Solar Storms and Crazy Compasses

Once upon a time, people noticed some of the rocks on the planet stuck to other rocks… and soon after floated a shard of metal in water and noticed that it pointed the same direction no matter how you rotated the cup.  We know today about the earth having a magnetic field that keeps the needle pointing in the same direction… at least, until a thunderstorm bolts through the area.  When this happens, the needle spins around and doesn’t settle on any one particular area… a problem if you’re a sailor at sea.

Other things can cause small pockets of changing magnetic fields on the earth, such as solar storms.  The sun burps and spits out high energy photons and other particles all the time, some of which make it to earth, but most of which harmlessly pass by.  The ones we notice, however, happen when a magnetic loop on the sun snaps and breaks free, causing high energy particles to zoom toward earth.  When this happens, we get the ‘aurorae’ at the poles and pockets of fluctuating magnetic fields that are detectable with a small homemade device called a magnetometer.

You’ll need one clear, plastic bottle (soda or large water bottle with the label removed), thin cotton thread, a small magnet, an index card, a tiny mirror or thin piece of mylar, one naked straw, glue, tape, scissors, yardstick or measuring tape, and a laser.  The basic idea is this:  using an amplifier (light shot over a distance), you can detect very small changes in the magnetic field using a magnet on a low-friction spring (the thread).

Attach the bar magnet onto the index card and glue the small mirror to the magnet.  Suspend the card from the bottle cap with a length of thin string (you can test out fishing line, single fibers from nylon rope, sewing thread, etc.) and stick the whole thing inside a plastic bottle.  (You can cut off the bottom of the bottle to use as a bell-jar.)

After the card settles down, it’s time to play with the experiment.  Shine your laser on the mirror at a wide angle, and you should see a dot on the wall.  Tape a piece of paper to the wall and carefully mark the position.  Over the course of a few hours, you will notice the dot “move”.  Mark the new locations with the time and date.  Make sure you’ve got a wide angle – there should be at least 90 degreed between the incoming and outgoing laser beam.

What kind of questions can you think of to ask about this project?

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