Helium

1 Although helium is the second-most-plentiful element in the cosmos — it's synthesized in stars by nuclear fusion — Earth is running short of the noble gas. Extracted from natural gas, our supply accumulated in the planet's crust over billions of years — the result of radioactive decay. One-third of that stash lies in the Texas panhandle, and if it continues to be consumed at the current rate, it'll be gone in nine years.

2 Macy's is rumored to be the second-largest helium customer in the world — Curse you, Red Baron! — but the element is used for more than just floating things. Two quick examples: It's perfect for pressurizing space shuttle fuel tanks (only helium remains a gas at the frigid temperature of liquid-hydrogen rocket fuel) and for cooling the superconducting electromagnets in MRI devices (helium boasts the coldest liquid state of any element).

3 Inhaling helium lets you croon like Alvin & Co. because the gas is only one-seventh as dense as air. When helium is streaming out of your lungs as you yodel, the sound waves produced by your vocal cords travel much faster, which alters the tone quality of your voice. The result: that endlessly funny squeak