Kelvin Trivia
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47 free Kelvin trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Kelvin is both a unit and a man, and this quiz covers both. On the unit side: why the scale starts at absolute zero, why you add 273.15, why the triple point of water was 273.16 K for 65 years, what the Boltzmann constant has to do with the 2019 redefinition, why 'degree Kelvin' was abolished, how the Rankine scale differs, and what 5772 K means when you point a camera at the Sun. On the man: the Belfast boy who entered Glasgow University at ten, the 1848 paper that proposed an absolute scale, the Carnot cycle and James Joule, the mirror galvanometer that saved the Atlantic telegraph and earned him a knighthood, the marriage proposal by signal flag, the compass, the water dropper, the wake pattern, the doomed 20-to-40-million-year estimate for the age of the Earth, and the seat in Westminster Abbey next to Newton. Every answer was checked against Wikipedia's articles on the kelvin, absolute zero, Lord Kelvin and the transatlantic cable, and the supporting sentence is attached to each question. For the wider field, try our Physics quiz.
30 of 47 questions with answers and explanations. Play the quiz
Q 01The kelvin is the base unit of temperature in which set of units?
The International System (SI)
The International System (SI). The kelvin is one of its seven base units, yet outside the laboratory most people meet it on light-bulb packaging, as a colour temperature.
Q 02The cosmic microwave background, the afterglow of the Big Bang, has cooled to roughly what temperature?
2.7 K
2.7 K. The light set out at about 3,000 K when the first atoms formed, and the stretching of space ever since has cooled it to within three kelvins of the coldest possible temperature.
Q 03What do you add to a Celsius temperature to convert it to kelvins?
273.15
273.15. A kelvin is exactly the same size as one step on the Celsius scale, so the two differ only by this fixed offset, which is why water freezes at 273.15 K.
Q 04Kelvin's first published papers, written at 16 and 17, defended which French scientist's theory of heat flow?
Joseph Fourier
Joseph Fourier. By his own account he mastered Fourier's book on heat in a fortnight at 15, and when British critics attacked it he rushed into print to defend it.
Q 05Kelvin spent his career in Glasgow, but in which city was he born?
Belfast
Belfast. He left as a boy when his father, a teacher there, won a professorship at Glasgow and moved the whole family to Scotland.
Q 06Kelvin entered the University of Glasgow at ten; which subject did his father teach there?
Mathematics
Mathematics. His father drilled his sons in the latest methods at home, and ten was a less startling age to enrol than it sounds: Scottish universities then competed with schools for the brightest boys.
Q 07As a Cambridge student in 1843, Kelvin won a university championship in which sport?
Rowing
Rowing. He won the Colquhoun Sculls for single scullers while at Peterhouse, then went off to a Paris laboratory to learn the hands-on experimenting his mathematical training had left out.
Q 08Kelvin's title refers to what natural feature near his Glasgow laboratory?
A river
A river. The Kelvin runs through Glasgow past the university, and when he needed a title in 1892 he paired its name with Largs, the seaside town where he had built his house.
Q 09In 1995 physicists cooled rubidium atoms to less than a millionth of a kelvin and created which new state of matter?
Bose–Einstein condensate
Bose–Einstein condensate. Einstein had predicted it seventy years earlier: chilled that far, the atoms all drop into the same lowest energy state and, in the Nobel committee's phrase, sing in unison.
Q 10Which physicist, doubted by Thomson when they met in 1847, became his chief collaborator on heat?
James Prescott Joule
James Prescott Joule. By 1851 Thomson had publicly, if cautiously, endorsed Joule's claim that heat is a form of motion, and the pair's experiments went on to produce the Joule–Thomson effect.
Q 11Kelvin's scale was built on the theoretical heat engine of which French engineer?
Sadi Carnot
Sadi Carnot. His ideal engine depends only on the temperatures it works between, which let Thomson define a scale that was, in his words, 'quite independent of the physical properties of any specific substance'.
Q 12In 1911 which metal, chilled to 4.2 K, became the first material seen to lose all its electrical resistance?
Mercury
Mercury. Heike Kamerlingh Onnes watched its resistance vanish completely rather than fade away, named the effect superconductivity, and collected a Nobel Prize two years later.
Q 13Which of Kelvin's relatives coined the term 'triple point' in the early 1870s?
His older brother James
Q 21A lamp's kelvin rating compares its light with the glow of which idealised object?
A black body
A black body. The rating is the temperature at which such an object would glow the same colour, and a filament bulb comes so close to being one that its rating is nearly its real temperature.
Q 22The Sun's visible surface, the photosphere, is at roughly what temperature on the Kelvin scale?
5,800 K
5,800 K. Oddly, the thin corona high above the surface is far hotter than the surface itself, a reversal that has long puzzled solar physicists.
Q 23Compared with a 2,700 K bulb, how does the light from a lamp with a 6,500 K colour temperature look?
Bluer and cooler
His older brother James. An engineering professor, he named the state in which solid, liquid and gas coexist, and eight decades later the triple point of water became the fixed point that defined William's unit.
Q 14From 1954 to 2019 the kelvin was pinned to water's triple point, which sits how far above its ordinary freezing point?
0.01 °C
0.01 °C. The triple point was preferred to melting ice because water sealed in a glass cell settles at exactly the same temperature every time, in any laboratory.
Q 15Which word did the 1967–68 General Conference on Weights and Measures strike from the kelvin's official name?
Degree
Degree. Until then the unit was the 'degree Kelvin', written °K; since the change it has stood alone like the second or the kilogram, so a temperature is simply so many kelvins.
Q 16The 2019 redefinition of the kelvin fixed the exact value of what?
The Boltzmann constant
The Boltzmann constant. It ties temperature to the energy of moving particles, so the kelvin now rests on a number fixed in nature and no longer on the behaviour of a sample of water.
Q 17Which Vienna-based organisation issued the standard water used to calibrate thermometers?
The IAEA
The IAEA. Its Vienna Standard Mean Ocean Water is not seawater but a recipe fixing how much heavy hydrogen and oxygen the water holds, because even tiny isotope differences shift the triple point.
Q 18Which SI derived unit is the only one with a special name derived from the kelvin?
The degree Celsius
The degree Celsius. Although Celsius is the older scale, the SI now defines it through the kelvin: a Celsius reading is officially a kelvin value with a fixed number subtracted.
Q 19When Anders Celsius first drew up the scale whose step the kelvin borrows, what did zero mark?
Boiling water
Boiling water. Celsius ran his scale upside down, with melting ice at 100, and it was flipped into the order we know only around the time of his death in 1744.
Q 20Which absolute temperature system uses Fahrenheit-sized degrees instead of Celsius-sized ones?
The Rankine scale
The Rankine scale. A Glasgow engineer, William Rankine, proposed it in 1859, and it lives on in fields such as aerospace engineering where the heat sums are still done in Fahrenheit.
Bluer and cooler. The everyday names run backwards from the physics: the hotter a glowing object, the bluer its light, so the lamps we call cool carry the higher kelvin numbers.
Q 24An object at room temperature, about 293 K, gives off its own radiation mainly in which part of the spectrum?
Infrared
Infrared. Everything warmer than the coldest possible temperature glows, but the glow only reaches the visible when an object is several hundred kelvins hotter, which is why a thermal camera can pick out a warm body in the dark.
Q 25The Unicode 'Kelvin sign' (U+212A) exists, but what does the Unicode standard recommend using instead?
The ordinary capital letter K
The ordinary capital letter K. The special character survives only so that old text converts cleanly; Unicode treats it, like the ohm and angstrom signs, as identical to the plain letter.
Q 260 K corresponds to what temperature in Fahrenheit?
−459.67 °F
−459.67 °F. Kelvin's generation called this point 'infinite cold', and it behaves like a limit: experiments have come within billionths of a kelvin of it without ever arriving.
Q 27Which Frenchman reasoned in the early 1700s, while improving the air thermometer, that cold must have a lowest limit?
Guillaume Amontons
Guillaume Amontons. He noticed that cooled air pushes back with less force and reasoned that at some temperature its spring would vanish altogether, a point beyond which nothing could be colder.
Q 28Which element stays liquid at normal pressure even at temperatures near 0 K?
Helium
Helium. Its atoms are so light and cling to each other so weakly that their quantum jitter stops them locking into a solid unless about 25 atmospheres of pressure squeezes them together.
Q 29Kelvin helped lay the 1858 Atlantic cable, whose first public message went from Queen Victoria to which US president?
James Buchanan
James Buchanan. The greeting crawled through painfully slowly, and within weeks the cable had fallen silent; eight years passed before a lasting link was made.
Q 30Which instrument, patented by Thomson in 1858, made the weak signals of the Atlantic cable readable?
The mirror galvanometer
The mirror galvanometer. A tiny mirror twisted by the faint current threw a spot of light along a scale, so the beam worked as a long, weightless pointer that even a whisper of signal could move.