
CERN’s Large Hadron Collider achieves the hottest manmade temperatures ever - ananyob
http://blogs.nature.com/news/2012/08/hot-stuff-cern-physicists-create-record-breaking-subatomic-soup.html
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pif
> to momentarily create a quark gluon plasma, a sub- _atomic_ soup

It's even a sub- _nuclear_ soup. It's not obvious until you think to it, but
an atom is just enormous when you're talking at nuclear scale: a typical
nucleus in its atom is like a tennis ball in a stadium!
[http://public.web.cern.ch/public/en/research/MinChall-
en.htm...](http://public.web.cern.ch/public/en/research/MinChall-en.html)

~~~
Retric
What I find mind blowing is there at energy levels where making these mater
mater vs mater energy collisions is practicably meaningless. At 7Tev a
collision between 2 protons has enough energy to create over 3,500 proton
anti-proton pairs. And honestly anything that makes antimatter collisions seem
like small potatoes is just insane.

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ctdonath
What constitutes "hot" at such a small scale?

Years ago I addressed "hot" in terms of molecular speed, applying relativistic
limits, calculating an upper limit on temperature and finding a large, but not
inconceivable, maximum. Alas I've lost the paper (which was probably wrong
anyway, but it was a fun exercise). The question has long bugged me: is there
a real upper limit on temperature?

~~~
theorique
There's certainly a relativistic limit - i.e. if the mean velocity of randomly
oscillating particles in the gas / liquid approaches c. (I leave aside the
question of what is used to confine such highly energetic matter)

~~~
Jabbles
That in itself wouldn't limit the temperature. The average speed of the
particles could approach c and their average energy would continue increasing.

Molecules will break apart above a few thousand degrees. If you take a gas
(say Helium) above a certain temperature (probably ~1e4 K) the collisions
between the atoms will knock the electrons off and you'll be left with a
plasma.

Confining a plasma could either be done with magnets (e.g. a fusion reactor),
or with more plasma! (in the case of stars, where the gravity keeps itself
from exploding).

Above 1e7 K you start to get fusion of Hydrogen, and I think above 1e11 K
pretty much any nucleus will fuse/break down.

So it's difficult to say there's a maximum temperature, as it's quite hard to
define.

What's your maximum temperature? About 41'C... above that and you'll die...

~~~
polysaturate
That last line worries me...I live in phoenix and most summer days are above
110' F...41'C is 105.8' F :/

Hopefully there is some clarification to explain how I won't die...

~~~
biot
I've been in a dry sauna as the temperature gradually reached its max peak of
105 C. At that temperature, the trick is to not move so that there's a
relatively static layer of air around you. You also have to breathe slowly so
as not to burn your nostrils/throat. And you perspire like crazy and the
evaporation of your perspiration cools your body. It's still crazy hot though
and you can't last very long before having to exit.

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cshimmin
Late to the party, but I thought I'd clarify on what temperature really means.

Many people are familiar with temperature as characterized by "average thermal
velocity" of, say, air molecules. However, in statistical mechanics (the
physics of many particle systems), temperature is _defined_ in terms entropy
and energy.

Specifically, temperature is the rate-of-change of _energy_ with respect to
_entropy_. (In math: T = dU/dS.) This arises as a natural definition if you
think of temperature as "the thing that is equal between two systems in
thermal equilibrium".

Think about it this way: A cup of water and an ocean have VASTLY different
energies. Similarly, the ocean has an enormous entropy compared to the cup.
However, if they're at the same temperature, the unit change of entropy per
energy added is the same.

Coming back to the article, the temperature being reported by ALICE is derived
from the entropy and energy of the collisions. Specifically, they're looking
at quark-gluon plasma from the heavy-ion collision at LHC.

Under normal conditions, quarks and gluons are _confined_ to hadrons like
protons and neutrons. Quark-gluon plasma occurs only at extreme energies, and
in these collisions it is a essentially a chaos of quarks and gluons. The
chaos (entropy) is not a thermal property but rather largely comes from the
nature of the strong force. So, changing the energy of a quark-gluon plasma
doesn't have a huge effect on its entropy. Conversely, you could say it takes
a lot of energy to change the entropy, and so by the definition of
temperature, you get a very large value!

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unreal37
Before reading the article, I wondered how hot that would be, like 5000
degrees C or something. For reference, the surface of the Sun is approx 10000
F/5500 C.

They're claiming 5.5 trillion degrees Celsius. My mind is unable to comprehend
that. A billion times hotter than the surface of the Sun...

~~~
aroberge
Don't confuse the temperature at the surface of the Sun (5000 C or so, which
is quite cool) with the temperature in the interior of the Sun (15 000 000 C
or so ... quite a bit hotter). Still, it pales in comparison with the
temperatures achieved in that experiment.

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rplnt
Did they just totally ignore units in the whole article? (Yes, they did).
Anyway, in the comments author said it's in degrees Celsius, if anyone was
wondering (as at that scale the difference is quite big).

~~~
aroberge
What did you expect: Farenheit?... Any scientific paper will refer to
temperature either in Kelvin or Celsius ... and the difference between the two
at that scale is _quite small_.

~~~
rplnt
Yeah, K/°C difference is small, but I didn't expect Kelvin as it isn't a
"degree". And I don't know that site/portal/.. If it were US newspaper, I
would expect it to be in degrees F without mentioning it. It happens.

Also, any scientific paper should use units. But to be fair, even though the
difference between Farenheit and Celsius is huge at this scale, I can't really
imagine it or compare it.

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web007
Anyone know how this compares to the NIF in terms of temperature? They talk
about terawatts and megajoules versus degrees, and as a non-physics geek I
can't equate the two.

NIF press release, 522.6TW and 1.855MJ -
<https://lasers.llnl.gov/newsroom/project_status/index.php>

~~~
aroberge
Nor should you (be able to equate the two). Very roughly speaking, temperature
is akin to a measure of the average energy density. Joule is a measure of
energy and watt is a measure of energy per unit time. So, they give you a
measure of how fast they delivered the energy (in terawatts), how much energy
was delivered (in megajoules) but this does not tell us anything about the
temperature at which the sample was heated since we don't know the size of the
target.

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netvarun
Out of curiosity. How do they handle such heat? I mean won't it melt anything
around it? Also, how did they measure it? [I am assuming it was measured using
a sophisticated thermal imaging camera, though I would like to think that some
brave soul stuck in a huge badass thermometer inside the cauldron =)]

~~~
Jabbles
They handle the heat by having an inconceivably small amount of matter at that
"temperature". They measure it by looking at the resulting particles and
working out how much energy the collision had, and converting between units of
energy and temperature.

There are some problems with describing the energy of a particle accelerator
as a "temperature", but it makes the article more accessible and
understandable, which is surely a good thing.

~~~
jessriedel
I don't think there's much of a problem with calling it a temperature. They
don't use that term when describing merely one particle scattering off
another, they only use it when they are colliding whole nuclei and there are
enough particles to observe a thermal distribution. The key part about having
a temperature is to have a distribution of modes (e.g. free particle momentum
states) and that there is enough mixing around between these modes to generate
a thermal distribution.

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Create
just for the record and to please the prospective downvoting mob, here are my
experimental observations consistent with the cern experimental domain in
order to warn any non-westerners:

"The cost [...] has been evaluated, taking into account realistic labor prices
in different countries. The total cost is X (with a western equivalent value
of Y) [where Y>X]

source: LHCb calorimeters : Technical Design Report

ISBN: 9290831693 <http://cdsweb.cern.ch/record/494264>

about integrity:

<http://cdsweb.cern.ch/record/1127343?ln=en>

~~~
cygx
From looking at the abstracts and your quote, I don't see anything
particularly unreasonable. What exactly do you want to tell us? Capitalism is
evil and public relations morally wrong?

~~~
Create
Propaganda meets reality: none of the statements below are actually true:

"Message from the Director-General

CERN is an Equal Opportunities employer. Our Equal Opportunities policy is
founded on four main pillars:

 _in recruitment and career development, the Organization will not
discriminate against any applicant or employee on the grounds_ of sex, ethnic
_origin_ , disability, sexual orientation, religion, _nationality_ or age;
respect and dignity for all in the workplace; support for working parents;
work-life balance." --

[http://equal-opportunities.web.cern.ch/equal-
opportunities/W...](http://equal-opportunities.web.cern.ch/equal-
opportunities/Welcome.php)

