Near the heart of Scotland lies a large morass known as Dullatur Bog. Water seeps from these moistened acres and coalesces into the headwaters of a river which meanders through the countryside for nearly 22 miles until its terminus in Glasgow. In the late 19th century this river adorned the landscape just outside of the laboratory of Sir William Thompson, renowned scientist and president of the Royal Society. The river must have made an impression on Thompson--when Queen Victoria granted him the title of Baron in 1892, he opted to adopt the river’s name as his own. Sir William Thompson was thenceforth known as Lord Kelvin.
Kelvin's contributions to science were vast, but he is perhaps best known today for the temperature scale that bears his name. It is so named in honor of his discovery of the coldest possible temperature in our universe. Thompson had played a major role in developing the Laws of Thermodynamics, and in 1848 he used them to extrapolate that the coldest temperature any matter can become, regardless of the substance, is -273.15°C (-459.67°F). We now know this boundary as zero Kelvin.
Once this absolute zero temperature was decisively identified, prominent Victorian scientists commenced multiple independent efforts to build machines to explore this physical frontier. Their equipment was primitive, and the trappings were treacherous, but they pressed on nonetheless, dangers be damned. There was science to be done.
Prior to this 19th-century cold rush, most European scientists believed that coldness itself was an actual physical substance--made up of atoms of an airborne primordial gas. This explained why water expanded upon freezing--it was taking in a large amount of these cold particles. Physicist Robert Boyle dispelled this notion in 1665 by painstakingly weighing water before and after putting it outdoors on a freezing night, demonstrating that only its volume had changed, not its mass. This helped naturalists to start hypothesizing in the right direction, but in 1783, renowned French chemist Antoine de Lavoisier undid most of this progress by popularizing his own theory that heat is an invisible, weightless, self-repellent vapor called caloric, and that coldness is merely a depletion of the same. This "dark heat" theory was also wrong, but it modeled observations so well that it remained dominant for almost a century.
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