This happens because the temperature at which oxygen changes from a gas to a liquid is about 13 degrees Celsius above that of nitrogen. The oxygen can be seen dripping from the can just as on a humid day you can see drops of water condense and drip from a can you take from the refrigerator.
Though you technically can join the military up to age 42, if you're 35 or over you'll need an age waiver if you've never been in the military before.
Last month, U.S. Rep. Paul Broun Jr. (R-GA), tried to push through legislation that would allow people of any age to join the military as long as they could meet the minimum health and fitness requirements. The House voted 256-164 against the military age restrictions measure.