Why is the sea blue?
A question that led to a Nobel prize for Sir C.V.Raman
One fine summer, a young physicist from India - C.V.Raman was traveling aboard a ship. It was his first trip across the Mediterranean Sea. Its sparkling blue waters kept him mesmerised as he stood on the ship’s deck. Suddenly, on an impulse he dug into his coat pocket and pulled out a pocket spectroscope (I’ll tell you what this is, in a minute) and a prism. He was unusual in many ways. Most people carried a few bars of chocolates or a small diary in their pockets. His pockets jingled with other scientific instrument-like trinkets.
This week’s edition is a Science special, commemorating National Science Day in India. It falls on Feb 28. Wishing all curious souls a Happy Science Day!
C.V.Raman stood on the deck of the ship and looked at the blue waters through the prism and the spectroscope he was holding. What was he trying to see?
This was in the year 1921. Up until then, most people believed that the sea reflected the colour of the sky. Hence the Mediterranean and all other seas were blue. But C.V.Raman was standing aboard a ship when a storm was beginning to gather. The sky was getting grey and dark. Yet, the ocean’s waters remained absolutely blue. So he knew that the sea could not simply be reflecting the sky. There had to be more to this.
A scientist called Lord Raleigh had earlier explained why the sky was blue.
Sun light consists of many colours (e.g. red, orange, green, purple, blue). Imagine if we saw all of these colours, we’d have a multi-coloured zebra-like striped sky :) Lord Raleigh found out that the air molecules absorbed some colours, while dispersing some others. Air molecules scattered blue rays the most - hence the blue sky! He called this the Raleigh scattering! Lord Raleigh went on to declare to the world that the sea simply reflected the sky, and hence it too was blue!
C.V.Raman stood on the deck of his ship pondering if Lord Raleigh was correct. His prism and spectroscope were showing him something else. The rays that entered the waters of the Mediterranean were also getting scattered. The scattered rays were mostly blue, and sometimes green. His hunch was that water too behaved like air. It too absorbed the reds and oranges and the yellow. Water too scattered the blue rays wide and far, and that was why it was blue (even when the sky was dark and grey during a storm).
It wasn’t enough that his prism and spectroscope were showing this. He had to conduct experiments in his laboratory and prove them to the rest of the world. How long would you have thought this would have taken him?
The answer - 7 long years (how did he not get bored?)
In 1928, one spring morning as he sat in his laboratory, his hunch was proven. Scientists across the world were stunned by his discovery. People started making trips to the beach, looking at the water in wonder and awe. The scientific community was whispering a new term - ‘The Raman effect’! This was the discovery that won this young physicist C.V.Raman a Nobel Prize in 1930. It was also the first time an Asian had won the Nobel for anything!
Trivia for the day
A pocket spectroscope is a bit like a paper box. It allows light to come through one hole . This light passes through a material (e.g. diamonds or water molecules) and the light gets reflected in different colours and at different angles.
It’s a lot fancier that it sounds! You can find them with people who deal with gemstones like rubies and pearls.
What has India’s National Science Day have to do with this story? You can find out exactly how this story is connected to the Science Day in this podcast!
Did you like reading this short and concise piece on science? Click on ‘like’ or ‘comment’ or ‘share’ and show me how well you liked this piece. Also, do you think there may be other reasons for the sea being blue? If so, I’d love to hear it. Click on ‘comment’ and tell me what you think!