Light in Conflict

Engraving of Newton using a prism
to split white light into different colors.

One of the topics in my Light, Color and Vision course is the historical development of our understanding of light, color and vision, from early Greek philosophers to Albert Einstein. A critical and somewhat tragic chapter is that of the Englishmen Robert Hooke and Isaac Newton, colleagues and rivals during the dawn of modern science.

Robert Hooke (1635 – 1703) was a highly skilled experimenter who contributed to the study of Mars and Jupiter, behavior of gasses, understanding of elastic media (e.g. mechanical springs), fossils, and early microbiology, having built the first compound microscope. He was a leading member of the Royal Society, the world’s first scientific organization, through which he had contacts—and sometimes disputes—with many of the leading Europeans in the field of natural philosophy. Isaac Newton (1642 – 1727) was a first-rate mathematician, who invented calculus and gave a rigorous mathematical foundation to the study of motion of objects. Among other things, he had discovered that white light could be split into a rainbow through a prism, and developed the corpuscle theory of light, in which light was pictured as carried by miniscule, massless particles, with different colors corresponding to corpuscles of different sizes. Their relationship got off to a rough start when Hooke strongly criticized the first paper Newton submitted to the Royal Society discussing his discoveries and thoughts about light. It deteriorated further over Newton’s theory of gravitation, for which Hooke tried to claim partial credit and Newton went out of his way to deny.Newton then withheld publication of his book on optical phenomena until after Hooke’s death to deny him the opportunity to criticize it, and while Newton served as president of the Royal Society, the only known portrait of Hooke and a collection of his writings disappeared.

The two men’s theories of light were incompatible with each other.  Hooke pictured light as disturbances that propagate through a medium, like ripples on the surface of a pond, while Newton saw it as tiny balls passing through space and bouncing off surfaces. Waves are collective motions while particles are discrete things.  Which theory provided the best description of reality was an important question, but their disagreement went far beyond that to one of self exaltation and discrediting of the other, even to the point (at least in the case of Newton) using power and personal reputation to repress views with which he disagreed.  It worked for a while—for the next century most scientists held to Newton’s corpuscle theory, but then work by scientists including Thomas Young, Augustine Fresnel and James Clerk Maxwell increasingly supported its rival, and by the nineteenth century wave theory emerged victorious.

The victory was so complete that when a young, then unknown Albert Einstein published a paper seeking to explain a perplexing phenomena know as the photoelectric effect, he felt obliged to insist that his radical solution was a mere heuristic and shouldn’t be understood as a physical reality.  His idea was that light energy comes in discrete packets and different colors corresponded to different amounts of energy, a very particle-like behavior. Despite his claims of it being mere heuristic, the scientific community initially reacted quite negatively, and some historians believe that this idea delayed his receiving the Noble Prize.   Yet discoveries over the next couple decades showed that not only light, but also electrons, protons, and other subatomic entities are strictly neither waves nor particles in the classical sense.  They possess both particle-like properties and wave-like properties.  They are strange entities that are so different from everyday experience that even the best minds have a hard time explaining them conceptually, despite having mathematical equations that describe their behavior well allow allow us to design semiconductors and lasers.  In the end, Hooke and Newton were both partially right, and reality is stranger and more subtle than either imagined.

I look at the battles between Hooke and Newton, and it reminds me of the so-called debates on origins.  There are plenty of people on both sides that are so convinced that they possess the truth that they will attack the integrity and intelligence of their opponents, repress dissent in the classroom or the pew, and even undermine the idea that objective truth exists.  But I wonder if anyone really has the complete truth.  After all, both sides have persisted now for several generations, and it is rare for ideas and positions that contain no truth whatsoever to last that long.  I believe there are good reasons to believe that both sides are correct in some aspects.  When I consider the work of an infinite creator and how our universe and life came to be, I suspect that reality is stranger and more subtle than any of us can imagine.