Spin The Globe
summary: The sun rises in the east and sets in the west. We all know why, because the earth rotates once a day on its axis. But can you look at a map of the South Pole and tell which way it spins? Find out here. http://astro.uchicago.edu/cara/southpole.edu/spin.html
I. JUST THE FACTS?
The earth,s rotates once every 24 hours. This daily 360 degree rotation is the reason that the sun rises in the east and sets in the west, and why we have day and night. The earth rotates about its axis which is an imaginary straight line that extends from the geographic North Pole in the north through the center of the earth to the geographic South Pole in the south. The geographic poles are defined by this axis of rotation and are the points that a globe spins on.
The map you will be spinning represents a pretty large object. The continent of Antarctica has 17,968 km of coastline. It is approximately 14 million square kilometers in area. That is a little less than 1.5 times the size of the United States. 95% of Antarctica is covered by an enormous thick ice sheet.
This ice is on average about 2 km thick, and is up to 4.3 km thick. It totals about 31,000,000 cubic kilometers of ice, that's 24 million trillion kilograms, which is 93% of the world's ice and 76% of the world's fresh water, or 1/3 of all the world's water. Each year the amount of ice that flows off the continent alone is a staggering quantity, the glaciers discharge 900 trillion kilograms of ice a year.
II. DON'T GET HURT / WATCH OUT!
Be careful with the thumbtacks if you use them. Also, be careful not to spin the world backwards as this would cause a lot of confusion.
III. PURPOSE
Determine which way the earth rotates from a southern perspective, and in the process become familiar with global geography.
IV. WHAT DO YOU THINK?
Look at the map of Antarctica/Southern Hemisphere provided (see left), and guess which way the Earth moves. (clockwise or counterclockwise)? Why?
V. STUFF
Scissors
Copy of a Map of Antarctica/Southern Hemisphere, one that includes the tips of nearby continents. Online maps that you can use for this activity: medium-sized (23k) and large (38k). See also the CIA map of Antarctica. Other maps of the southern hemisphere would also be helpful.
Cardboard (a big enough piece to fit the map)
Thumbtack
Pencil
Globe and/or map
Stick-it note
Pen
VI. JUST DO IT
A. Using a Map
Cut out the map and place it on the cardboard so that you can spin it freely. Place a thumbtack through the South Pole into the cardboard. Note: BE CAREFUL not to stick the tack into any furniture. Spin the map and decide which way it really moves. (Think about where the sun rises and where it sets if you are unsure). Use the pencil to mark the direction on the map that you believe it should spin. Note and record if this is clockwise or counterclockwise.
B. Using a Globe
Hold the globe below you so that the North Pole Points down, and when you are looking down at it, you see Antarctica (this is the opposite of how globes are normally set up). Decide which way Antarctica really spins. Mark an arrow on the stick-it note, and place it on the globe near the South Pole with the arrow pointing in the direction you think the globe should be turning. Note and record if you are spinning the globe clockwise or counterclockwise from your southern perspective of the globe.
VII. SCORE BOARD
Record your guess, and why you think it turns clockwise or counterclockwise.
VIII. DO YOU SEE WHAT I SEE?
The map or globe should spin clockwise.
IX. EXTENSIONS
Did you changes the laws of nature? The sun rises in the east and sets in the west, but things get a little tricky at the South Pole, because every direction is north from the South Pole! In order to avoid confusion, in Antarctica the convention of "grid directions" has been adopted in Antarctica. Everyone agrees to use this system so that we can talk about east, west, north, and south.
According to the grid convention north is the direction that one would travel if they followed an imaginary line called the Prime Meridian along the surface of the globe. The Prime Meridian extends from the South Pole, passes through Greenwich England and ends at the North Pole. The Prime Meridian is an imaginary line from one pole to the other that divides the globe into East and West just as the equator divides it into north and south. It is defined to be zero degrees longitude.
Sketch the Antarctic continent, and mark any important features that you recognize. Label the other land masses on the maps, tips of the other continents that are represented. Orient your map to the grid convention. The Ross Sea and ice shelf should be at the bottom of the page and the Marie Byrd Land should be on your left.
Then north is up, south down, east is right, and west is left as a map is conventionally drawn (see for example the CIA map which is orientated this way). Add lines to indicate the grid directions on your map of Antarctica (assuming you have a copy you can write on and not a book or a map that you should not mark).
Still unsure? Look for more clues in the tips of the continents. Find the curved hook that seems to extend toward Antarctica's own hook, the Antarctic Peninsula. That hook is the bottom of South America, the tip of which is part of Chile. Look on a map that shows all of South America, notice that the tip of Chile curves toward the East (it is a bit like a backward j).
Now rotate your map such that the sun moves from the inside of the curve of our backward j to the outside. The sun rises in the east in Chile, and sets in the west. So, your world should be spun clockwise.
At the Equator the distance between degrees of longitude is about 111.32 km and at the Poles the distance between degrees of longitude is zero. Why is this?
X.REFERENCES EARTHSEARCH:
- A Kids's Geography Museum in a Book by John Cassidy, Klutz Press: Palo Alto, 1994.
- http://astro.uchicago.edu/cara/southpole.edu/spin.html
- http://www.scirp.org/Journal/PaperInformation.aspx?PaperID=81133
- The Moon Meets All Requirements of the IAU Definition for “Planet” http://www.scirp.org/journal/ijaa/
