Have you ever thought about time that why it always moves forward and never backward, why? This question is still making physicists curious. But, there are some physical cases which are time-reversible, they actually look same in both ways. For example, gravity works in the same way irrespective of the flow of time, a planet will follow the path of a star in exactly the same way, just with the direction of that orbit reversed. But there is one feature of the universe that is reliant on the path of Time flow: the Second Law of Thermodynamics.
This states that the disorder of a closed system must increase, never decrease.
It’s commonly known as “entropy,” and that’s why broken eggs don’t unexpectedly look the way they were before, or why dead things don’t quickly come back to life. Inefficiency and disorder are easy, order and complexity are difficult; complex systems like stars and planets and human beings may arise locally, but they require an excessive amount of energy to create, which only increases the whole entropy of the system.
This is why the Second Law of Thermodynamics is universally recognized as the mechanism directly depending on time.
In order to understand the roots of Time’s Arrow, two Armenian physicists, A. E. Allahverdyan and V. G. Gurzadyan, started searching for “dark energy” and the Second Law of Thermodynamics. Dark energy is a secretive amount that is proposed as a clarification for why the universe is continuing to expand.
These scientists tested, with the help of a simulation, how the orbit of a planet would change, and how it relates to the concept of Dark Energy. What they found was fascinating, to say the least: if dark energy is absent, or if gravity pulls space together, a planet simply orbits its star in the accepted fashion, regardless of whether time runs “forward” or “backward.”
Which means there is a time-based directionality when dark energy is familiarized—in one direction, we see a planet escaping a star’s gravity; in the other, a planet is held by a star and becomes a part of its entourage.
The research that has been published in Physical Review E, authors are saying that the dark energy is responsible for Time’s arrow. But there is nothing definite about the research. Some factors suggest that may be Second Law of Thermodynamics and dark energy are basically the two sides of the same phenomenon. You can learn more here.
So next time you’re late—just blame it on dark energy.