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CD Science

CD_autolev_cropA friend recently commented that she
had boxes of CDs to get rid of now that all of her music is stored on her phone and computer. This got me thinking – what could be done with these discs besides the infinite mosaics found on Pinterest?

The hovercraft is the classic CD vehicle – and the easiest to make. Just grab a balloon and a water bottle cap with a little glue. Detailed instructions from ScienceBob are here.  You will inflate the balloon and let it out slowly through the water bottle cap. The air provides a low friction cushion for the CD to float on. How long does your craft hover? Does the size of the balloon affect how long and how high the hovercraft floats?

CDs make excellent wheels. A piece of cardboard for the car body, bamboo skewers for the axel, a rubber band for the engine and you are ready to roll! Detailed directions are here. Explore how the size of the rubber band or the number of windings affect how fast and far your car can travel. Can you redesign your car to carry a load such as a tennis ball?

CDs were made for spinning! There are two simple toys you can make with a CD – a traditional top and a button spinner. Both of these can be used to explore the mixing of colors.

Give a CD to a child and the first thing they will notice are the rainbow colors. A CD stores data in grooves and pits, not unlike a vinyl record, except that they are read by a laser beam instead of a stylus. The pits and grooves reflect light such that it spreads the light out into its colors. Shine a flashlight on the CD so that it reflects on to the wall and you will see a spread of colors. Try different types of light such a LED, fluorescent light or incandescent light. Videos of different the different patterns created by these lights and a more detailed description of the science are found here.

Take it a step further and use a CD to make a spectrograph. Different colors of light will create different patterns. You can create a variety of colors by burning salts.

If you’ve got some cases to go with the CDs then use them to germinate seeds. Remove the black insert (that the CD snaps into) and cut a paper towel to fit inside the case. Cut a slot in a water bottle (with the cap on) for the case to fit into and place the case in the bottle hinged end first. Fill the bottle about half full of water so that it wicks up the paper towel. When the paper towel is wet, remove the case and press some seeds (radish works well) into the paper towel just above the top of the bottle. Replace the case into the bottle and set the whole contraption in a sunny window. After a day or two the seeds will sprout and you can start experimenting. What happens if you turn the seeds upside down or sideways? What affect does fertilizer or pesticides have on the seeds? What other questions can you investigate?

If you’re up for a bit of fun, check out this cool trick from the Crazy Russian Hacker. The CD is made of plastic, a polymer that can be stretched like a balloon when heated.