–The Ten Most Beautiful Experiments by George Johnson

In 1665, Isaac Newton completed his studies at Trinity College, but the outbreak of a severe plague compelled him to seek refuge in the countryside. Confined to a family farm, Newton seized the opportunity to delve into the realms of mathematics, motion, and light. While some ancient thinkers, including Plato and certain Presocratics, once believed that light originated from the eyes, Aristotle challenged this notion, asserting that colors were a fusion of light and darkness. By Newton’s era, a more lucid understanding was taking shape, and philosophers were actively shaping the refined science of optics.

In understanding the behavior of light, scholars have established that when it encounters a mirror, the angle at which it strikes equals the angle at which it reflects. Furthermore, when light travels across a transparent medium and returns to the air, it undergoes bending or refraction.

In his essay “Dioptrics,” French philosopher René Descartes put forth a speculative idea suggesting that the origin of color arises from spinning globules of aether, with faster rotations resulting in redder light. Another prominent figure in this exploration was Robert Hooke, a distinguished European scientist succeeding Descartes. Renowned for his skillful manipulations of nature, Hooke served as the first curator of experiments for the Royal Society of London. Hooke confidently asserted his understanding of color and light, describing blue as an impression on the retina caused by an oblique and perplexing pulse of light, where the weakest part precedes and the strongest follows.

Experiments by Isaac Newton

Carefully examining existing knowledge and adding his own insights, Isaac Newton approached the world as if seeing it for the first time, like a blind person gaining sight. He made a fascinating observation that dark or semi-transparent substances, when ground into powder or shaved, appeared lighter due to the multitude of reflective surfaces created in the process. Newton experimented by placing a flat lens against one with a gently curved surface, creating a mesmerizing pattern of colorful swirls known as Newton rings.

Adjusting the lenses, he noted that the colored circles grew or shrank based on how closely they were pressed together, and new circles emerged in the middle. Newton then took his apparatus into a room and exposed it to a blue ray from a prism, revealing a monochromatic display of dark and light circles. While Hooke had previously described a similar phenomenon, Newton delved deeper, making it uniquely his own.

Isaac Newton’s fascination with the subject intensified, leading him to conduct personal experiments using a thin, blunt probe known as a bodkin. With meticulous care, he inserted the bodkin and pressed it against his eyeball, observing the emergence of various white, dark, and colored circles. Repeating the experiment in daylight, with nearly closed eyes, Newton witnessed a significant, wide bluish-dark circle with a smaller, brighter spot at its center. This personal exploration added a hands-on dimension to Newton’s study of optics, providing him with unique insights into the patterns and colors perceived through direct manipulation.

Isaac Newton proceeded to delve into the anatomy of the eyes, realizing that visual vibrations travel through the optic nerves to reach the brain. To understand the substance carrying these visual imageries, he dissected the tissues around an animal’s eye. While some believed in the idea of animal spirits being responsible for this process, Newton conducted an experiment that ruled out such a notion. In his pursuit of eliminating the possibility of animal spirits, Newton, driven by curiosity, created a small circular hole in his window shutter one day. Using a prism in the path of a sunbeam, he projected a spectrum onto the darkened room’s far wall, describing the experience as initially delightful due to the vivid and intense colors. Repeating the experiment ensured that his observations were not influenced by accidental factors, as he consistently obtained the same array of colors when placing the prism in various positions.

These experiments led to a surprising conclusion for Isaac Newton, as he embarked on what he termed his Experimentum Crucis. By this point, he likely had a sense of what to expect. In one of his experiments, Newton projected the spectrum onto a wooden board, drilling a hole to allow each color to pass through the prism individually. Progressing from red to blue, each color exhibited increasing bending, leading Newton to articulate that “light consists of rays differently refrangible.” Once separated, a color remained unalterable, challenging the prevailing belief that colors were quantifications of light derived from the refraction or reflection of natural bodies.

Isaac Newton returned to Cambridge and ascended to the prestigious position of Lucasian Professor of mathematics, where he delivered lectures on color and light. His inventions, compact yet more powerful than conventional telescopes, impressed the Royal Society. In 1672, the society published Newton’s paper “New Theory About Light and Colour” in the Philosophical Transactions. However, Hooke attempted to undermine Newton’s work, asserting that he had already conducted similar experiments with results explainable by his own theory.

Isaac Newton’s Legacy

In the present era, Newton’s comprehension of the light spectrum became the basis for spectroscopy, a vital tool in fields like chemistry and astronomy. His findings also impacted colorimetry, which is crucial in sectors such as photography and digital imaging. Moreover, his optical principles contributed to progress in designing lenses, optical instruments, and technologies like fiber optics, LEDs, and digital imaging devices. In summary, Isaac Newton’s contributions remain highly influential in the development of various technologies related to light and color.