Known for a famous Shakti Pitha of Odisha, the
Bhagabati temple of Banapur in the district of Khurda is situated nearly 100 km
away from the state capital Bhubaneswar. Many people used to throng the shrine
for the fulfillment of their cherished wishes and to seek blessings from the
deity. They are amazed to see the magical prowess of the deity in realizing
their dreams come true. They are also no less amazed to find a strange piece of
stone floating in a tank of water in the Goddess Lakshmi temple situated within
the same premises.
The
Legend
The legend
has it that a former priest of the temple, during his tour to Southern India,
has collected the stone from Rameswaram near the Setu Bandha, the mythological
bridge believed to have been built by Lord Rama in the era of Treta.
Lord Rama constructed the Setu (the bridge) across the sea to Lanka, the
capital city of the demon king Ravana to free his beloved wife Sita who was
abducted and captivated by Ravana. However, all the efforts by his army of monkeys
to build a bridge across the deep sea were unsuccessful as the stones sank in
water. Two monkeys named Nala and Nila (Sons of Lord Viswakarma, the God of
Architect) who had a blessing earlier from their father, came to the rescue and
touched the stones with their hands. With their magical touch, the stones
became lighter and started floating in water like corks. Thus the massive task
of building the bridge across the sea could be accomplished! Rama Setu took 5 days to be built by an army of 10 million
powerful monkeys under the supervision and guidance of the architects Nala and
Nila.
It was believed that the Banapur stone might
be one of such Ram Setu stones.
The Ram Setu
Now
called the Adam’s Bridge, the Ram Setu is a
stretch of 30 km long and 3 km wide structure between India and Srilanka. It starts
from the Dhanushkodi tip of India’s Pamban Island and ends at Sri Lanka’s
Mannar Island. At present, some of the sandbanks are dry and the sea in the
area is very shallow, being only 3 to 30 ft deep at places hindering
navigation. As per the temple record, it was passable on foot and completely
above sea level up to the 15th century until a cyclone deepened the channel in
the year 1480. The estimated age of the structure Rama Setu is about 1.7 million
years.
Science Behind the Floating Stone
On
close examination of the stone of Banapur, it was found to be porous and punctuated
by numerous holes occupied by air. Hence, the Volume of the stone is greatly
increased compared to its Mass. According to Archimedes Law for Floatation of
bodies, a body will float in water if the Weight of the liquid displaced by the
body (the upward thrust due to Buoyancy) is equal or more compared to its own
Weight (the downward Force due to gravity).
The
Banapur stone being spongy, its Volume is more compared to a normal stone of
the same weight, and hence, it displaces more water. This leads to the contribution
of more upward buoyant Force that overcomes the Weight of the body to keep it
floating.
The
law governing the floatation of bodies also states that the density of a floating
body must be equal to or lower than the density of water. Although the density
of the pure rock alone that makes up the stone is more than the density of
water (1 g/c.c.), the average density of the stone, however, should be less
than the density of water as we have to take into account of the density of air
present within the holes that make up the stone. This explains the floatation
of the Banapur stone from density standpoint also.
Pumice Stone Theory
According to one theory, the Banapur stone
collected from Ramashwaram might be a Pumice stone. Pumice is a strange piece of lightweight, glassy, and porous
volcanic rock that floats in water. It 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 1600 degrees Celsius. When the lava
comes out of the volcano, it meets the cool atmospheric air which is around 25 degrees
Celsius resulting in very rapid cooling.
Air and water embedded in the viscous lava bubble out as the pressure
falls. The huge difference of temperature makes the lava freeze almost
immediately. Hence, the bubbles get trapped inside the freezing stone, giving
it a very spongy appearance. In certain types of pumice, the bubbles can make
up to as much as 90% of the total volume.
However,
there are some pieces of evidence to debunk the Pumice Stone theory. First, there is no
volcano nearby Ramaswaram. Secondly, floating stones of Rameshwarm are not as
light as the normal pumice stones and don’t have the chemical composition
similar to actual pumice rocks.
Modern View
X-ray studies at the Lawrence Berkeley National Laboratory
of the U.S. Department of Energy have helped scientists to solve the mystery as
to how Pumice is able to float in water for a long time unlike a water-soaked
sponge that quickly sinks in water. It was originally thought that the pores of
pumice are sealed from outside disallowing water to enter into it. However,
pumice pores are found to be actually largely open and connected networks of clear
channels. Researchers found that the gas-trapping
processes in pumice stones are related to Surface Tension, a phenomenon
exhibited only at the surface of a liquid that behaves like a skin allowing certain
aquatic creatures to walk on water.
To understand what's at work inside the
pumice, the team used wax to coat bits of water-exposed pumice sampled from
Medicine Lake volcano near Mount Shasta in Northern California and Santa María
volcano in Guatemala. They then used an X-ray imaging technique known as
Micro-tomography to measure accurately the concentrations of water and gas present
within the pumice samples.
The scientists conclude that water fills
up only some portion of the pore space. The water surrounds and traps gases in
the pumice forming bubbles that make the stones buoyant. Surface Tension serves
to keep these bubbles locked inside for prolonged periods. The researchers have
also developed a formula for predicting how long typical pumice stone will
float based on its size.
Hence,
the mystery of the floating stones of Banapur (and Rameswaram) continues and poses
to be an ever enchanting subject for researchers in the days to come.
Nikunja Bihari Sahu
Education Officer
Regional Science Centre
Bhopal
A student with the Floating Stone of Banpur
The Floating Stone of Banpur
Temple of Goddess Lakshmi that houses the Floating Stone of Banpur
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