Newton on Light Diffraction

Newton felt there were some properties a wave theory of light simply could not explain, such as diffraction. For example, diffraction is the property of waves that allow them to bend around objects and spread through openings. In the case of sound waves, it’s why a sound in one room can often be heard in another room farther away by someone not directly in the path of the oncoming sound; the sound wave travels from the one room, spreading out through the doorway into the other room where it’s then heard. Light doesn’t appear to behave this way, after all, you can’t see around corners – can you? The diffraction of light is usually unnoticeable because light waves have such short wavelengths – much smaller compared to the wavelengths of sound waves. Nonetheless, light will diffract if the opening is small enough.

Newton’s Intervening God

While Newton saw the world as following definite laws, he also imagined an intervening God to keep things running smoothly.

Energy vs Momentum Conservation

Hints of energy being conserved, much like momentum, were showing up by the 1840s. But unlike momentum conservation, which by comparison was quickly accepted and understood (pretty much by 1687 with Newton’s Principia), energy conservation remained a mystery until 1850.

Newton Waited to Publish Opticks

In 1666, Newton bought his first prism with the motivation of disproving Descartes wave theory of light. In 1672, he gave a brief account of his findings, in the form of a letter, to the Royal Society, whereby – after a bit of convincing – it was published in the Philosophical Transactions of the Royal Society. Although not unanimous, Newton’s work met with much praise. However, one critic’s words would resound with Newton, thus beginning a lifetime feud.

Robert Hooke (1635–1703), who was considered the expert on the subject in England, sent a lengthy critique. In short, it pretty much said Hooke had performed all the same experiments, drawn different conclusions, and that Newton was outright wrong. In 1704, Newton finally published a full account of his theory of light in Opticks. To be sure, Newton had already drafted a treatise covering much of this work by 1672,