The first landing on the moon on July 21, 1969 proved that conditions on the moon are extremely unpleasant. During the long lunar day, which is equal to about 14 times of ours, the sun strikes down from a cloudless sky. At noon the temperature is well above the boiling point of water ; of course, it would not be possible for human beings to survive in such great heat. As soon as noon has passed the temperature beings to fall for there is no water vapor to act as a blanket to prevent the heat from escaping. Toward evening the fall of temperature is very rapid and by sunset it is freezing hard.