Light Theory: from Ancient to Modern Times

Light Theory: from Ancient to Modern Times
By Jack Millard

Light is, and always has been fundamental to life. Although ancient civilizations knew little about how light actually works, they still recognized its importance to life. In fact, "light" - specifically, the conflict between light and darkness, or good and evil - was arguably the basis for all ancient religions and even those still practiced today. One of the first scientific breakthroughs in our understanding of light can be traced back to the Egypt about one millennia ago. A scientist by the name of Alhazen transformed the concept of light prevalent at the time: he discovered that light rays come to the eye from (the sun), and not vice versa. He came to this conclusion in pursuing a fascination with rays of sunlight in prison. After being freed, he published his theories and shared this discovery with the world. It was not, however, until European crusaders took this knowledge back to Europe that the West became familiarized Alhazen's knowledge. Although the dark ages retarded scientific learning substantially, a European monk by the name of Bacon was able to study Alhazen's work thoroughly. We accredit Bacon with advancing our understanding of the curvature of light. Intrigued by his observation that objects a far distance away appeared seemingly identical in size to his own finger (in the proper perspective, of course). He proceeded to realize that curved glass can, likewise, make distant objects appear near. By making of sense light and nature without the Bible, however - particularly in studying rainbows - Bacon was deemed a heretic by the Church. Bacon's insistance that everything observable happens according to natural law was too much for the Church to accept, and as a result, he was imprisoned in Paris. Two of light's next most important scientists were Isaac Newton and Descartes, two prominent thinkers of the Protestant and Catholic Churches, respectively. Descartes proposed that God was like a divine clock maker and that the universe operated according to a series of natural laws over which God is divinely sovereign. He championed the eye as an ultimate optical instrument, and in finding that it operated in accordance with his mechanical view of the universe, he came to some profoundly incorrect conclusions. In Descartes' mechanical universe, light was considered pure - like God. Colors were considered distortions of pure, white light that became visible when prisms allegedly slowed light down from its purest form. Newton, however, realized how fundamentally flawed this theory was. He endeavored to prove that prisms analyzed light and undermine Descartes' findings. Much of his efforts were motivated by the tension between Catholics and Protestants: Newton, a devout member of the Anglican Church, believed he could better the standing of the Protestants and thus considered his work divinely encouraged. Newton's conclusion that prisms analyze light and separate it into its real base colors - red, blue, and yellow - conclusively refuted Descartes. Although Newton incorrectly believed there to be seven colors separated by prisms (there are only six), his findings have been fundamental to all modern understandings of light.