We did a little blurb about this topic last year. Today, we wanted to expand on the question with a bit more detail since the answer can be complex, and at the same time, extremely interesting. We wanted to try and break it down a bit more so that it would have some appeal to our casual readers.
However, before we can delve into what the hottest temperature is, we first need to know what absolute zero is. Strange as it sounds, there is a connection.
Absolute zero is the absolute lowest temperature in standard physics and in nature. Absolute zero is 0 on the Kelvin scale, or -460F/-273C. Because atoms slow down (vibrate slower and slower) as the temperature drops, they completely stop once they reach 0 Kelvin. At this temperature (absolute zero), there is absolutely no motion – even at the subatomic level. Everything is frozen, even time.
Try to imagine driving a car down the road and eventually slowing down as you approach a stoplight, then coming to a stop. Being stopped is absolute zero. Attempting to go below absolute zero would be like trying to get your car to go slower than completely stopped.
Is There An Absolute Hot?
The jury is still out it seems. The answer can be yes, no or maybe, depending on which theoretical physicist you’re talking to. Some physicists have postulated that absolute hot may actually be a negative number.
Negative & Infinite Temperature
Most theoretical models cannot reach negative temperatures, because adding energy to make it hotter will increase its entropy. However, there are some magnetic based systems which could be an exception to this rule. Such systems have a maximum amount of energy that they can hold. This means that as they approach their maximum energy, their entropy actually begins to decrease. Due to the mathematics, and decreasing entropy, the temperature becomes a negative number.
Don’t be fooled however, a substance with negative temperature is not colder than absolute zero; rather, it is hotter than infinite temperature.
Some physicists posit that the highest temperature is Planck Temperature. They claim it is the highest possible temperature that matter could theoretically exist at. It is approximately 1.41679 x 10^32 Kelvin. That’s roughly 100 million million million million million degrees. For comparison, the center of our sun bubbles along at chilly 15 million degrees °C.
Scientists believe that our universe has already experienced the Planck temperature at one point in time, though it was so brief, you may have missed it. It would have occurred at 10^-43 of a second after the moment of the Big Bang, the great cataclysm in which our universe was born. If we tried to go hotter than Planck temperature, physics as we know it break down. This is why many assume it to be highest temperature in conventional physics.
Bonus factoid: The hottest temperature ever reached on Earth was 3.6 billion °F. It was achieved by the Z machine at Sandia National Laboratories. The Z machine is the world’s largest X-ray generator.
C. Kittel, H. Kroemer (1980). Thermal Physics (2 ed.). W. H. Freeman Company. ISBN 0-7167-1088-9.
Parihar; Widom; Srivastava (2006). “Thermal Time Scales in a Color Glass Condensate”. Physical Review C 73 (17901). doi:10.1103/PhysRevC.73.017901
Mosk (2005). “Atomic Gases at Negative Kinetic Temperature”. Physical Review Letters 95 (4). arXiv:cond-mat/0501344