Light summary

If you know some Arabic, you might know that the word manara means lighthouse or “place of light." It’s from this word that the minaret, the tower from which a muezzin calls Muslims to prayer, gets its name.

That’s because light is a divine force in Islam. The Qur’an says that God will lead the faithful “from darkness to the light.” It also says that “He will bestow on you a light to walk in,” and “the man from whom God withholds His light shall find no light at all.”

As the Renaissance came to a close, European countries began making significant developments in the natural sciences. It was during this period that followed in the seventeenth and eighteenth centuries, now known as the scientific revolution, that the empirical investigation of light began in earnest.

One of the first people to study light scientifically at this time was Johannes Kepler. In 1604 he published a treatise on optics in which he described a fundamental law of light. He said that the intensity of light weakened with the square of the distance from which it was observed. So if you move a candle ten feet away, you perceive its light to be one-hundredth as bright as it was when you were standing right next to it.

So, light was garnering scientific attention and inspiring great works of art, but at the beginning of the nineteenth century, it was still poorly understood. In fact, all that was really known was how to calculate the angle at which light deflected as well as its approximate speed, that it broke down into colors and was composed of particles – or was it waves?

Luckily, a new generation of students emerged to investigate further. In the early nineteenth century, evidence was found to support the wave theory of light. It was all thanks to the English scientist Thomas Young, who, in 1802, devised what’s now known as “Young’s experiment," a test that’s been called the single most influential experiment in modern physics.

At the end of the nineteenth century, the German physicist Albert A. Michelson made the foolhardy claim that the potential for new discoveries in the physical sciences was extremely slim. But we all know that great discoveries continued to be made and many of them led to Einstein’s description of light as quanta.

In the early twentieth century, scientists were still trying to confirm if light was made of particles or waves, when, in 1905, Albert Einstein offered another description – quanta, or packets of energy.