The Bell on the Holy Island

During the beginning of the 20th century, on a small island in the sea north of Germany, there lived a group of devout people who believed that one should attend mass at least four times a day. They despaired about their neighbours on the same island, who, although also devout, did not attend as regularly. They thus considered this sorry state of affairs with their padre and came to a bright solution: They decided to build the highest tower possible and cast the largest bell they can muster to hang in the tower. Every time they go to mass this bell will be rung so that everybody on the island will hear it. This must surely remind them that there is mass and thus encourage them to attend.

Unfortunately these devout people were a bit overambitious. When the tower and the bell were completed, they found that the bell was too large and too heavy to be lifted to the top of the tower. With the best equipment they could muster at that time, they could only succeed to lift the bell about 10 centimetres from the ground. It became clear that even if the bell could be lifted to the top of the tower, it would be impossible to swing it in order to get any sound from it. This was a very sad situation, since the bell had the volume to be heard over the whole island, and when testing it by tapping with a hammer, it had also the most divine sound. It would have been the ideal bell to attract the attention of everybody.

The bell master came up with a solution: He proposed that they should keep the bell at its present height and cast two smaller bells to be lifted into the tower. He will then devise a mechanism so that the tongue of the large bell can be swung within the bell when the other two bells are also tolling. A miracle happened! The three bells together made the most beautiful music ever heard. People even came from all over mainland Europe just to listen to this marvellous sound.

During 1925 a young German physicist visited the island. One day he was walking past the bell tower while the bells were tolling. He looked up at the two smaller bells swinging in the tower and then at the stationary bell at the foot of the tower in absolute astonishment. He was considered to be a brilliant theoretical physicist, but was not very adept when it came to practical matters. After the mass this physicist went to the padre and asked him the following: “Padre, I understand why the two bells in the top of the tower are tolling since they swing and thus encounter their tongues which hang stationary when they are not swinging. But this stationary bell below the tower confounds me: How can it toll without swinging?” So the padre answered: “My son, what we do is to swing the tongue within the bell”.

The young scientist answered: “But padre, I have come to the conclusion that one should only accept what one can observe and measure. Anything else is not worthwhile knowing since it cannot be known. I do not see any tongue swinging within this bell even when I peek below the rim of the bell, and since all church bells the world over only toll when they are swung against their tongues, it is impossible for me to accept that there is a tongue swinging within the bell”. No matter how much the padre tried to convince this young man that there is a tongue swinging, he could not succeed. The padre finally argued that if you tilt the bell by a certain amount you will be able to see the tongue.

The young physicist asked the padre if he would allow him to pay for, and obtain the equipment to tilt the bell so that he could see whether there is a tongue. To end the argument, the padre agreed. This was duly arranged and when the physicist looked, he saw that there was indeed a tongue hanging against the side of the tilted bell. He then asked the padre to swing the tongue so that the bell can toll. The padre informed him that this was only possible once the bell has been restored to its non-tilted position. “Aha said the physicist I told you that the tongue cannot swing”. The padre informed him that it can swing but only once the bell is in a position so that the tongue cannot be seen. 

The young physicist looked very worried for a while, but suddenly his eyes lit up and he exclaimed: “Aha, now I understand: When I cannot see the tongue it can swing and toll the bell but when I see it, it cannot. Thus by observing the tongue it acts differently than it can when I do not observe it. Thank you padre, you cannot imagine how much you opened my eyes. I am spending a post-doctoral year in Copenhagen, and your bell has solved a very important problem in physics with which I have been wrestling over the past months”...