Build a Tin Can Telephone!

Sound is made of VIBRATIONS — tiny back-and-forth movements that travel through air as invisible waves. When you talk, your vocal cords vibrate. Those vibrations travel through air to your friend's ear.

But sound can travel through solids too — and it travels FASTER through solids than air! A tin can telephone uses this: your voice vibrates the can bottom, vibrations travel along tight string, and the second can turns vibrations back into sound.

The string MUST be tight. Loose string absorbs vibrations instead of carrying them. Think of it like a highway — a smooth straight road carries cars fast, but a bumpy winding road slows everything down.