Why can't time come back?

"Time is what keeps things happening at a single time," American science fiction novelist Ray Cummings wrote in "The Girl in the Golden Atom" , the novel that summarizes The power of time is quite unique. But how does time show everything once? Which mechanism pushes time forward rather than returning?

In a recent study published in the journal Physical Review Letters, a group of theoretical physicists re-investigated the "Arrow of Time" - a concept that describes the journey stop ahead of time - and give a different perspective on how time is expressed on universal scales.

For a long time, time has been described by a "hypothesis of the past" , assuming that any system is started from a low thermodynamic state and then controlled. by thermodynamics, its thermodynamic temperature increases. In short: the past is low thermodynamics and the future is high thermodynamics - a concept also known as the thermodynamic time asymmetry.

In everyday life, we can see there are many examples of the rise of thermodynamics, as the gas spreads in the room or the melted stone. In these examples, we can observe an irreversible increase in thermodynamics (and thus a disturbance, change).

If this is applied on a universal scale, it is assumed that the Big Bang explosion created the Universe in a low thermodynamic state, ie the minimum thermodynamic state. Over an endless period of time, because the Universe has expanded and cooled down, the thermodynamics of this large-scale system has increased. Therefore, according to the above hypothesis, the basic time is linked by the degree of thermodynamics, or disturbance, in our Universe.

However, this hypothesis still has some problems.

Immediately after the Big Bang, there is some observational evidence that indicates that the environment of the Big Bang is extremely hot with the extremely chaotic state of elementary particles. As the Universe matured and cooled, gravity began to have a greater influence, making the Universe more and more orderly and more complex - from cool clouds of gas, stars formed and The planets evolved from gravity collapse (gravitational collapse: a phenomenon also known as gravitational meteor , when the universe has terrible explosions that end the life of massive stars Weighing 3-8 times the Sun, the star's core collapses due to running out of fuel, gravity helps to link it down, forming a neutron star or a black hole - PV). Finally, the elements can combine together into organic matter, gradually evolving to bring life and people, thereby forming concepts of space and time. Thus, on the whole of the Universe, "chaos" has decreased significantly, rather than increased as the "hypothesis of the past" has assumed.

Perimeter Institute scientist Flavio Mercati of Ontario Physics (Ontario), who is co-investigating, argues that this is how the thermodynamic problem is measured.

Since thermodynamics is a physical quantity with different representational dimensions (like energy and temperature), an external frame of reference is required to be measured."This can be done with the subsystems of the universe when the rest of the universe will be established as a reference for them. N whole universe - by definition - nothing outside. respectively to be able to identify these things, "Mr. Mercati wrote in an email reply to Discovery News science and technology news.

So, if it is not thermodynamics, what can direct the universe time forward?

Complexity (complexity, in chaos theory) is a dimensionless (dimensionless) quantity that, in its most basic form, describes how complex a system is. Therefore, if you look at our Universe, complexity is directly linked to time, as time goes by, the Universe becomes increasingly more structured, ie more orderly.

"The question we sought to answer in our study was: what sets these systems in such a very low thermodynamic state at the beginning? Our answer is: important its forces and trends in creating order and structure from chaos, " Mr. Mercati said.

To experiment with this idea, Mr. Mercati and colleagues created basic computer models to simulate particles in a model universe. They found that regardless of how the simulation is run, over time the complexity of the universe is always increasing and never decreasing.

From the Big Bang explosion, the Universe started in the lowest complex state (such as "hot soup bowl" of chaotic particles and energy). Then, because the Universe cooled down to a state where gravity began to take its place, gas gathered together, stars formed and galaxies developed. The universe becomes more complex and gravity is the driving force for this complexity.

When the Universe reaches adulthood, subsystems become independent enough so that other forces form the conditions for the time arrow present in low thermodynamic systems. In these subsystems, like daily life on Earth, thermodynamics can displace, creating a thermodynamical arrow of time.

On a universal scale, our perception of time is controlled by the continuous growth of the complex, but in these subsystems, the dominant thermodynamics.

"The universe is an increasingly complex structure," Mr Mercati said. "The universe is made up of large galaxies separated by large distances. In the very long past, they were much closer to each other. Our guess is: our time perception is the result of a law of irreversible growth of the complex ".

The next step of the research will be to look for observational evidence, which Mercati and the team are working on.". we do not know if there are any (observations) that support us but we know the kind of experiment that can test our ideas. These are cosmic observations."

Currently, he does not disclose what kind of cosmic observations will be studied but says they will publish information in an upcoming interesting study.

Reference: Discovery News / Popsci.