Maximum heat?

[Guest kyle8921]

The lowest possible temperature is -273 C, so is there a highest possible temperature too, or does it only depend on how much heat a specific substance can take before it vaporizes, or dissapears?

[Qfwfq]

You can always make sure it doesn't get away! There isn't an upper limit in principle on temperature, there are only practicle matters.

[nkt]

  Qfwfq said:

You can always make sure it doesn't get away! There isn't an upper limit in principle on temperature, there are only practicle matters.

I'm not so sure that is true. We can cheat, and look at the physical limit to any system of particles, the speed of light.

 

If we look at the definitions of temperature, (this may be rusty) we see that it is the random movements of phonons through the structure, and the bulk increase in energy.

 

Obviously, once a certain temperature is reached, we get a bulk effect called melting, then boiling. Eventually you get a plasma, where the electrons themselves get kicked off the orbits around the atom. Now, at this point, the "temperature" is very high, but the particles are rarifed, so have a low density, and so the specific heat tends to be very low. However, this means that the plasma particles are flying about, colliding at random. The limit to how fast they can fly is, therefore, limited only by the energy you put in. This in turn is limited by how fast the particle can actually go, which is c. (Of course, it can only reach c for an infinite energy input, and so you are limited by that)

 

Now, if someone wants to go look up the formula that lets you turn particle velocity into temperature, and plug in 2.998 * 10^8 m/s, that should tell us the maximum possible temperature for that particle.

 

I suspect it will be quite warm! :shrug:

[Qfwfq]

Check your argument over again. Most of all:

  nkt said:

The limit to how fast they can fly is, therefore, limited only by the energy you put in. This in turn is limited by how fast the particle can actually go, which is c. (Of course, it can only reach c for an infinite energy input, and so you are limited by that)

A bit contradictory. SR certainly doesn't put an upper bound on kinetic energy. I also fail to see your point about density and similar things. Even with three molecules per cubic mile you can have a high temperature. A temperature can even be given to the vacuum, see radiation temperature.

 

  nkt said:

Now, if someone wants to go look up the formula that lets you turn particle velocity into temperature, and plug in 2.998 * 10^8 m/s, that should tell us the maximum possible temperature for that particle.

Which formula? Relativistic or not relativistic?

 

BTW, temperatures can be negative according to the definition of the Boltzmann formula as long as you consider a subsystem with a limited energy spectrum, such as a spin gas. Much of a lab curio though, but when the negatemerature is induced it will go toward equilibrium with the rest by the route through infinity (down to -inf and then from there down to the surrounding temperature).

[UncleAl]

The lowest achievable temperature is an epsilon above absolute zero. The highest possible temperature is an epsilon below absolute zero (population inversion). Or, if you like, the highest possible temperature is a Planck mass-equivalent of energy occupying a Planck volume of space.

[spennithorne]

Please explain the "highest possible temperature is an epsilon below absolute zero (population inversion)" phraseology. Thanks. :rant:

[nkt]

  Qfwfq said:

A bit contradictory. SR certainly doesn't put an upper bound on kinetic energy. I also fail to see your point about density and similar things. Even with three molecules per cubic mile you can have a high temperature. A temperature can even be given to the vacuum, see radiation temperature.

Isn't that my point? You have one measure for the energy density, and another for the temperature. Bulk movement of matter is kinetic energy, rather than heat. However, taken to the logical limit, a single particle could be accelerated to whatever "temperature" was wanted. However, once the particle was accelerated to an epsilon below c, it wouldn't be possible for it to go any faster, and therefore could not get any "hotter".

 

  Qfwfq said:

Which formula? Relativistic or not relativistic?

It would need to be modifed for relativity.

 

Spennithorne, epsilon is a mathmatical construct which means "a small positive infinitesimal quantity", usually denoted ε.

[Qfwfq]

You are still contradictory nkt, I think you ought to check your calculus a little bit.

  nkt said:

It would need to be modifed for relativity.

;)

 

Why not?

[Qfwfq]

  spennithorne said:

Please explain the "highest possible temperature is an epsilon below absolute zero (population inversion)" phraseology.

Any negatemperature is higher that any positive temperature, at least regarding which system will absorb heat and which will release it.

 

The "epsilon below" is a loose way of putting it. Strictly, the zero is an upper bound and not a maximum. For any t = 0 - ε it can have a value between that and 0, but it can't be exactly 0.

[inuyashakusho]

if you think about it there must be a maximum heat because if absolute zero is when atoms are completely still then there must be a temperature at which atomic movement reaches the speed of light, which is the fastest that anything can go unless going through a wormhole

[engware]

Hi there:

 

Combustion wise, the flame temperature indicates the maximum possible achievable temperature.

 

Combustion needs to be at stoichiometric conditions assuming complete combustion takes place.

 

Increase in both fuel and oxidant preheat temperature further increases the flame temperature.

 

Thanks,

 

Gordan

[P-man]

HOw is it impossible ot go under -237 degrees? Is it just on Earth? Because on Pluto I htought it reached tmeperature of -285.

[InfiniteNow]

  P-man said:

HOw is it impossible ot go under -237 degrees? Is it just on Earth? Because on Pluto I htought it reached tmeperature of -285.

 

Depends on what scale you use. I imagine you're thinking Fahrenheit... which would go down to -459.67

 

 

Absolute zero

  Quote

Absolute zero is a fundamental lower bound on the temperature of any macroscopic system. It is a temperature of 0 K, −273.15°C, or −459.67°F. It is unachievable in practice but it exists as a limit for real physical phenomena, and it was inferred by extrapolation from kinetic theory, and from other considerations in theoretical physics.

 

Alternate definitions are that absolute zero is the temperature at which no further energy can be extracted from a physical body, or the temperature at which the entropy change of an adiabatic process vanishes. On the other hand, defining it as the temperature at which all motion ceases would go against quantum mechanics requirements which states that even at absolute zero some motion remains.

[P-man]

Well I was actually talking Celcius. Fahrenheit is impossible to understand.

[InfiniteNow]

Considering that, you may want to verify both the number and the scale you got for the temperature on Pluto.

 

Here's what I found:

 

 

http://web.mit.edu/newsoffice/2002/pluto.html

 

  Quote

Pluto's atmospheric temperature varies between around minus 235 and minus 170 degrees Celsius, depending on the altitude above the surface.