Why Stephen Hawking says universe can create itself from nothing?

[Mordred]

I read that article before the other thread you mentioned. I ran into the problem of finding references to Bunch-Davies vacuum. As a result I've been having trouble understanding it. Anyone have a good reference link?

Edit a couple of posts occired while I wad typing I am referring to the last post by Naty

 

[big_bounce]

This statement makes no sense whatsoever. Energy is a physical property of matter (pedantically, it is a property of every quantum-mechanical field).


This is also incorrect. Just because we don't know how these physical quantities arose, that doesn't mean that you get to automatically substitute your favored explanation in its absence.

Best to say just kinetic energy is a property of matter , because energy is a quantity which comes in many forms .
Anyway see the figure from University oregon :
http://abyss.uoregon.edu/~js/images/energy_to_mass_Uni.gif

We know matter has charge , momentum .
Can you explain how momentum and charge and other quantities came from pure energy universe ?
If there was nothing expect energy these quantities came from what ?

 

[Naty1]

I ran into the problem of finding references to Bunch-Davies vacuum.

Here is something I recalled from bapowell:
Post #38, here...

https://www.physicsforums.com/showthread.php?p=3848630&highlight=bunch+davies#post3848630

It is true that any particles hanging around at the start of inflation were most certainly redshifted away, exponentially diluted by inflation. However, it's not this simple, because if there are particles present at the start of inflation, then the fluctuations are not born in the vacuum as per the standard density perturbation calculation. If the initial state was thermal rather than vacuum (known as the Bunch-Davies vacuum), then the perturbations are affected; in particular, power is suppressed on large scales (see http://arxiv.org/abs/hep-ph/0508070). Non-vacuum initial states can also generate non-Gaussian temperature fluctuations: http://arxiv.org/abs/0710.1302.

Now, the reference that Marcus linked to is to my knowledge rather novel, having to do with the stimulated generation of quanta during inflation on account of the presence of particles at the beginning. So, even though the original particles are redshifted away, their presence induces measurable effects on the evolution of perturbations.
If the negative gravitational pressure of inflation 'got stuck' briefly on an energy plateau, why not other factors conducive to particle production..like,maybe, virtual particles of the vacuum??...antimatter?? were NOT diluted...
The virtual particles are not diluted because they are continuously being created!...

 

[Mordred]

Thanks Naty that thread you posted is a great help

 

[Chalnoth]

Are these necessarily different perturbations...??

In a very new series of papers from Ashtekar, et al, [recently discussed here] it seemed the authors had found consistent inflationary perturbations all the way back in the Planck regime...

No. One is talking about small perturbations that grow to become differences in density from place to place. The other is talking about the beginning of inflation itself.

Using LQG ideas and techniques, we have extended the inflationary paradigm all the way to the deep Planck regime. At the big bounce, one can specify natural initial conditions for the quantum state Ψo that encodes the background homogeneous quantum geometry, as well as for ψ that describes the quantum state of perturbations. There is a precise sense in which generic initial conditions for the background lead to a slow roll phase compatible with the 7 year WMAP data...

[I think Marcus had started a thread referencing these papers, but I did not record the thread link..]


A Quantum Gravity Extension of the Inflationary Scenario
Ivan Agullo, Abhay Ashtekar, William Nelson
(Submitted on 7 Sep 2012)
http://arxiv.org/abs/1209.1609

In the bounce model, the initial start of inflation is a consequence of the previous collapse, and has nothing to do with quantum vacuum fluctuations at all. This is a completely different model from the one I described previously (and personally, it's one I am incredibly skeptical of, due to entropy considerations).

 

[Chalnoth]

Best to say just kinetic energy is a property of matter , because energy is a quantity which comes in many forms .

Nope. All energy is a property of some sort of field (which I was loosely calling 'matter').

Kinetic energy is an energy of motion of a particle.
Mass energy is the energy in the internal degrees of freedom of something (e.g. most of the mass of protons is in the binding energy between the quarks, and the masses of the quarks themselves stems from an interaction with the Higgs field).

Other forms of energy are about aggregate behavior of multiple particles/fields.

 

[Chronos]

From a quantum point of view, 'nothing' would be unstable because it would be a pure state.

 

[rbj]

From a quantum point of view, 'nothing' would be unstable because it would be a pure state.

i wouldn't mind if someone would explain to me what is meant by a pure state and why that affects its stability.

i was watching an interview with Michael Shermer (on closertotruth.com) where he said things very similar to what he wrote in http://www.skeptic.com/eskeptic/12-07-11/ .

i sort of get that something is "stickier" than nothing.

it's like if you have nothing, and and every perturbation of it that makes it different, gets you something. then if you have something, there are infinitely many perturbations that are still something. only one very unlikely perturbation of something results in nothing. that appears to make something more stable than nothing.

something is like the toothpaste outa the tube. kinda hard to get it all back in.

that's the best understanding of the case i could make. but it's not a very causal model of reality, but neither, i guess, is QM.

BTW, in case you think that i only see things from my "own worldview", if you're not familiar with Shermer, please check him out.

 

[Mordred]

I had to read that a few times to get the gist of it lol. It sounds like once you have something its difficult to return to nothing. Theres some logic to that.
I wish I could help you on pure states. My current QM knowledge only amounts to understanding pure states in regards to spin. So its better if someone else answer that query.
I've read some of Shermers articles, some of them I thoroughly enjoy.

 

[Tanelorn]

Interesting thread…

Is this equivalent to saying that nothing temporarily became something before eventually returning to nothing?

Is this saying that the Universe began with an unwinding or releasing of potential energy from some kind of highly compressed state of space time? And also that the energy released by this event created sub atomic particles which eventually formed the various forms of matter and energy that we see today? And further that this matter will ultimately decay to nothing thus returning the Universe to its initial state of nothingness?

If so doesn't this still need the energy to come from somewhere at the beginning?

 

[dkotschessaa]

Hi folks:

Not an easy answer, even among "experts."

Here's Lawrence Krauss speaking on this topic - hour long video:

https://www.youtube.com/watch?v=0ZiXC8Yh4T0

Here's a bunch of physicists, and a mathematician having basically the same argument you guys are having at a recent "debate."

2013 Isaac Asimov Memorial Debate: The Existence of Nothing

https://www.youtube.com/watch?v=1OLz6uUuMp8


What I took away from the second (haven't watched the first) is that our definition of "nothing," as Degrasse Tyson points out, seems to change over time. We tend to call "outside" stuff "nothing," then we start to realize that that nothing has certain properties (like energy). Then we start to question whether that really qualifies as a "nothing." Eventually we might say, "ok, so that's not a nothing - so what's outside that?"

This debate (I wouldn't really call it a debate - more of how these guys talk casually on these topics) is pretty entertaining.

Enjoy.

-Dave K

 

[Chalnoth]

A description I used to use all the time just came back to me:

One thing that we found out with quantum mechanics some decades ago was that the mere potential for there to be photons, electrons, and other assorted particles in existence forces those particles to pop in and out of the vacuum all the time. Maybe, if we gain a deeper understanding of physics, we will find that the mere potential for a space-time to exist forces space-times to pop into existence in an analogous way.

 

[skydivephil]

I think this is what Vilenkin was getting at in his 1982 paper:
http://mukto-mona.net/science/physics/a_vilinkin/universe_from_nothing.pdf
What do you think?

 

[dkotschessaa]

http://www.csmonitor.com/Science/2013/0325/Scientists-examine-nothing-find-something[/URL]

"Two studies of vacuums suggest that the speed of light in a vacuum might fluctuate, pointing the way to a quantum mechanical explanation for why the speed of light and other so-called constants are what they are."

Ah, nothing. It ain't what it used to be...

 

[Chronos]

A pure quantum state is unstable due to quantum fluctuations. It requires, however, a time-like operator for phase changes to occur. But, time is also not immune to quantum fluctuations. A perfect convergance of these events appears a prerequisite for the emergence of our universe. Does that imply quantum states are fundamental constructs of reality - perhaps. It is, however, difficult to imagine reality with fewer variables.

 

[nazarbaz]

If you don't buy the "universe from nothing" hypothesis you'll be stuck with some sort of eternal or infinite physical structure that has no beginnings and no endings to trigger the epiphany of our universe or many other ones... The two contradictory hypotheses (although it's not obvious that they are mutually exclusive) are equally mind boggling and unlogical from the standpoint of our ordinary perception...
May be the problem itself is meaningless... Fundamental questions must be asked though : what could be a time duration and a cosmological generation process from a pre-cosmological point of view ? Linear or non linear, Classical, semi-classical, deterministic, non deterministic, causal or non causal ? Are quantum mechanics and general relativity appliable to the "landscape" supposedly prior to our universe ?
We don't have a clue to answer these questions and I suspect that we're not even setting the problem as it should be with our dichotomy between spontaneous and random generation or eternity and infinity... What is this idea of an inside of the universe and an outside to it, first ?

 

[Crazymechanic]

Well I will add that some people are usually confusing things and biasing opinions and usually not only the philosophers , poets, religious fanatics are doing that also the mathematicians and physicians are doing the same mistake.

Mathematics is one way of describing something or the inner working or mechanism of it but logic is a much bigger subfield than mathematics as there is logic in mathematics just as much there is logic when two people love each other get married and raise children.Now good parents love their children and the average human being thinks it should be that way because it just seems logic to us , yet there is no mathematics involved.
Let's not confuse logic as logic can be and has to be in any field if someone wants to get to a better understanding or a goal because I don't know how nature does it (haven't talked to her lately) but we humans need logic and only upon that we can build something that works for our understanding to understand the universe, or stars or whatever is there.

Now to @Micromass how have we arrived at any new experimental evidence ? We follow some kind of logic that we think is underlying in a certain process and then do the experiment , now not always has this been the case but in many times stuff has been predicted years before the actual proof took place.The problem is I believe and my knowledge so far tells me so (logic again) that there are certain things we will just have to follow our best logic because we will not be able to reproduce them ever , theoretically doesn't count here, things and events like the big bang , light (em radiation)itself was born with it we have no probe that we could stick into see what was before the singularity not to mention that we cannot go backwards in time even if we one day will have such a probe (very unlikely) Now as some people already told here I think that when talking about these cosmological events the best way we can assure and test our theory is with logic, math and empirical leftovers like the CMB radiation and in the future possibly from better understanding of black holes and their singularities and other cosmological events that are or will be going on at the time.
And even with that we will never be able to be 100% sure.But then again there are very few things in advanced physics theories that can be 100% accurate as we are in a forever (atleast from our point of view) advancing towards something better and more precise.

Now to address the OP question I think Stephen Hawking says so because his Stephan Hawking , and another man in the same rank as him could disagree with that or partly agree or anything else because this particular thing is a part of a bigger theory but this part cannot be verified empirically atleast not now so in this case it is just a reasonable speculation actually.We have to remember that speculation is not always the one that comes from crackpots telling you that Earth is flat , speculation can also be at much advanced levels and it occurs whenever someone either rejects the empirical truth and makes his own biased and flawed opinion or when someone knows something up until a point beyond which he can't or doesn't know further and then he has to begin to make a further argument based on his logic and maths but still until proven it is a mere speculation so everyone can fall victim of this no matter how intelligent or high the rank.It's up to everyone to decide do they agree or not.When empirical evidence kicks in then there is no more a choice for disagreement rather just understanding the facts.

And yes to WannabeNewton even though this is a scientific debate I would not be that determined and cruel towards philosophy.Even though it doesn't deal with things like 2+2 but then again one has to ask himself are we just pure devices with some understanding or is there more to life than that.Now before we don't have all the answers and arguments either for or against that I would be more careful to put some disciplines in the trash can.Who knows you might have to later pick them up and reevaluate.

 

[eltodesukane]

Why not?

We are here, somehow out of nothing!

Let me quote from this link:
http://ned.ipac.caltech.edu/level5/Guth/Guth3.html
The resolution to the energy paradox lies in the subtle behavior of gravity. Although it has not been widely appreciated, Newtonian physics unambiguously implies that the energy of a gravitational field is always negative a fact which holds also in general relativity. [..] The possibility that the negative energy of gravity could balance the positive energy for the matter of the Universe was suggested as early as 1932 by Richard Tolman, although a viable mechanism for the energy transfer was not known.

During inflation, while the energy of matter increases by a factor of 10^75 or more, the energy of the gravitational field becomes more and more negative to compensate. The total energy - matter plus gravitational - remains constant and very small, and could even be exactly zero. Conservation of energy places no limit on how much the Universe can inflate, as there is no limit to the amount of negative energy that can be stored in the gravitational field.

 

[Chronos]

Stephen Hawking is talking about a special case of 'nothing', which is a quantum state of the vacuum. A philosophical state of 'nothing' has no causal properties. The only choices I see are:
1] the universe supernaturally arose from a state of philosophical 'nothingness'
2] it arose from a quantum state [implying quantum states are somehow 'fundamental']
3] it has always existed, but, undergoes periodic phase changes [which ducks the question entirely]
Many scientists are attracted to choice #3, although it is no more satisfactory than 1 or 2.

 

[Chalnoth]

Stephen Hawking is talking about a special case of 'nothing', which is a quantum state of the vacuum. A philosophical state of 'nothing' has no causal properties. The only choices I see are:
1] the universe supernaturally arose from a state of philosophical 'nothingness'
2] it arose from a quantum state [implying quantum states are somehow 'fundamental']
3] it has always existed, but, undergoes periodic phase changes [which ducks the question entirely]
Many scientists are attracted to choice #3, although it is no more satisfactory than 1 or 2.

There are some difficulties with something arising out of nothing, when nothing doesn't experience time.

I really don't think you can describe a universe that is finite into the past in such terms. Rather, you'd have to have something similar to Hawking's no boundary proposal, where the "beginning" that we see is quite analogous to the north pole: the north pole is only special because of our definition of "north".

 

[eltodesukane]

"There are some difficulties with something arising out of nothing, when nothing doesn't experience time."
I agree with you.
Maybe the mere self-consistence of a mathematical structure makes it real.

 

[jerryboy]

The problem, whether you believe the universe was a nothing or a something is that the meaning of ...let's call it "something" with infinite energy and density is essentially meaningless because anything collapsed into singularity will take on the same characteristics. Take a loaf bread and crunch it into a singularity. You still get infinite temperature and density. These characteristics are artifacts of the mathematical equations but meaningless in the real world. This is because the singularity has no space. Without mass temperature and mass or density are meaningless. Krauss does have a whole book on this but his evidence is based on quantum vacuums which are definitely not nothings. If true then why haven't these expressed themselves in our universes by opening new universes here and there spontaneously, or even Black Holes, he presents no evidence that singularities are unstable. Harris is brilliant when it comes to Dark energy and matter, but when it comes to cosmology he's out of his league . The little gap between nothing and everything that ever was and every will be, cannot have characteristics since it is nothing.

 

[Chalnoth]

"There are some difficulties with something arising out of nothing, when nothing doesn't experience time."
I agree with you.
Maybe the mere self-consistence of a mathematical structure makes it real.

I think this is probably closer to the truth. Though sadly, we may never know.

 

[CosmicEye]

Watch Stephen Hawking's Grand Design. There was one where he talks about the relationship of time and the Big Bang, but also answers your question with logic that it came from literally nothing. Personally I lean towards the M-theory but it was something great to think about.

 

[nazarbaz]

Maybe what we call time (the flow of change from past to future states) is simply an equivalent to a quantum fluctuation of space: the degrees of freedom in which one single moment occur.
Ok, I'm speculating.

 

[A_Seagull]

mathematics is about quantity (among other things like structure, but mainly about quantity). except in the boolean sense, logic need not be. and although quantity can be assigned boolean variables, it need not be. "value" is not exactly the same thing as "quantity".

logic, as a discipline, contains mathematics (when quantity is introduced to the discussion), and science (when the empirical and material are introduced to the discussion), and sociology, politics, and law (when human beings and human behavior are brought into the discussion), and, if i dare say so, religion (when notions of God and the metaphysical are brought into the discussion). and even this statement from me is also not sufficiently broad.

Mathematics is actually about numbers. At least pure mathematics is. In order for mathematics to be applied to physics and other aspects of the real world some form of mapping is required that associates some part of mathematics with some aspect of the real world.

Strictly speaking deductive logic only applies to the labels that are words and not to the meanings of those words. The meanings of the words are too complex to be manipulated by simple logic. In this respect, mathematics and logic are distinct systems. Though by extending the axioms of each there may be overlap.

 

[Chalnoth]

Mathematics is actually about numbers.

No, it really isn't. Mathematics is about the study of self-consistent logical structures. Some of those include numbers, or can be represented in terms of numbers, but numbers are only a tiny part of the picture.

At least pure mathematics is. In order for mathematics to be applied to physics and other aspects of the real world some form of mapping is required that associates some part of mathematics with some aspect of the real world.

As the real world must be self-consistent, there is a mathematical structure which is the real world. We don't yet know what that structure is, but the purpose of physics is, essentially, to discover it.

 

[jerryboy]

Concentrated potential energy Prior to Planck time is an interesting hypothesis. But then where did that energy come from and what caused it to breach the Planck Boundary. Did this energy create itself from nothing and how did time create itself from pure energy. Are we then embarking on a new causal chain ending where? Pre-Planck energy is a something. Every something must have a cause. Only nothing can be not caused. The hypothesis only ivents a new causal layer leaving and requiring a new explanation and new cause. Problem not solved.

 

[A_Seagull]

No, it really isn't. Mathematics is about the study of self-consistent logical structures. Some of those include numbers, or can be represented in terms of numbers, but numbers are only a tiny part of the picture.


As the real world must be self-consistent, there is a mathematical structure which is the real world. We don't yet know what that structure is, but the purpose of physics is, essentially, to discover it.

I am not sure that it is particularly effective to claim that all self-consistent logical systems are a part of mathematics. What about Conway's game of life - is that to be considered a part of mathematics?

Even parts of mathematics are not entirely consistent with itself. For example modular arithmetic uses the same symbols as ordinary mathematics but its theorems are distinct. They require an identifier to show that they are not a part of ordinary mathematics e.g. 3+5=2 (mod 6).
If a system is self consistent within itself, what advantage is obtained by claiming that it is a part of the system of mathematics?

Regarding the nature of the physical universe, one does imagine that it is 'self consistent', but this may not necessarily be so. There could be an inherent inconsistency but one which is minor amount that it only destabilises universe at a rate which is slow enough as to be insignificant on a timescale of billions of years.
It could even be argued that the universe requires some form of instability or inconsistency, for otherwise it could never have been formed in the first place.
There is also the possibility that there is an inherent randomness in the universe that defies logical analysis as suggested by the results of Q M experiments.

There is also the problem of how it is possible to know whether the mathematical representation of the physical world is actually the one by which the universe actually operates. The mathematical representation may be highly accurate but no one seemed to be no definitive way of determining whether it is actually identical with the physical world.
For example, it has been noted that the universe works using modular arithmetic - modulo (10^~300). How would it be possible to distinguish the universe using ordinary mathematics (modulo infinity if you like) and one using modulus of a finite number?

 

[Chalnoth]

I am not sure that it is particularly effective to claim that all self-consistent logical systems are a part of mathematics. What about Conway's game of life - is that to be considered a part of mathematics?

Yes. It's a cellular automaton.
http://en.wikipedia.org/wiki/Cellular_automaton
"A cellular automaton (pl. cellular automata, abbrev. CA) is a discrete model studied in computability theory, mathematics, physics, complexity science, theoretical biology and microstructure modeling."
(emphasis added)

Even parts of mathematics are not entirely consistent with itself. For example modular arithmetic uses the same symbols as ordinary mathematics but its theorems are distinct.

This isn't an inconsistency in any real sense. An inconsistency is where within a particular mathematical structure, it is possible to prove a statement to be both true and false. This isn't possible as long as the rules of the mathematical structure are followed (because allowing such inconsistencies allows any statement in the structure to be simultaneously true and false).

Regarding the nature of the physical universe, one does imagine that it is 'self consistent', but this may not necessarily be so. There could be an inherent inconsistency but one which is minor amount that it only destabilises universe at a rate which is slow enough as to be insignificant on a timescale of billions of years.

Without consistency, nothing can make sense. For example, if I allow integer division by zero, I can prove that any number is equal to any other number, which completely destroys the ability of the theory to do anything at all.

That said, real structures used to describe our universe do have inconsistencies within them, but these are generally taken as evidence that the theory is incorrect in that regime. And, in fact, if we take the predictions of the theory seriously in those regimes where the theory becomes inconsistent, the theory loses all predictive power (because it can be used to predict anything). So what is done in practice is to cut out the part of the theory where the inconsistency arises (usually, but not always, this comes from some sort of division by zero).

It could even be argued that the universe requires some form of instability or inconsistency,

Instability and inconsistency are very different things. There is no sense in which an inconsistency propagates: if the inconsistency isn't strictly hidden and blocked from any interactions with the rest of the mathematical structure, it makes the structure completely and utterly meaningless.

 

[A_Seagull]

That said, real structures used to describe our universe do have inconsistencies within them, but these are generally taken as evidence that the theory is incorrect in that regime. .

And perhaps the theory is incorrect in every regime.

 

[Chalnoth]

And perhaps the theory is incorrect in every regime.

At some degree of accuracy, sure, they're necessarily incorrect everywhere due to the existence of inconsistencies. However, they are excellent approximations in all situations we've yet measured.