Absolute zero

Absolute zero

In Brief

Bloom is familiar with the scientific idea of an "absolute zero" at which heat is completely absent, though his belief that it is "thousands of degrees below freezing point" is mistaken. The best understanding in 1904 was that the absolute minimum temperature of matter was several hundred degrees below the freezing point of water on the three scales that Bloom thinks of: "Fahrenheit, Celsius or Réaumur." In Celsius, a.k.a. Centigrade, it was (and still is) thought to be approximately -273 degrees. Temperatures nearly that low have been found in "interstellar space."

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17th century natural philosophers, notably Anglo-Irish chemist Robert Boyle, discussed the idea of a primum frigidum or pure cold that must exist somewhere in the world. 18th century physicists, notably Guillaume Amontons, explored the idea experimentally and calculated that the lower limit of temperatures would occur in the range of -240 to -273° Celsius or -400 to −459° Fahrenheit, though prominent astronomer Pierre-Simon Laplace and chemist Antoine Lavoisier argued in a 1780 joint publication that the number was probably, as Bloom thinks, "thousands of degrees below freezing." 19th century scientific advances suggested that the experimentalists' range was much more likely. In the 1870s, 80s, 90s, and early 1900s experimenters succeeded in liquifying various gases (first air, then oxygen, hydrogen, and helium) and measuring lower and lower temperatures (-319, -360, -421, and -452°F, respectively). Theorists of the time calculated that the absolute minimum would be about -459°F or -273°C, and it remains in that range today. In 2014 Italian scientists produced the lowest temperature yet measured: -459.659°F or -273.144°C.

Although absolute zero is a theoretical limit never found in actual matter, scientists have neared it in the laboratory and found it approached in "interstellar space" as well. The coldest temperature yet measured in space is about -272°C or -457° Fahrenheit. In "Réaumur," the obsolete scale named for 18th century French scientist René Antoine Ferchault de Réaumur, it is approximately -217°.

JH 2022
1998 Hubble Space Telescope image of the bowtie-shaped Boomerang Nebula in the constellation Centaurus, the coldest known place in the universe with a temperature of -272° Celsius. Source: Wikimedia Commons.