The Arrow of Time

The arrow of time can be reversed by experiments for the generation of convergent waves, but it follows that it fulfills the conditions for the generation of convergent waves, which require more order than the conditions for radiation waves. Note that in the rare case where the wave function of the universe contains a possible contraction, the entropy of the universe can rise or fall, putting the arrow into a false state in which time runs backward.

The second law suggests that time flows from the past to the present and into the future, while the universe passes from an ordered (low entropy) state to a disordered (high entropy) state. The urge to maximum entropy is an irreversible process in the universe that determines the time and is reversible by physical laws. The clear entropy measurement law is presented as a way of separating between past and future thermodynamics and the arrow of time is cited as the reason why we forget the past but not the future, even though entropy and disorder in the past are much lower than in the future.

In thermodynamics, the time arrow provides the second law of thermodynamics, which states that entropy in an isolated system tends to increase over time. In summary, the universe began in a low-entropy, smooth gravitational state, in which gravitational activity was concentrated in a single ordered dilation mode, with only the slightest irregularities superimposed between the modes. The "arrow of time" in thermodynamics can therefore be regarded as a consequence of the initial conditions of the early universe.

This unidirectional transition from order to disorder culminating in cosmic heat death imposes an omnipresent time arrow upon the universe that leads the point from the past to the future to degeneration. This paper shows in various ways that the "arrow of time" in quantum cosmology arises from asymmetries in the quantum conditions of our universe, where the dynamic law of time is neutral. The cosmological time arrow is associated with a dependent thermodynamic arrow as the universe expands and heads toward the ultimate heat death (the Big Chill) where it moves toward increasing entropy and eventually reaches a point of maximum entropy where the amount of usable energy becomes negligible (zero).

It is not clear how quantum arrows of time are related to other arrows if they exist, but they may be associated with thermodynamic arrows of nature that tend to collapse wave functions into higher entropy states rather than lower ones. The theory of quantum decoherence explains how wave function collapse asymmetrically occurs in time, and the second law of thermodynamics can be derived from the quantum arrow of time and the thermodynamic arrow of time.

The natural laws of time are symmetrical, and the arrow of time can be found in the initial conditions, but it is circular in the concept of the initial, current, and terminal states defined concerning time. The laws are reversible, and scientists since Isaac Newton have understood that the motion of a system can be calculated by assuming that the final conditions work in time.

The Newtonian laws, Maxwell's equations, Einstein's general theory of relativity, and quantum mechanics remain unchanged if we reverse the direction of time and substitute t to represent time with t. True, time runs in one direction for all observers. But different observers, who move through space at different speeds and in different directions, experience the flow of time differently.

It is fitting, Barbour said, that observing the behavior of a simple group of particles provides the first crucial clue to understanding the arrow of time in the actual universe that ultimately leads to the solution of the problem. Scientists have proposed many solutions to the reversibility paradox, also known as Loschmidt's paradox, which they have been trying to understand since Johann Loschmidt began addressing the problem in 1876 by trying to embed irreversibility in physical laws by postulating a low initial state of entropy. When one system is in equilibrium, it pushes irreversibility to evolve itself over time, and when two, the concept of "irreversibility" has another dimension: it can be understood as a nonlinear process, meaning that a system can change its shape and never return to its original state in the future (Hubble's Law is an example of an irreversible process).

Most physicists agree that the second law of thermodynamics is crucial to explaining the time arrow, but they want to develop a simpler theory to explain the time flow. Advocates of a cosmological explanation of the arrow of time see themselves as explaining the origin of the necessity of low entropy cosmic conditions. The finding that a special starting condition is required for the arrow differs from the conventional statistical school, which derives its origin from this starting condition.

Since the underlying dynamic law is symmetrical over time, the same reasoning leads to the conclusion that the gas has a high entropy state t =0. This simulation states that there is no time arrow in the actual universe.

If you live in a box where demons are undetectable, much like you live in a pocket of the universe and can see entropy decrease as time passes around you. Arrows of time are associated in the future with other arrows of time because it reflects the direction in which the universe becomes larger by definition. In Arthur Stanley Eddington's work, he identified cosmological arrows in the direction the universe expands, as shown in Edwin Hubble's The Time Arrow, which he defined as a thermodynamic arrow.