Falsification of eternal inflation

[Chalnoth]

Steinhardt makes a good point:

Now you should be disturbed. What does it mean to say that inflation makes certain predictions—that, for example, the universe is uniform or has scale-invariant fluctuations—if anything that can happen will happen an infinite number of times? And if the theory does not make testable predictions, how can cosmologists claim that the theory agrees with observations, as they routinely do?

I don't think that's a very good point. If it were, then quantum mechanics itself would make no predictions whatsoever. But it does: it makes probabilistic predictions. And when you have large numbers (the number of fluctuations in the early universe was very large), the statistics of those numbers becomes highly predictable, even if, in principle, anything can happen.

The primary issue that he does have a good point on is, to me, the measure problem. I am extremely skeptical of his discussion about the cyclical universe, however, as that seems to completely violate everything we know about thermodynamics.

 

[Calrid]

Has anyone pointed out that inflation is obviously eternal since nothing exists outside of time and there has never AFAIK been a time when the Universe was not inflating.

I'd like to think bangs and crunches were true because there should be evidence in this universe of them. But most likely it's just heat death and the slow demise of time itself. Or maybe in the quantum dominated almost void it starts all over again!

 

[offroff]

Chalnoth,
Yeah, we really need probabilistic predictions but one of the arguments in this thread was that we can't use that on an infinite set.

My initial argument was maybe flawed but in theory there must be a prediction how the typical evolution of life in the multiverse looks like. Do you agree?

 

[Chalnoth]

Has anyone pointed out that inflation is obviously eternal since nothing exists outside of time and there has never AFAIK been a time when the Universe was not inflating.

It doesn't work that way, actually. Basically, if you look at the way inflation works back into the past, unless you would like to impose an infinite degree of fine tuning, you end up with a singularity in the finite past. It seems clear that this singularity is rather unphysical, and thus inflation began as a result of some physical process in the finite past.

Even eternal inflation falls for this difficulty, and thus eternal inflation is generally considered to only be eternal in the future, not the past. There is nothing fundamental about inflation that requires it to have the properties for it to be eternal.

 

[Chalnoth]

Chalnoth,
Yeah, we really need probabilistic predictions but one of the arguments in this thread was that we can't use that on an infinite set.

I already mentioned that the problem is the measure problem, not the general property of quantum mechanics that "everything happens".

 

[dm4b]

offroff, yes that was the article, thanks! Maybe, since I am slow at work today, I will take the time to read it now ;-)

 

[dm4b]

Well, I just read that article. This paragraph stuck out for me:

"Its raison d'être is to fill a gap in the original big bang theory. The basic idea of the big bang is that the universe has been slowly expanding and cooling ever since it began some 13.7 billion years ago. This process of expansion and cooling explains many of the detailed features of the universe seen today, but with a catch: the universe had to start off with certain properties. For instance, it had to be extremely uniform, with only extremely tiny variations in the distribution of matter and energy. Also, the universe had to be geometrically flat, meaning that curves and warps in the fabric of space did not bend the paths of light rays and moving objects."

So, inflation was brought about so the Universe would not be dependent upon a set of highly unlikely initial conditions?

But, maybe the Universe really was born out of a set of highly unlikely initial conditions.

Sort of like buying a lottery ticket. Many folks think that with 180 million to 1 odds, it's a waste of time ... they say, "you can NEVER win". Well, every other month, or so, somebody does win. Those people usually wouldn't question whether or not they CAN win anymore .. because they just did.

Maybe questioning the fact that the Universe started off with unlikely properties, wasn't the best idea? Maybe, it really did. Well, we have to question, but perhaps it has brought us full circle, with a tour through a not-meant-to-be theory called Inflation? And, in doing so, we become faced with even worse scenarios along these lines - "bad" inflation being more likley than "good" inflation, and even no inflation being more likely than inflation, etc.

Anyhow, with all that said, I thought the original Big Bang theory had other gaps in it other than unlikely initial conditions? Is that correct?

 

[Chalnoth]

So, inflation was brought about so the Universe would not be dependent upon a set of highly unlikely initial conditions?

But, maybe the Universe really was born out of a set of highly unlikely initial conditions.

Well, it was. Inflation doesn't solve this problem. In fact, it basically has to be this way, because entropy has been increasing ever since.

Sort of like buying a lottery ticket. Many folks think with 180 million to 1 odds, it's a waste of time ... they say, "you can NEVER win". Well, every other month, or so, somebody does win. Those people usually wouldn't question whether or not they CAN win anymore .. because they just did.

The thing is, if you take the naive view of this, just using entropy, you run into the Boltzmann Brain problem: small fluctuations out of entropy are much more likely than large fluctuations. So it's much easier to get, for example, a single galaxy using this view than a whole universe. It's even easier to just get a single solar system. Easier still to just get a mind that merely thinks it sees an external universe, then immediately winks out of existence (the Boltzmann Brain).

But we know that's obviously wrong, so there had to be some interesting physics that let you get enough real universes produced that the real observers outnumber the Boltzmann Brains.

 

[dm4b]

Well, I've lost access to that article, so I can't comment on the first part. Sounds like maybe I've misunderstood something a bit though.

As far as the Boltzmann Brain - hadn't heard of it before. But, I just read this on wiki:

"our current level of organization, having many self-aware entities, is a result of a random fluctuation, it is much less likely than a level of organization which is only just able to create a single self-aware entity."

This logic seems over-stretched to me, because life, once started, appears to be a self-organizing "force". In some sense, it constantly fights against entropy. We're basically dying from the day we are born, but there are forces in the body that renew and heal us all the time, which keep us going.

In addition, a "single self aware entity", takes many millions of years of evolution to form. They don't just instantly pop out of nowhere from a random fluctuation. In addition, once the stage is set for one to evolve, it is set for many to evolve. That's just sort of how life seems to work. I doubt you will find a self aware entity anywhere in the Universe with a lonely history completely unique to itself.

So, the reasoning in the Boltzmann Brain problem makes sense to me right up to the part where it considers the "Brain", or until it considers life.

 

[dm4b]

The thing is, if you take the naive view of this, just using entropy, you run into the Boltzmann Brain problem: small fluctuations out of entropy are much more likely than large fluctuations. So it's much easier to get, for example, a single galaxy using this view than a whole universe. It's even easier to just get a single solar system. Easier still to just get a mind that merely thinks it sees an external universe, then immediately winks out of existence (the Boltzmann Brain).

Now, that I think twice about it, the Boltzmann Brain doesn't make sense to me at all, lol.

Could a Universe exists that actually consisted of a single galaxy. Or, a single solar system?

How could a solar system exist, w/o prior generation of stars that put out, in their deaths, some of the heavier elements that planets are made of. Could a galaxy exist, as we know it, without other galaxies?

In addition, it seems to argue that the order from most complex to most simple is, our Universe, a galaxy, a solar system, a self aware entity.

I would argue the order should be Our Universe with self-aware entities, Our Universe without self-aware entities, a galaxy, a solar system.

I think the whole idea ignores all the interdependencies that are required for the existence of the "objects" it takes under consideration.

Anyhow, I guess this is getting off topic ...

 

[Chalnoth]

Now, that I think twice about it, the Boltzmann Brain doesn't make sense to me at all, lol.

That's sort of the point. It's an "argumentum ad absurdum", aka and argument from contradiction. If you consider a universe to simply be a particularly large fluctuation out of equilibrium, then you inevitably arrive at the conclusion that individual brains popping in and out of existence, as rare as they are, are far more common than real observers. And that is nonsense: it contradicts the observation that we are real.

So if your theory predicts that Boltzmann Brains are more common than real observers, that theory is wrong. That was my point.

 

[dm4b]

That's sort of the point. It's an "argumentum ad absurdum", aka and argument from contradiction. If you consider a universe to simply be a particularly large fluctuation out of equilibrium, then you inevitably arrive at the conclusion that individual brains popping in and out of existence, as rare as they are, are far more common than real observers. And that is nonsense: it contradicts the observation that we are real.

So if your theory predicts that Boltzmann Brains are more common than real observers, that theory is wrong. That was my point.

Well, I get that. I'm just not sure that our theories really predict that.

It seems to me it's assuming something is common, only because we are neglecting the fact that many other things are also required, and must come first, due to the interdependent nature.

If you look at it that way, perhaps the small fluctuations can't really bring about anything. It's only a large one, which can bring about everything we see that can, in reality, actually achieve anything. It's the whole show or nothing.

I don't know if this is the right way to think about things. It just seems like the other view is missing something too.

 

[Calrid]

It doesn't work that way, actually. Basically, if you look at the way inflation works back into the past, unless you would like to impose an infinite degree of fine tuning, you end up with a singularity in the finite past. It seems clear that this singularity is rather unphysical, and thus inflation began as a result of some physical process in the finite past.

Even eternal inflation falls for this difficulty, and thus eternal inflation is generally considered to only be eternal in the future, not the past. There is nothing fundamental about inflation that requires it to have the properties for it to be eternal.

I'm not sure everyone would agree with that assertion or that its even justifiable.

Eternal means existing always, from our perspective the universe has always existed since outside of time makes no practical sense. It does not I think mean what you think it does. The universe has always been in a stage of inflation since t>0 or when time and hence space exists if you like. The so called singularity or point of origin at t=0 is undefined for obvious reasons. If we prove that there was a before t = 0 empirically this may change. At the moment such a contention is still speculative so any conjecture is rather philosophical atm.

 

[offroff]

dm4b,
Boltzmann brains is not offtopic, my thoughts about ultraquick evolution is similar (my argument failed though). I think we need to be aware that there are a lot that needs to be explained. A cosmological theory that explains physics is not enough, it also needs to be in line with philosophy, psychology and biology as well. I think physicists should know that :)

 

[Chalnoth]

Well, I get that. I'm just not sure that our theories really predict that.

Boltzmann Brains are a definite prediction of a naive thermal fluctuation model, where one tries to explain the low entropy in the early universe by just saying, "Well, thermal fluctuations out of equilibrium happen all the time, maybe the early universe was just a particularly big thermal fluctuation."

Most think that the small physical size of the inflationary epoch likely has something to do with this, and there are some reasonable explanations that solve the problem. Eternal inflation, by the way, isn't one of them.

 

[Chalnoth]

I'm not sure everyone would agree with that assertion or that its even justifiable.

Eternal means existing always, from our perspective the universe has always existed since outside of time makes no practical sense. It does not I think mean what you think it does. The universe has always been in a stage of inflation since t>0 or when time and hence space exists if you like. The so called singularity or point of origin at t=0 is undefined for obvious reasons. If we prove that there was a before t = 0 empirically this may change. At the moment such a contention is still speculative so any conjecture is rather philosophical atm.

Uh, what? There is no reason whatsoever to believe that inflation at the start of our observable universe was the beginning of all time and space.

 

[Calrid]

Uh, what? There is no reason whatsoever to believe that inflation at the start of our observable universe was the beginning of all time and space.

There's no reason to believe it wasn't either. That is the point. It's a philosophical issue really isn't it.

Since all we know or theorise on is the evolution of the Universe at t>0 or post whatever the singularity was, or in a phase of expansion then not only has inflation always happened but from our perspective it is also eternal as far as is known. Any meaningful proposition that has any observable evidence, can only be determined when time and space existed from inside our reality. Will that always be so I have no idea, maybe?

 

[Chalnoth]

there's no reason to believe it wasn't either. That is the point.

Oh, there is certainly a very good reason. If a physical process can happen once, chances are it can happen many times. Claiming that the physical process that started our universe only happened once is special pleading, and exceedingly unlikely.

But the original point was just that from our perspective the universe is eternal, which is hard to argue with unless you have proof otherwise.

That has nothing to do with whether or not inflation itself is future-eternal.

 

[Calrid]

Oh, there is certainly a very good reason. If a physical process can happen once, chances are it can happen many times. Claiming that the physical process that started our universe only happened once is special pleading, and exceedingly unlikely.

Do you have any evidence?

Special pleading it is not. What you are doing is begging the question.

I make a case that neither is distinguishable going on the evidence we have anyway. I provide an alternative merely to demonstrate this is still a purely philosophical issue.

That has nothing to do with whether or not inflation itself is future-eternal.

I never said it did, now did I? However it could be true. It could be that there is no evidence of previous Universes and never will be. This could be for one of two reasons, neither of which has anything more evidence based support. This is and has been the only universe (big bangs and collapses would also be in that category) or the evidence is just not available to us from inside the universe and hence the answer to the question is eternally moot.

 

[Chalnoth]

Do you have any evidence?

Special pleading it is not. What you are doing is begging the question.

Um, no. This is just the way math works. It is far more difficult to have just one member of a class of objects than it is to have an entire class of objects. Basically, in order to have just one member of a class of objects, you need all of the axioms required to get the entire class of objects, plus some more to specify the single member.

That's why it's special pleading: you need to add additional restrictions to get just one.

I make a case that neither is distinguishable going on the evidence we have anyway. I provide an alternative merely to demonstrate this is still a purely philosophical issue.

This is why we have Occam's Razor. If a model requires additional assumptions, it's probably wrong. Specifying only a single universe requires additional assumptions, so it's probably wrong.

 

[Calrid]

Um, no. This is just the way math works. It is far more difficult to have just one member of a class of objects than it is to have an entire class of objects. Basically, in order to have just one member of a class of objects, you need all of the axioms required to get the entire class of objects, plus some more to specify the single member.

That's why it's special pleading: you need to add additional restrictions to get just one.

So maths makes proof now how trite.

You need to have internal inflation and collapse with quantum "starting"/"ending" conditions which explain fluctuations in constant properties actually.

It requires nothing other than a philosophy atm to imagine these things. Maths does not and has never constituted a proof of anything on its own, nor does your theory that there are infinite universes or x universes distinguish itself from any eternal expansion and collapse theory. It is assuming the antecedent aka begging the question.

You are assuming that the "end" of space and time before collapse is dominated by classical phenomena and that the singularity behaves in a classical manner after collapse. I think its pretty certain that entropy is not a process that tends to produce reversible consequences anyway, again your assumptions are flawed. Both theories could produce an extraordinarily wide variety of starting conditions. Neither is distinguishable in science as yet.

This is why we have Occam's Razor. If a model requires additional assumptions, it's probably wrong. Specifying only a single universe requires additional assumptions, so it's probably wrong.

Ockam's razor is a tendency it is certainly not a scientific principle, or we'd still be sitting in caves debating which of the four elements made up wood.

Clearly quantum mechanics is far more complex than the pre quantum models, and general and special relativity are far more involved than Newtons ideas about time and space.

If you are going to use philosophical principles as proofs at least acknowledge this is still a philosophical question. And as yet there are no clear answers that are scientific.

Occam's razor is that the most parsimonious theory tends to be right more often. I don't believe yours is tbh.

 

[Chalnoth]

Occam's razor is that the most parsimonious theory tends to be right more often.

And positing one single universe requires more assumptions than positing a class of universes. You not only have to posit the physical process, and everything that involves, in starting the universe off, but you also have to assume it only happens once. And because the assumption is specific to the thing being claimed, it is special pleading.

You don't get out of special pleading by saying, "Well, maybe I'm right after all!" Yes, maybe you're right. But most likely you're wrong, as you already admitted.

 

[Calrid]

And positing one single universe requires more assumptions than positing a class of universes. You not only have to posit the physical process, and everything that involves, in starting the universe off, but you also have to assume it only happens once. And because the assumption is specific to the thing being claimed, it is special pleading.

You don't get out of special pleading by saying, "Well, maybe I'm right after all!" Yes, maybe you're right. But most likely you're wrong, as you already admitted.

I never said it only happens once quite the opposite the big bang could of happened an inconceivable amount of times, I just said that the Universe goes through endless bangs and collapses, which means there is only one Universe. Obviously it follows then it is eternal, it could be I'm wrong but using philosophically specious maxims won't prove that, evidence might. I am agnostic if anything.

Assuming that it must have multiple universes is in fact begging the question and still is since either hypothesis seems to be able to produce physically diverse universes, either over time or all at once. To distinguish the two you would have to prove that either of these assumptions was more likely true than the other at least and or that the other could not happen. To make it science you would need evidence.

It's not special pleading please stop saying that, it doesn't make sense as I am not making any claim of one theory being better than another for a reason I am assuming. It is a simpler version than yours I think (for whatever that is worth which is nothing pretty much) which makes your assumption that the only valid solution requires multiple Universes suspect. You have assumed that the only reasonable explanation involves multiple universes but this is not something that is true. I also suspect Lee Smolin would beg to differ since it is for the most part his "theory" du jour.

Like with most of these argument simpler tends to devolve into what you consider simple. Is it simpler to have only one universe with an indeterminate number of a bangs and crunches or multiple universes. I'd say just one universe with an entropic progression producing many varied parameters but its probably a matter of taste and how you weigh complexity.

There is nothing hypothetically limiting either "theory" from being true, likewise there is nothing that distinguishes them atm.

If I am using special pleading to say that the two "theories" are indistinguishable I have no idea where?

I don't get why you think I am claiming one wins over the other because of any assumption, quite the contrary both are legitimate hypothetically, neither distinguishes itself beyond that though.

 

[Chalnoth]

I never said it only happens once, I just said that the Universe goes through endless bangs and collapses, which means there is only one Universe. That is eternal, it could be I'm wrong but using philosophically specious maxims won't prove that, evidence might. I am agnostic if anything.

It's still special pleading to assume only one universe, however. In any event, I find such a scenario obscenely unlikely, because it seems to violate entropy considerations.

And yes, I will keep saying special pleading, because it's the correct word to use. Special pleading is when you make up an assumption just to apply to the argument at hand. Without the assumption of a single universe, you get a proliferation of universes and have fewer assumptions.

Multiple universes isn't an additional assumption. It's the default: it's what you get when you fail to add the assumption of a single universe.

 

[Calrid]

It's still special pleading to assume only one universe, however. In any event, I find such a scenario obscenely unlikely, because it seems to violate entropy considerations.

And yes, I will keep saying special pleading, because it's the correct word to use. Special pleading is when you make up an assumption just to apply to the argument at hand. Without the assumption of a single universe, you get a proliferation of universes and have fewer assumptions.

Ok then keep misapplying the term, to be special pleading I would have to be making a case that something is true or more likely, when I am making a case that neither can be distinguished as of yet. I am not making a case for either so special pleading is inapt.

Your idea that more universes makes it simpler than 1 universe is spurious also. One universe with multivariate constants if anything is simpler.

You assume there are multiple universes without telling us why one eternally expanding and collapsing universe cannot produce the same observable results, which of course I'm sure many scientists would contend with. Why is Smolin's theory of eternal collapse and inflation less likely than yours? What distinguishes the two?

Multiple universes isn't an additional assumption. It's the default: it's what you get when you fail to add the assumption of a single universe.

Huh default is not even a philosophical term it's just arm waving, what makes any of these positions the default exactly?

It's what you get when you fail to add the assumption of multiple universes.

Or more precisely when you can determine why one should be more likely than the other or the other false.

In any event, I find such a scenario obscenely unlikely, because it seems to violate entropy considerations.

Can you explain this further? What about entropy concerns forbids theories like this?

The Big Bounce is a theorized scientific model related to the formation of the known universe. It derives from the cyclic model or oscillatory universe interpretation of the Big Bang where the first cosmological event was the result of the collapse of a previous universe.[1]

Expansion and contraction

According to some oscillatory universe theorists, the Big Bang was simply the beginning of a period of expansion that followed a period of contraction. In this view, one could talk of a Big Crunch followed by a Big Bang, or more simply, a Big Bounce. This suggests that we might be living in the first of all universes, but are equally likely to be living in the 2 billionth universe (or any of an infinite other sequential universes).

The main idea behind the quantum theory of a Big Bounce is that, as density approaches infinity, the behavior of the quantum foam changes. All the so-called fundamental physical constants, including the speed of light in a vacuum, were not so constant during the Big Crunch, especially in the interval stretching 10−43 seconds before and after the point of inflection. (One unit of Planck time is about 10−43 seconds.)

If the fundamental physical constants were determined in a quantum-mechanical manner during the Big Crunch, then their apparently inexplicable values in this universe would not be so surprising, it being understood here that a universe is that which exists between a Big Bang and its Big Crunch.
[edit] Recent developments in the theory

Martin Bojowald, an assistant professor of physics at Pennsylvania State University, published a study in July 2007 detailing work somewhat related to loop quantum gravity that claimed to mathematically solve the time before the Big Bang, which would give new weight to the oscillatory universe and Big Bounce theories.[2]

One of the main problems with the Big Bang theory is that at the moment of the Big Bang, there is a singularity of zero volume and infinite energy. This is normally interpreted as the end of the physics as we know it; in this case, of the theory of general relativity. This is why one expects quantum effects to become important and avoid the singularity.

However, research in loop quantum cosmology purported to show that a previously existing universe collapsed, not to the point of singularity, but to a point before that where the quantum effects of gravity become so strongly repulsive that the universe rebounds back out, forming a new branch. Throughout this collapse and bounce, the evolution is unitary.

Bojowald also claims that some properties of the universe that collapsed to form ours can also be determined. Some properties of the prior universe are not determinable however due to some kind of uncertainty principle.

This work is still in its early stages and very speculative. Some extensions by further scientists have been published in Physical Review Letters.[3]

Peter Lynds has recently put forward a new cosmology model in which time is cyclic. In his theory our Universe will eventually stop expanding and then contract. Before becoming a singularity, as one would expect from Hawking's black hole theory, the Universe would bounce. Lynds claims that a singularity would violate the second law of thermodynamics and this stops the Universe from being bounded by singularities. The Big Crunch would be avoided with a new Big Bang. Lynds suggests the exact history of the Universe would be repeated in each cycle. Some critics argue that while the Universe may be cyclic, the histories would all be variants.

http://en.wikipedia.org/wiki/Big_Bounce

Just AAMOI.

 

[dm4b]

It's still special pleading to assume only one universe, however. In any event, I find such a scenario obscenely unlikely, because it seems to violate entropy considerations.

I can't help but wonder if we need to think outside the box ( of spacetime ) on this one.

What I mean is that entropy really only functions within spacetime. How can entropy increase without time? How can you get a fluctuation without time?

If spacetime was created at t=0, applying thinking/logic that is linear in time is not going to fit the bill before that. How can we say a fluctuation gave rise to spacetime, since the fluctuation would have had to happen "before" time existed, in order to give rise to it.

Unless we are going to say time existed always, just to get out of that trap. But, that doesn't really seem all that pleasing either.

 

[Chalnoth]

Ok then keep misapplying the term, to be special pleading I would have to be making a case that something is true or more likely, when I am making a case that neither can be distinguished as of yet. I am not making a case for either so special pleading is inapt.

Doesn't really matter. You're still making the case that the two ideas are roughly equivalent when they're not even close to being so.

Your idea that more universes makes it simpler than 1 universe is spurious also. One universe with multivariate constants if anything is simpler.

Not based upon any relevant definition of simplicity. Fully-define one universe, and you automatically get lots of others unless you explicitly exclude them. That explicit exclusion makes the one universe idea the more complex one.

Can you explain this further? What about entropy concerns forbids theories like this?

Because it's cyclical. At least in a simplistic view, you can't go from "entropy always increases" to a cyclical universe. In order for me to come close to believing this, they'd have to show that entropy increases continuously throughout the whole process. This would mean, among other things, that each "bounce" was different from the last.

Never mind that given the observed acceleration of our observable universe, this picture looks exceedingly unlikely to apply to our universe.

 

[Chalnoth]

I can't help but wonder if we need to think outside the box ( of spacetime ) on this one.

What I mean is that entropy really only functions within spacetime. How can entropy increase without time? How can you get a fluctuation without time?

Well, the main issue here is that we don't know how to sensibly talk about a universe without a spacetime. But even if you want to consider a universe starting literally out of nothing, the default expectation would be for it to start in a generic state, not in a very special one. And a generic state is, by definition, a high-entropy state. So even with a universe beginning out of nothing, you run into the exact same entropy considerations.

 

[Calrid]

Doesn't really matter. You're still making the case that the two ideas are roughly equivalent when they're not even close to being so.

Ok let's cut the bs. Can you justify this or not? If not then there's no point talking about it. Show me how one of these theories is more likely than the other?

How would you go about it without evidence anyway. All the well crafted philosophy in the world has never made anything true without evidence, it could be that there has only ever been one universe and God made it for all I know. As much as I don't believe that to be true I cannot prove it absolutely is not.

Not based upon any relevant definition of simplicity. Fully-define one universe, and you automatically get lots of others unless you explicitly exclude them. That explicit exclusion makes the one universe idea the more complex one.

Simplicity is a qualitative term and hence has no explicit use. I disagree less variables means a simpler system. Do you see what I mean. This contention has no more use to science than your bench mark idea had, which was bizarre by the way.

Because it's cyclical. At least in a simplistic view, you can't go from "entropy always increases" to a cyclical universe. In order for me to come close to believing this, they'd have to show that entropy increases continuously throughout the whole process. This would mean, among other things, that each "bounce" was different from the last.

Er that makes no sense, entropy is still increasing when it bounces, things don't get more organised when compacted they are all just as disorganised hence the multivariate starting conditions. Your arguments make no sense there is no philosophical contention to these theories let alone scientific ones.

Entropy is a philosophically contentious term in itself at least as it applies outside of heat concerns. More or less organised is extremely anthropocentric. What makes a neutron star more organised than a cloud of hydrogen anyway? Doesn't even make any philosophical sense from an unbiased point of view. In fact what makes a human being more organised than a vat full of the same chemicals exactly?The universe is still technically the same size as t>1 as it is when it is t>100000 sextilion anyway just as it has the same amount of energy at the singularity as it does at heat death.

Even if entropy is reversed it is unlikely we will see the same patterns emerging in reverse anyway.

Never mind that given the observed acceleration of our observable universe, this picture looks exceedingly unlikely to apply to our universe.

Yet another religious statement you have failed to justify.

Clearly you have not studied the model enough to comment on it anyway. The op starts with the contention that the view eternal expansion is losing support. Whether it is or it isn't its interesting, even if it proves nothing.

Of course I haven't even started on other theories that don't rely on multiple universes, like big bangs becoming ever more likely after heat death and the approach of the end of "time" and thus there are infinite universes contained in the same universe not seperate. One universe that lives on the remains of another. There's another one you couldn't possibly begin to dismiss with such worthless philosophical nothing.

Philosophical wibble $\neq$ science and it never will be, I hope. Although clearly String Theorists would like Nobel Prizes to be handed out for their philosophy. :tongue:

 

[Max™]

Occam's razor is a tendency it is certainly not a scientific principle, or we'd still be sitting in caves debating which of the four elements made up wood.

Water and Earth, hafter converting Air using the Skyfire for an energy source to activate the catalysts, obviously.

Occam's razor is that the most parsimonious theory tends to be right more often. I don't believe yours is tbh.

No, the razor says nothing about accuracy, it says when given a choice between different explanations of a phenomenon, the one which requires the least assumptions while providing the same utility as an explanatory framework should be preferred.

Additionally it is more difficult to test a hypothesis which multiplies entities needlessly, so the subtle selection pressure of physically possible experiments would naturally favor the most simple models.


As for eternal inflation, I'm still a fan of the black hole -> selection ideas, though the CCC idea is neat enough that I still need to look at it sometime, I always liked Penrose.

 

[Calrid]

Water and Earth, hafter converting Air using the Skyfire for an energy source to activate the catalysts, obviously.

Yes but what about the 5th element by which I mean not Mila Jovovich in skimpy clothes, but spirit.

No, the razor says nothing about accuracy, it says when given a choice between different explanations of a phenomenon, the one which requires the least assumptions while providing the same utility as an explanatory framework should be preferred.

Additionally it is more difficult to test a hypothesis which multiplies entities needlessly, so the subtle selection pressure of physically possible experiments would naturally favor the most simple models.As for eternal inflation, I'm still a fan of the black hole -> selection ideas, though the CCC idea is neat enough that I still need to look at it sometime, I always liked Penrose.

Ok that's just semantics but fine. Occams razor is a means to select methods which will then more likely provide a better answer (whatever the hell that means) doesn't really change anything or differ from what I said or where my argument was going, if we look at the context of the argument, rather what he was saying was that a property means that a hypothesis has more likelihood of being correct. This is clearly not true I quite agree with you on this even if I didn't make that clear at first.

should be preferred because of what? it's likelihood to be what? Simpler or have some form of qualitative value beyond just the simple? We're talking about science here so the razor to have any meaning needs to be grounded in the scientific method first.

It seems to me just saying it should be preferred because it is easier to test is trite and not what it really should mean in this context, as if we have no pragmatism we end up disappearing up our own axiom. In this argument we are talking about things that are unable to be distinguished which already means Occams razor is moot. Ultimately a property real or imaginary is not sufficient to make an argument logical and it certainly isn't in science.

The fact is in this discussion he is actually trying to suggest that a philosophical assumption constitutes a scientific one or some probabilistic chanciness of being right, I disagree that Occams razor has a quantitative truthiness value unless there is already a theory. So in essence we probably agree but disagree on semantics. It could be that the GUT is made up of one law or trillions, nothing rests on philosophy, everything rests on evidence.

A hypothesis does not stand or fall on its ability to be tested or the ease in doing so, it stands or falls on being right.

Which is both the curse and salvation of string theory incidentally.

This is why we have Occam's Razor. If a model requires additional assumptions, it's probably wrong. Specifying only a single universe requires additional assumptions, so it's probably wrong.

Besides I was responding to this so you should probably take it up with him. :tongue:

He was the one suggesting simplicity suggests correctness, I was the one disagreeing.

 

[Chalnoth]

Ok let's cut the bs. Can you justify this or not? If not then there's no point talking about it. Show me how one of these theories is more likely than the other?

What, do you want a derivation of Occam's Razor? Um, okay.

Let's imagine that we have a set of theories, and we divide them into three groups.

Group A are theories which describe all current evidence and have N assumptions.
Group B are theories which describe all current evidence and have N+1 assumptions.
Group C are theories which either don't describe all current evidence, or use some different number of assumptions.

Now, the additional assumption in group B gives members of this group more freedom: they can be far, far more different from one another than the members of group A. This indicates that the members of group A are more likely to be close to reality (because they are closer to one another) than the members of group B.

Of course, we can't say that the members of group A are likely in an absolute sense, because we don't know if N is the minimum number of assumptions possible, and future experiment may rule out the members of group A entirely. However, due to the much greater number of members of group B, any specific choice of a member of group B is still unlikely to be correct.

 

[Calrid]

What, do you want a derivation of Occam's Razor? Um, okay.

Let's imagine that we have a set of theories, and we divide them into three groups.

Group A are theories which describe all current evidence and have N assumptions.
Group B are theories which describe all current evidence and have N+1 assumptions.
Group C are theories which either don't describe all current evidence, or use some different number of assumptions.

Now, the additional assumption in group B gives members of this group more freedom: they can be far, far more different from one another than the members of group A. This indicates that the members of group A are more likely to be close to reality (because they are closer to one another) than the members of group B.

Of course, we can't say that the members of group A are likely in an absolute sense, because we don't know if N is the minimum number of assumptions possible, and future experiment may rule out the members of group A entirely. However, due to the much greater number of members of group B, any specific choice of a member of group B is still unlikely to be correct.

I don't know why you are answering this point as I and other posters have pointed out Occams razor is worthless without a theory with which to compare yours and my two suggestions are hypothesis. So if you want to compare String theory say (with multiple Universes) and Bounce theory with just one then all you have is a matter of opinion. If you're trying to suggest which one you think is most likely to be true fine I agree to some extent that many universes is quite attractive, however its qualities do not denote its degree of verracity. I disagree with your assertions simply because they are opinions, but then discussions on hypotheticals are always a matter of opinion since facts are not present. I could quite easily argue FSM done it and that therefore the values are what they are because FSM is perfect, and you wouldn't be able to disprove that either, philosophically or scientifically for that matter.

You can't get around basic scientific axioms like the method by arguing about the philosophy of a subject, even if you are a String Theorist, or a Cruncher you still aint going to win no Nobel science prizes for a matter that has yet to be tested.

I'm not saying you are a String theorist btw although you might be, I am just using them as examples of "theories" that are often at odds in terms of the origins of the Universe.

I seem to use this phrase a lot lately but it is very apposite:

"Existence is not a predicate."

Emanuel Kant.

It was actually mooted to contend with the ontological argument, but it does just as well here. No scientific theory is based on a quality something has real or imagined, it is based on a quantity. Weighing hypothesis is a pointless exercise, because without any means to test them they are equally undistinguished. God does not exist because he is the greatest thing you can imagine any more than multiple universes is truthier because of some razor, both predicates are axioms without a basis.

In physics, maths is the engine, and evidence is the axle on which the wheels turn. You are going nowhere without either.

I disagree that multiple universes is simpler, you'd do better to dispute that, the fact is though that either way if you win that point nothing has been settled.

Here's an example of two valid areas where we can contend on the basis of occams razor although nothing will be settled absolutely:

MoND (Modified Newtonian Dynamics) and Dark matter are both theories that explain the discrepancies in cosmology with tentative evidence. Which one would you contend is the simplest or most parsimoniuous. Which one would you then suggest was most likely true? What made you come to that conclusion? Was it simplicity, the maths, or the evidence?

End of the day its a nice and practical means of applying science but the results of experiment trump pithy philosophical axioms. If gravity is really weaker at greater distance by a relation that isn't exactly the inverse of r^2 then it will mean that Dark matter is either wrong, or that it is an incomplete answer. Whether it was a simpler solution or not counts for nothing and in fact you could probably argue MoND is simpler but it is not really very easy to model mathematically so it displeases people on aesthetic grounds. Another quality that means nothing in science incidentally.

Incidentally both MoND and dark matter could be true, its an option most people don't usually consider.

And as I said you kind of destroy your own point anyway because we don't have any theories all we have is ideas atm.

Long story short as I'm boring myself now:

On your basis FSM wins because it is a simpler explanation which is kinda funny really.

FSM fits because it has only one assumption and that is god created everything just so hence reality.

Assuming that there are multiple universes is just as big an assumption (by which I mean it requires the same number of assumptions 1) as assuming there is one that endlessly recycles itself also so again that destroys your point they aren't even distinguished here.

I'd like to hear your default argument again that was triffic, completely ungrounded but very interesting..?

 

[Chalnoth]

I don't know why you are answering this point as I and other posters have pointed out occams razor is worthless without a theory with which to compare.

We're comparing two theories:
Our universe exists.
Our universe exists + it's the only one.

The first one is more likely, because it doesn't have the additional assumption of uniqueness.

 

[Calrid]

We're comparing two theories:
Our universe exists.
Our universe exists + it's the only one.

The first one is more likely, because it doesn't have the additional assumption of uniqueness.

No we aren't what evidence do you have there are multiple universes?

You show me yours and I'll show you mine.

These are two competing hypothesis. Unless something dramatic happened and either Smolin or Susskind found evidence of multiple universes, stroke collapses while I wasn't looking.

Are you trying to suggest we know how the the universe came into being and what's more we know what is beyond it? Interesting...

Our universe exists and there are countless universes.
Our universe exists and there is only one universe.

Now you are being deliberately disingenuous.

Neither is more likely as I and someone else already pointed out that's not what Occams razor says nor does it have anything to do with weighing up hypothetical concerns in science.

Again uniqueness? Another qualitative statement, you appear to like quality over quantity. I wouldn't advise a career in science if that is the case. Although it makes a good rule of thumb in day to day life. :tongue: