By Gail Murzello and Xuan
We all know a tiny speck of sand will sink when dropped into water. It makes sense to think that rocks from natural substances composed of solid crystals of different minerals that have been fused together into a solid lump, would naturally sink.
Literature analysis: Ramayana
Fig 1: Ram Sethu is believed to have been built by Lord Rama's army to cross the sea as written in the Ramayana
Ramayana is a famous story not only in India but also in many parts of Asia, such as Thailand, Indonesia, Cambodia, Malaysia and Singapore.
Ramayana is a tale about how Prince Rama led an army of monkey-soldiers across a bridge made of stones to defeat a demon who had captured his wife. It is said that the monkey soldiers threw stones in the ocean after the Prince made a prayer before they built this bridge. Today, the bridge is known as the Rama-Setu or Adam’s bridge. If you are not familiar with this story, the following animation may help you understand the story a bit better: https://www.youtube.com/watch?v=pp59n0So-XE
Ram Setu/Adam’s Bridge
Fig 2: Rama Setu/Adam’s bridge taken from Google Map
Geographical facts:
The distance between the end of Rameshwaran, Pamban island in Tamil Nadu and Sri Lanka’s Mannar Island is roughly 30 miles (48 km) long and 1- 10 metres deep. This bridge was reportedly passable on foot up to the 15th century. Temple records seem to suggest that the Ram-Setu bridge remained above sea level till a cyclone happened in 1480 (1).
Scientific inquiry:
For the sake of scientific discussion, we assume that the events of Ramayana are true and that there was such a prince who wanted to save his wife. Let’s look at the possibility of that happening.
1. Floating bridge or not?
Those who have visited Rameshwaran temple would be familiar with this stone. When you push it down, it floats up.
Fig 3: This stone weighs a lot but amazingly they float in the water.
There are some stones that float in water. One such stone is the pumice rock. Could the bridge possibly be built from such rocks?
Pumice rocks are a product of volcanic eruptions. They are lightweight and porous -trapping pockets of gas hence making them capable of floating in water(2).
It’s true — some rocks can float on water for years at a time. However, they will eventually sink like how a sponge (3) does when it absorbs water. According to the story, Prince Rama and his entourage made both their trips using the same bridge. It is a safe assumption that during those days of fighting to rescue Rama’s wife, the rocks did not sink, ensuring the safe return of the prince, his wife and his entire army.
To build such a floating bridge, the soldiers would have needed enough pumice rocks to form at least a 30km bridge. The rocks to build the bridge may not have been tightly packed and would have gaps between them and soldiers would jump to the end. This could be to minimize the number of rocks used or maybe they just did not have sufficient rocks to build such a long bridge.
2. Where did this pumice rock come from? Are there volcanoes in India?
There are a total of 7 volcanoes in India. Ruling out those in Haryana, Maharashtra and Gujarat, there are 4 volcanoes left. These volcanoes are situated in the Andaman Sea area, namely Narcondam, Barren and Baratang island. Given their close proximity to India, it could very well float to Rameshwaran.
Fig 4: Picture of a current direction in Winter (Dec – Feb)