Primordial Universe Made of Strange Particles

The primordial universe was made of nothing but quarks and gluons for its first ten microseconds. Find out how tracing strange quarks helps solve the mystery of the Big Bang.

I can still remember the final exam for my university astronomy course back in 1983. The last question asked for an essay on how the universe started and how it would end.

It was tough to put the many ideas we had learned about this topic into words while under pressure. I passed, but I’ve never made any practical use of that knowledge since, and none of it is worth knowing anymore.

Back then, nobody knew the answer to a lot of questions about the primordial universe. Even the world’s top cosmologists weren’t sure which of several competing ideas was the right one.

researchers found the cosmic microwave background

The big bang theory had caught on with most people by then because researchers had accidentally found the cosmic microwave background radiation. The cosmic microwave background (CMB) is a faint trace of high-frequency radio waves we find in the sky in all directions and it proves that the big bang took place.

The big bang was popular on campus because it lined up with ideas like Aristotle’s unmoved mover and a biblical creator. It made us think we were having profound debates on the meaning of the primordial universe long into the night in our cramped residence houses

Scientists have filled in a lot of gaps in the primordial universe model since then. For example, we now know that the expansion of the universe is accelerating.


That’s led us to realize that dark energy and dark matter make up about 95% of the known universe. We’ve also managed to pin down the exact time that the big bang made the universe expand at 13.8 billion years ago.

It’s impressive how accurately scientists have modelled the expansion and cosmic inflation of the early universe. They’ve been able to trace the primordial universe back to within a fraction of a second after the big bang. Paul M. Sutter provides an easy to read overview of the current models in his book, Your Place In The Universe: Understanding Our Big, Messy Existence.

Equally remarkable, though, is that they haven’t managed to solve the puzzle of what went on in that first ten microseconds in the life of the primordial universe. One scientist who has contributed immensely to shedding light on this mystery is Dr. Johann Rafelski from The University of Arizona and CERN.


Dr. Rafelski thinks that during those first 10 microseconds of time in that hot dense primordial universe,  there were only two kinds of particles, quarks and gluons. Last week, he published a diary of his career spent working on this model in the European Physical Journal (EPJ) Special Topics.

Quarks are the elementary particles that make up the protons and neutrons in the nucleus of atoms that we all learned about in high school. They have various properties, including a so-called flavour and an electrical charge.

Quarks also have a second type of charge called a colour charge. We can’t really see quarks, so we don’t know what colour they are, but scientists have named the three charges after the colours blue, green and red just to give them a name.


Normally, we don’t see quarks floating around on their own. Their colour charge causes something called colour confinement which keeps them inside neutrons and protons.

Gluons “glue” quarks together inside those neutrons and protons. Neutrons and protons are types of hadron particles along with mesons,

In an earlier article, we talked about the phases of matter. We all know about the first three from thinking about water.


These are solid, liquid and gas, like ice, water and steam. We explained in that previous article that there’s a fourth phase of matter called plasma that we see on the sun.

In the primordial universe, quarks weren’t confined inside hadrons like they are now. In that heat, there was no colour confinement, and they were free-floating as were gluons.

And so, during that brief blink of an eye, the fifth phase of matter arose. The particles mixed up a hot soup that scientists call quark-gluon plasma (QGP).


Proving this hasn’t been easy for scientists like Dr. Rafelski. One thing that has helped is that quarks have that other property called “flavour.”

The six flavours are up, down, strange, charm, bottom and top. (Particle physicists have an odd sense of humour about naming things.)

Dr. Rafelski and his peers are most interested in the “strange” flavour when they study the first few microseconds of the primordial universe. The phase of matter that he calls QGP happens to produce lots of strange quarks.


By finding ways to trace strange flavoured quarks, he and his peers managed to find traces of the QGP phase of matter in the here and now. That discovery led to researchers smashing together heavy nuclei and lighter protons in head-on collisions at CERN’s famous Large Hedron Collider.

Dr. Rafelski winds up his diary with some insights into the successes and failures of his research, with notes from peer reviews and his own thoughts looking back. He stresses that “many pressing questions remain to be answered.”

He’s still sharing his experience with younger colleagues in the world of theoretical physics. He hopes that his younger peers will press on with studying what we can find out about QGP from tracing strange quarks.


Every culture has a story about where the universe came from and why there’s something instead of nothing. It’s a question we all ask ourselves sooner or later and the answers we come up with give life meaning.

The trouble is that in the 20th century, science tore up a lot of old stories and left us thinking that there was no truth left in them. Even so, it left us with a new story that we all know is accurate and that we can all share.

Scientists like Dr. Rafelski have spent a lifetime filling in the gaps in that story’s plot. Finding out what really went on in those first ten microseconds is the key to understanding how something came from nothing in the quantum fluctuations of the primordial universe.

We always have more to learn if we dare to know.

Learn more:

Exploring strangeness and the primordial Universe
Discovery of Quark-Gluon Plasma: Strangeness Diaries
Your Place In The Universe: Understanding Our Big, Messy Existence
The 5 Big Questions We Need Cosmology to Answer
Ancient Galaxies and Even Older Dark Matter
Hubble Constant: How Fast Are We Going?


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