## Earth s Magnetic Field

Earth’s Magnetic Field AIM: How is Earth’s magnetic field similar to a bar magnet? A compass is a magnet that is allowed to pivot and used to determin...
Author: Toby Thomas
Earth’s Magnetic Field AIM: How is Earth’s magnetic field similar to a bar magnet? A compass is a magnet that is allowed to pivot and used to determine your direction. Compasses have a magnetic north and south pole. Look at the diagram to the right which represents the Earth’s magnetic field. Label the north and south GEOGRAPHIC POLES on the diagram. Label the north and south MAGNETIC POLES on the diagram.

Interpret what you have labeled.

Q.1. You are using a compass to determine North and notice that it is slightly off. Based upon what we did in the lab, provide two explanations as to why the compass is not pointing to the North Pole.

Importance of Earth’s Magnetic field

Conclusions: 1

What is Latitude? Latitude is defined as a measurement of distance in degrees north and south of the equator. There are 90 degrees of latitude from the equator to each of the north (90°N latitude) and south (90°S latitude) poles. The equator has a latitude of 0 degrees. Latitude lines are pictured on the globe to the right. Latitude lines are parallel, that is they are the same distance apart. In fact, they are sometimes called parallels. Positions on latitude lines above the equator are called “north” and are in the northern hemisphere. Miami, Florida, for example, is nearly twenty-five degrees north of the equator. Its approximate latitude is written as 25°N. Positions on latitude lines below the equator are called “south”. Porto Alegre , Brazil, for example, is near the thirty degree latitude line too, but in the southern hemisphere. Its latitude is written as 30°S.

a.

Lines of latitude are

b.

There are

c.

The equator is

d.

Another name for latitude lines is

e.

The equator divides the earth into

to the equator. degrees of latitude north and south of the equator. degrees. . equal parts.

A.

D.

G.

J.

B.

E.

H.

K.

C.

F.

I.

L.

Practice finding the latitudes of a number of places using the globe to the left.

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What is Longitude? Longitude is defined as measurement of distance in degrees east or west of the prime meridian. The prime meridian divides the earth in half and is referred to as 0° longitude. The prime meridian, as do all other lines of longitude, passes through the north and south pole. This is shown in the diagram to the right. Longitude lines are not parallel. They make the earth look like a peeled orange. There are 180 lines of longitude on the each side of the prime meridian. On the opposite side, the prime meridian is not zero degrees but 180 degrees. Here, it is called the International Date Line. Longitude lines to the left of the prime meridian give locations west, in the western hemisphere. Longitude lines to the right of the prime meridian give locations east, in the eastern hemisphere. Miami, Florida, for example, is near the 80° line of longitude. It is west of the prime meridian and is written 80°W.

h. i. j.

Longitude lines give directions

k.

There are meridian.

Longitude lines connect the

with the

The line of 0° longitude is called the and

. .

of the prime

degrees of longitude each side of the prime

The lines of longitude on the diagram to the right are 15° apart. Notice that some of the lines are not numbered, that there are blank boxes on those lines. Study the numbers on the other lines, then print the proper numbers in the boxes. What are the longitudes of the following points shown on the map? Remember: You must write E for east, or W for west to properly identify the location.

A.

C.

E.

G.

B.

D.

F.

H. 3

Using your knowledge of longitude and latitude, determine the approximate locations of the each symbol. Remember to list latitude first (with North or South) and longitude second (with West or East).

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Longitude, Latitude and the MLB

Purpose: When longitude and latitude lines are used together to form a grid, the set of numbers are called coordinates. You will use the coordinates below and the included map to locate the cities at those locations. You are to name the city state and the MLB Baseball team that competes in that city.

Latitude Longitude 41oN 74oW 40oN 105oW 34oN 84oW 29oN 96oW 39oN 84oW 38oN 123oW 42oN 88oW 47oN 122oW 39oN 90oW 42oN 82oW 43oN 71oW 34oN 117oW 39oN 76oW

City

1. To locate exact places on the earth, one must look at a. the intersecting lines of latitude and longitude b. the lines of latitude only c. the lines of longitude only d. a neighboring area to describe the location

3. On a globe, the Equator is the a. Horizontal, center line b. Vertical, center line c. 30 degree line d. 180 degree line

State

MLB Team

2. Latitude lines on a globe run from a. north to south b. east to west c. north to east d. south to west 4. Coordinates can be written like this: a. 20 degrees S, 140 degrees W b. 40 degrees N, 120 degrees W c. 20 degrees S, 160 degrees E d. All of the above 5

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Using the Globe for Longitude and Latitude Use the globe to determine the latitude and longitude for the following cities. Keep in mind that most of these cities will not be located exactly on a marked line; therefore you must carefully estimate the latitude and longitude by mentally subdividing the boxes.

City, Country

Latitude and Longitude

London, England Kiev, Ukraine Paris, France Seoul, South Korea Sydney, Australia Toyko, Japan Seattle, Washington USA Lima, Peru Madrid, Spain Cairo, Egypt Beijing, China Mexico City, Mexico New York, New York USA Capetown, South Africa Wellington, New Zealand Conclusion: What do you find most challenging when using latitude and longitude?

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Longitude and the time of day are closely related. People consider ‘Noon’ to be the time of the day when the sun is highest in the sky. If it is noon here at RMS, what time would it be in Los Angeles?

Time Zones and Longitude

Noon occurs at the same time at all places along a single line of longitude. Which way do longitude lines run? The Earth rotates from west to east, which causes noon to occur at different times along different lines of longitude. About 130 years ago, many towns across the USA each had their clock set a little differently. The situation was very confusing for travelers and trade. Why do you think that is the case?

In 1883 an international conference set up times zones. A time zone is a band of longitude about 15 degrees wide in which the time is the same. This is because the Earth rotates 15 degrees every hour. How many degrees make up a circle? After 24 hours, the Earth has completed one rotation (a day). The boundaries are not straight lines so that a city or county is not split into different time zones. If you travel several hundred kilometers east or west, you will probably cross a time zone. When traveling west you subtract an hour. When traveling east you add an hour.

A place has been established on Earth where the day changes. This place is the IDL and is located in the Pacific Ocean and bends to avoid large land masses. It is located in the center of a time zone. The clock time is the same on either side of IDL, but the date differs. You gain a whole day when you cross the IDL going west, and lose a day when traveling east.

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Time Zones in the USA There are 4 time zones that make up the USA. They are: Eastern Time Zone

Central Time Zone

Mountain Time Zone

Pacific Time Zone When you travel from the East Coast towards the West Coast, you subtract 1 hour after crossing a time zone. If you head the opposite direction you add 1 hour after crossing a time zone. Try the following: 1. If it is 7 AM in LA, what time is it NYC?

2. What time zone is Washington State in?

3. If you take off in a fast plane from NY at 3 PM, and travel in 3 hours to LA, what time will it be when you land?

4. You are in Seattle and you want to watch a Mets home game that starts at 7:15. What time should you turn on your TV?

5. You are in Boston on New Year’s Eve and want to call a friend who lives in Las Vegas at the stroke of midnight there. What time should you place your call?

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Polaris

How to Determine your Latitude? If you stand at the North Pole and look directly up above your head, you will see a star called Polaris, or the North Star (img. A). This star is visible from any location in the Northern Hemisphere.

img. A

If you measure the angle between the horizon and Polaris, that angle will be equal to your latitude. Before you can do this, you must be able to locate Polaris amongst the many stars visible in the night sky. In order to do this, you must locate the constellation Ursa Major, also known as the Big Dipper. This constellation “points” directly to Polaris (img. B). Once you find Polaris, you need to use an instrument called an astrolabe (img. C) to measure the angle between the horizon and Polaris. This img. B angle is equal to your latitude.

North Pole

Equator

Polaris

The Big

Look at the image on the left. This man is using an astrolabe to measure the angle between the horizon and Polaris, which, in this example, is equal to 43°. The latitude of this observer is 43° N. It must be north because this technique does not work in the Southern Hemisphere as Polaris is not visible south of the equator.

img. C

✷KEY IDEA✷

YOUR LATITUDE IS EQUAL TO THE ALTITUDE OF POLARIS IN THE NORTHERN

Latitude/Polaris Practice 1. What is the altitude of Polaris here in Roslyn (approx. 41°N)? 2. What happens to the altitude of Polaris as you move north in the northern hemisphere? 3. What happens to the altitude of Polaris as you move south in the northern hemisphere? 4. What happens to the altitude of Polaris as you move due west from Roslyn to Chicago? 5. If the altitude of Polaris in Roslyn is 41° tonight, what will its altitude be tomorrow night? 6. How does Polaris appear to change position during the night? 7. How do stars near Polaris appear to change position during the night? 8. What is the altitude of Polaris at the North Pole? 9. What is the altitude of Polaris at the equator? 10. If you cannot see Polaris on a clear night, state something concerning your position on the Earth’s surface? 11. If you are facing Polaris, which compass direction is at your back? 12. If you are facing Polaris, which compass direction is to your left? 13. If you see Polaris at an altitude of 90o, where are you?

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14. If you see Polaris at an altitude of 90o and then look around, what direction are you looking?

15. As you move north in the northern hemisphere, what happens to your weight?

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