Ready for a dive? Into the 'matter universe'?

We have according to the standard theory quarks and gluons making protons and neutrons inside the atoms nucleus. A atom is 99.999~ space and then some few quarks.

"The mass of a proton is about 938 MeV. It consists of three quarks, each of which have a mass on the order of 3 MeV (more or less, not very accurate.) There is a huge discrepancy between 938 and 9. The remainder of the mass of the proton is the potential and kinetic energy of the gluons holding the whole thing together. The correct vision of a proton is a little subatomic gluonic lightning storm, buffeting three nearly insignificant quarks. "

Then we have "four fundamental forces at work in the Universe: the strong force, the weak force, the electromagnetic force, and the gravitational force. They work over different ranges and have different strengths. Gravity is the weakest but it has an infinite range. The electromagnetic force also has infinite range but it is many times stronger than gravity. The weak and strong forces are effective only over a very short range and dominate only at the level of subatomic particles. Despite its name, the weak force is much stronger than gravity but it is indeed the weakest of the other three. The strong force is, as the name says, the strongest among all the four fundamental interactions.

We know that three of the fundamental forces result from the exchange of force carrier particles, which belong to a broader group called ‘bosons’. Matter particles transfer discrete amounts of energy by exchanging bosons with each other. Each fundamental force has its own corresponding boson particle – the strong force is carried by the ‘gluon’, the electromagnetic force is carried by the ‘photon’, and the ‘W and Z bosons’ are responsible for the weak force. Although not yet found, the ‘graviton’ should be the corresponding force-carrying particle of gravity.

The Standard Model includes the electromagnetic, strong and weak forces and all their carrier particles, and explains extremely well how these forces act on all the matter particles. However, the most familiar force in our everyday lives, gravity, is not part of the Standard Model. In fact, fitting gravity comfortably into the framework has proved to be a difficult challenge. The quantum theory used to describe the micro world, and the general theory of relativity used to describe the macro world, are like two children who refuse to play nicely together.

No one has managed to make the two mathematically compatible in the context of the Standard Model. But luckily for particle physics, when it comes to the minuscule scale of particles, the effect of gravity is so weak as to be negligible. Only when we have matter in bulk, such as in ourselves or in planets, does the effect of gravity dominate. So the Standard Model still works well despite its reluctant exclusion of one of the fundamental forces."

And it's here the 'missing God particle' (Higg's particle/field) comes in creating 'Gravity' from a QM perspective. Why QM wants particles is because it treats SpaceTime as having a 'granularity' even if very fine, a 'quantum-bit' if you will.

So now you know how the standard theory thinks of atoms. And also a little about what 'forces' that keeps them 'together'. So, when we get to the point, according to the theory of entropy, where all 'work' is done in the universe. That is no more usable 'energy' everything should be a uniform 'mass' of 'something'. Matter is usable energy so that has to go. Suns too, so what do we have left? A gluon soup maybe, something outside General relativity at least, if it is right, to small to make sense (Under Plank size as I think) and belonging solely to the quantum world.

And photons are a nice choice

If it was the question becomes how big such a universe could be? According to Mach principle I believe you need matter to have a 'space', correct me if I'm wrong there

So with only massless timeless photons?

Phiuff..

(The sound of a universe disappearing)