Rocking with RHIC

Pete (big-pete) writes "Scienceblog carries a copy of an article which describes some unexpected results found when Physicists started slamming gold atoms together at high speeds. The resulting temperature was tens of thousands of times hotter than the cores of the hottest stars, but the resulting stream of particles did not behave as predicted. The original article is also available from the University of Rochester's news site here."

Idiocy is grand

[nocomment]

This may seem like a stupid question to some of you, but how do you measure the temperature of an atom?

Re:Idiocy is grand

[frawaradaR]

You don't, since temperature is a statistical measure, corresponding to the mean energy of moving particles in a fairly large collection of particles. What is meant by the temperature of an individual particle is thus simply the temperature that would be if the particle's energy was translated into heat in a particle collection.

Re:Idiocy is grand

[0x69]

Ummm...when you're smashing gold nuclei together fast, there are hundreds or thousands of particles involved - plenty to talk about temperature in the statistical sense. (The two gold nuclei contain hundreds of neutrons & protons, each made up of several quarks and held together by other particles... Nuclei don't act like immutable little ball bearings at the impact speeds these folks are using; it's more like shooting paintballs into each other.)

Re:Idiocy is grand

[Frodo2002]

I did my masters thesis some years ago on statistical models of quark-gluon plasma (QGP). As said by others, temperature is a statistical thing. A measure of the average kinetic energy of the particles in the particular statistical ensemble. What is suprising is that such a small number of particles can behave in such a way that they can be described by a statistical ensemble at all. Point is that treating the collision like this works. The theoretical curves fit *most* of the data exceedingly well. This is how one can infer the temperature of the QGP: namely assume a thermalized statistical ensemble (of some sort: either grand canonical or more sophisticated) and find what temperature fits the data. This is the "temperature" of your QGP. (If there is such a thing for such a small ensemble.)

Whew!

[gnovos]

The resulting temperature was tens of thousands of times hotter than the cores of the hottest stars, but the resulting stream of particles did not behave as predicted.

Considering that one of the predictions, if I remember correctly, was the possibility of creating a new vaccum state that would rocket out from the earth at the speed of light destroying all the universe that lay in it's path... I'm pretty relieved that the behavior was a little different than expected. :)

Re:Whew!

[0x69]

Considering how many similar prior collisions there have been in the history of the universe, this doesn't sounds like a rational prediction.

Probably a scare rumor started by a neighbor worried that the big atom smasher would goof up his TV reception.

Damn Skippy

[Kibo]

They actually had to write up an enviromental impact statement outlining how unlikely it was that our explorations might destroy the universe. IIRC. I think they predicted that something 5000 lead lead collisions of a similar nature occure every year in the universe. Heh. Humans rock. We beat that by a million times in the breifest of moments. I like to think that's where my tax dollars went.

I'm completely out of my depth, but as I understand the experiment the really vast gold atoms don't behave like billard balls. They are little pancaked discs that have this swarm of virtual particles around them, and when two of these atoms approach each other those swarms interact. That interaction sort of drags on the atoms stealing a little of their kinetic energy. But the atoms are movie so fast they out run this virtual reaction. So there's this little pocket of space that gets that extra energy, a lot of extra energy for it's volume. It ends up being heated to something like 2 trillion degrees, and we get to recreate yet another state of matter (three states my ass!). Not to mention getting a chance to push the universes clock back to something on the order of the first trillionth of a second, or even earlier!

That's just cool.

Re:Whew!

[Peter T Ermit]

Yes... some people believed that collisions would cause us to revert to a lower energy state of the vacuum. (Or that it would create black holes or strangelets.) The protesters caused enough trouble that Brookhaven had to commission a study [bnl.gov] to show that it wouldn't happen because cosmic-ray collisions can be even more energetic (and for other reasons).

Nowadays there are protests every time a new accelerator starts up.

Re:Whew!

[helix400]

I found this relating to the RHIC and quark-gluon plasma. Its an interesting link that explains more about this "doomsday" scenario and why it wont happen.

http://www.everything2.com/index.pl?node=strangele t [everything2.com]
(The link works, for some reason, Slashdot put a space in the link's description.)

---
Abortions for some, miniature American flags for others! - Kodos

Re:Whew!

[Peter T Ermit]

Unfortunately, the author of that link doesn't know diddly. (Not your fault, but figured I'd straighten it out for the record.)

[A strangelet is] a substance formed when present energy is sufficient to allow quarks and gluons to overcome the strong nuclear force and become uniform matter.
Nope. The strong nuclear force isn't overcome at all. A strangelet is a substance formed by with an equal mix of up, down, and strange quarks. The whole mess is bound by gluons (which carry the strong force). Strange matter is, in theory, at a lower energy state than ordinary nuclear matter.

The strangelet itself is a possibility of quark matter which occurs when an up quark and down quark combine to form a strange quark, one that does not exist under normal conditions. If a large number of these transformations occured at the same time, a strangelet could be formed: quark matter consisting entirely of strange quarks. Nope, and nope. Up and down quarks don't combine to form strange quarks. A strange quark is formed via the weak nuclear force -- either an up or a down quark turns into a strange quark, a lepton, and an antilepton (if I've managed to keep my Feynman daigrams straight). And strangelets are made of up, down, and strange quarks, not just strange quarks.

There are other basic mistakes, but I figured I'd correct at least the definition of strange matter.

Re:Whew!

[helix400]

Hey, nice job clarifying that. Its one thing to be able to say that you know its wrong. Its another to back that up so well. =)

Very confused article.

[Peter T Ermit]

For example, the researchers didn't "...[collide] the circular gold atoms slightly off-center" in order "to simplify their observations." The atoms just collide off center most of the time naturally.

A bit denser, but much more accurate story about RHIC is here. [unm.edu]

Backwards Alchemy

[Tidan]

For years scientits and crazy people have been trying to turn gold into metal. Now they've done the opposite, and what do they get? Really big temperatures hotter than the the hottest stars.

I guess all those alchemists who thought that adding fire to metal would make gold were right after all...

And for a complete waste of time, go play alchemy [yahoo.com].

Uh..

[Hard_Code]

it's probably not a problem.. probably.. but I'm showing a small discrepancy in.. well, no, it's well within acceptable bounds again. Sustaining sequence.

Egad...

[Multiproximus]

"When we first presented this at a conference in Stony Brook, the audience couldn't believe it," says Manly. "They said, 'This can't be. You're violating boost invariance.'" And boost invariance was my favorite theory! How sad to see it slammed. ;-( R.I.P. B.I.