Question

what is the reason of floating stones of ram setu

Answer 1

because some vacuum is present in it

Answer 2

According to Hindu belief Ram Setu was built by Lord Rama to cross the sea. Stones used to make the bridge floated on water because Rama was written on stones. But there is a complete scientific explanation why stones floated on water & why now Ram Setu is under water.I start from the scientific fact that if air is trapped within silica it would look like a stone but would be very light and float.Another example is Ice.When put into  liquid, ice floats on liquid & after some time it sinks.Another example is of “Pumice” stone .

Pumice is the hardened foam of lava when it comes out of a volcano. The inside of a volcano has very high pressure, and can be as hot as 1600oC. When the lava comes out of the volcano, it meets the cool air or sea water.

Then air and water that were mixed in the lava bubble out. Due to temperature differences it freezes and so bubbles trapped inside them.Hence weight is reduced so it floats.

Dense stones do not float on water. But because pumice is full of air bubbles, it is less dense than water. So in the beginning it will float. But in time, water will enter the bubbles driving out the air. Slowly, the pumice sinks.This also explains why the Ram Setu is under water today. Pumice doesn’t float forever.

If you visit a volcanic island (like Barren Island in the Andamans, or Anak Krakatau in Indonesia), you can see several acres of pumice around the shore.