A hilarious theory has been given as to what the Ark of the Covenant really is.
Erich von Daniken gave this theory in his book "Signs of the Gods." There are numerous holes in the theory, but I give it nonetheless purely for a laugh. However, this makes a great conversation peice.
The Ark of the Covenant was a gift from aliens to Moses. This gift was a plutonium powered manna making machine. In many different texts it says that only certain people, such as the elders or the religious leaders, could go near the Ark of the Covenant. These special people also wore special clothing. The preistly robes apparently had a hidden purpose. This clothing was lead plated to protect against the radiation from the plutonium.This is perhaps the radiation is just a little hard to believe.
Later in history, the Jews are conquered by one of many different peoples. In order to suppress the Jews, their captors stole the Ark of the Covenant to crush their spirits. The Ark of the Covenant was eventually locked up since anyone who came near would die a "strange death." This was obviously due to the massive radiation.
However, much later, the Jews decided to find the Ark of the Covenant and steal it back. The Jews who stole it back were completely unaware of the 'real' purpose of the machine. They just wanted their sacred relic returned to them. Since they were obvilious to the purpose of the machine, they did not have the necessary clothing to protect them. According to Daniken, by this time the radiation from the plutonium inside had reduced to a safe level. This explains how they survived.
There are still traces of plutonium left in the Ark of the Covenant, it is possible to track the location of this sacred relic. According to Erich von Däniken, this lies in Ethiopia somewhere. The problem is, he doubted the Ethiopian government would let people into the country to search for the Ark of the Covenant with geiger counters, or whatever other instrument would be needed to find it.