[Aeris (OP)]

Here's something that's been on my mind for awhile that I simply cannot wrap my head around. The second law of thermodynamics states that the entropy of the entire universe can only increase and that any and all instances of entropy decreasing in a given region of space must be met with a simultaneous increase in entropy that is greater in number. Not only does this shoot down the possibility of a 100% efficient machine (heaters that use heat pumps don't count), but it also makes things such as heat spontaneously flowing from cold to hot environments without outside input, useless forms of energy such as waste heat being used for work without outside input and energy being extracted from regions of space in thermal equilibrium impossible. Yes, scientists did once measure a small, spontaneous decrease in entropy on a microscopic level, but not only did that last less than two seconds, but entropy then INCREASED even more than it originally would've before just to compensate for that little thermodynamic hiccup.

This leads me to my question on the Big Bang. Assuming the first law of thermodynamics held up even before the formation of the singularity, all the energy that currently exists in the universe has always existed and never did not exist. Considering that the existence of a God/creator/deity/whatever you wanna call it cannot be proved and the fact that the idea of a universe being created from nothing (NOT a Quantum Vacuum, I'm talking about actual nothingness. As in, the absence of everything that makes up our universe, including time, space, matter, energy and even the laws of physics), is both difficult to comprehend and impossible to test/verify, this idea is honestly not that difficult to accept and is (at least in my opinion) actually quite sensible. With that in mind however...

'Deep Breath'

What the actual hell?! How on Earth did the entropy of the early universe start of so low? I mean, all the energy in the entire universe was concentrated into a single region of space the size of an atom without any outside force or input whatsoever? And the energy lurking within the singularity manifested as heat that created matter?! That literally breaks all of the rules established by entropy! How the hell is the Big Bang Theory not considered the ultimate violation of the second law of thermodynamics and more importantly, why has this instance of entropy spontaneously decreasing all on its own only ever happened ONCE in the entirety of existence? How did the Big Bang possibly find a way to circumvent the merciless beast that is entropy?

'Phew!'

Sorry if I went on a bit of a tangent there. I'm just really curious to learn more about the way our beloved universe works and this is something I REALLY wanna know ever since I finally got a proper grasp on what entropy actually is (don't worry, it only took me like, 3 years to get there).

Btw, this is my first time posting something on this forum. Hi everyone

PS: I tried to respond to some answers below and may have got the formatting all wrong. Is there some place here that can teach me how to respond to answers the correct way?         

[Halc]

This leads me to my question on the Big Bang. Assuming the first law of thermodynamics held up even before the formation of the singularity, all the energy that currently exists in the universe has always existed and never did not exist.

The big bang theory says nothing about the formulation of singularity or suggests a meaningful time outside of spacetime, which is what 'before the bang' is. So while a valid topic, it isn't a big bang topic. To suggest a time before the bang is to suggest that space is contained within time which contradicts relativity's spacetime where time and space are part of the same geometry with neither containing or supervening on the other, as you seem to be doing.

the idea of a universe being created from nothing

That is indeed a problem for those that consider the universe a 'created' thing, which seems to be a category error. Objects within time get created. The word is inapplicable to the container of time itself. But humans typically cannot detach from the bias that all things are contained by time, hence being in need of creation.

What the actual hell?! How on Earth did the entropy of the early universe start of so low?

The cosmologists actually attempt to answer that one, citing inflation theory for instance, also explaining why it's so flat.

I mean, all the energy in the entire universe was concentrated into a single region of space the size of an atom

This isn't right. The theory doesn't say it was either contained in a small region of space (making it sound liket the rest of space was empty), nor that it was ever the size of an atom. What comprises today's visible universe was indeed compressed into that size, but that's just a tiny fraction of the universe, compressed say 37 orders of magnitude from today's density, but an infinite universe compressed 37 orders of magnitude is still infinite.

And the energy lurking within the singularity manifested as heat that created matter?! That literally breaks all of the rules established by entropy!

Yes it does. I don't think it was 'heat'. The cosmologists describe the conditions to their satisfaction since yes, such a simple description violates all kinds of rules. Keep in mind that the energy wasn't necessarily positive since there's an awful lot of negative energy present as well, and still is. Energy is conserved only in geometries that are static over time, and our universe isn't described by any static geometry (such as the Milne model). Just saying that the 2nd law doesn't hold in our universe. Carroll put out a paper showing this.

Btw, this is my first time posting something on this forum. Hi everyone

So I see. A big welcome to you from me, and from others I'm sure.

[evan_au]

How on Earth did the entropy of the early universe start of so low?

Not on Earth!

[Eternal Student]

Hi Aeris,

   Welcome to the forum.  That's a good first post.  There's a lot of good questions and great thoughts here.

Assuming the first law of thermodynamics held up even before the formation of the singularity,

    Halc didn't comment on this bit directly.   It doesn't seem that there was any time before the big bang.   There is no reason to assume the first law of thermodynamics or any principle of Physics should apply before the big bang.  "Time" seems to emerge as a property we can identify only after the big bang.

 

why has this instance of entropy spontaneously decreasing all on its own only ever happened ONCE in the entirety of existence?

   It has happened more than once.  Entropy can be defined using statistical mechanics rather than classical thermodynamics.   In systems where changes are assumed to occur randomly, then sometimes entropy does decrease.   The law of entropy is often regarded just as a statistical law.  For large systems with many particles interacting it is overwhelming likely that entropy will increase but there is a small chance for a decrease.  We don't see the entropy of the entire universe decreasing because that system is so large (contains so many particles and interactions) that the chances of this happening are insignificant.  However, for smaller closed systems within the Universe we can observe entropy decreasing.
    If you're interested look up some articles about the "Poincare recurrence theorem"  (here's a Wiki link to start with:  https://en.wikipedia.org/wiki/Poincar%C3%A9_recurrence_theorem).    There are some systems that start in a low entropy state and evolve to what is, on average, a higher entropy state but if the system continues to have random changes then sometimes entropy decreases.  If you wait long enough, then just by random chance, the initial state will have re-appeared again somewhere over that time.

Best Wishes.

[Aeris (OP)]

The big bang theory says nothing about the formulation of singularity or suggests a meaningful time outside of spacetime, which is what 'before the bang' is. So while a valid topic, it isn't a big bang topic. To suggest a time before the bang is to suggest that space is contained within time which contradicts relativity's spacetime where time and space are part of the same geometry with neither containing or supervening on the other, as you seem to be doing.

So... am I talking about an outdated/incorrect variation of the Big Bang theory then? I distinctly remember the description of a small, dense super hot region of space containing all of the universe's energy that expanded outward to fill empty space. As for the thing about time, that part I never understood since time is little more than the process of entropy gradually increasing overtime. Assuming the big bounce theory is correct, there's absolutely no reason whatsoever to think that there was nothing in the universe before the big bang began. If that theory turns out to be incorrect though and heat death will be the way the universe actually end, well... actually let's talk about that.



Yes it does. I don't think it was 'heat'. The cosmologists describe the conditions to their satisfaction since yes, such a simple description violates all kinds of rules. Keep in mind that the energy wasn't necessarily positive since there's an awful lot of negative energy present as well, and still is. Energy is conserved only in geometries that are static over time, and our universe isn't described by any static geometry (such as the Milne model). Just saying that the 2nd law doesn't hold in our universe. Carroll put out a paper showing this.[/quote]

So... I'm right then? The big bang really did violate the second law of thermodynamics? Assuming that really is the case, that leaves me with so many other questions. Will the universe stay dead forever once maximum entropy has been achieved? Will time and space even exist after that? What even is space in the context of the big bang? How does all the rate of the universe's expansion and the amount of dark energy needed to drive it fit in with all of this?

Thx for the reply though, I really appreciate it  

[Aeris (OP)]

Halc didn't comment on this bit directly.   It doesn't seem that there was any time before the big bang.   There is no reason to assume the first law of thermodynamics or any principle of Physics should apply before the big bang.  "Time" seems to emerge as a property we can identify only after the big bang.

 I'm sorry, what?! Time emerged after the big bang? That doesn't make an atom of sense. Time is quite literally, the process of entropy gradually increasing overtime. What, will time still exist after maximum entropy has been achieved? Is the universe on some kind of eternally long lasting loop of low entropy to high entropy to back to low entropy and rinse and repeat? The idea that conservation of energy not applying to the universe before the big bang also doesn't make sense to me. I don't subscribe to the God theory at all, but I subscribe to the idea of something emerging from nothing, actual nothingness, even less. Just saying it out loud makes me genuinely feel like my IQ is dropping. What's SO special about the period of time before the big bang that energy was able to spontaneously materialize into existence without a given cause?       

 It has happened more than once.  Entropy can be defined using statistical mechanics rather than classical thermodynamics.   In systems where changes are assumed to occur randomly, then sometimes entropy does decrease.   The law of entropy is often regarded just as a statistical law.  For large systems with many particles interacting it is overwhelming likely that entropy will increase but there is a small chance for a decrease.  We don't see the entropy of the entire universe decreasing because that system is so large (contains so many particles and interactions) that the chances of this happening are insignificant.  However, for smaller closed systems within the Universe we can observe entropy decreasing.
    If you're interested look up some articles about the "Poincare recurrence theorem" There are some systems that start in a low entropy state and evolve to what is, on average, a higher entropy state but if the system continues to have random changes then sometimes entropy decreases.  If you wait long enough, then just by random chance, the initial state will have re-appeared again somewhere over that time.

So... entropy, when it REALLY feels like it, can and eventually will decrease all on its own without an outside force acting on it, it's just so statistically unlikely to happen that us humans will all be long dead before we witness it occur on anything higher than a microscopic scale? Does that mean that even after the entropy of the universe reaches its maximum, a new universe will begin again all on its own, thus destroying the notion that heat death won't be the final curtain for all of existence?

Also, side question. I know this is a forum for questions about science, but are questions relating to science-fiction acceptable? Can I at least reference them in my question and ask things like "Could something like this be recreated in real life?" or "Is this particular thing in the story based off of something in the real world?"?

Oh, and thx for the response btw really appreciate it  

[Eternal Student]

Hi.

   Let's start with your questions about the terms of use of this forum:

Also, side question. I know this is a forum for questions about science, but are questions relating to science-fiction acceptable? Can I at least reference them in my question and ask things like "Could something like this be recreated in real life?" or "Is this particular thing in the story based off of something in the real world?"?

    First of all I am not a moderator or involved with the administration of this site.  My opinion is just my opinion not the law.
   It would seem acceptable to talk about some science fiction in the way you have outlined.   Just make it clear that it was based on science fiction and you are asking if there is any real scientific basis for it.   There is also a  "Just Chat" section where the rules are much more relaxed.  Just about anything can go in there.
- - - - - - - - - - -
Aeris said:

I'm sorry, what?! Time emerged after the big bang? That doesn't make an atom of sense. Time is quite literally, the process of entropy gradually increasing overtime.

   I like the fact that you are open to idea that time might very well be defined this way.  Yes, time may be nothing more than the evolution of entropy.   Personally, I think this idea is as good as any.
   Let's start from the beginning:   Time is an extremely complicated thing.  There are many articles and many physicists that will tell you we have no idea what "time" is.   In the early days of Physics (let's say up to Newton) it seemed like there was a perfectly straightforward universal time, it all made sense and everyone knew what it was all about.   Special Relativity came along and demonstrated that the rate of flow of time is not universal, it is dependent on relative motion between two observers.  General Relativity came along soon after and we saw that spacetime can be warped in all sorts of ways.  We abandoned many notions we had about the nature of time.
    One of the strange things about time as opposed to some other spatial co-ordinate is that we only seem able to move forward in time and not backward.  Physicists have examined most of the theories and principles of Physics we have and noticed that most of them are extremely symmetric in the time co-ordinate.  There is no obvious reason why time couldn't move in the other direction.   Thermodynamics and entropy seems to be the main exception to this.  You can read more (or watch You Tube videos) about entropy and "the arrow of time" if you're interested.
    There are also Physicists examining the idea that time is just an emergent property.   What does this mean?  It suggests that time is not a fundamental quantity or property, instead it could be something that makes sense and can be defined only in larger systems and it is just a combination and interplay of more fundamental quantities.  Example:  "Beauty" is a property that a human being might have but this is an emergent property that only the whole system can have.  If you pull the human being apart, then the molecules don't have this quantity or property of beauty.  They have other properties like mass and volume but not beauty.  Put the molecules together again and you have a bigger system where the quantity of beauty emerges - it can be defined and identified. 

   Anyway, time is complicated and we could fill an entire forum talking about what it is or isn't.  (Just to be clear, it's not as if I know what time is any better than anyone else).  Let's just go with your (Aeris) suggestion.  Time is intrinsically linked to changes in entropy.  Modern cosmology does not usually concern itself with what happend before the big bang.  Indeed the very notion of "before" the big bang is hard to define.  For some reason there was a low entropy state and from there entropy was able to increase and evolve.  Considering time as the progressive increase in entropy, time can sensibly be defined from the big bang but NOT before it.

What, will time still exist after maximum entropy has been achieved?

   That is a good question.  Time has lost it's meaning or importance when the universe reaches a final "heat death".  No physical or chemical changes will ever happen.  There is no way to know how much time has elapsed.  It doesn't really matter if time still exists or not - it's not important and nothing depends on it.  The passage of time is no longer observable.  If we define something "existing" as something that is observable or has the ability to make an observable change in our real universe, then time does not exist anymore.  There is no intrinsic way to measure time in such a universe and it makes no difference whether it exists or not.
 

The idea that conservation of energy not applying to the universe before the big bang also doesn't make sense to me.

   Ignoring the complication that you have said "before the big bang",  we could just challenge the idea of conservation of energy directly.  There is another recent thread here where Energy and especially gravitational potential energy was discussed, if you're interested   (https://www.thenakedscientists.com/forum/index.php?topic=82871.0) but that will take some time to read.  I'll just take a small section out of this now:

   energy is not conserved in general relativity.  -  Sean Carroll  https://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/      That article will only take 5 minutes to read and it's well worth your time in my opinion.

   There's a lot more we could discuss but I've already spent too long and bored everyone.  I'll sign off for now.

Best Wishes to you and I'm glad you're interested in Physics.

[Aeris (OP)]

"First of all I am not a moderator or involved with the administration of this site.  My opinion is just my opinion not the law.
It would seem acceptable to talk about some science fiction in the way you have outlined.   Just make it clear that it was based on science fiction and you are asking if there is any real scientific basis for it.   There is also a  "Just Chat" section where the rules are much more relaxed.  Just about anything can go in there."

Ok. Thx.
- - - - - - - - - - -

"I like the fact that you are open to idea that time might very well be defined this way.  Yes, time may be nothing more than the evolution of entropy.   Personally, I think this idea is as good as any."

This actually isn't my idea, but I appreciate the fact that you used it for the sake of making your answer easier for me to understand (I'm honestly not THAT smart lol).

"There are also Physicists examining the idea that time is just an emergent property.   What does this mean?  It suggests that time is not a fundamental quantity or property, instead it could be something that makes sense and can be defined only in larger systems and it is just a combination and interplay of more fundamental quantities.  Example:  "Beauty" is a property that a human being might have but this is an emergent property that only the whole system can have.  If you pull the human being apart, then the molecules don't have this quantity or property of beauty.  They have other properties like mass and volume but not beauty.  Put the molecules together again and you have a bigger system where the quantity of beauty emerges - it can be defined and identified."

That's... a really flipping cleaver way to put it I'm surprised I haven't heard time being described like that more often by scientists. 

"Anyway, time is complicated and we could fill an entire forum talking about what it is or isn't.  (Just to be clear, it's not as if I know what time is any better than anyone else).  Let's just go with your (Aeris) suggestion.  Time is intrinsically linked to changes in entropy.  Modern cosmology does not usually concern itself with what happend before the big bang.  Indeed the very notion of "before" the big bang is hard to define.  For some reason there was a low entropy state and from there entropy was able to increase and evolve.  Considering time as the progressive increase in entropy, time can sensibly be defined from the big bang but NOT before it."

So... cosmologists can't say definitively why the early universe started off in a state of such low-entropy, but they theorize that there was a property in the universe, be it a physical one or even an emergent one that didn't exist until after the big bang, and that was what ultimately kickstarted the universe's quest to establish thermal equilibrium? Am I even close?
 
"Ignoring the complication that you have said "before the big bang",  we could just challenge the idea of conservation of energy directly.  There is another recent thread here where Energy and especially gravitational potential energy was discussed, if you're interested but that will take some time to read.  I'll just take a small section out of this now:"

Yeah, that was a poor choice of wording on my part. Also I had to cut the link out of my reply since for some reason, the website won't let me post a reply with it. It looks interesting though, and I'm gonna read it more thoroughly this evening. Thx.

[Halc]

The conversation is moving faster than I can follow, so forgive if any of this is repetitive.

About posting about Sci-Fi: Just-Chat section is probably best for discussing non-science like "how do light-sabers work?". A few things might be eligible for the main sections like "Is technology X in Star-Trek" theoretically possible? I mean, those guys showed communicators long before cell phones were a thing, but of course the one's in the show don't work via conveniently nearby cell towers, and their range is almost always limited by the plot requirements of the episode.

So... am I talking about an outdated/incorrect variation of the Big Bang theory then?

Probably a pop-version, never something that was once the current state of the theory. There are countless sites, even reputable ones, that describe the early universe as a small speck of sorts. It's smaller, but not small.

I distinctly remember the description of a small, dense super hot region of space containing all of the universe's energy that expanded outward to fill empty space.

It expanding into empty space is definitely wrong. Such a thing is impossible since that much matter in a small space would form a black hole and it would never expand outward at all. The density of the universe was uniform everywhere at all times, and the expansion is the metric expansion of space itself, not the movement of material into empty space.

If that theory turns out to be incorrect though and heat death will be the way the universe actually end

The universe will end in heat death. The probability of otherwise goes down with time faster than entropy increases. Perhaps a better way to work what E-S said is to look at it from a multiple world point of view. Anything possible happens in some world out there, so maybe this temporary divergence from heat death happens in some seriously improbably world, but in all likelihood you're not going to measure that one were you to hang around long enough to find out.
Quantum mechanics figures heavily into this discussion and one must be clear on how one phrases a statement. In standard copenhagen interpretation, the universe will end in heat death, period.

So... I'm right then? The big bang really did violate the second law of thermodynamics?

Nobody said that. There isn't such a law spanning outside our spacetime. It seems to be a law of our spacetime.
Once again, Sean Carroll seems to publish several articles about some of the speculation in these areas.

Will time and space even exist after that?

Without measurable change, will time be meaningful at all? Will there be a direction to it? As ES says, this is a good question and depends on your definition of time. Entropy does not define time, but it does define an objective direction to it. Given the heat death state, the 4 dimensions of spacetime would seem to be all equivalent and there would be no distinguishing space from time.

So... cosmologists can't say definitively why the early universe started off in a state of such low-entropy, but they theorize that there was a property in the universe, be it a physical one or even an emergent one that didn't exist until after the big bang, and that was what ultimately kickstarted the universe's quest to establish thermal equilibrium?

This sound quite reasonable to me.

[Aeris (OP)]

"The conversation is moving faster than I can follow, so forgive if any of this is repetitive."

Fine by my. Repetition and colorful imagery is pretty much the only way I can learn anything in science

"About posting about Sci-Fi: Just-Chat section is probably best for discussing non-science like "how do light-sabers work?". A few things might be eligible for the main sections like "Is technology X in Star-Trek" theoretically possible? I mean, those guys showed communicators long before cell phones were a thing, but of course the one's in the show don't work via conveniently nearby cell towers, and their range is almost always limited by the plot requirements of the episode."

Neat. I'll post hard science-fiction questions on the main forums, and everything lower than that on the just-chat section on the website


"Probably a pop-version, never something that was once the current state of the theory. There are countless sites, even reputable ones, that describe the early universe as a small speck of sorts. It's smaller, but not small."

"It expanding into empty space is definitely wrong. Such a thing is impossible since that much matter in a small space would form a black hole and it would never expand outward at all. The density of the universe was uniform everywhere at all times, and the expansion is the metric expansion of space itself, not the movement of material into empty space."

Ok. Well at least I won't make this mistake again the next time I describe the big bang theory to someone else.

"The universe will end in heat death. The probability of otherwise goes down with time faster than entropy increases. Perhaps a better way to work what E-S said is to look at it from a multiple world point of view. Anything possible happens in some world out there, so maybe this temporary divergence from heat death happens in some seriously improbably world, but in all likelihood you're not going to measure that one were you to hang around long enough to find out.
Quantum mechanics figures heavily into this discussion and one must be clear on how one phrases a statement. In standard copenhagen interpretation, the universe will end in heat death, period."

The first and last parts of this paragraph seem to state that heat death has a 99.99999% chance of happening and that the other options have such a laughably low chance of happening that they're not even worth considering. Also unsure what you mean by "The probability of otherwise goes down with time faster than entropy increases". Also, also, if heat death really is the most likely way the universe will end, that pretty conforms the theory that this universe's lifetime is its only lifetime, and this pretty much changes my question from "Did the Big Bang Break the Second Law of Thermodynamics?" to "If everything in existence has a cause, what was the Big Bang's cause?". Like what, the universe used to be a collection of empty space and useless energy that one day, for seemingly no reason whatsoever, expanded into a sea of radiation that gave rise to matter and stars, but don't you all worry folks, it's only ever gonna do this a single time and then once it's over and done with, it's dead forever because it somehow created a magical property that makes entropy work the way described by thermodynamics? That sounds difficult for me to believe." 

"Nobody said that. There isn't such a law spanning outside our spacetime. It seems to be a law of our spacetime.
Once again, Sean Carroll seems to publish several articles about some of the speculation in these areas."

What outside? There's nothing outside our spacetime (other universes don't count as they presumably have their own versions of spacetime and are purl theoretical."

Sorry for the late reply btw.

[evan_au]

Assuming the big bounce theory is correct

That was a reasonable assumption up until the accelerating expansion of the universe was discovered in the 1990s.
- By the 2000s, the bounce fell flat.

The Big Bounce theory assumed that gravity would slow the expansion of the universe to a stop, after which it collapsed again (possibly to rise again, after a "bounce" which somehow resets the entropy of the universe).
- Astronomers studied distant galaxies to determine if the density of the universe would: (1) slow it to a stop and collapse or (2) it would keep expanding, but at ever-slower rates.
- What they discovered was a surprise: (3) the expansion would not only continue, but would get faster over time.

That unexpected result earned the discoverers a Nobel Prize in 2011. But it was a possible solution that had always been implicit in Einstein's General Relativity.
See: https://en.wikipedia.org/wiki/Accelerating_expansion_of_the_universe

[Halc]

Sorry for the late reply btw.

That wasn't late. This is.

Also unsure what you mean by "The probability of otherwise goes down with time faster than entropy increases".

Consider rolling a 100-sided die. Your score goes down one every time you don't roll a 7, and up one every time you do roll a 7. Near the beginning (low entropy) the chance of getting to +1 is still calculably nonzero, but once your score is -1000, the odds of throwing 1000 more 7's than not-7's is negligible. Hence the odds going down with increased entropy.

Also, also, if heat death really is the most likely way the universe will end, that pretty conforms the theory that this universe's lifetime is its only lifetime

Pay attention to the post by evan_au since one's interpretation of time is critical in showing what assumptions you are making with such a statement.

In the presentist view, the universe is 3D and evolves in place into new states. The universe is contained in a time which flows. Such a universe must start and then end such as you describe. It is reduced to the status of an object and thus is probably in need of being caused. These are real problems that must be solved by the premise of presentism, for which there is zero empirical evidence.

In the non-presentist view (commonly known as block, but there are some block-presentist interpretations, so 'block' does not necessarily imply the lack of presentism), all the events of the universe exist with equal ontological status. The universe contains time as a dimension. It is not contained by time, and thus is not a created thing, nor a thing which ages. By all events having equal ontological status, it means that there is no status of events being past or future, happened or not-yet-happened. They all just exist, and thus the entire history of the universe exists as one structure. To treat it as an object (suggesting it being created or ending or having a lifetime) is a category error. These concepts are meaningless to something not existing within time.
Einstein demonstrated the relativity of simultaneity which really throws a strong suggestion that presentism is wrong, but it cannot prove it. I've thought of some arguments against it, but one must go beyond special relativity to do it.

Like what, the universe used to be a collection of empty space and useless energy that one day, for seemingly no reason whatsoever, expanded into a sea of radiation that gave rise to matter and stars, but don't you all worry folks, it's only ever gonna do this a single time and then once it's over and done with, it's dead forever because it somehow created a magical property that makes entropy work the way described by thermodynamics? That sounds difficult for me to believe.

Me too. Hence my not taking that view.

What outside? There's nothing outside our spacetime

The phrase refers to an objective consideration of the universe (or other system), not actually observed from a specific point within said system.
The 'view from nowhere' is also sometimes used to express a similar concept.

[evan_au]

it's only ever gonna do this a single time and then once it's over and done with, it's dead forever because it somehow created a magical property that makes entropy work the way described by thermodynamics?  That sounds difficult for me to believe.

You could look at it this way:
- The Big Bang Theory suggests that the universe was in one state, then "inflated" suddenly, and now it is in a new state, with different physics.
- In some theories, this changing behavior is thought to be due to a ripple in the potential energy of a hypothetical particle called the "Inflaton"
- If this potential energy has one or more additional ripples, then another round of expansion may occur (but nobody knows - its all hypothetical).
https://en.wikipedia.org/wiki/Inflation_(cosmology)#Theoretical_status

One of the risks is that another round of expansion could start while we are still here, leading to the hypothetical possibility of a "Big Rip":
https://en.wikipedia.org/wiki/Big_Rip

PS: The universe doesn't really care what you believe.

[Aeris (OP)]

One of the risks is that another round of expansion could start while we are still here, leading to the hypothetical possibility of a "Big Rip":
https://en.wikipedia.org/wiki/Big_Rip

Meh, I'd rather have the universe reset it self indefinitely at random than stay dead forever (heat death).

PS: The universe doesn't really care what you believe.
[/quote]

Well that's a shame

[Eternal Student]

Hi again.

Meh, I'd rather have the universe reset it self indefinitely at random than stay dead forever (heat death).

   As discussed above, that's one possibility (if unlikely).   There are other possibilities which are, in my opinion, just as cheerful.

1.  No one has mentioned string theory yet as far as I can see.
   The Universe we experience seems to have 4 -dimensions (3 space + 1 time).  It is possible that all of this is contained on one brane  (abbreviation of "membrane") as considered in string theory.   These branes exist within a much higher dimensional space  (the exact number depends on which flavour of string theory you are using).  Anyway these branes vibrate and move about in that higher dimensional space.  Sometimes one brane collides with another and transfers energy to that other brane.   
    There are three issues of relevance:   (i)  This could explain something from your first post.  Why did all energy seem to be at one place for the big bang in this universe?  Possibly because it was the point of collision with another brane.
   (ii)  The brane that our universe is on may collide with another brane and transfer some energy to that brane.  While this would seem to drain energy from us and may be the end of our universe, it's the beginning for some other universe which might be just as interesting and valuable as our own,  possibly one which evolves it's own life and they can have their turn.
   (iii)  It's possible our brane may have another collision with some other brane but gain (rather than lose) some energy delivered in a small region.  This effectively gives us some more ordered or concentrated energy and extends our universe's life as far as ever increasing entropy is concerned.  (Although if you were near the region where the collision occurred it could be catastrophic - but let's just look at the potentially positive side).

2.    Black Holes and/or Holographic theory.
    Black Holes are truly interesting objects.  Most of the current thinking is that General relativity (GR) simply breaks down at the singularities of a BH,  so we might have some extremely dense matter within an event horizon but it won't be infinitely dense or "singular" in the mathematical sense.    However, suppose GR doesn't break down.  In this case we cannot include the central singularity of a BH into our models of spacetime.  Whatever it is, if it exists in any sense, then it is outside of our spacetime.  The possibilities are then endless - if an object passes into the singularity at the central region of a Black Hole does it enter another universe?   Are there other universes already embedded within our own and are we ourselves living in a universe that is inside a Black Hole?
    There's a vaguely related theorem often called the Holographic theory or Holographic principle.  Anyway, the relevance of this is that all the information necessary to create a 3-Dimensional universe can be encoded on a 2-D surface like the event horizon of a Black Hole.

Best Wishes.

[Aeris (OP)]

Hi again.

Meh, I'd rather have the universe reset it self indefinitely at random than stay dead forever (heat death).

   As discussed above, that's one possibility (if unlikely).   There are other possibilities which are, in my opinion, just as cheerful.

1.  No one has mentioned string theory yet as far as I can see.
   The Universe we experience seems to have 4 -dimensions (3 space + 1 time).  It is possible that all of this is contained on one brane  (abbreviation of "membrane") as considered in string theory.   These branes exist within a much higher dimensional space  (the exact number depends on which flavour of string theory you are using).  Anyway these branes vibrate and move about in that higher dimensional space.  Sometimes one brane collides with another and transfers energy to that other brane.   
    There are three issues of relevance:   (i)  This could explain something from your first post.  Why did all energy seem to be at one place for the big bang in this universe?  Possibly because it was the point of collision with another brane.
   (ii)  The brane that our universe is on may collide with another brane and transfer some energy to that brane.  While this would seem to drain energy from us and may be the end of our universe, it's the beginning for some other universe which might be just as interesting and valuable as our own,  possibly one which evolves it's own life and they can have their turn.
   (iii)  It's possible our brane may have another collision with some other brane but gain (rather than lose) some energy delivered in a small region.  This effectively gives us some more ordered or concentrated energy and extends our universe's life as far as ever increasing entropy is concerned.  (Although if you were near the region where the collision occurred it could be catastrophic - but let's just look at the potentially positive side).

2.    Black Holes and/or Holographic theory.
    Black Holes are truly interesting objects.  Most of the current thinking is that General relativity (GR) simply breaks down at the singularities of a BH,  so we might have some extremely dense matter within an event horizon but it won't be infinitely dense or "singular" in the mathematical sense.    However, suppose GR doesn't break down.  In this case we cannot include the central singularity of a BH into our models of spacetime.  Whatever it is, if it exists in any sense, then it is outside of our spacetime.  The possibilities are then endless - if an object passes into the singularity at the central region of a Black Hole does it enter another universe?   Are there other universes already embedded within our own and are we ourselves living in a universe that is inside a Black Hole?
    There's a vaguely related theorem often called the Holographic theory or Holographic principle.  Anyway, the relevance of this is that all the information necessary to create a 3-Dimensional universe can be encoded on a 2-D surface like the event horizon of a Black Hole.

Best Wishes.

Assuming either of these things have even the slightest chance of happening, I will happily take them over heat death any day of the week (except for the part where our universe looses energy from brane collision, that sounds even worse honestly).   

[evan_au]

Also see: https://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe

[evan_au]

Did the Big Bang Break the Second Law of Thermodynamics?

Theoretical Physicist Sean Carrol was asked about this. As I understand it, his reply was:
- No
- There is a black hole in the center of the Milky Way galaxy (about 4 million solar masses). The entropy of this black hole can be calculated. This one black hole today has more entropy than the entire universe at the Big Bang.
- Changing the volume of a system affects the entropy, since there are more physical places things can be, hence more microstates. So an expanding universe automatically leads to increasing entropy.

There are about 6 related questions here: https://www.preposterousuniverse.com/podcast/2021/09/16/ama-september-2021/
Start at 13:50 for the group of questions. Answers for this specific question start at 18:25, and go for about 6 minutes.

[alancalverd]

Scientific laws are descriptions, not prescriptions.

Assuming the Big Bang actually happened, it established the Second Law.

[Colin2B]

That is a good question, my young friend, to which my answer is NO!

I have a working model of the Universe .......

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