The light and the sea

In his controversial work on the theory of colours ( Farbenlehre) the German poet Johann Wolfgang von Goethe wrote — “Unless our eyes had something of the sun, how could we ever look upon the light?” He was echoing ancient solar theologies which considered the ‘sun as a living God’, a sentiment shared by the artist JMW Turner. Through his study of vision, light and landscapes, Turner, one of the greatest artists, was the first to tear down the distinction between subject and object, presaging what would be later known as impressionism.

Encyclopaedia Britannica describes his transition thus: “While Turner’s earlier paintings and drawings show the most accurate observation of architectural and natural detail, in his later work this precision is sacrificed to general effects of colour and light with the barest indication of mass. His composition tends to become more fluid, suggesting movement and space...” Turner’s favourite subject was the sea, and this was no coincidence — the British Empire was at the peak of exploration, holding colonies as far as China and India. He once asked sailors to lash him to the mast of a boat for hours, so he could observe a storm in the ocean.

Like Turner, the physicist CV Raman was struck by the colour of the Mediterranean Sea during a voyage to Europe. It was believed that the blue of the sea was due to the sky’s reflections. Raman knew that reflected light is polarised and can be cut off using a Nicol prism. He wrote in a letter to the journal Nature, “Observations made in this way in the deeper waters of the Mediterranean and Red Sea showed that the colour, so far from being impoverished by suppression of sky-reflection, was wonderfully improved thereby. A similar effect was noticed, though somewhat less conspicuously, in the Arabian Sea. It was abundantly clear from the observations that the blue colour of the deep sea is a distinct phenomenon in itself..” Seven years later, Raman confirmed this in 1928 — a change in the colour of light due to scattering by molecules — which came to be known as the Raman effect. “The spectrum of the scattered light gives clues about the molecular structure of the material under study,” explain historians Rajinder Singh and Falk Reiss.

They also pointed out that “there was much scepticism in Germany about the reality of the phenomenon Raman and his collaborators announced”. Germany was the stronghold of quantum physics, and they were suspicious of his use of direct vision, simple spectroscopes and sunlight to make his observations. Eventually vindicated with the Nobel Prize, Raman did not fail to point out that nature had endowed human beings with a sophisticated optical instrument in the form of the eye. His lack of mathematical rigour had succeeded where they failed; he had the evidence of light’s quantum nature, as Einstein predicted... while they did not.

By a strange thematic continuation, all the Calcutta scientists who led the sharp but brief renaissance of Indian science were, in one way or another, studying light. Meghnad Saha examined the pressure exerted by light, SN Bose the quantum statistics of photons, and CV Raman the scattering of light by matter.

Art and science have always evolved by studying optics closely. After Newton had split the light into its rainbow spectrum with a prism, the study of materials using the particular spectrum they emitted — spectroscopy — became extremely important. Because light was found to interact with chemicals, it led to great advances in photography. Parallel to this, Oersted found that an electric current running in a wire disturbed the needle of a nearby compass, linking the sciences of magnetism and electricity. Ultimately, in the hands of Maxwell, electromagnetism and optics would be unified, upon the realisation that light is an electromagnetic vibration through space.

Just as a magnet exerts its pull along a line between its poles, a wave of light travels in a certain plane. This plane can be turned or rotated when it passes through a crystal or liquid — a phenomenon called polarisation. It was while studying the polarisation of microwaves through living tissue that JC Bose was compelled to invent his wireless coherer in the 1890s. Instead of wireless technology, Bose was mainly interested in the interaction of electromagnetic waves and matter, and how it produced sentient life.

Over the centuries mankind has accumulated instruments that probe farther than the human eye, but we observe phenomenon through hundreds of different technology layers. Telescopes in space look at galaxies, transmitting to the Earth data, which are processed into images by computers. The complexity of the Large Hadron Collider can hardly be overstated. In the end, however, these images of nature must pass through the limited faculties of the human eye. It would seem, this ever-lengthening cascade of instruments observing instruments is only as strong as the weakest link.

(2015 has been declared The International Year of Light by the United Nations.)

Rohit Gupta explores the history of science as Compasswallah

Follow Rohit on Twitter @fadesingh