The sound of Rainbow

Is what we see is what it is? Do we see the entire picture with these modest assembly of rod and cone cells in our eyes? What does it mean to “see”? **cue the Vsauce music** lol jk

So I was reading this book “A pale blue dot” by Carl Sagan, one of the most influential personalities of the last century. This book is about how far we have ventured into the frontiers of space and what lies ahead for humanity. I had a few intriguing thoughts while reading these lines,

“What we perceive as color is how our eyes and brains read the wavelengths of light. We might just as reasonably translate wavelengths of light into, say,  heard tones rather than seen colors — but that’s how our senses evolved”

Evolution is curious, all our senses and organs have a specific purpose. Necessity and the ever going battle for survival over eons of exposure to the external world have modified our body to suit the needs to perpetuate life. Take for example our eyes. It is a possibility that a billions of years ago when we were floating in the oceans as primordial single cellular organisms, a chance mutation during their regular asexual cell division in a particular group of organisms might have caused them to develop light sensitive pigments. Over the course of time these pigments might have given them the upper hand in the search for food than those organisms without the pigment. The more you could see where food is the better are your chances of eating, surviving and reproducing. Fast forward a billion years here we are with our Ray bans’ covering our eyes. What if those chance mutations had gone in a different direction?

What if we had evolved to see sound and hear light?

Its’ not a far fetched sci-fi concept. Basically all our sensory organs are what we in our electrical engineering call as transducers. What’s a transducer? Anything that responds to the physical world quantities such as temperature, light, heat etc. and converts it into an equivalent electrical signal is a transducer. We don’t see through our eyes or hear with our ears. All those happen in our brain. Our humble organs are biological transducers converting external inputs into electrical signals. But these are extremely tiny electrical signals. If we were to sever the optical nerve (the nerve that bridges our eyes to the visual sensory part of our brain) and directly feed in the electrical signals at the right voltage to the nerve it is possible to see even without our eyes. The same goes for our ears. The ear drum vibrates on sound and converts it to pulses.  So all you need is an equivalent electrical signal representation of that physical quantity to be able to perceive it. Cool now let’s see the sound aspect of light. How could that be possible?

Well it is possible. Turn on your radio. Oh its’ bohemian rhapsody! Turn the radio up. That Queen Song from radio is sound. How did it originate? The radio receiver in our home converted the radio waves broadcast from the radio station into electrical signals and the speakers converted this electrical signals into sound. Perfect. Now what are these radio waves? Radio waves are nothing but light too. Light that we can’t see because our eyes are not sensitive to this particular light. You remember the predator movie? The alien could see only the infrared light. For our consideration lets’ take light as a wave (but actually light is both a particle and wave – ya its bizarre. That complicates stuff so let’s make it simple for now). A wave like the wave we surf in our beaches except that the dimensions of waves that our eyes pickup are extremely tiny. How tiny? one in hundred thousandth of a centimeter tiny. But there are longer waves too like the radio waves and even more tinier waves like x rays.

Light spectrum of different wavelengths (courtesy: khan academy)

So sound is a wave we all know that, light is a wave too. Do you see the connection now? So instead of converting light to electrical signals our eyes would be picking up the compression and expansion waves in air caused by sound. Imagine seeing the doppler effect of a train. You could literally see the waves getting compressed as the train approaches and expanding as the train recedes from you. Meanwhile, it would be a very noisy world if we were able to hear all the range of lights. What if we were able to hear only the sound of the visible part of light and see the enthralling music of Beethoven? Imagine the possibilities. You would wake up to the haunting melody of sun. Every human being would sound different from their features. Polite good mornings from strangers walking by color your world with a luminescence. Poets and writers indulge in describing the symphony of their world through their words of music. Reading a book is to listen to the words. Oh how I would like to hear the music of Robert frost and Wordsworth. Adele and Enya paint heavenly pictures with their soul voice. Above all I await eagerly for the sound of rainbow on every rainy day.