What is the nature of entropy ?

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Jan 20, 2022
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When you get right down to the makeup of an atom it's quit amazing solid exists.
A tiny bit of energy orbiting something that isn't more than a ball of energy.
Take away all the space involved and you are not left with much.
Take away all the nothing between the tiniest things and you have nearly nothing.
A handful of electrons that themselves are probably filled with mostly nothing.

Hats of to the designer of that idea :)
..but in its confined atomic state/structure, energy is paradoxically both inert and fluid, locked in a stable, devoted relationship with its parts; therefore, fluid energy emerges as mass --not to over simplify it all, but it's kinda like energy charged Gorilla Glue -- mass exists as solidified energy.
 
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..but in its confined atomic structure, energy is paradoxically both inert and fluid, locked in a stable, devoted relationship with its parts; therefore, fluid energy emerges as mass --not to over simplify it all, but its is kinda like energy charged gorilla glue ...humm
Fun to think that all we see in the universe is mostly duck tape, might be gorilla glue though. Needs a study :).
Repulsive and attractive forces making everything we see with little real substance to everything.
 
Jan 20, 2022
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Fun to think that all we see in the universe is mostly duck tape, might be gorilla glue though. Needs a study :).
Repulsive and attractive forces making everything we see with little real substance to everything.
...you mention..."everything we see..." In large part, we know the observable universe by light. Pardon my ignorance, I must ask, "Does light have mass?" What is the structure of a photon?
 
Jan 28, 2022
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No, entropy will not decrease in a shrinking universe, entropy increases continuously in any closed system. It could not go the other way unless the arrow of time was reversed.
Excuse me I am new here. Is a shrinking universe a closed system cos to me it suggests it is going in an opposite direction and might keep changing indefinitely. Also I heard about going in cycles throughout single point things. I saw somewhere about what is the entropy where it changes and would the entropy the same in all these point changes. Makes my 'ead 'urt.
 
Nov 19, 2021
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Welcome to SDC!
Entropy is not hard to understand. It is a measure of "disorder" or the opposite of the "usefulness" of the heat in a system. A "system" is anything you can draw a circle around and not let heat into or out of. The universe is a good example. A thermos bottle is another good example. Inside each you have a fixed amount of heat BUT you have a multitude of ways the heat can be distributed. For example you can have a thermos with ice in the bottom half and boiling water in the top half. That system has a lot of order to it, the hot area is on top and the cold area on bottom, and is ripe for "usefulness" as you could set up a heat engine, allow the heat to flow from the hot water to the ice and make hay with the work done. It would start out with a low entropy. At the end of the day, the entire thermos would be full of room temperature water. That condition has no ability to do work, thus is not "useful" thus has a very high amount of disorder and a high entropy. The movement of heat from hot to cold is inexorable thus entropy always increases. They always say a "closed system" so no one cheats and goes outside the system to get some more hot water.
 
Jan 28, 2022
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Thank you for your friendly reply, but if a system contracts don't the contents go back to where they started and doesn't that mean back to the same entropy and I saw something about universes being parts of bigger universes and collections of universes. What if you don't know about a nearby universe and heat gets in from it? If you think you are in a separate universe and you aren't then how can you know what the entropy does?
 
Nov 19, 2021
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By definition, any universe that we could share information with would be part of our universe and not another one.
If our universe contracted to a single point then there could be no distance to separate two masses of a different temperature thus the entropy would be the highest possible number.
Our speculation about point universes, such as the beginning of the Big Bang is complicated by the fact that our physics cannot apply. Prior to 10^-45 of a second, the energy of each particle was so great that its wavelength was less than the distance between particles thus no particle could communicate with another one in order to exchange heat. Another way to look at it: each particle was a tiny black hole, unable to communicate outside its event horizon.
But, no matter what you do, entropy of the universe always increases.
 
Jan 28, 2022
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Thank you again for your kind reply. I am not trying to be difficult but have difficulty in understanding some of these things. You said

If our universe contracted to a single point . . . the entropy would be the highest possible number.

But, no matter what you do, entropy of the universe always increases.

If the entropy is the highest possible number at a single point (does this mean like the big bang) then how can it increase when the universe started?
 
Nov 19, 2021
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Don't worry about not understanding the Big Bang or Quantum Mechanics. No one understands them so you are in good company.

First of all, we cannot speculate about a single point as our physics breaks down. But when the universe had significant size, there were fluctuations which had arisen from quantum considerations. In other words, in the beginning, one side of the universe was slightly hotter than the other side. This was built in from whenever it was our physics started being able to explain it. That tiny difference multiplied by the total mass of the universe was a powerful source of work, thus a low entropy.
There is nothing that indicates that our universe will stop expanding and then collapse to a point. All indications are that the rate of expansion is actually increasing. Over time, say 10^100 years, all the particles in the universe will have been converted into field energy. There will be no particles to interact thus no time. You cannot have time without at least two particles to move relative to each other. Without time, no more heat exchange can occur. At that point the entropy will be maximum. According to Roger Penrose, the universe will start over at that point.
 
Jan 28, 2022
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Thank you for that, but I am afraid it is a bit over my head. I suppose it depends on that unknown bit how it starts all over.
 
Aug 14, 2020
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Most modern physicists have time as straight arrow, just as they have 13.8 billion light years as straight arrow as straight arrow can possibly get. But the ancient Greeks had time turning, time the circling of time, always turning (turn = verse (uni-verse = one turn, to turn, in-turn (en-trope))).

Where entropy is always headed is forward to the beginning of time (t = 0). Time as pasts (-) > futures (+) is always relative. If you were a traveler in the middle of interstellar, or intergalactic, space looking out to the surrounding universe you would find yourself in the exact midst of times (pasts (-) > futures (+)) as a time traveler with an infinite choice of space-time wormhole-like corridors to travel this past to future, or that past to future, or some other past to future. You could arrive anywhere along the way, but the path on would always be monotonously past to future with arrival, all arrivals, 'Now' (t = 0): All those arrivals in space-time appearing suspiciously the same overall universe as when you began. You traveled an open systemic universe. You arrive at locally closed systemic destinations. Your means of travel, locally to you, its body, including your body, itself being closed systemic (relativistic).

Where is the future? At 13.8 billion light years (that is minus 13.8 billion years) from you wherever you are, the future (t = 0) is plus 13.8 billion years to that minus 13.8 billion years, or spatially, 13.8 billion times 6 trillion miles from you (t0 = t0). It could be any distance, plus trillions times trillions, times trillions, of years to a minus trillions times trillions, times trillions of years, or spatially trillions times trillions, times trillions x 6 trillion miles from you (t0 = t0). As the saying goes, no matter where, no matter when, the reality of the future is always and universally 'Now' (t = 0). Those ancient Greeks had it right regarding time always turning ("universe" ('en-trope')). Always turning to, thus always returning to, beginning. Always at time's 0-point. Hawking's "Grand Central Station" of Universe (U) with that special, universal, clock (single handed, single digited (0-point)) mounted at and above its exact center point.
 
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Most modern physicists have time as straight arrow, just as they have 13.8 billion light years as straight arrow as straight arrow can possibly get. But the ancient Greeks had time turning, time the circling of time, always turning (turn = verse (uni-verse = one turn, to turn, in-turn (en-trope))).

Where entropy is always headed is forward to the beginning of time (t = 0). Time as pasts (-) > futures (+) is always relative. If you were a traveler in the middle of interstellar, or intergalactic, space looking out to the surrounding universe you would find yourself in the exact midst of times (pasts (-) > futures (+)) as a time traveler with an infinite choice of space-time wormhole-like corridors to travel this past to future, or that past to future, or some other past to future. You could arrive anywhere along the way, but the path on would always be monotonously past to future with arrival, all arrivals, 'Now' (t = 0): All those arrivals in space-time appearing suspiciously the same overall universe as when you began. You traveled an open systemic universe. You arrive at locally closed systemic destinations. Your means of travel, locally to you, its body, including your body, itself being closed systemic (relativistic).

Where is the future? At 13.8 billion light years (that is minus 13.8 billion years) from you wherever you are, the future (t = 0) is plus 13.8 billion years to that minus 13.8 billion years, or spatially, 13.8 billion times 6 trillion miles from you (t0 = t0). It could be any distance, plus trillions times trillions, times trillions, of years to a minus trillions times trillions, times trillions of years, or spatially trillions times trillions, times trillions x 6 trillion miles from you (t0 = t0). As the saying goes, no matter where, no matter when, the reality of the future is always and universally 'Now' (t = 0). Those ancient Greeks had it right regarding time always turning ("universe" ('en-trope')). Always turning to, thus always returning to, beginning. Always at time's 0-point. Hawking's "Grand Central Station" of Universe (U) with that special, universal, clock (single handed, single digited (0-point)) mounted at and above its exact center point.


Although I often find your writing style difficult to interpret , there is much of it I do understand and agree with. So please "Keep up the good work!"

IMO. If space-time is cyclic it can be both finite and infinite. Each cycle would be finite, but there could be an infinite number of such cycles. Once the spatial element of an instance of space-time has reached it's ultimate extent, it must progress farther around the circumference of the circle of time. because the arrow of time is irreversible. Its rather like moving on the surface of a sphere although the motion is uni directional it will always return to its point of origin.
As the instance of space-time continues forward on its journey toward what was its initial starting point, both its temporal and spatial element, and all contained within it, would once again be scrunched into a singularity. IE(Space 0 time 0 ) Time, ("whatever time ultimately turns out to be???") continues on its path in the same direction around the circumference and initiates a fresh instance of space-time. Crunch, bang . Crunch,bang. add infinitum,

Although there are some amongst us who profess to know all there is to know about entropy. entropy is actually an effect of transformations of space- time, a subject we know next to nothing about. We can offer our opinions on what these phenomena are and how they interact. but there is no definitive proof of their nature. We exist within an instance of expanding space-time, so we can only observe, measure, or calculate, how entropy behaves in an instance of expanding space time. As for what might occur in an instance of contracting space-time, well, we can only speculate. (which is actually a fun thing to do.)

Long live metaphysics!!!
 
Feb 7, 2022
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So, if entropy cannot decrease in-total in a closed system, and the universe, by definition, is a closed system, then that would seem to preclude any collapse of the universe back into the form it had at the Big Bang, because that would imply that the whole process of the development of the universe to the condition that we see (part of) it today could repeat.

And, since "dark energy" is what is proposed for keeping the universe from collapsing, then it seems that dark energy and entropy should have some interrelationship. In theory - since we really don't know that there is such a thing as dark energy or how it works to change space.

Entropy seems like the one concept that precludes a cyclic universe, and would seem to impose a once-and-done universe.

But, we seem to forget that our universe's postulated beginning was completely devoid of order, and yet all of those postulated sub-sub-sub-atomic particles somehow appeared out of energy and organized themselves into light atoms (i.e. hydrogen and helium, maybe lithium), formed stars and organized themselves into heavier elements, formed molecules and organized themselves into planets, formed larger molecules and organized themselves into live entities, and evolved into the living things we call humans. That sure seems like a lot of spontaneous organization for an infinitesimally tiny wad of an enormous quantity of energy!

Taking all of that spontaneous organization into account, are we sure that entropy must always increase?
 
Nov 19, 2021
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Yes, we are sure. Any localized decrease in entropy must be accompanied by a larger increase somewhere else.

Entropy is simply the amount of heat in a system that is unavailable to do work.
In order to do work, any heat parcel must be able to transfer some heat to a cooler parcel. If you put a hot parcel and a cool parcel in an insulated box, eventually the heat from both will meld and the interior will be all at one temperature. There is the same amount of heat in the box, but none of it is available for work. This is maximum entropy. There is no process that can reverse that situation except if operated on by an outside force and that would violate the principle of a closed system.
 

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