![]() The story behind Fraunhofer being around to make his discovery is so unlikely it’s almost a fairy tale. In the early 1800s, a young glassmaker named Joseph von Fraunhofer was studying this effect when he discovered something that would shape the course of science for centuries to come. When light passes through a glass prism, it is split into what most of us call a rainbow and scientists call a spectrum. Fluorescent bulbs: New lines of lightįluorescent light bulbs embody an entirely different quantum principle: spectral lines. It was the dawn of quantum mechanics.Įvery time you flip on an old-school incandescent bulb, you are lighting the bridge between the 19th century and the quantum age. At small scales, it’s lumpy, coming in bits, which Planck dubbed “quanta” – the Latin word for packet. This was – and is – the solution to the ultraviolet catastrophe: energy doesn’t get smeared evenly across all frequencies, because energy isn’t something you can evenly smear. It turned out that they did, in fact, have a minimum size. As Boltzmann had chopped gas up into atoms, Planck sliced energy up into packets, and he used Boltzmann’s statistical approach to calculate how small these packets could be. So it must have been with desperation that Planck turned to Boltzmann’s method to tackle the ultraviolet catastrophe. He wasn’t even convinced that atoms and molecules existed. He’d even written a statistical version of the Second Law, in which entropy increases on average, but may decrease temporarily because of momentary fluctuations. Ludwig Boltzmann had developed a model of heat in gases that chopped the gas up into molecules and then considered their average position and velocity using statistics. He believed that the Second Law was rigorously true in all circumstances, but not everyone at the time thought so. Planck had built a career by clarifying the subtleties of the Second Law of Thermodynamics, which states that entropy always increases. Like everyone else, he struggled with it for years. But, like everyone else, he couldn’t make a model that worked. ![]() The ultraviolet catastrophe should have been right up his alley. He was a leading mind in thermodynamics, a branch of physics that defines the relationship between heat and other forms of energy. ![]() Unlike most people who remake science, Planck was no hip young thinker: he was in his forties, with a comfortable position at the University of Berlin and a membership in the Prussian Academy. The problem came to be called “ the ultraviolet catastrophe.”Įnter Max Planck. That’s not what’s happening – good news for those who like toast, but bad news for 19th century physics. If each frequency got an equal smear of energy, then the high end of the spectrum would have more energy – and a run-of-the-mill toaster would produce blinding ultraviolet light and deadly X-ray radiation. At the high end of the spectrum, the frequencies are closer together. This seemed reasonable but resulted in a nonsensical prediction. The best scientific models of the day said that the energy of the glow should be smeared evenly across all frequencies. Why should everything at the same temperature emit the same colour light? Physicists love a good phenomenological question, and at the end of the 19th century, this one was all the rage. Heat it to 1,100☌, and it will be yellow. Heat something – embers, glass, clay, steel, the little wire filament in a light bulb, anything – to 800☌, and it will glow red. In fact, all hot things glow in the same way. The first light bulbs were incandescent, which is a physicist’s way of saying that they glow because they are hot, and hot things glow. Old-school bulbs: The dawn of the quantum world In fact, a tour through the history of the light bulb can double as a tour through the history of science, where small puzzles can lead to big breakthroughs and esoteric little observations can – given enough time – light up the whole world. But though we’re learning to harness the quantum properties of the world in new ways, the deeper truth is that the world has always been quantum.Įven that icon of old-school invention – the light bulb – is a quantum technology. When we think quantum technology, we think exotic. Unimaginably powerful quantum computers, unbreakable quantum encryptions, ultraprecise quantum sensors.
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