Elementary Particles: Before Atoms

HOW DOES ONE IGNITE A UNIVERSE?
One does not do it all at once...

...for in the beginning, one has only nothing to work with.

In the beginning...

No stars.
No worlds.
No atoms.

Nothing you would recognise as a thing.

The early universe was extremely hot and dense, and it was expanding.

During the Quark-Gluon Plasma Epoch, quarks and gluons were not confined inside individual protons and neutrons as they are in ordinary matter today.

Electrons and many other particles were also present.

There were no atoms, molecules, stars, planets or cells yet.

Of course, “nothing” is a matter of perspective.

Look more closely.

An elementary particle is a particle with no known smaller internal structure.

That does not mean scientists have proved that nothing smaller could ever exist. It means that, with the evidence we currently have, no smaller structure has been found.

Up quarks, down quarks and electrons are elementary particles.

Protons and neutrons are different: they contain smaller particles. Atoms are a later level of structure again.

Most of what was there need not concern us.

These three, however... keep watching.

Matter particles in the Standard Model include two broad families called quarks and leptons.

The up quark and down quark are quarks.

The electron is a lepton.

Other kinds exist, but these three are the particles we need to follow on the route towards ordinary atoms.

People notice things.

I notice the spaces between them.

A condition changes.

Something that could not exist...
suddenly can.

As the universe expanded, it cooled.

At very high temperatures, quarks existed in the quark-gluon plasma. As the temperature fell, the conditions changed.

Quarks could become confined inside larger composite particles called hadrons.

Both up quarks and down quarks would become parts of protons and neutrons. Electrons followed a different route and remained elementary.

There.

CLICK.

One thing has become another thing’s beginning.

The quark-gluon plasma did not last.

As the universe cooled, quarks became confined inside hadrons.

Two hadrons matter particularly for the next stage of our story: the proton and the neutron.

These will later become the main particles inside atomic nuclei.

The next lesson looks inside them.

WHAT EXISTS NOW?
protons · neutrons · electrons

Up and down quarks have not disappeared; they now exist inside protons and neutrons.

You see?

One does not make a universe all at once.

One lets each moment inherit the consequences of the last.

NEXT: PROTONS AND NEUTRONS