Instructions for Students: Building "Terrabagga"

Overview: You will build a simulated planet with a magnetic core. The core will consist of a battery with "donut" magnets taped onto the ends, creating the equivalent of a larger bar magnet. The core will be wrapped in a crumpled paper bag (the bulk of the "planet"). The bag will be held shut by rubber bands, which will also serve as latitude and longitude lines dividing the "planet" into eight segments. You will use a magnetometer to determine which octant of the planet the north and south magnet poles are beneath. You will record this info, then swap planets with other groups and repeat the "finding the poles" process on several different "planets".

Refer to our Terrabagga photos page to see pictures of the stages of this procedure.

Step-by-step Instructions:

  1. The first step in building a world with a magnetic field in it is to create the dipolar magnet that will go inside the world. Take the two magnets and place them on top of each other so that the magnets are attracted to each other. Now without flipping either magnet over, place the top magnet on the top of the battery. Tape this magnet in place. Place the bottom magnet on the bottom of the battery (remember, the side that was facing up, should now be against the casing of the battery). Tape this magnet in place.
  2. Next turn the paper bag inside out. This creates a clean surface that will be labeled later on. Work the bag by crumpling it and folding it.
  3. When the bag is turned inside out and is pretty workable, place your battery (with the magnets taped on) inside the paper bag. It does not matter which way the battery is facing. Work the paper bag around the battery to create a nice smooth (fairly round) world. Try to center the battery/magnet in the middle of the "planet". If one pole is too close to the surface, the opposite pole may be buried too deeply to sense with the magnetometer. You may wish to use the optional plastic bag to add extra padding to the "planet's" interior to help center the magnetic core, or you may want to "double-bag" the "core" to accomplish the same result (i.e. first wrap the plastic bag around the "core", then surround both with the paper bag).
  4. Now it's time to put the rubber band markers on your world. The first rubber band can just be placed wherever it's most needed to hold your world together. Just stretch the rubber band around your world.
  5. Now stretch one more rubber band across your world. This rubber band should meet at right angles with the first rubber band so that your world is now split into 4 equal segments. Pick one of the intersections of your two rubber bands to be the geographic north pole. Make sure the north pole is facing up.
  6. Now it's time to label parts of your world. Note that the rubber bands make a "X" when looking down on the north pole. The four "branches" represent four lines of longitude separated by 90; the prime meridian at 0, 90 west longitude, the international dateline at 180, and 270 west longitude (which is the same as 90 east longitude). Pick one of the two rubber bands to label first (either one - it doesn't matter which you do first). Use the marker to write a zero on the rubber band on one side of the North Pole, then write "180" on the same rubber band on the opposite side of the North Pole.
  7. Now turn your world so that you are looking at the prime meridian (the line of zero longitude) with the "North Pole" up. Everything east (right) of the prime meridian all the way to the international dateline is the eastern hemisphere. Everything west (left) of the prime meridian all the way to the international dateline is the western hemisphere. Label the part of your (unlabelled) rubber band that lies in the eastern hemisphere 90 E, because it represents the longitude of 90 degrees east. Label the part of that same rubber band that lies in the western hemisphere, 90 W, because it represents the longitude of 90 degrees west.
  8. Next add the third rubber band to your world. This rubber band should stretch across both of the other rubber bands meeting those rubber bands at right angles. This rubber band is your world's equator, so it should be stretching across the middle of your world. Once that rubber band is in place, label that rubber band "equator". Everything above equator towards the geographic north pole is the northern hemisphere and everything to the south of the equator is the southern hemisphere. Your world should now have eight equal segments.
  9. It's time to label the 8 segments. The segments in the northern hemisphere should be labeled 1-4 with segment 1 being between 0 and 90 E. Segment 2 is then between 90 E and 180, segment 3 is between 180 and 90 W and segment 4 should end up being between 90 W and 0. The segments in the southern hemisphere should be labeled 5-8 with segment 5 being below segment 1 and so on so that segment 8 is below segment 4.
  10. Make up a name for your "planet". Write the "planet's" name on the "planet" somewhere (at the geographic south pole would be good).
  11. Use your magnetometer to test where the magnetic north pole of your world is. The magnetometer end labeled north should dramatically point in where the magnetic north pole of your world is. Write the segment number where you find the magnetic north pole of your world onto your student worksheet. Follow a similar process to locate the magnetic south pole of your "planet".
  12. Trade planets with another group. Use your magnetometer to locate the north and south magnetic poles of several planets and record that information on your worksheet.

The source of this material is Windows to the Universe, at http://windows2universe.org/ from the National Earth Science Teachers Association (NESTA). The Website was developed in part with the support of UCAR and NCAR, where it resided from 2000 - 2010. © 2010 National Earth Science Teachers Association. Windows to the Universe® is a registered trademark of NESTA. All Rights Reserved. Site policies and disclaimer.