In order to take Galilean Relativity to the next level, Albert Einstein found himself relying on certain advances which had been made toward the end of the nineteenth century regarding the speed of light and the peculiarities therein. But to understand this, one must work their way up through the history of light.
Aristotle and Light
In the beginning of science there was Aristotle. In terms of looking at the world from a “scientific” perspective, there was no one better in the Greek world (nor would there be until the Renaissance). For centuries, what Aristotle said was held as scientific scripture – unquestionable, lest one be accused of scientific heresy (just ask Galileo, who was forced to recant his own anti-Aristotelian views). While he was well-published in many areas, his views on the phenomenon of light was graciously simple: Light, he said, is nothing of substance. It is indefinable, featureless, and it is therefore pointless to contemplate its nature.
Scientists everywhere surely celebrated such a viewpoint from Aristotle, for it meant that they needn’t concern themselves with such things, nor did they for about two thousand years (with the notable exception of a few notable Arab scholars around the 11th century), until Johannes Kepler in 1604 published a book on Optics (as the study of light was then known) called Astronomiae Pars Optica (The Optical Part of Astronomy). In it, Kepler had some good insights, including the coining of the term “ray of light,” and became one of the first to associate the phenomenon of color with light (though he did so incorrectly). It was a small step, but it was a step nonetheless.
Light Becomes Science
Galileo, around the same time, performed a couple experiments regarding light as well, including one which attempted to determine the speed of light, if indeed there was one. When his calculations came back inconclusive, he determined that either light was simply too fast to measure with existing methods (which of course is the correct answer) or light didn’t travel at all, but simply was.
Several decades after Galileo, there were two important figures in the study of light – Isaac Newton and Christiaan Huygens – each with their own view on light. Newton, already monumentally famous in the scientific community, published a book called Optiks in 1704, wherein he postulated that, light did indeed travel (a fact which had just recently been proven by the Dutch astronomer Ole Romer, who also determined its speed somewhat accurately by very clever means), and it did so in the form of tiny particles (Newton called them corpuscles).
Huygens, on the other hand, postulated based on his own observations that light traveled in the form of waves, like water and sound. While Huygens’ view was much more accurate, he was, as Andrew Robinson wrote, “dimmed by the shadow of Newton,” and his theories were overlooked in favor of the popular genius.
Light in the 19th Century
It was not until the beginning of the nineteenth century (100 years later) that Huygens would finally be vindicated, this time by the brilliant polymath Thomas Young, who by way of an experiment known as “The Double Slit” (which would one day prove to be one of the most important experiments in scientific history, paving the way for quantum physics), wherein he proved that if a beam of light was separated and then allowed to overlap itself, it would “interfere” with itself in wave-like pattern. In this way, Thomas Young ushered in a brand new era in the study of light.
But light had plenty more mysteries up its sleeve.
For more information on physics, see Also:
Relativity and Electromagnetism
References:
Robinson, A. (2006). The Last Man Who Knew Everything. New York: Pi Press.
The New York Public Library. (1995). Science Desk Reference. New York, NY: Macmillan.
Gribbin, J. (2002). The Scientists: A History of the Science Told Through the Lives of its Greatest Inventors. New York: Random House.
