In A Totally Different Light

Light is both waves and particles, simultaneously. Is such a paradoxical nature of reality real, asks Mukul Sharma

The strange dual nature of light as accepted by modern physics makes a mockery of materialism and of those who think empirical knowledge can be a perfect discipline. It may also point to a reconciliation between science and spirituality — two vastly misunderstood magisteria that have been at each other’s jugular throughout history. In which context, it’s interesting that the phrase, “Let there be light” from the Book of Genesis in the Bible, metaphorically, also means spreading knowledge.

Yet, knowledge was the one thing missing from the best of minds when it came to fathoming what makes light tick. Ubiquitous as it was, it’s characteristics and method of propagation remained a mystery. In ancient India, the Sankhya school believed light was one of the five fundamental subtle elements from which emerged the gross elements and that it was continuous or wavelike, while the Vaisheshika school thought it consisted of a high velocity stream of fiery particles, which would mean they were atom-like. This wave-particle duality debate has raged ever since and continues to do so till today. 

Rene Descartes, the French philosopher and mathematician whose theory of light is regarded as the start of modern physical optics, was of the opinion that light was indeed made of waves. In a way, he was correct in assuming this, because only then can something like refraction be explained properly. But Isaac Newton, one of the greatest physicists of all time and a contemporary of Descartes disagreed; he was convinced light was corpuscular or composed of minute particles which were emitted by a light source. And because of his reputation, the particle theory held dominance till the turn of the 19th century.

That was when Thomas Young, the British polymath who’s been referred to as “the last man who knew everything”, performed his famous “double slit experiment”. It consisted of aiming a beam of light through a piece of cardboard with two holes in it and projecting the result on a screen behind. This seemed to totally disprove Newton and demonstrate once and for all that light did travel in waves, due to the interference patterns it generated on the screen.

That version of light lasted about a hundred years, till in 1905 Einstein published a paper showing that many metals emit electrons when light shines upon them. According to him, this meant light was made up of something that could knock off electrons from another material and that something had to be small pieces of discrete matter — known as photons — to do that and the whole world was back to regarding light as atomic in nature again. It was called the photoelectric effect and a great physicist got the Nobel Prize for it.

But now comes the fun part. The double slit experiment was, and has been, repeated several times since then and it’s been found that light behaves both as waves and particles — that too simultaneously! Apparently, it all depends on the way the experiment is performed, who is performing it and whether anybody is around to observe the results. Not only that, when instead of photons, electrons are used, they too behave similarly. Quantum physicists are aware of this weird double nature of all things at the microscopic level and say that what we actually see is what is ultimately observed. Can such a paradoxical nature of reality be real?

Likewise, attempts by mystics to communicate what their spiritual practices have disclosed always result in similar paradoxical statements for which mystics have become so famous. For example, this is how the Sufi Ibn Al-’Arabi characterised what he called the “Reality of realities”: “If you say that this thing is the temporal universe, you are right. If you say that it is God who is eternal, you are right. If you say that it is neither the universe nor God but is something conveying some additional meaning, you are right. All these views are correct for it is the whole, comprising the eternal and the temporal.”