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.
At that point, you would have to pay a penalty for late enrollment in Medicare Part B. Learn more about VA and Medicare. You have TRICARE for Life. If your military service entitles you to TRICARE for Life, you must sign up for Part B when you turn 65.