Sound: Ticker
 

	Fun Experiment to Try at Home!
		Purpose To determine whether gas or solid material is a better conductor of sound.   Materials - ticking watch   Procedure 1.  Hold a ticking watch at arm's length from your ear. Listen for the watch's ticking sound. 2. Press your ear to a table and place the watch on the table an arm's length from your ear. Again, listen for the watch's ticking sound.   Sum It Up! Solids are more efficient at transmitting sounds because the molecules in solids do not have to move as far before colliding with others to transfer their energy. Sounds transmitted through solids are louder (have more energy) and richer (have a wider range of frequencies) than those that are transmitted through air.

Astronauts touch helmets in order to communicate.
 
In space, such as on the moon, there is nothing to transmit sound. Unlike light, which can travel through space, sound needs a material, or medium, to travel through, such as a gas, solid, or liquid. Generally, astronauts speak to each other by using radios inside their helmets. This is because radio waves can travel through space. Another way astronauts in space can communicate is by touching their helmets together. Sound is transmitted through the solid material in the helmets.

For more experiments about space, read "Janice VanCleave's Solar System." (New York: Wiley, 2000.)