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Earth's Rotation, Inclination, and Geographic Grid

Question 1: Explain why physical distance from the sun alone cannot cause the seasons.

Question 2: Label the figure with the approximate date the earth is located in the four (4) given seasonal locations.

**Rotations:**

The earth rotates about its axis in a counterclockwise direction if viewed from space above the North Pole. The speed at which the earth spins may be described in terms of either angular velocity of linear velocity.

Question 3: Angular velocity is measured in degrees of arc per unti of time and is a constang for all points on the earth’s surface. To determine this rate, complete the following:

3a: Number of degrees in any circle: _________

3b: divided by the number of hours in one (1) day: ________ which is the angular velocity in degrees per hour.

Question 4: Linear velocity varies with latitude and is calculated by dividing the length of a parallel of latitude by the number of hours in a day. Calculate the linear velocity for the following latitudes:

Latitude Approximate Length (miles) Linear Velocity (miles/hour)

0 24900 _______________

15 24060 _______________

30 21645 _______________

45 17640 _______________

60 12480 _______________

75 6465 _______________

90 0 _______________

Do you think the speed of the rotation has any bearing on seasonal effects?

**Inclination and Parallelism:**

The earth’s rotational axis extends from the North Pole to the South Pole through the center of the earth. The axis is 66.5 degrees away from the plane of the earth’s orbit and 23.5 degrees away from the perpendicular to that plane. Observe:

Question 5: Label the approximate dates on the image above.

Question 6: Explain why parallelism is necessary for seasons to occur.

Question 7: Explain how the apparent sun angle or circle of illumination relates to the location of the Arctic and Antarctic Circles:

Question 8: Explain how the apparent sun angle or the circle of illumination relates to the location of the Tropic of Cancer and Tropic of Capricorn

Question 9: If the rotational axis of the earth was to shift from its current location to 30 degrees away from vertical, how would that affect the location of the Arctic and Antarctic Circles and the Tropics of Cancer and Capricorn?

Question 10: Why are there always equal amounts of daylight and darkness at the equator?

**The Geographic Grid:**

Most are familiar with the graphing along an x-y grad and similar planar relations can be expressed on the earth’s surface. However, because the earth is an oblate spheroid, its grid is somewhat more complex than the coordinate geometry of a Cartesian plane. The geographic grid is based on angular measurement (degrees, minutes, & seconds of arc) from the center of the earth. Latitude measures angular distance north and south of the equator and longitude is the angular distance east or west of the Prime Meridian. This measurement system was created by the British to assist in their global colonial process and the Prime Meridian was conveniently placed just outside of London, so, in a way, longitude measures distance east or west of Greenwich, England. The symbols used for this is a small circle for degrees, a single mark for minutes (‘) and a double mark for seconds (“). Lines connecting points of equal latitude are called parallels and lines connecting points of equal longitude are called meridians.

Question 11:

Using a Google Maps or Google Earth, give the location of the following to the nearest whole degree:

11a: Edmonton, Alberta

11b: Cork, Ireland

11c: México City, México

11d: Tshwane (Pretoria), South Africa

11e: Orlando, Florida

11f: Punta Arenas, Chile

11g: Nome, Alaska

Question 12: Name the places located at the coordinates:

12a: 23 degrees S, 14 degrees E

12b: 40 degrees N, 105 degrees W

12c: 1 degree N, 104 degrees E

12d: 38.92 degrees N, 79.85 degrees W