The difficulty comes from the fact that our mind, with which we try to understand the world, and thus our existence, and our senses, with which we are a physical entity of this world that has a degree of freedom called time, oriented, which is the dynamic parameter and an extension in a 3-dimensional space, presenting 3 degrees of freedom, evolving according to the dynamic parameter which is time.
This suggests that our mind, whose material support is constrained by these laws, cannot extricate itself from them, at least totally.
However, when we study the universe, with our mind and its constraints, relativity shows us that these notions of time and space have no physical character but are only appearances of a more synthetic concept: space-time.
Since the universe, of which we are a part, has a space-time structure that we know how to describe analytically, even if our mind cannot synthesize it, it seems that it would be, by reasoning in terms of space-time only, forgetting time and space, that we should conduct our analysis.
The image should be more synthetic and would undoubtedly point us towards a different interpretation of our understanding of the universe and our destiny.
Thus the temporal schema of our existence in solidarity with that of creation, evolution and eventually the end of our universe is isomorphic to that of the existence of the human, which is characteristic of a blatant « naïve » anthropomorphism.
The same approach in terms of space-time binds us to the universe in a more structural way because we are part of it: the existence of the universe includes our own, not in a temporal way but in a structural way. Its evolution is then a property resulting from the fact that it is described in terms of space and time (and not space-time) in accordance with our subjective feeling in our consciousness of existing: we use our « sensible » concepts to describe a universe, which yet the same consciousness, through mathematics and theory, recognizes that it is not correctly describable in terms of space and time.
It should be noted that in some Nordic cosmologies, the image of the snake biting its own tail, suggests another hypothesis to explain cosmology, that of the loop. Indeed, a « linear » description (by an unclosed universe line) suggests an origin and an end that can be pushed back indefinitely. Physics does not like the infinite, but it is still necessary to specify how it is considered.
The Standard Model of cosmology places the « origin (the big bang) » of the universe at 13.7 billion years ago (a finite value, in cosmological time linked to the Robertson-Walker metric) in our past. But we know that in our current time, this big bang is pushed back to infinity from our past, which means that no matter what instruments we have at our disposal, which would free ourselves from all the constraints limiting our vision in the past, we would never see the big bang in a finite time. We see that the notion of infinity is to be considered with caution.
The space-time loop is interesting at the conceptual level. In general relativity there are mathematical solutions, (Kerr’s black holes for example) that include regions in space where time loops are possible) We start from a point A with coordinates x0, y0, z0, t0 and by following a time-type universe line (proper time grows continuously along this universe line) we arrive at the same point A.
Assuming that these solutions are of a physical nature, or that it does not require resources that are out of reach, in energy for example as the calculations show (see Kerr’s black holes and time machines) this opens up interesting perspectives.
But to go into the past, you have to exist in your present.
If we travel on a line of universes in a time loop, each point of the loop has been our present: we are still in our present and we age according to our proper time that marks the loop!
In general relativity with negative energy we can travel to the past, but we have to understand what this means. It is a loop in space-time, an unusual structure but which does not, a priori, generate creation.
We know the paradoxes of time: if in the past, we kill our father before being conceived, do we cease to exist?
this, by this way, would provide a better « stability » to the history of the universe and could be taken into account by introducing multiverses.
To be continued…