Definitions

# temperature

[tem-per-uh-cher, -choor, -pruh-, -per-cher, -choor]
temperature, measure of the relative warmth or coolness of an object. Temperature is measured by means of a thermometer or other instrument having a scale calibrated in units called degrees. The size of a degree depends on the particular temperature scale being used. A temperature scale is determined by choosing two reference temperatures and dividing the temperature difference between these two points into a certain number of degrees. The two reference temperatures used for most common scales are the melting point of ice and the boiling point of water. On the Celsius temperature scale, or centigrade scale, the melting point is taken as 0°C; and the boiling point as 100°C;, and the difference between them is divided into 100 degrees. On the Fahrenheit temperature scale, the melting point is taken as 32°F; and the boiling point as 212°F;, with the difference between them equal to 180 degrees. The Réaumur scale, used in some parts of Europe, also sets the melting point at zero, but it has an 80-degree temperature difference between 0°R; and the boiling point at 80°R;. The temperature of a substance does not measure its heat content but rather the average kinetic energy of its molecules resulting from their motions. A one-pound block of iron and a two-pound block of iron at the same temperature do not have the same heat content. Because they are at the same temperature the average kinetic energy of the molecules is the same; however, the two-pound block has more molecules than the one-pound block and thus has greater heat energy. A temperature scale can be defined theoretically for which zero degree corresponds to zero average kinetic energy (see gas laws). Such a point is called absolute zero, and such a scale is known as an absolute temperature scale. The Kelvin temperature scale is an absolute scale having degrees the same size as those of the Celsius temperature scale; the Rankine temperature scale is an absolute scale having degrees the same size as those of the Fahrenheit temperature scale. The relationship between absolute temperature and average molecular kinetic energy is one result of the kinetic-molecular theory of gases. See heat; thermodynamics.
temperature, body: see body temperature; fever.

In meteorology, an increase of air temperature with altitude. Such an increase is a reversal of the normal temperature condition of the troposphere, where temperature usually decreases with altitude. Inversions play an important role in determining cloud forms, precipitation, and visibility. An inversion acts as a lid, preventing the upward movement of the air below it. Where a pronounced inversion is present at a low level, convective clouds cannot grow high enough to produce showers and, at the same time, visibility may be greatly reduced by trapped pollutants (see smog). Because the air near the base of the inversion is cool, fog is frequently present there.

Measure of hotness expressed in terms of any of several arbitrary scales, such as Fahrenheit, Celsius, or Kelvin. Heat flows from a hotter body to a colder one and continues to do so until both are at the same temperature. Temperature is a measure of the average energy of the molecules of a body, whereas heat is a measure of the total amount of thermal energy in a body. For example, whereas the temperature of a cup of boiling water is the same as that of a large pot of boiling water (212°F, or 100°C), the large pot has more heat, or thermal energy, and it takes more energy to boil a pot of water than a cup of water. The most common temperature scales are based on arbitrarily defined fixed points. The Fahrenheit scale sets 32° as the freezing point of water and 212° as the boiling point of water (at standard atmospheric pressure). The Celsius scale defines the triple point of water (at which all three phases, solid, liquid, and gas, coexist in equilibrium) at 0.01° and the boiling point at 100°. The Kelvin scale, used primarily for scientific and engineering purposes, sets the zero point at absolute zero and uses a degree the same size as those of the Celsius scale.

List of orders of magnitude for temperature
Factor Multiple Item
10−∞ 0 K absolute zero: free-bodies are still, no interaction within or without a thermodynamic system
10−30 particular speeds bound paths to exceed size and lifetime of the universe
(see least-energy in orders of magnitude (energy))
10−18 1 aK macroscopic teleportation of matter
10−15 1 fK atomic waves coherent over inches
atomic particles decoherent over inches
10−12 1 pK 100 pK, lowest temperature ever produced, during the nuclear magnetic ordering at Helsinki University of Technology's Low Temperature Lab
450 pK, lowest temperature sodium Bose-Einstein condensate gas ever achieved in the laboratory, at MIT
10−9 1 nK 50 nK, Fermi melting point of potassium-40
Bose melting point of bosonic atomic gases
Doppler-locked refrigerants in laser cooling and magneto-optical traps
10−6 1 μK nuclear demagnetization
1.7 mK, temperature record for helium-3/helium-4 dilution refrigeration
2.5 mK, Fermi melting point of helium-3
300 mK in evaporative cooling of helium-3
700 mK, helium-3/helium-4 mixtures begin phase separation
950 mK, melting point of helium
microwave excitations
100 1 K 1 K at the Boomerang nebula, the coldest natural environment known
1.5 K, melting point of overbound helium
2.19 K, lambda point of overbound superfluid helium
2.725 K, cosmic microwave background
4.1 K, superconductivity point of mercury
4.22 K, boiling point of bound helium
5.19 K, critical temperature of helium
7.2 K, superconductivity point of lead
9.3 K, superconductivity point of niobium
101 10 K Fermi melting point of valence electrons for superconductivity
14.01 K, melting point of bound hydrogen
20.28 K, boiling point of bound hydrogen
33 K, critical temperature of hydrogen
44 K mean on Pluto
53 K mean of Neptune
63 K, melting point of bound nitrogen
68 K mean of Uranus
77.35 K, boiling point of bound nitrogen
90.19 K, boiling point of bound oxygen
92 K, superconductivity point of Y-Ba-Cu-oxide (YBCO)
everyday substances near liquid air's temperature with incipient Fermi-condensate populations result in spontaneous luminescence, loss or lack of hysteresis, inductive and capacitive electronic moments that readily adsorb or expel or float upon unlike substances:
10² 100 K infrared excitations
165 K, glass point of supercooled water
183.75 K (–89.4 °C), coldest air recorded on Earth
273.15 K (0 °C), melting point of bound water
~293 K, room temperature
373.15 K (100 °C), boiling point of bound water
647 K, critical point of superheated water
See detailed list below
10³ 1 kK visible light excitations
1170 K at large log fire flames
1670 K at blue candle flame
1811 K, melting point of iron (lower for steel)
1870 K in Bunsen burner flame
1900 K at the Space Shuttle Orbiter hull in 8km/s dive
2022 K, boiling point of lead
2320 K at open hydrogen flame
3683 K, melting point of tungsten
3823 K, melting point of a diamond
3925 K, sublimation point of carbon
4160 K, melting point of hafnium carbide
4700 K, triple point of overbound carbon
5100 K in cyanogen-dioxygen flame
5516 K at dicyanoacetylene (carbon subnitride)-ozone flame
5650 K at Earth's Inner Core Boundary
5780 K on the Sun
5933 K, boiling point of tungsten
6000 K, mean of the Universe 300,000 years after the Big Bang
7020.5 K, critical point of carbon
7736 K, a monatomic ideal gas has one electron volt of kinetic energy
ultraviolet excitations
anionic sparks
104 10 kK 10 kK on Sirius A
10-15 kK in mononitrogen recombination
15.5 kK, critical point of tungsten
25 kK, mean of the Universe 10,000 years after the Big Bang
28 kK in record cationic lightning over Earth
32 kK on Sirius B
37 kK in proton-electron reactions
about 300 kK at 17 meters from Little Boy's detonation
Fermi boiling point of valence electrons
X-ray excitations
106 1 MK γ-ray excitations
1–10 MK in the Sun's corona
13.6 MK at Sun's core
100 MK, needed for controlled nuclear fusion
510 MK, plasma in Tokamak Fusion Test Reactor
109 1 GK 1 GK, everything 100 seconds after the Big Bang
3 GK in electron-positron reactions
10 GK in supernova explosions
10 GK, everything 1 second after the Big Bang
1012 1 TK 0.5–1.2 TK, Fermi melting point of quarks into quark-gluon plasma
3-5 TK in proton-antiproton reactions
Z0 electronuclear excitations
10 TK, 100 microseconds after the Big Bang
300–900 TK at proton-nickel conversions in the Tevatron's Main Injector
1015 1 PK 0.3–2.2 PK at proton-antiproton collisions in same
1018 1 EK 2–13 EK at heavy nuclear conversions in the Large Hadron Collider
1021 1 ZK heart of galactic clusters-mergers
1024 1 YK 0.5–7 YK at Ultra-High-energy cosmic rays collisions
1027 grand symmetry-breaking grand unified theory excitations
temperature 10−35 seconds after the Big Bang
1030 1.4 K, Planck temperature of micro black holes
temperature 5 seconds after the Big Bang
1033 Landau poles

## Detailed list of temperatures from 100 K to 1000 K

Most ordinary human activity takes place at temperatures of this order of magnitude. Circumstances where water naturally occurs in liquid form are shown in light grey.
Kelvins Degrees
Celsius
Degrees
Fahrenheit
Condition
100 K −173.15 °C −279.67 °F
125 K −148 °C −234.4 °F superconductivity point of Tl-Ba-Cu-oxide
138 K −135 °C −211 °F superconductivity point of Hg-Tl-Ba-Ca-Cu-oxide
143 K −130 °C −202 °F mean "surface" temperature of Saturn
152 K −121 °C −185.8 °F mean "surface" temperature of Jupiter
184 K −89.2 °C −128.6 °F coldest temperature recorded on Earth
194.6 K −78.5 °C −109.3 °F sublimation point of carbon dioxide (dry ice)
210 K −63 °C −81.4 °F mean surface temperature of Mars
234.32 K −38.83 °C −37.9 °F melting point of mercury
255.37 K −17.78 °C 0 °F coldest brine-ice solution found by Fahrenheit
272 K −1.1 °C 30 °F temperature of frigid ocean waters
273.15 K 0 °C 32 °F melting point of water (at STP)
278 K 5 °C 41 °F recommended temperature for refrigeration of food
287 K 14 °C 57 °F mean surface temperature of the Earth
294 K 20.5 °C 69 °F lowest human body temperature survived
295 K 21 °C 70 °F room temperature
304 K 31 °C 88 °F melting point of butter
308 K 35 °C 95 °F warmest sea temperature measured, at the Red Sea
310 K 37 °C 98.6 °F standard human body temperature
315 K 42 °C 107 °F usually fatal human fever temperature
331 K 58 °C 136.4 °F hottest temperature recorded on Earth, at El Azizia
336 K 63 °C 145 °F milk pasteurization temperature
343 K 70 °C 158 °F temperature of hot springs at which some bacteria thrive
355 K 82 °C 180 °F recommended coffee brewing temperature
373.15 K 100 °C 212 °F boiling point of water
400 K 127 °C 260.6 °F hottest temperature of Concorde nose tip
452 K 179 °C 354.2 °F mean surface temperature of Mercury
600.65 K 327.50 °C 621.5 °F melting point of lead
737 K 464 °C 867.2 °F mean surface temperature of Venus
755 K 482 °C 900 °F a typical electric oven on the self-cleaning cycle
933.47 K 660.32 °C 1220.6 °F melting point of aluminium
1000 K 727.15 °C 1340.87 °F