Quark Gluon Plasma: The smoothest soup in the Universe

https://news.mit.edu/2010/exp-quark-gluon-0609

What’s cooking everyone! It’s your scientific sensei @jioh here with another chapter in my series of “Physics for Dumb Dumbs”. Today we’ll talk about a very special state of matter that flows smoother than buttered crawfish out a bucket! Our super hot, super dense particle soup, Quark Gluon Plasma. 

Now to talk about QGP, first we’re gonna have to go over a little concept known as “colour confinement”.  We all know of electric charge,  a proton has positive charge and an electron has negative charge and a neutron has neutral charge etc.  We know that opposite charges attract each other like magnets.  So if we have a positive charge and a negative charge together in space, they will pull themselves towards each other.  Simple right? Now colour confinement is a slightly trickier story.

Protons themselves are made up of an even smaller particle called the quark. The quark comes in many different flavours (e.g. up, down, charm, etc.) but also has its very own concept of “charge” to describe its interaction with another super small particle known as the gluon. Now this version of charge is a little bit different to electric charge, instead of their being a positive and negative charge we now have 3 different types denoted by red, blue, and green. This is aptly referred to as “colour charge” and the study of this complicated physics is known as “Quantum Chromodynamics”, or more simply QCD.  

We’re not going to go too far into the details of how colour charge works, but one thing to realise is that this attractive force is considerably stronger than that of electric charge. Because of this, once quarks and gluons have arranged themselves into some sort of “colour neutral” arrangement, it is near impossible to pull them apart. In fact, it takes so much energy to pull apart a colour neutral quark-gluon formation that if you were to use some hypothetical pair of ultra small tweezers  to try and pull them apart, you would end up using so much energy that instead of succeeding you would actually end up creating another quark gluon pairing that would preserve the colour neutrality of the system! This immense difficulty in separating the different colour charges is known as “colour confinement”.

Colour confinement can thus only be broken in very specific situations. One needs to induce a system of either extreme heat or extreme density. Luckily for us, we have some very special machines around the world that are capable of producing just that, the particle accelerators. As you can imagine, smashing two particles together at just slightly below light speed manages to create an environment of such high heat that colour confinement can be broken and all the quarks and gluons can, for a very short period of time, move freely in a pseudo-liquid known as “Quark Gluon Plasma”.  The existence of this new state of matter was theorised in the mid 80’s with experimental evidence being produced in both CERN and Brookhaven in 1999 as a result of slapping gold nuclei against each other. It exists for only a brief moment, as the soup rapidly cools down after the collision and the cooled down quarks and gluons quickly stick back together into their confined structures.   Because of this, it is very difficult to observe QGP itself and there are still many, many questions on its physics.

The most interesting property of QGP is actually just how fluid it is. In fact, by some metric it could be considered the most viscous fluid known to man.  Viscosity basically relates to the ease in which a liquid flows, and QGP has been found to flow easier than any other fluid we know of. 

Anyways, looking at the clock it’s time for me to bounce! Hopefully you all enjoyed the little taste I gave ya of nature’s smoothest soup and you’ll be hungry for the whole bowl! Don’t forget to like, comment, and subscribe, and turn post notifications on for when I drop my next lesson.

Dattebayo!