When a law of physics applies equally when time is reversed, it is said to show T-symmetry; in this case, entropy is what allows one to decide if the video described above is playing forwards or in reverse as intuitively we identify that only when played forwards the entropy of the scene is increasing. Because of the second law of thermodynamics, entropy prevents macroscopic processes showing T-symmetry.

The Second Law of Thermodynamics says that entropy only ever increases spontaneously. ... So what is IMpossible is a reversal of the "entropy only increases spontaneously" rule. But non-spontaneous processes, which require energy input, result in entropy decreases all the time.

Isam Alkhalifawi Nikolay Dolchinkov

Science fiction writer Issac Asimov explores this question in his short story The Last Question https://en.wikipedia.org/wiki/The_Last_Question and says if entropy could be reversed then a new universe could be created by reversing all chaos and decay in the present universe. A link to the short story is given below :

https://templatetraining.princeton.edu/sites/training/files/the_last_question_-_issac_asimov.pdf

and

What a wonderful experiment regarding algorithms for time reversal thank you Dr. Aparna Sathya Murthy

Ranjan Parekh nice suggestio, will read it Sir

Rabin Thapa Interesting topic...following..

Of course, when we put things closer together, we are reversing entropy

Entropy of a system is always increasing. This is the principle of entropy increase. The entropy decreases for a cooling process in a cycle but the cycle overall entropy increases. Reversible processes are ideal processes that practically do not exis.

time reversal is possible only in movies and fiction books.

Dear Ahmad K. Sleiti Michael Raftery Md. Israt Hasan thanks for adding your view, much appreciated!

You are most welcome Rabin Thapa.

A fun topic: Entropy reversal occurs everyday in living systems. It is spontaneous process which verifies its legitimate natural tenancy for growth and repair. Yes the overall process obeys the 2nd law. In life forms, negative entropy eventually gives way to entropy increase However, we see that their is also a natural tendency not only intrinsic but for building cities etc. A 2nd law paradox. If you are interested in my paper you can get it on Research Gate or IEEEE. In the paper I show that it obeys a living system Carnot cycle.

Living System Negative Entropy Reliability, Old Trees and a Fifth Law for Thermodynamics on Negative Entropy

Of course that entropy can be reversed. Already Ludwig Boltzmann stunned his contemporary fellow researchers by the words: "Entropy usually increases in closed systems but in some rare cases can decrease."

What did he mean by those words? Particles of gas are moving in different directions by various speed and collide. Usually, collisions lead to an increase of unavailable information in the system. It becomes messier. In rare cases, the system's unavailable information can decrease. An example would be spontaneous arranging atoms in a corner of a room.

Living systems are capable to decrease their order, in other words, to decrease the amount of unavailable information within them. The price is that this decrease is done by an increase in entropy of surroundings. We eat food that is organized and expel completely disorganized matter.

The key part of the 2nd law is disorder is spontaneous in as you say closed systems that is the paradox in living systems as well since growth and repait r spontaneous form of order

Logical action is needed to decrease in entropy or prevent (reduce/counteract) the increase in entropy, i.e. a special program is needed - in living organisms DNA is such a program written in a very logical way.

Without order we would not have disorder ergo negative entropy proof

Alec Feinberg Andrzej Kasperski Jiří Kroc Md. Israt Hasan thanks dear all for your wonderful answers much appreciated

Systematically it must!!

Feasibility issues are always to be considered.

It is a very strange discussion: You have to distinguish entropy from entropy production. Some references can be found in:

W. Muschik (2018), Second Law and Non-Equilibrium Entropy of Schottky Systems {Doubts and Veri cation{, Entropy 2018, 20, 740; 1-15, DOI 10.3390/c20100740.

Good point, for example we can increase or decrease entropy, per entropy flow which can be positive or negative say by adding or taking away heat form the system, then the system mass may not permanently change . If the heat causes some damage to the system mass, this is entropy generation and you have weakened the system. So the entropy of the system can only decrease. Now back to living systems. Here is where it is strange. Due to repair and growth, entropy of the system can spontaneously increase. Yet the entropy of the universe overall will increase.

The Second Law of Thermodynamics says that entropy only ever increases spontaneously. ... So what is IMpossible is a reversal of the "entropy only increases spontaneously" rule. But non-spontaneous processes, which require energy input, result in entropy decreases all the time.

So how do you explain living system spontaneous growth and repair!!

The 2nd Law is being misquoted by nearly everyone here. Ludwig Boltzmann famously demonstrated that entropy's increase or decrease is a matter of probabilities. While it is exceptionally rare, entropy can spontaneously decrease. Further, there has been little discussion of the nature of the system involved. The universe is a closed system and overall the entropy of the universe cannot be reversed. However, it is absolutely possible that a subsystem, a majorized set, etc., can experience a reverse, a lowering, in entropy by borrowing energy/work from a source outside the subsystem and adding it to the subsystem. Last, regarding plant life and other living systems: Energy is borrowed from the sun for repair and life itself.

John that is misleading. There are two kinds of entropy. Entropy flow s can be positive or negative but entropy generation S in keeping with the second law can only increase. dS= or >0 is the second law. If a systemm is isolated entropy flow is 0 While entropy generation can increase causing spontaneous degradatio. Then the systems free energy will decreased These r practice terms. certainly probably has its place but not required in these definitions.

I don't think we are saying anything different, really. Trying to explain one of the most difficult and misunderstood concepts in physics in 4 sentences is certainly a challenge! To be clear: Entropy in a closed system cannot be reversed. My point is that no matter the system, there are more possible disordered states than ordered states. Therefore, all closed systems over time will tend to high entropy as changes between events progress. Obviously, in the very short term, entropy can decrease due to statistical probability, but it is exceptionally rare. The actual equations for entropy are: S=kB ln W for conditions in which pi are equal or more commonly S= --- kB SUM pi ln pi where they are not. I think clarifies my position. Thank you for pointing out the undue brevity of my earlier answer.

If entropy increases also the disorder increases. Thence at the beginning there was a perfect order and we are going towards chaos. If you agree with this point of view entropy can be reversed putting order. However time keeps on running because you did not erase the past.

Not a physicist at all but here goes.

Entropy always increases in the closed system of our universe. Locally, entropy can decrease by increasing the usable energy in that sub-system, for example your refrigerator decreases entropy.

I believe that this has to do with heat transfer. One would have to find a way for "cold transfer" to reverse entropy and thus the flow of time, that is a temperature below absolute zero that would allow for "cold" to transfer instead of heat.

Thanks, dear all for your particular interest in this mind-bending question.

Entropy can be reversed but u have to do work on it which incraeses the energy of the system which makes it unstable

Yes, True, you can "reverse" entropy locally, however, doing so still does not make time flow backward because the universe is increasing in entropy in the aggregate.

Im not expert on both math and physics but I have written an article upon entropy which is not published in any journal. I think that we can use goldbach primes with logic of smaller randomness amplitude goes to bigger one in every each microsystem.These golbach primes let us to se spacetime operators manage all microsystem with randomness amplitudes(irreversible energy/ this energy term can be used for photon particle-wave duality later) What I wonder is numbers universe can gain a new identity to be used in our universe for the entropy subject which is utterly complicated or not? you can click the article pdf below If you want to share your valuable thoughts that would be good for me to fix my mistakes. I am independent researcher and I have an article related with multiplication algorithm in my profile, algorithm that I revise is new idea.

I make some changes in article and I uploaded again in my profile

Dear Oğuzhan Dervişağaoğlu Daniel Blanchett Anup Gurung Diego Ceotto your views are highly appreciated

Im uploading it again after make some correction

Primes with respect to goldbach conjecture which represent as the numbers' world which can be converted to the our universe to understand the entropy which have irreversible amplitudes and these amplitudes will be united with their conjugations .Density operators can manage the processes of amplitudes which means primes such as 3+5 , 3+7... will be first microsystem of universe and second one is 5+7,5+11, 5+13... In the first microsystem number 3 will be constant amplitude and in second microsystem 5 will be constant value. These numbers can gain an identity in quantum mechanics and they can become as 1 dimension vectors and in xyz coordinate sistem, can go forward. and ct also must be adding into process. Derivative of expected value of density operator(spacetime operator) will show us entropy of universe. (density. ct.x.y.z will be ırreversible energy and entropy; probability factor. density.ct.x.y.z +contiunity factor) Dirac delta function will represent the process before big nang and 1 dimension With the length of infinity which is dirac delta function will be a system decoder of universe in goes forward in time. I am an amateur on physics and math. İf there are people who are expert in these kind of fields that I mention above, They can share their ideas and experiences and furthermore they can declare their point of view about this prediction which is not professional.

Oğuzhan Dervişağaoğlu thanks for your vision

Rabin Thapa Thank you for giving me the oppurtunity to share my idea about entropy