Can entropy be decreased permanently and entropy of the universe decreases and moves to zero?
In short, according to our current understanding of physics, entropy in a closed system can never permanently decrease, and the overall entropy of the universe will always tend to increase.
Here's a breakdown of the key points:
The Second Law of Thermodynamics: This fundamental law states that in an isolated system (one with no exchange of matter or energy with its surroundings), the total entropy will always increase over time. This means systems naturally tend towards disorder and randomness.
Local entropy decrease: While entropy cannot permanently decrease in a closed system, it can be seemingly reduced in localized areas. For example, living organisms maintain order and complexity by extracting energy from their environment and dissipating heat. However, this process ultimately increases the overall entropy of the larger system, including the organism and its surroundings.
The universe as a closed system: As far as we know, the universe is a closed system, meaning there's no external exchange of matter or energy. Therefore, the total entropy of the universe can never permanently decrease. It will keep increasing as a whole, even if there are local pockets of decreasing entropy.
What about the Big Bang?: The Big Bang theory suggests the universe started in a very low entropy state. However, this doesn't contradict the Second Law. The Big Bang is considered an open system, and the subsequent expansion and evolution of the universe have led to a vast increase in entropy.
Future possibilities: We don't know everything about the universe, and our understanding of physics is constantly evolving. Some hypothetical scenarios, like the functioning of a Maxwell's demon, raise questions about the potential for entropy decrease. However, these scenarios have significant limitations and haven't been proven possible within the current framework of physics.
Therefore, while we can observe and create temporary order in localized areas, the overall trend in the universe points towards increasing entropy. This doesn't imply the end of everything, but rather a universe constantly evolving towards states of greater disorder.
There is a great video that explains the meaning of entropy all in detail and why it tends to increase: https://www.youtube.com/watch?v=DxL2HoqLbyA
Murtadha Shukur
"The universe as a closed system: As far as we know, the universe is a closed system, meaning there's no external exchange of matter or energy. Therefore, the total entropy of the universe can never permanently decrease. It will keep increasing as a whole, even if there are local pockets of decreasing entropy."
That does not correspond to what our present cosmological models say. The universe is expanding at essentially constant energy density. That means its total energy is continually increasing. So it is not a closed system, and statements about its total entropy increasing or decreasing are somewhat moot. Since the total energy increases, the total entropy probably increases, too, but the entropy density (and with it local disorder) might well decrease...
"What about the Big Bang?: The Big Bang theory suggests the universe started in a very low entropy state. However, this doesn't contradict the Second Law."
Right. Because the second law does not say anything about initial conditions.
"The Big Bang is considered an open system, and the subsequent expansion and evolution of the universe have led to a vast increase in entropy."
The big bang is a process, not a system. If the universe is a closed system now, it was one at the big bang, too. There was no "closing event" between the big bang and now. If the universe is an open system, it was open at the big bang, too. In which case the second law would not predict the necessity of an entropy increase, because it applies to isolated systems only.
I have a simple easy-to-digest definition for entropy- without statistics or chaos and disorder involved.
Entropy is defined as the degree of uniformity(of momentum) in the system. If the momentum is the same everywhere, no work can be done and entropy is maximum. If there is a difference in momentum, fast-moving parts can cause the slow-moving parts to increase the velocity/energy, and work is done- as in water turning a turbine.
So the law of entropy would be in long particle interactions, fast particles lose speed, and slow particles gain speed till we get equilibrium. This is a result of energy and momentum conservation of course.
The arrow of time comes out naturally here- as the process proceeds in a single direction toward equilibrium. The fact that heat(internal kinetic energy) can flow only from a hot medium to a cold medium is the simple consequence of the above.
When considering the universe, we need to take gravity as well. Gravity is always attractive and as such introduces non-uniformity. In a star, the surface is at zero pressure and the center is at its highest. If two stars collide and explode, internal matter is thrown out suddenly creating a huge nonuniformity in the space around. So, while electromagnetic forces cause the entropy in the universe to increase, gravity causes entropy to decrease. The radiation we get from the sun for example is a result of gravity heating the star and causing it to radiate to us energy that is at a very low entropy we use on Earth then reject it back but at a longer wavelength/more uniform and of less use- I am referring to the video in Sebastian Ille answer.
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