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.
One would think that age to enlist in the US military would be a simple category. One is either old enough, or too old, right? Unfortunately, it doesn't quite work that way. Under federal law, the minimum age for enlistment in the United States military is 17 (with parental consent) and 18 (without parental consent). The maximum age is 35.