hot+air+balloon

Where to begin with weather balloons. There are so many fascinating things to learn about these "giants" in the sky. The craze with the balloons started way back during world war dos. They are used to measure temperature, humidity, wind speed, and various other things in the upper atmosphere. The balloons are filled with helium or hydrogen. They float because the gas is lighter then the air around it. As the atmospheric pressure decreases the gas inside the balloon expands.

Hyperbaric chambers have been used since the 40's to treat divers who have decompression sickness. Now a days, a modern HBO unit is used to treat football injuries. The device compresses the air around the injured player. The player is breathing oxygen through a mask. The higher air pressure in the chamber causes the blood vessels to constrict, reducing the swelling. One of these chambers can also be used to treat heart attack victims.