The doors have a differential pressure of 8 lbs per sq. inch holding it closed.I was flying when the pilot had just instructed you are free to move around in the cabin. This older man, maybe in his 80s +, stood up and walked to the door and started pressing on it. The flight attendant quickly told the man to move away from the door. I don't believe he could have opened the door but to this day, I don't have a clue as to what in the world he was thinking in that moment.