Khối lập phương thâm nhập thủy tinh

On a plinth sits a square tube about 30 cm high which has 3 large round openings at the front and rear,i.e. one can see right through it. There are slots in the sides of the tube through which the magician pushes two heavy,polished stainless steel sheets,which divide the tube into 3 compartments.

Then the magician takes a 10 cm,harmless looking cube and throws it into the tube from above. The cube comes to rest on the uppermost metal sheet. The tube is covered with a lid so as to separate the cube from the outside world.

The magician touches the metal barrier with his index finger,letting