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# I mean, let's pretend we made a hard vacuum in a jam jar
and let's also pretend that we had some sort of indestructible thermometer that somehow didn't occupy any matter, situated in the centre of the hard vacuum. Some sort of ethereal temperature reading device. Just humour me for a moment.

If we took that jam jar and buried it in the snow for a thousand years, would the thermometer change temperature? What if we then put it in the oven for a thousand years? Any changes?

Would the original temperature of the room the vacuum was created in count as 'having temperature'?
(I helped save b3ta! gronkpan @vomitinglarry.bsky.social, Tue 30 Dec 2008, 9:59, archived)
# Well, apparently macroscopic temperature is defined by the flow of heat from one body to another
so...

arrgh. I know that you are right - but surely the energy from the oven has to be transmitted across the vacuum somehow, er.

Perhaps I'm not much of a physicist :(

edit : also this has all the makings of a xkcd strip! throw in some analogy/weak pun about relationships and we're there!
(I helped save b3ta! The Alchemist king of the needlessly complicated, Tue 30 Dec 2008, 10:04, archived)
# It's ok, neither am I
I just like to argue sometimes.
(I helped save b3ta! gronkpan @vomitinglarry.bsky.social, Tue 30 Dec 2008, 10:07, archived)
# the thermometer in the middle of the ideal vacuum would not change temperature
there's no matter for heat conduction to the middle of the jar.

The external temperature of the jar would have temperature (assuming it has some heat capacity)

(k3b/-\b Peace man., Tue 30 Dec 2008, 10:11, archived)
# so if it doesn't change, it stays at the same temperature it was at when the vacuum was created?
it still "has temperature"?

I agree that it wouldn't have any "heat energy", but it would still "have temperature".

I'm in a finger-quotes mood right now.
(I helped save b3ta! gronkpan @vomitinglarry.bsky.social, Tue 30 Dec 2008, 10:15, archived)
# *thinks*
I think the act of creating the ideal vacuum with lead to something having 0 (absolute) temperature

hangon! all of this can't happen in the first place. If there is no temperature, by definition, then at absolute zero and that violates one of the laws of thermodynamics.


(k3b/-\b Peace man., Tue 30 Dec 2008, 10:22, archived)
# THANKYOU
I was going more for the definition of measurement rather than the whole thermodynamics thing, but we both got to the same place in the end.

Of course, we could start talking about entropy but that would just start a whole other shitstorm.
(I helped save b3ta! gronkpan @vomitinglarry.bsky.social, Tue 30 Dec 2008, 10:28, archived)
# Wait, entropy would stop a shitstorm, not start it
I still think I'm doing pretty well considering I've been drinking for seven hours now.
(I helped save b3ta! gronkpan @vomitinglarry.bsky.social, Tue 30 Dec 2008, 10:30, archived)
# FUCKING ENTROPY
(I helped save b3ta! gronkpan @vomitinglarry.bsky.social, Tue 30 Dec 2008, 10:38, archived)
# Naa
The temperature on the thermometer wouldn't change because the amount of heat energy held by the thermometer itself would remain the same, since the vacuum around it would stop any heat energy from being lost or gained.
(orukusaki actually fucking posted something for a change, on, Tue 30 Dec 2008, 10:31, archived)
# You're forgetting that this is a magical thermometer that doesn't occupy any matter
It wouldn't have any heat energy.
(I helped save b3ta! gronkpan @vomitinglarry.bsky.social, Tue 30 Dec 2008, 10:34, archived)
# If the thermometer is hotter than the surroundings
then it would slowly cool down. If it was colder, then it would slowly heat up.

Think of a vacuum flask - sure, it keeps hot things hot and cold things cold, but not for ever! Damn you and your hollow promises of eternal piping hotness, vacuum flasks!
(salty_sea_dog Pillaging since 1886. Oh, and "Yahaarrrr" as well., Tue 30 Dec 2008, 11:04, archived)
# NO NO NO
The thermometer doesn't occupy any matter. It behaves exactly like its surroundings. This is crucual to my point.

I can't remember why but it is.
(I helped save b3ta! gronkpan @vomitinglarry.bsky.social, Tue 30 Dec 2008, 11:10, archived)
# If the thermometer doesn't occupy any matter
how can it give a temperature reading? I is confuzzled.
(salty_sea_dog Pillaging since 1886. Oh, and "Yahaarrrr" as well., Tue 30 Dec 2008, 11:19, archived)
# It's a theoretical thermometer
(I helped save b3ta! gronkpan @vomitinglarry.bsky.social, Tue 30 Dec 2008, 11:33, archived)
# Heat can be transmitted by radiation
That's how it gets from the Sun to us, so for the thermometer experiment, it would slowly reach the temperature of it's surroundings, but it would be pretty slow as the only transmission of heat would be radiation.

Anyway, the 3K microwave background is actually called that because it has the spectrum of a black body at 3K, it doesn't necessarily imply that space is at 3K.

Because of the lack of pressure, any moisture on the surface of your body would pretty instantly vapourise - this would extract a lot of heat energy from surrounding tissues, so if you had your eyes open then they'd probably start freezing pretty quick. But it would be a race to see whether they'd explode out of your head due to the pressure gradient first.
(salty_sea_dog Pillaging since 1886. Oh, and "Yahaarrrr" as well., Tue 30 Dec 2008, 11:01, archived)