Feel the hotness

We all know about absolute zero, right? You know, the theoretical lowest limit of temperature?

Because of course temperature is really just a measure of the energy of atoms and molecules randomly jiggling around. So absolute zero is when they’ve stopped jiggling and are completely motionless. And since you can’t move slower than stopped, you can’t get lower than absolute zero.

But what about the other direction? Is there a maximum temperature to the universe? An absolute hotness, if you will (and I will)?

Theoretically, yes there is. This mightn’t seem possible, as you’d think the jiggling energy could just keep increasing forever. But as energy increases, it affects the way the fundamental forces of the universe behave.

In particular, there’s an energy at which gravity becomes a purely quantum force. And because gravity is intimately connected with the structure of space-time, the laws of physics as we know them break down and reality itself turns into a sort of quantum foam.

Quantum foam
Quantum foam, a lumpy mess of distortions and fluctuations in space-time at the Plank scale

This energy – or the temperature it corresponds to – is known as the Planck temperature, and it’s the theoretical maximum temperature of the universe.

And it’s pretty hot. Roughly about 1.4×1032 Kelvin, or if you prefer, 140 nonillion Kelvin. If you prefer your temperatures in Celsius, it’s still about 1.4×1032 °C (at that level they may as well be the same).

Of course, once we truly understand the quantum nature of gravity, we might find it’s possible to go beyond this temperature. Or it could be that the maximum is at a different level entirely – for more on these possibilities, see the PBS Nova column on Absolute Hot.

And for some more milestones on the temperature scale, click through after the jump.

(These are mostly taken from Wikipedia – see their article on orders of magnitude in temperature for even more detail.)

Absolute zero: 0 K, or −273.15°C.

Coldest ever temperature in a laboratory: 100 pK, or 1.0 × 10-10 K, 0.000 000 000 1 degrees above absolute zero. Achieved in 1999 at the Low Temperature Laboratory of the Helsinki University of Technology, by nuclear magnetic ordering of rhodium atoms.

Bose-Einstein condensates: a minimum of 450 pK,achieved in 2003 at MIT, using sodium atoms in the quantum ground state.

Solid helium: less than 950 mK.

Superconducting magnets used in the Large Hadron Collider: 1.9 K, cooled with liquid helium.

Cosmic microwave background radiation: 2.725 K (the energy leftover from the Big Bang, after about 13.7 billion years).

Liquid helium: less than 4.2 K.

Liquid hydrogen: 20.28 K.

Liquid nitrogen: 77 K (−196 °C)

Dry ice: -78.5 °C

Lowest temperature on Earth: −89.2 °C (−128.6 °F; 184 K) at the Russian Vostok Station in Antarctica on 21 July 1983.

Lowest temperature in Australia: −23 °C (−9.4 °F) at Charlotte Pass, NSW on 29 June 1964.

Highest temperature in Australia: 50.7 °C (123 °F) at Oodnadatta, South Australia on 2 January 1960 (although 53 °C was recorded at Cloncurry, Queensland on 16 January 1889, but it was measured with non-standard thermometer).

Highest temperature on Earth: 57.8 °C (136  °F) at Al ‘Aziziyah, Libya on 13 September 1922.

Saunas: between 70°C (158 °F) and 100°C (212 °F).

Earth’s mantle: from 500 °C at the crust, to over 4000 °C at the core.

Centre of the Earth: about 5,505 °C (5,778 K).

“Surface” of the Sun (photosphere): 5,778 K

Hottest laser: ~3 million K at the National Ignition Facility at Lawerence Livermore National Laboratory, on 2 November 2010.

“Atmosphere” of the Sun (corona): ~5 million K

Centre of the Sun: ~16 million K

Nuclear fusion reactors: highest achieved was 510 million K at Tokamak Fusion Test Reactor, Princeton Plasma Physics Laboratory.

Supernovae: about 10 GK or 10 billion K (exploding stars)

Quasars: 700 GK or 700 billion K

Quark-gluon plasma: 0.5–1.2 TK, or 0.5–1.2×1012 K, or 0.5–1.2 trillion K (when the strong nuclear force, which holds protons and neutrons together, breaks down).

Hypernovae (collapsar) or gamma ray burst: 45–67 TK or 45–67 trillion K (exploding stars, 100 to 300 times the mass of the Sun).

Large Hadron Collider (protons): ~1.6×1017 K, or 160 quadrillion K (collision between two protons, each with an energy of 7 TeV).

Large Hadron Collider (lead nuclei): ~1.3×1019 K, or 13 quintillion K (collision between two lead nuclei, each with an energy of 574 TeV).

Ultra-high-energy cosmic ray collisions: 0.5–7×1024 K, or 0.5–7 septillion K

Absolute hotness: 1.4×1032 Kelvin, or 140 nonillion Kelvin. About 10 trillion times the energy of the Large Hadron Collider.

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