What is the nature of entropy ?

[Erasmus]

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.

 

[voidpotentialenergy]

..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.

 

[Erasmus]

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?

 

[voidpotentialenergy]

...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?

Light or photons do have mass.
It's tiny per photon but measurable.

 

[freda777]

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.

 

[billslugg]

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.

 

[freda777]

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?

 

[billslugg]

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.

 

[freda777]

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?

 

[billslugg]

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.

 

[freda777]

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.

 

[billslugg]

Don't worry, the unknown bit will always remain unknown.

 

[Atlan0001]

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.

 

[Curiosity killed the cat]

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!!!

 

[Unclear Engineer]

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?

 

[billslugg]

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.

 

[Unclear Engineer]

Bill, as an engineer, I am well aware of the calculations for entropy in macroscopic systems that humans design and operate.

However, when we get into the quantum level or the cosmological level, we seem to have some problems using our explanations of entropy, or even our explanations of particles and waves. We really do not have the experiences that make most of our ideas at those levels seem real or even possible. We just have experimental results that we cannot explain except by adding new parameters designed to make things "fit" (e.g., dark matter and dark energy), accepting "duality" of things like electrons and photons as sometimes particles and sometimes waves, and explaining "spooky action at a distance" by giving it a name ("entanglement").

So, can we really rely on a calculation of heat transfer between 2 beakers of water in a closed box to tell us how things must behave at quantum or cosmological levels? Or, will we need to "find" another parameter that allows us to at least mathematically conceptualize how entropy can decrease?

My question, about how the structure that we see in physics today could arise out of an unstructured blob of energy, was intended to provide a challenge to the idea that we really know what we are talking about when trying to apply thinking about entropy to thinking about whether it is possible for the universe to be cyclic. I am having some serious difficulty understanding why a collapse of the whole universe into a tiny ball of nothing but energy could not then repeat what we currently can see and currently theorize came from such a tiny ball of pure energy.

I am just questioning why we would think that we can extrapolate our experiences with entropy into quantum and cosmological levels when we have so much difficulty extrapolating our other human experiences to those levels. One conceptualization of entropy is that it is a measure of disorder, which is why I framed my question in the context of the order that seems to have occurred in the transition of unordered energy into atoms, molecules, and even life.

So, to put it another way, I am asking you to think outside that box.

 

[Starcrow]

(...) as both Einstein and Makowski said we must stop thinking of space and time as being separate phenomenon. In reality they form a single phenomenon known as the space-time continuum. (...)

Maybe you meant to say "Minkowski"? Later on you say: "I have the greatest respect for Roger Penrose, but he is a mere mortal like you and I, so I reserve the right to question even him." That means you'll enjoy physicist Alexander Unzicker's YouTube channel called "Unzicker's Real Physics", which includes a series on what he terms "overhyped physicists" and also a video titled "How Hermann Minkowski led physics astray", which rejects the "spacetime continuum" concept:

• "Space and time are different phenomenologies. Glueing them to a 4-D spacetime is a denial of reality."
• "There is no reason why nature should show its four dimensions in such a peculiar 3-1 dimensional manner. "

 

[Curiosity killed the cat]

Maybe you meant to say "Minkowski"? Later on you say: "I have the greatest respect for Roger Penrose, but he is a mere mortal like you and I, so I reserve the right to question even him." That means you'll enjoy physicist Alexander Unzicker's YouTube channel called "Unzicker's Real Physics", which includes a series on what he terms "overhyped physicists" and also a video titled "How Hermann Minkowski led physics astray", which rejects the "spacetime continuum" concept:

• "Space and time are different phenomenologies. Glueing them to a 4-D spacetime is a denial of reality."
• "There is no reason why nature should show its four dimensions in such a peculiar 3-1 dimensional manner. "

 

[Curiosity killed the cat]

• "Space and time are different phenomenology's. Gluing them to a 4-D spacetime is a denial of reality."
• "There is no reason why nature should show its four dimensions in such a peculiar 3-1 dimensional manner. "

I can't understand the reasoning behind making the above statements. Surely anyone with an interest in physics should already know that 4-D spacetime is not intended as a description of space-time. Using three spatial dimensions, plus one of time, is an excellent method of determining the position of other objects, relative to the position and orientation of an observer, but I don't think it was ever intended as a description of the nature of space-time.

Thinking of space-time as a single phenomenon is certainly counter intuitive, but at a base level they are not so dissimilar, they are both separations, albeit of two seemingly different phenomena . It is actually the speed of causality which binds space and time together, and prevents effects from preceding their cause, this speed limit is an essential component of our reality. and it is a speed limit which also applies to light.
If we use the speed of causality/light as a common denominator then a measurement of distance can be given as a measurement of time, or vice-versa. So...They are not so different after all !

Minkowski stated that the interaction between space and time within the continuum, is what preserves our independent reality, and Einstein in his statement added that it is the interchangeable nature of space and time, which makes the speed of light a constant. This makes perfect sense to me, and if something isn't broken, there is no point in trying to fix it
I will of course watch the videos you suggest, but unless they contain something unimaginably profound, I must remain a proponent of Minkowski and Einstein's theories.

 

[Unclear Engineer]

I am somewhere in the middle on this space/time discussion.

Basically, I am not convinced that the product c times t can always be treated the same as x, y, and z physical dimensions. Maybe our mathematical model is too simple.

General relativity contains a "cosmological constant" that has been problematic since its first introduction. First, it was an issue with regard to matching celestial observations about apparent motions of stars. More recently, it has been a problem with respect to using existing quantum theories to estimate its proper value. - discrepancies are huge.

So, my question is whether the "cosmological constant" is, in fact, a constant to begin with.

Further, is it really a scalar quantity, or should it have been modeled mathematically as another tensor parameter in what is otherwise a tensor equation?

The General Relativity equations are already extremely difficult for us to solve, so making the "cosmological constant" a tensor variable would probably be mind-blowingly difficult to deal with.

The current General Relativity model has only been solved by assuming "symmetry" back to the "Big Bang" at time = zero. And, that has been making me wonder, recently, about the time-line for the evolution of our universe before the time of our earliest "observation", which is the cosmic microwave background radiation. The current "solutions" for the tiny fractions of a second after the "time = zero" point rely on "symmetry", according to what I have read. Does that assumption of "symmetry" assume that time must be smaller if space is smaller?

 

[Catastrophe]

current "solutions" for the tiny fractions of a second after the "time = zero"

Are these not derived from energies related to very high temperatures close to t = o? Are these high temperatures "safe" bearing in mind the breakdown between t = 0 and accepted BBT? Hence, are these very small time intervals safe?

On another matter what do you think of the idea (not mine) of using a 4-dimensional graph, with time represented as ct, that is with dimension of space?

Cat

 

[Unclear Engineer]

Cat, Not clear to me what you mean by "safe".

What I tend to think about is the amount of confidence that a result is accurate. Typically, that is represented as a numerical range around the numerical result in which the actual value is thought to have 95% probability of being.

And, typically, those ranges are underestimated, sometimes by huge amounts. The problem with estimating uncertainty is that it can only be done for the aspects of the analysis for which the analyst knows that the inputs are uncertain, or maybe even that the choice of methods or model structure/characteristics is uncertain. An analyst has no way of assessing the uncertainty that is related to things that he doesn't even know exist or are relevant.

In cosmology, it would be very hard to make uncertainty calculations about things that are almost completely dependent on theories with structures and parameters that cannot be verified by experiments. However, it might at least be an eye-opener for people to compare the values they derive from their theories to the values derive from competing theories.

 

[Catastrophe]

OK, what I mean by "safe" is a reasonable deduction based on reasonable input - better, reliable deduction based on reliable input.

What I am looking at here (and I enter my usual caveat that I am not committed to any particular theory) is that I place equal importance to a cyclic Universe as to a singularity. In fact, without being committed to a cyclic scenario (and I am not actually going "beyond" = "before" t = 0) I at least give thought to the possibility (imaginary though it is) that whilst high temperatures may be involved in a cyclic model, they might not be verging on "infinite" (= very, very high) as in the postulated singularity. I do seriously doubt the singularity concept. Just an imaginary idea (like most if not all in this area of cosmology) is that the build up entering a black hole does not have to have the "infinite" (see above) temperatures ascribed to a singularity. The input to the BH may exit as a BB - that might be concurrent with much, much lower temperatures.

All just imagination swirling around the event horizon, but that, imho, applies to a great deal of cosmology. Maybe these extreme temperatures were not indeed the case, and thus energy inputs were lower, and these times were actually considerably longer. That is, if we should even be talking about time in our present units.

Cat

P.S. I am not very happy with minute fractions of "time" being applied in cosmology. Fine for atoms, but in cosmology/astronomy we are much more used to a "geological" time scale. I am sure people will start throwing contrary examples at me (fine), but such minute time scales for such momentous events do not sit well with me.

 

[Curiosity killed the cat]

I am somewhere in the middle on this space/time discussion.

Basically, I am not convinced that the product c times t can always be treated the same as x, y, and z physical dimensions. Maybe our mathematical model is too simple.

General relativity contains a "cosmological constant" that has been problematic since its first introduction. First, it was an issue with regard to matching celestial observations about apparent motions of stars. More recently, it has been a problem with respect to using existing quantum theories to estimate its proper value. - discrepancies are huge.

So, my question is whether the "cosmological constant" is, in fact, a constant to begin with.

Further, is it really a scalar quantity, or should it have been modeled mathematically as another tensor parameter in what is otherwise a tensor equation?

The General Relativity equations are already extremely difficult for us to solve, so making the "cosmological constant" a tensor variable would probably be mind-blowingly difficult to deal with.

The current General Relativity model has only been solved by assuming "symmetry" back to the "Big Bang" at time = zero. And, that has been making me wonder, recently, about the time-line for the evolution of our universe before the time of our earliest "observation", which is the cosmic microwave background radiation. The current "solutions" for the tiny fractions of a second after the "time = zero" point rely on "symmetry", according to what I have read. Does that assumption of "symmetry" assume that time must be smaller if space is smaller?
[/QUOTE