Arctic Circle, the Sun is above the for 24 continuous hours at least once per year, in conjunction with the Arctic's Summer Solstice. Likewise, in conjunction with the Arctic’s Winter Solstice, the Arctic sun will be below the horizon for at least 24 continuous hours.

Does Fairbanks, experience a polar day or night? Explain your reasoning.

No. It is located south of the Arctic Circle.

Navigating on earth requires knowing your position (longitude and latitude) and the position of where you are going. Modern devices such as GPS receive signals from several circling the globe that triangulate your position using these multiple reference points in space. You can also use a magnetic .

Locate on your globe the positions of the north and south magnetic poles. What is the approximate longitude and latitude of the north and south magnetic poles?

Longitude Latitude Front

South Magnetic Pole 63o S 138o E s w o d n i W 83o N 114o W

N The needle of the magnetic compass always points to the magnetic north pole. Using the compass determine the direction of magnetic north and draw an arrow indicating the direction of magnetic north on the illustration of the laboratory.

SCALE

The of the globe gives the relationship between length measured on the globe and the corresponding distance on the ground. The amount of REDUCTION that has taken place is normally identified somewhere on the globe commonly referred to as the scale. On most maps, the map scale is represented by a simple fraction or ratio. This type of description of a map's scale is called a fractional scale. For example, a map where one unit (centimeter, meter, inch, kilometer, etc.) on the illustration represents 1,000,000 of these same units on the actual surface of the Earth would have a representative fraction of 1/1,000,000 (fraction) or 1:1,000,000 (ratio). Of these mathematical representations of scale, the ratio form is most commonly found on maps.

What is the scale of your globe? 1 : 41,849,600

Where in the World 3 Wrap a string around the globe at the equator and determine the circumference of the globe at the equator in meters. Using the globe’s scale estimate the circumference of the earth in kilometers. Compare your calculation with the known circumference of 24,900 or 40,074 km.

Approximately 96.0 cm (0.960 m) for the circumference of the classroom globe.

41,859,600 x 0.960 m = 40,185,216 m = 40,185 km (fairly accurate!)

The International Space Station orbits the earth approximately 350 km above the surface. How far above the surface of the globe (in centimeters) is the space station orbiting? (Hint: Set up an equivalent ratio of the globes circumference and the earth’s circumference)

96.0 cm / 40,074 km = x cm / 350 km 0.86 cm above the globe

The orbits the earth at a distance equal to 60 earth radii (approximately 400,000 km). For the size of your globe determine how far (in meters) the moon orbits the earth. circumference = 2 π radii or radius = circumference / 2 π 96.0 cm / 2 π = 15.3 cm x 60 = 918 cm = 9.18 m

The earth orbits the sun at a distance that is 370 times the distance to the moon, or approximately 150,000,000 kilometers. For the size of your globe determine how far (in meters) the earth orbits the sun.

9.18 m x 370 = 3397 m = 3.397 km (approximately 2 miles!)

The nearest to our solar system is Alpha Centauri, located 41,500,000,000,000 (41.5 trillion) kilometers away. For the size of your globe, Alpha Centauri would be nearly 1,000,000 kilometers away!

TIME ZONES

The of day is determined by position of a meridian (line of longitude) relative to the sun. If it is noon at a given meridian (facing the sun) it is on the diametrically opposite meridian (180o). The globe is further divided into 24 time zones each equidistant (approximately) around the globe.

If the earth spins about its axis once in 24 hours (360 degrees), how many degrees of longitude is each ? 360o / 24 hours = 15o / hour

GMT () uses the time in Greenwich England (Prime Meridian or 0o longitude) so that locations east or west are either ahead or behind GMT. What is the longitude of Boston? 72o W 72o / 15o = 5 hours (round to nearest whole number) Are we ahead or behind GMT? Behind By how many hours? 5 hours If it is 3:00 pm in London, then what time is it in Boston? 10 am If it is noon in Providence, what time is it in , CA? Providence: 72o W Los Angeles: 120o W Difference in longitude: 48o 48o / 15o = 3 hours 9 am in Los Angeles If it is 10:00 pm in Providence, what time is it in ? Providence: 72o W Paris: 2o E Difference in longitude: 74o 72o / 15o = 5 hours 3 am the next day!

Where in the World 4

Opposite the globe from the Prime Meridian is the INTERNATIONAL DATE LINE, the starting point for each new day. When traveling westward across the Date Line, the date will be set one day ahead and when crossing the Date Line heading eastward, the calendar will be reset one day back.

Using the current day and time in Providence, what is the day and time for the following cities?

It is now 2:00 pm on Thursday in Providence

Longitude Longitude Time Zones Time / Day Difference Paris, 2o E 72 + 2 = 74o 5 (later) 7 pm Thursday , South 18o E 72 + 18 = 90o 6 (later) 8 pm Thursday , 116o E 72 + 116 = 188o 13 (later) 3 am Friday Fairbanks, Alaska 148o W 148 – 72 = 75o 5 (earlier) 10 am Thursday

GREAT CIRCLE ROUTES The shortest distance between two points is a straight line, but not on a ! Flatten out a globe to a flat map requires compressing the features about the equator and exaggerating the scale near the poles. The amount of distortion is significant only if the map shows a large portion of the earth's surface, such as a hemisphere or the entire world. At the scale of a city or even a small country, the inaccuracies caused by projecting the spherical surface to a flat page are not very great.

A great circle is a trace on the surface of the earth that shows the shortest distance between points along that line. The great circle route follows the sphericity of the globe, any shortest route is the one following the curve of the . A great circle is created whenever a sphere is divided exactly in half by a plane (imaginary flat surface) passed right through its center. One and only one great circle can be found that will pass through two specified points on the surface of a sphere.

Imagine traveling from Chicago (42o N latitude) to Tokyo (36o N latitude). You might anticipate that an airplane would head west and even a little south. But the shorter route is the great circle route, which can be simulated by stretching a piece of string tautly between the two cities on the globe.

Use a short piece of string and connect Tokyo with Chicago. Where does the great circle path take you on the globe?

While it appears that the most direct route from Chicago to Tokyo is due West, the Great Circle Route passes through Alberta, , southern Alaska, and the Bering . This is the shorter distance between two points on a sphere.

Measure the distance between Tokyo and Chicago. Using the scale of your globe determine the approximate distance between these cities.

25 cm 10,500 km

Describe the great circle paths between the following cities:

Toronto, Canada to , Thailand

Hudson Bay, , Russia, China

Melbourne, Australia to ,

South and along the Eastern coast of S. America

Seattle, WA to Moscow, Russia.

Over the North Pole Where in the World 5