Hot temperatures

Everybody (I hope) knows that the lowest temperature that something can be is absolute zero, 0 Kelvins or just damn cold.

I heard recently that there is a maximum temp. known as Planck’s temp ad is 10 to the power of 32 Kelvin.

Is this true? How can you have a maximum temperature?

There is a theoretical maximum temperature, and I believe it’s called the Asimov temperature, since Isaac Asimov proposed it in one of his science columns.

Basically, you convert all the matter in the universe into energy except for one electron (you need the electron otherwise there’s nothing to measure). Then you calculate the temperature of that electron. It’s pretty damn hot.

“East is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does.” – Marx

Read “Sundials” in the new issue of Aboriginal Science Fiction.

You figure the size of the universe, diameter that is. Then you figure how many degree marks would fit on a thermometer that size.

As the universe gets bigger, the maximum temperature gets bigger too.

:slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile: :slight_smile:

I’m posting this from a friend of mine who doesn’t have Web access.
Well I think, if you convert all the available mass in the earth to
energy and leave a sole electron
Then with all the extra energy, the available bands for the electron to
settle in would be less as the overall energy would be unstable, thus, the
electron would be need more energy then usual to move about or even stay in
its rest position, therefore the temperature of the electron would rise
dramatically, a hot electron I think they call them! In a semiconductor as
you raise the temperature of the device, the electrons, due to the extra
heat, gain more energy and can move ballistically. But they remain at a
higher temp, due to the device been heated up!


You are all talking about, of course, taking Satan’s rectal temperature?

Hey, um… where are we?

Thanks Torq.

Another example of asking questions before
checking the archives, oops!

In case you wanted it in a more day-to-day scale, in Celsius the Planck temperature would be
10^31 + 273.15 C

It’s left as an exercise for the alert reader to translate it into Fahrenheit. :slight_smile:

La franchise ne consiste pas à dire tout ce que l’on pense, mais à penser tout ce que l’on dit.
H. de Livry

damn those typos! that was supposed to be
10^32 - 273.15 C

La franchise ne consiste pas à dire tout ce que l’on pense, mais à penser tout ce que l’on dit.
H. de Livry

There must have been some sort of problem in the copy-editing stage, because it looks as if Cecil refers to “degrees” Kelvin on several occasions, which would be the sort of elementary error he would never make.


The Planc temperature is the temperature of a BlackBody. A blackbody is an
imaginary body whichis so called because it absorbs all incident radiation.
In a BB the temperature of the matter and the temperature of the radiation
are in equilibrium and for a given temperature everything is known in terms
of atomic populations. All the transitions are in equillibrium. So every
radiative de-excitation is balanced out by a radiative exitation. As soon
as a photon is generated close to the centre of the sun it is reabsorbed
again after travelling a few µm’s. It is then promply re-emitted in another
direction. This random walk process repeats itself until photon finally
reaches the outer layer of the sun and then it escapes and maybe goes to
earth. But it takes over a million years for the photon to travel from the
centre to the edge of the sun and only 8mins from the sun to Earth. The
Suns Corona is hotter than the centre though because there is more freedom
of moement of the molecules. I think its like when steam is hotter thean
boiling water. Anyway when they use lasers to generate fusion on earth they
create a plasma with a BB temperature of ~300eV with 1eV = 11600K . So
whats the hottest temperature? I dont bloody know !

I assume you are quibbling over “degrees Kelvin” rather than “Kelvins”. If it’s changed, it’s changed fairly recently – my old Handbook (44th edition) says “degrees Kelvin”.

John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams

It seems there’s some confusion here, despite Cecil’s column.

First, there seem to be TWO “Planck Temperatures”. I’m basing this on an Alta Vista search for the term, which turns up several pages which look vaguely crackpottish to me, Cecil’s column, a couple of “introduction to cosmology” pages which mention the term in passing (all of which use it in more or less the same way, though they don’t all have the same value… see below), and an answer key to a quiz which as far as I can tell (the full text of the QUESTIONS wasn’t provided) is using “Planck temperature” in a way that may be related to the “black body / cavity radiation” answer above. More specifically, they’re calculating the surface temperature of a planet and calling that the “Planck temperature”. Obviously, this is not anywhere near 10[sup]32[/sup] Kelvins.

The actual value of the Planck temperature (in the same sense that Cecil uses it) is not exactly 10[sup]32[/sup] Kelvins. Unfortunately, I can’t tell you what it is, because I can’t find it in any source I trust and the values I find in sources that I don’t trust (the web pages mentioned above) vary considerably, from 1.4 to 3.something times 10[sup]32[/sup].

It’s definitely NOT known to so many significant figures that it makes any difference whatsoever if you express it in Kelvins or degrees Celcius.

The change to “Kelvins” from “degrees Kelvin” was made in 1967. However, while the “Definitions” section of my 60th edition CRC HoCaP correctly explains this, the VERY NEXT ENTRY still uses (degree symbol) K, which terminology was by that time 12 years out of date.

I can’t believe I spelled “Celsius” wrong above. Next time I should proofread better…

The term “degree Kelvin” was adopted by the 10th CPGM in 1954 (CPGM = “Conférence Générale des Poids et Mesures”, or General Conference on Weights and Measures", the authority as established by the Paris Meter Convention [“Treaty of the Meter”] of 1875).

The 13th CPGM in 1967 brought it into line with other SI units by changing it to the “kelvin” (if you want to be really picky, the upper-case “K” is not correct for the name of the unit, only the abbreviation). The 13th Conference also allowed that the degree Celsius is acceptable for expressing a difference or interval in temperature and is, of course, exactly equal to the kelvin in this context.

So, if your handbook was published between 1954 and 1967, it was correct at time of printing.

ben, feeling rather smug.