The history
From desert ice houses and clay water pots to vacuum flasks and the glowing math of Planck: how people learned the three ways heat moves.
People kept water cool and stored ice long before anyone knew what heat was. For a long time scientists thought heat was an invisible fluid that soaked from hot things into cold ones. Cannon makers, stargazers and mathematicians slowly showed that heat moves in three ways: it creeps through solids, rides along with moving air and water, and flies across empty space as invisible rays.
1701
Rule for how fast things cool
Isaac Newton, published anonymously in London
1800
Heat rays beyond visible light
William Herschel, Slough, England
1822
Full mathematics of heat conduction
Joseph Fourier, Paris
1856
Carbon dioxide linked to a warmer Earth
Eunice Newton Foote, Albany, New York
1879
Sensible estimate of the Sun's temperature
Josef Stefan, Vienna
1892
Vacuum flask
James Dewar, Royal Institution, London
1900
Energy in quanta
Max Planck, Berlin
1931
Aerogel
Samuel Stephens Kistler, California
400 BCE – 1700
Builders and potters use shade, thick walls, wind and evaporation to keep things cold, long before anyone can explain why it works.
400 BCE
c. 400 BCE (often cited)
In the deserts of Iran, people built tall domed ice houses called yakhchāl with very thick walls. Ice made on cold winter nights was stored deep inside and could last into summer. Sources often say they go back to about 400 BCE, but the exact start is not certain.
Why it mattered. Thick walls slow conduction, and the tall dome lets warm air rise out, so these buildings used heat transfer long before anyone could explain it.
1700 – 1830
Scientists name an invisible heat fluid called caloric, then find cracks in it: endless heat from friction, rays beyond red light, and a mathematics of heat creeping through solids.
1701
A short paper in Latin called Scala graduum caloris appeared without a name in the Royal Society's journal. It is known to be Newton's work. It suggested that a hot object cools faster when it is much hotter than its surroundings, and slower as the gap shrinks.
Why it mattered. It was the first rule for heat transfer and is still the starting point for how engineers describe cooling by moving air.
1787
1787 and 1789
In 1787 a new book of chemical names, written by Guyton de Morveau with Lavoisier and others, used the word calorique for the stuff of heat. In his famous 1789 textbook Lavoisier spread the idea: heat was a weightless fluid that flowed from hot bodies into cold ones.
Why it mattered. The caloric idea was wrong, but it gave scientists a clear picture to test, and the tests changed everything.
1791
Prévost argued that every object is always sending out heat, no matter how cold it is. A hot object and a cold one both radiate, but the hot one sends out more. When the two sides trade equally, their temperatures stop changing.
Why it mattered. His theory of exchanges is why we say snow in your hand is not sending you cold: your hand is simply losing more heat than it gets back.
1797
Rumford noticed dust inside a large thermometer rushing up and down in two opposite streams as the liquid cooled. He worked out that liquids and gases carry heat mainly by moving: warm parts rise and cool parts sink. He also found that fur and wool keep us warm by stopping air from moving.
Why it mattered. This is the idea we now call convection, the second of the three ways heat travels.
1798
At the Munich arsenal, Rumford put a cannon barrel in water and turned a blunt drill inside it. After about two and a half hours the water boiled, and the heat seemed to keep coming for as long as the drill turned. He told the Royal Society in London that heat could not be a fluid that runs out, but must be a kind of motion.
Why it mattered. It was a big early blow against the caloric theory and pointed toward heat as energy.
1800
Herschel split sunlight into a rainbow with a prism and put thermometers in each colour. The temperature rose from violet to red, and it was even higher just past the red end, where there was no visible light at all. He called these invisible rays calorific rays.
Why it mattered. He had found infrared, the invisible light that carries heat by radiation, even across empty space.
1804
Leslie filled a metal cube with hot water and gave each side a different surface, some shiny and some dull or blackened. All four sides were at the same temperature, yet the dull sides sent out much more heat than the shiny ones. He described this in his 1804 book on the nature of heat.
Why it mattered. It shows why shiny surfaces, like the silvered walls of a vacuum flask, are good at holding heat in.
1822
1822 (first presented 1807)
Fourier worked out how heat creeps through solids: it flows from hot to cold, faster when the temperature changes steeply and faster in some materials than others. He first presented this work in 1807 and published his full book, The Analytical Theory of Heat, in 1822. To solve his equations he invented Fourier series, which are now used everywhere from music to phones.
Why it mattered. Fourier's law is still the rule engineers use for conduction, the first of the three ways heat moves.
1824
1824 and 1827
Fourier calculated that a planet as far from the Sun as Earth should be much colder than it is. He suggested the air might act a little like the glass panes of a heat box made by the Swiss scientist Saussure, letting sunlight in but holding heat back. It was an early, rough version of what we now call the greenhouse effect.
Why it mattered. It connected radiation to the temperature of a whole planet for the first time.
1830 – 1900
Experimenters find that some gases trap heat rays, that good absorbers are good emitters, and that hot things glow by a precise rule.
1856
23 August 1856
Foote put thermometers inside glass cylinders filled with different gases and set them in sunlight. The cylinder with carbonic acid gas, which we call carbon dioxide, heated up the most and took longest to cool. Her paper was read at a science meeting in Albany by Joseph Henry of the Smithsonian, and she suggested that more of this gas in the air would make the Earth warmer.
Why it mattered. She was the first known person to link carbon dioxide with a warmer planet.
1859
Tyndall sent infrared heat through long tubes of different gases and measured how much got through with a sensitive heat detector. Oxygen and nitrogen let almost all of it pass. Water vapour and carbon dioxide soaked it up, with water vapour the strongest absorber in air.
Why it mattered. His careful measurements showed exactly how gases in the air can trap radiated heat.
1859
1859 to 1860
Kirchhoff showed that, at the same temperature, a surface that absorbs a kind of light well also gives it out well. He imagined a perfect absorber that soaks up every ray that hits it, and called it a black body. He said its glow should depend only on its temperature, but nobody yet knew the formula.
Why it mattered. The hunt for the black body formula led straight to quantum physics.
1879
1879 (Boltzmann 1884)
Using Tyndall's measurements of a glowing platinum wire, Stefan found that the heat an object radiates grows with the fourth power of its absolute temperature. Double the temperature and the glow grows sixteen times. In 1884 his former student Boltzmann showed why this must be true.
Why it mattered. With it Stefan gave the first sensible estimate of the Sun's surface temperature, about 5,400 °C.
1892
1892 (Thermos 1904)
Dewar needed to keep liquefied gases extremely cold, so he made a glass vessel inside another with a vacuum between them. With no air in the gap, heat cannot cross by conduction or convection, and a silvered coating cuts down radiation. Dewar never patented it, and in 1904 two German glassblowers, Reinhold Burger and Albert Aschenbrenner, sold it as the Thermos.
Why it mattered. One simple object blocks all three ways heat moves, which is why your flask keeps chai hot for hours.
1896
Arrhenius did long calculations by hand about how carbon dioxide in the air traps heat radiated by the Earth. He worked out that changing the amount of the gas could raise or lower Earth's temperature by several degrees. He was trying to explain the ice ages.
Why it mattered. It was the first attempt to put numbers on how much carbon dioxide warms the planet.
1900 – today
Quantum physics explains glowing, engineers turn convection into numbers, and inventors build flasks, aerogels and clay coolers that control where heat goes.
1900
14 December 1900
Planck finally found the formula for how much of each colour a black body gives off at any temperature. To make it work he had to assume energy is given out in tiny fixed packets, which he called quanta. He won the Nobel Prize in Physics for 1918.
Why it mattered. His law explains the colour of a red hot coil and the infrared glow of your skin, and it began quantum physics.
1915
Nusselt published a paper called The Fundamental Law of Heat Transfer. He showed how to describe heat carried by moving air or water using a few numbers without units, so tests on a small model could predict a big machine. One of these, the Nusselt number, compares convection with plain conduction.
Why it mattered. Engineers still use his numbers to design radiators, engine fins and cooling fans.
1931
Kistler found a way to dry a jelly without letting it collapse, leaving a solid made almost entirely of tiny trapped pockets of air. He described these aerogels in the journal Nature in 1931. They are so light and cloudy that people nickname them frozen smoke.
Why it mattered. Air trapped in tiny pores cannot flow, so aerogels are among the best heat insulators ever made.
1995
1990s
Bah Abba put a small clay pot inside a bigger one and filled the gap with wet sand. As water evaporates from the outer pot it takes heat with it, keeping vegetables inside cool and fresh for days without electricity. It uses the same trick as the clay matka in Indian homes, and it won him a Rolex Award for Enterprise.
Why it mattered. It shows that evaporation, the same cooling that makes sweat work, can help farmers where there is no power.
By the numbers
Carbon dioxide lets sunlight in but absorbs heat radiated by the ground, just as Foote and Tyndall found. Its share of the air has risen every decade since careful measurement began in 1958. Data: NOAA.
Did you know?
A clay matka cools water because a little water seeps through the clay and evaporates from the outside, carrying heat away with it.
Herschel never used the word infrared. He called his discovery calorific rays, and the name infrared came decades later.
James Dewar never patented his vacuum flask. The Thermos company patented and named its version in 1904.
Eunice Foote did not read her own paper in 1856. Joseph Henry of the Smithsonian read it for her.
Without greenhouse gases trapping heat rays, Earth would radiate like a ball at roughly minus 18 °C.
Air is a poor conductor of heat, so fur, wool and aerogel all keep you warm mostly by trapping air so it cannot move.
The people
1751 – 1839 · Philosopher and physicist · Republic of Geneva (Switzerland)
Said that everything glows with heat, even ice, just some things more than others.
1753 – 1814 · Soldier, inventor and physicist · Massachusetts, then Britain and Bavaria
Boiled water by boring cannons and watched hot liquids rise and cold ones sink.
1738 – 1822 · Astronomer and musician · Hanover, later England
Found invisible heat rays just past red light using thermometers and a prism.
1768 – 1830 · Mathematician · Auxerre, France
Wrote the law of how heat creeps through solids and invented new maths to solve it.
1819 – 1888 · Scientist, inventor and women's rights campaigner · Connecticut, United States
Showed in 1856 that carbon dioxide heats up most in sunlight, three years before Tyndall's work.
1820 – 1893 · Physicist · County Carlow, Ireland
Measured exactly how water vapour and carbon dioxide soak up heat rays.
1835 – 1893 · Physicist · Carinthia, Austrian Empire (a Carinthian Slovene)
Found that radiated heat grows with the fourth power of temperature.
1842 – 1923 · Chemist and physicist · Kincardine, Scotland
Invented the vacuum flask to keep liquid gases cold and never patented it.
1858 – 1947 · Physicist · Kiel, Germany
Found the exact law of how hot things glow and started quantum physics.
1964 – 2010 · Teacher and inventor · Nigeria
Spread a two-pot evaporation cooler that keeps food fresh without electricity.
Where it happened
Sources
Dates marked “c.” are approximate, and historians sometimes disagree about who was first. If you spot a mistake, tell us.
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