Also, it can be done in five minutes if you find the materials.
It DOES nothing, but, to keep it short if a magnet moves near a conductive something it creates electric currents in it. In the tube they go around the circumference of the tube and create their own magnetic field, which repulses our magnet. And this makes it fall 4 times slower.
Step 1: Find the tube
Step 2: Now the magnets
Step 3: Finished
When you are sure you understand the theory completely, stick the magnets inside the tube and have fun!
PS I've tried to attach a file with a totally useless something (and it is in Russian), but there is a wonderful picture there that explains everything if you meditate over it for 15 minutes.