L ast week Unesco kicked off a year-long educational, cultural and scientific celebration of light from its Paris headquarters. I believe that light was an inspired choice as a theme for worldwide multi-faceted activities. Let me tell you why.
Have you ever wondered at the infinitely varied beauty of the reds of sunset? Have you ever asked why the sky is blue, why clouds are white or grey, why leaves are green, how the rainbow forms, why those stars and planets come in different colours, and about other marvels of nature? Everyone knows that these beautiful phenomena are due to some interplay of light and matter; many people know that they involve light reflection, refraction, scattering, etc, and that physics and geometry, not to mention our minds (through “optical” illusions), play complementary roles to produce those effects. But few people have realised the central role that light plays in our lives, from socio-economic activity to medicine and technology, through our huge scientific progress of the past few centuries.
In his recent book Intellectual Curiosity and the Scientific Revolution, the historian Toby Huff explains that the invention of the telescope was the most important scientific development before the 20th century. Most people have never looked through a telescope and would not comprehend why it is placed at the top of the list. After all, as I stress to my students, a telescope is nothing more than two lenses held at the right distance from each other, and all it does is help collect more light from faraway, faint objects. But the telescope changed our view of the universe; and simultaneously, its brother, the microscope, ushered in a revolution in biology and nature around us. All this by simply collecting more light into our eyes. After that, the imprint of light on some chemical materials led to the invention of photography (“photo” meaning light in Greek, and “graph” meaning drawing or writing), and the rest is history, as they say.
History is actually one important aspect of this year’s celebration of light. In particular, Al Hassan Ibn Al Haytham, the 11th century Arab physicist who is often regarded as “the father of modern optics”, will be specially highlighted. Indeed, this year will mark the 1,000th anniversary of the publication of his monumental Book of Optics (Kitab Al Manazir), which revolutionised both the physics of optics (how light travels, how it reflects and refracts and forms shapes and images) and the science of vision (how light enters the eyes, how it refracts through the eye’s lens and forms an image on the retina, etc.). Al Haytham published numerous books on various light phenomena, including The Light of the Moon, The Light of the Stars, The Rainbow and the Halo, etc.
Other historical angles to this year’s cele-bration include: The 50th anniversary of the discovery of cosmic microwave background radiation, the “light” relic of the Big Bang that our eyes cannot see, but our detectors can record from all directions in the sky (as is known, our eyes can only see a limited range of the spectrum of “light” that nature produces); the 150th anniversary of Maxwell’s equations, which not only unified electricity and magnetism as two facets of the same phenomenon, but showed that they propagate at the speed of light, i.e. that optics is just another aspect of electro-magnetism; and the 200th anniversary of the proof (by the French scientist Fresnel) that light is a wave phenomenon (light was later shown to have a dual “personality”, behaving as either waves or particles depending on the environment) ...
Powerful laser beams
Today, light has an extraordinary impact on our lives, from economics to culture, and from medicine to science and technology. Photonics (light-related technologies) have been estimated to currently have a global market of $400 billion (Dh1.47 billion) ... expected to double within five years! Lasers, which were invented 55 years ago; fibre optics, which were invented some 40 years ago; and LEDs, whose development received the 2014 Nobel Prize in Physics, have all become ubiquitous around us. Have you wondered how (powerful) laser beams can stay thin all the way to the moon and back? How a tiny laser beam can read a library of books on a small disk (DVD)? How lasers have become essential to many medical procedures, from angioplasty to Lasik surgery? And how those tiny LEDs have invaded our environments — from TV screens to car lights and highway sign announcements?
Light also plays important roles in our cultural lives, from creative lighting of various spaces (inside and outside buildings) to the usage of glass (e.g. colour-stained windows), and of course in photography and cinematography.
For all these reasons, Unesco has partnered with more than 100 institutions in 85 countries to organise a variety of educational and outreach activities around light throughout 2015. It aims to raise awareness around the role that light (natural and technological) plays in our lives today, and the incredible developments that the science and technology of light have witnessed in the last few decades. Light was a brilliant choice (no pun intended) as the central theme for 2015. I hope everyone enjoys and learns much from this year of light.
Nidhal Guessoum is a professor of physics and astronomy at the American University of Sharjah. You can follow him on Twitter at: www.twitter.com/@NidhalGuessoum.