In the early universe everything was just a hot plasma of quarks gluons and electrons (and some other particles like neutrinos, and photons). as it cooled, quarks would have combined into protons and neutrons, and some more exotic baryons perhaps, as well as mesons like the pions. Baryons are made of 3 quarks with some glue (gluons) and mesons are quark and anti-quark pairs with some glue. But what would have also formed would have been glueballs. The theory of strong interactions QCD says they exist, and recently some have been observed.

The thing about glueballs is that they have mass. The lightest found so far has a mass of 2.4 Gev (about 2 and one half times that of a proton). There will be many heavier glueballs.

We do not know how many were produced in the early universe. They may even be a numerous as baryons, so a substantial part of the universe’s mass is in glueballs.

Once a glueball is made is interacts only through gravity. It is colour neutral, so there are no strong interactions per se. It is electrically neutral, so does not experience any electromagnetic force. It is also weak/flavour neutral so does not experience any weak interactions. So a glueball only experiences gravity.

It interacts even less than a neutrino, which is so weak that 100 trillion (100,000,000,000) pass through the human body every second.

Glueballs would eventually succumb to gravity as baryons do and they will form material objects with and maybe without baryons, like stars, planets, black holes etc, but we still cannot detect them other than via their mass.

Theoretically is is possible to have a largely glueball objects that we would not even see in any way. One could be travelling towards planet Earth and we would not even see it was coming. In practice the glueballs would be attracted to baryons like the proton and neutron and just form part of the mass of that star or planet.

I have proposed that glueballs may explain dark matter.

If there are many glueballs inside planets and stars, this means we have over-estimated the protons and neutrons in each.

What we can see in the universe is just 5% of what is out there. More than 25% is dark matter (or glueballs in this case).

I have also speculated about what dark energy is. It acts like a repulsive gravitational force inside our universe which is making it expand faster and faster. Ordinarily the attractive gravitational force should slow down the expansion of the universe and it should collapse in on itself. Instead of postulating dark energy or a repulsive 5th force, I put inflation down to the fact that we exist inside a pre-existing universe, and all the universe outside us, or universes, or even universes with bigger universes ad infinitum, is what is pulling us apart.

I have gone further and proposed a theory that we are an exploding black hole, which is eventually became a white hole (the big bang). So we are an exploding black hole inside a pre-existing universe. The cause of the explosion is the Pauli Exclusion Principle in quantum mechanics. The fermions (particles of half-integral spin) of the universe do not want to be in the same state at the same time. This is an infinite force.