4 ms·

> There's no theoretical limit for temperature I suppose when the particles reach lightspeed?

killjoywashere 10y ago
The archtype of temperature is a black body radiator. Classically, you make a block of metal (ceramic, whatever), with a spherical cavity and drill a small hole into the cavity. Then you draw a vacuum and heat the cavity, point a scope at the hole, and measure the spectrum of ligh tcoming out. In this circumstance, there is no mass that limits the energy: you are measuring the temperature of a black, empty vacuum; thus there is no upper limit.
- jahnu 10y ago
  > Then you draw a vacuum and heat the cavity What are you heating if it's a vacuum? How can you heat nothing?
  - TeMPOraL 10y ago
    You're measuring radiative heat, which indeed exists for most of its time in nothing. I guess that the idea of GP is that you could make the heating block arbitrarily big (say, size of the universe) and have it dump all its radiative heat into that cavity.
    - jahnu 10y ago
      I see. Thanks. The difficulty here is people don't often specify if they mean heat in the form of kinetic energy or radiation. Much like how people say things like "releasing energy" without specifying the form of energy.
- zeroer 10y ago
  When you heat something, you have to add energy to it. Mass and energy are equivalent; both warp spacetime. You will, in fact, reach a temperature where your block of metal collapses.
  - killjoywashere 10y ago
    I was simply trying to explain to my P that temperature is not dependent on the speed of a massive particle.
    - zeroer 10y ago
      OK, but arbitrarily high temperatures necessitate arbitrarily high mass-energy densities, and the latter won't happen without a gravitational collapse.
- dTal 10y ago
  I'm sorry, but this is a complete misapprehension of "black body" radiation and your experiment is nonsensical. "Black body" refers to an object that absorbs all incoming radiation, and nothing to do with the "a black, empty vacuum". The spectrum of such an object therefore is entirely radiative (no reflection) and depends only on its temperature. As a sibling points out, a vacuum cannot be heated - there is nothing to heat - and does not have an emission spectrum. Your experiment would simply measure the spectrum of the bottom of the hole you drilled.
thomasahle 10y ago
I see that I am mistaken: The temperature is a function of the particles energy, not its speed. The energy at light speed is infinite, so that doesn't really pose a temperature limit. There does however seem to be an quite widely assumed maximum temperature: the Planck temperature of about 1.417×10^32 Kelvin.

The archtype of temperature is a black body radiator. Classically, you make a block of metal (ceramic, whatever), with a spherical cavity and drill a small hole into the cavity. Then you draw a vacuum and heat the cavity, point a scope at the hole, and measure the spectrum of ligh tcoming out. In this circumstance, there is no mass that limits the energy: you are measuring the temperature of a black, empty vacuum; thus there is no upper limit.

jahnu 10y ago
> Then you draw a vacuum and heat the cavity What are you heating if it's a vacuum? How can you heat nothing?
- TeMPOraL 10y ago
  You're measuring radiative heat, which indeed exists for most of its time in nothing. I guess that the idea of GP is that you could make the heating block arbitrarily big (say, size of the universe) and have it dump all its radiative heat into that cavity.
  - jahnu 10y ago
    I see. Thanks. The difficulty here is people don't often specify if they mean heat in the form of kinetic energy or radiation. Much like how people say things like "releasing energy" without specifying the form of energy.
zeroer 10y ago
When you heat something, you have to add energy to it. Mass and energy are equivalent; both warp spacetime. You will, in fact, reach a temperature where your block of metal collapses.
- killjoywashere 10y ago
  I was simply trying to explain to my P that temperature is not dependent on the speed of a massive particle.
  - zeroer 10y ago
    OK, but arbitrarily high temperatures necessitate arbitrarily high mass-energy densities, and the latter won't happen without a gravitational collapse.
dTal 10y ago
I'm sorry, but this is a complete misapprehension of "black body" radiation and your experiment is nonsensical. "Black body" refers to an object that absorbs all incoming radiation, and nothing to do with the "a black, empty vacuum". The spectrum of such an object therefore is entirely radiative (no reflection) and depends only on its temperature. As a sibling points out, a vacuum cannot be heated - there is nothing to heat - and does not have an emission spectrum. Your experiment would simply measure the spectrum of the bottom of the hole you drilled.

thomasahle 10y ago

I see that I am mistaken: The temperature is a function of the particles energy, not its speed. The energy at light speed is infinite, so that doesn't really pose a temperature limit. There does however seem to be an quite widely assumed maximum temperature: the Planck temperature of about 1.417×10^32 Kelvin.