The mystery of floating stones

It is mentioned in the epic Ramayana that Ram Setu was built by the son of Lord Vishwakarma when Lord Rama needed to cross the sea to reach Lanka. The bridge known as Adam's Bridge is said to be built of floating stones. The epic mentions that whenever the name of Lord Rama was written over any stone, it started to float in the sea water.

Some such stones are said to be scattered at Rameswaram during the Tsunami and one of them was brought to Patna to prove the evidence of Rama and the bridge. The proof was given in the form of this video :

http://videos.oneindia.in/watch/1897/floating-stone.html

Even after watching this video many people won't believe it. And I can understand it. It defies logic and reason. But is it actually so? How can this mystery be explained?

About 4 years back, I was in Rameswaram and in one of the several hundreds of temples, I saw not one, but 12 such stones! They were of various shapes and sizes.

Here is a possible explanation : Before I start, I mention it very clearly that the following explanation, though not verified through thorough experiments, is supported by some of the observations that can be made by watching the video itself and some other experiments I did myself.

Any object when immersed in a liquid would displace some part of the liquid. This is so because when it is immersed in the liquid, it would occupy some of the volume that was earlier occupied by the liquid.

Any object floats in any liquid when the weight of the liquid, displaced by the fraction of the object immersed in the liquid, is equal to the entire weight of the object itself. Thus the fraction of the object immersed in the liquid depends on the relative densities of object and the liquid. For example when ice floats in water, approximately 90% of the volume of ice is immersed in water and only 10% remains outside water.

These stones might be special in the sense that they might be hollow from inside. They may have some air cavities inside them, so that the weight of the water displaced by them is more than their own weight. These air cavities need not be uniformly located inside these stones.

Logic behind the explanation :

I'll mention about the two surfaces of the stone. First surface ( which I'll denote by surface A ) has "Ram Setu Shila" written over it in Hindi in red. The other surface is opposite to this surface ( I'll denote it by surface B).

If we watch the video carefully, we'll notice that the weight of a stone of the size as shown in the video would be definitely more than 15 Kgs. A stone of this size would weigh not less than 30 Kgs. (Assuming the normal density that we observe in most of the commonly found stones). It is highly improbable that the density of the stone material would be lesser than that of water. Another observation that supports this explanation is that the stone shown in the video always floats with surface A exposed to the viewer and the surface B totally immersed in water. This suggests that the stone is not uniformly built and that the stone has higher average density near surface B as compared to the average density near surface A. If it were not so, then the stone would float even with surface A immersed. But it automatically realigns itself so that when it floats, surface B is immersed and surface A is exposed to viewer. ( This conclusion is drawn on the basis of the fact that according to Physics, stone would always float in such a position/configuartion where its potential energy is minimum.)

I did this experiment myself with stones in Rameswaram. All the stones there would also float with one particular surface always immersed in water and the other one always exposed to the viewer.

Thus we can say with reasonable level of confidence that the stones don't have uniform density and that more air cavities must be located near the surface which is exposed to the viewer when the stone floats (surface A in the case of stone of the video.)

I could have verified this theory myself by breaking one of the stones that I found in Rameswaram and looking for air cavities inside the stone. But had I attempted to do so, the temple priests would have broken my head :P