Well, is the Universe 26,7 or 13,6 billion years old?

The age of the universe is hard to detect. We can see the last flash of the Big Bang. And we can see the moment when radiation started to form material. But we cannot see the Big Bang itself. Many things remain unknown. The normal model of the Big Bang was that the effect, or "the bang," was stable. That means the Big Bang released material and energy into the universe. Or the Big Bang released energy that turned into material in space. When we observe the Big Bang using cosmological models, we are observing it from outside. 

We cannot see time dilation or energy relationships, and actually, we don't know if the Big Bang happened at the same speed all the time. There is a possibility that there were changes in the speed at which the Big Bang released energy. And if we think that we cannot see the entire Big Bang and only the last flash of that, we are not sure how long the Big Bang remained. Or how long it released energy until the first particles were formed. So we might think that the moment when the quark-gluon plasma formed was the moment when the universe formed. That point is 13.8 billion years in the past. But there is a possibility that electromagnetic radiation existed a long time before that.

When scientists calculate the age of the universe, there is always some kind of error. The problem is that things like time dilation in a young universe make it possible for the universe to look older than it is. But the problem is that the universe was different in its youth. Time dilation, energy level, and form of material were different. So we are not sure which age is right.

When we are looking at an image of the universe, we might see that galaxies are on a layer that looks like a ball. The reason we don't know the geometric shape of the universe is that we don't know how much dark matter there is. Another interesting thing is that there is some kind of effect that makes whirls in that layer, where almost all galaxies are.

There is a supermassive black hole, and then that thing makes a galaxy around it. There is a small possibility that the shockwave that left the Big Bang impacted some other wave movements. But that requires the existence of another universe. Or there is some kind of energy peak that is making those whirls.

In some models, dark matter is released into the universe in some other event than the Big Bang. The hypothetical effect that released dark matter is called the "Dark Big Bang.". 

The standard cosmological model is that the Big Bang released all particles. But the fact is that nobody is sure about that thing. Dark matter, along with dark energy, can exist before the visible material. And nobody is sure if dark matter and dark energy have any kind of connection with each other. But when we are trying to determine the age of the universe, we must realize that we must find the point where we begin our calculation.

The point could be the point where the high-energy universe started to take on the form in which we know it. That point would be the point where the first gluons or quarks formed. The idea is that particles form from the inside to the outside of atoms.

And in that model, the gluon would be the first particle of visible matter. The problem with all models is that we don't know the conditions in the young universe. We know that time dilation was stronger. The energy level was higher, and then the first plasma formed. The energy turned into gluons and quarks. The difference between quark-gluon plasma at CERN and in a young universe is that in a young universe, the quark-gluon plasma stands alone. There were no outside effects in that universe.

But quark-gluon plasma requires that there be quarks and gluons. Time dilation is a problematic thing in the calculations of the age of the universe. Time moves faster in our universe. The dark energy effect is stronger now than in an extremely young universe. In the universe, where there were no particles and impacting waves formed the first particles, there was no gravitation. Or gravitation was different than our universe. If there were WIMPs before the first visible matter particles, there was some kind of gravitational effect from WIMPs.

There is a possibility that there was no internal gravitational interaction before the first particles formed. There was something that created things like black holes in the young universe because wave movement formed material in the Schwinger effect that required the ability to change its direction. There must be something that made waves cross each other.

https://bigthink.com/starts-with-a-bang/universe-13-8-or-26-7-billion-years/