The only machine placed inside the time capsule which will continue to operate for 5,000 years is this plutonium atomic watch. The width of one division of its scale is about 3 mm. This indicates a period of 100 years. In other words,it is a watch which moves only 3 mm every 100 years.The principle applied to the operation of this watch is the fact that alpha particles radiated by plutonium 239 are transformed into helium gas. The increased gas slowly rotates the hand of the watch.It was developed specially to be included in the contents of this time capsule. There is no other watch like it.