In this trick, Copperfield invites his viewers to cooperate. They are asked to pick a number and then act according to his instructions. Watch the video.
This one is very easy and no mystery at all. You have probably figured it out by yourself. The result is always the same! It doesn't matter which number you choose. It doesn't matter in wich directon you move. You will always end on the moon. Try it as many times as you want. If you land on anything other than the moon, practice your counting.