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.
If you enter military service for more than 30 days, your employing office must give you a notice explaining that your enrollment may continue for up to 24 months and that you are responsible for the employee share of the premiums for the first 12 months and for 102 percent of the premium afterwards.