Why Stephen Hawking says universe can create itself from nothing?

In summary, Stephen Hawking says that the universe came from nothing, and that it required the energy of gravity and vacuum to balance out. He also mentions that energy cannot be created from nothing, and that all of the various particle production methods still hold true even if the energy density isn't zero.
  • #36
=sigh=
i noticed you avoided the question i asked.

oh well. it's tiresome to repeat, and my experience with you is that (repetition) is what has to happen to keep you on topic. or at least, on the narrow topic of the question asked.

Chalnoth said:
But when you say something is impossible, that requires a mathematical proof.

i wouldn't confuse the disciplines of "logic" and "mathematics". they're closely related disciplines but not the same. i would say that logic is a more primary discipline (i.e. mathematics necessarily employs logic but not the other way around). logic doesn't require quantitative foundation except for the boolean. i hope we don't get into a dispute of semantics.

and I've seen very goofy claims of "mathematical proofs" both from theists (like Stephen Unwin) who claim to "mathematically prove" God exists and atheists (like Richard Dawkins) who "mathematically prove" the opposite. both are goofy, so be careful with that semantic, Noth. you could be heading for a very unimpressive crash.

the question regarding what is possible is directed toward physical reality. so we're not talking about what is possible for Middle Earth and wizards like Gandalf the White vs. Gandalf the Gray. so, even though mathematics is necessary to describe physics (logic isn't enough, there are quantitative relationships involved), mathematics isn't sufficient. there are also the physical axioms.

i have a glimpse of the concept of a quantum fluctuation. i have a crude electrical engineer's concept of QM and understand what the quantity [itex]\Psi[/itex] is about. and regarding that, i understand that a particle like a subatomic particle can pop into existence at some place and time. or at least appear to when we measure things. the probabilities of such are reasonable for particles so small. but it seems like a fantastic stretch to apply that to entire universes. especially coming from people who reject the supernatural, it's as if they're just choosing a different supernatural, one more to their liking. I'm thinking of Dawkins, so please don't take this as directed toward you, Noth.

Now, it is conceivable that somebody might come up with a way to describe a universe's beginning without there being anything before (no space-time, no matter, nothing), but that comes with a significant problem: how do you describe 'nothing' mathematically?

empty set. i know, it's still a set. but that's why i am not on board with your semantic to begin with.

This doesn't mean it's impossible, but it does mean that we can't really start to examine the possibility without a coherent description of what 'nothing' actually means.

real "nothing" would be no physical quantity (what i like to call "stuff") and no relationships or law of interaction either. and no one around to behold it.
 
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  • #37
I notice you go to great lengths to avoid addressing real science issues by imposing logical constraints amenable with your world view, rbj.
 
  • #38
MathematicalPhysicist said:
That's really simple.

If you create something from nothing then that nothing becomes something, cause if it were nothing then how did we got something?

As I said it's not logical, and we might as well start believe in witches and fairies if that's what we come to believe.

I don’t agree. I explained it and you ignored my argument. What’s wrong with it?

To repeat:
Creation is going on all the time in so called empty space, with matter and antimatter particles annihilating each other, as a natural process.
If a similar process occurred at the start of the BB without a perfect annihilation, we would be left with separate amounts of matter and antimatter, adding to zero.

By the division of an original nothing into two positive and negative parts, there is a creation, but it doesn’t have to offend any laws of physics or logic, does it?

I agree that two separate and opposite quantities equating to zero are not nothing, but my explanation answers your question of how we got something from nothing, does it not?

Chronos said:
I notice you go to great lengths to avoid addressing real science issues by imposing logical constraints amenable with your world view, rbj.

I don’t know if the logical constraints which you say rbj seeks to impose are biased by his world view.

However, I do think that it is very necessary that we impose rational and logical constraints when we are addressing science issues, otherwise we get these accusations of witches and fairies.
Scientific theories and hypotheses have to stand the test of logic as well as mathematics.

.
 
  • #39
Johninch said:
Scientific theories and hypotheses have to stand the test of logic as well as mathematics.

Not at all. Scientific theories must only stand the test of experiment. If it turns out that experiment is incompatible with logic and mathematics, then logic and mathematics will have to change.
 
  • #40
micromass said:
Not at all. Scientific theories must only stand the test of experiment. If it turns out that experiment is incompatible with logic and mathematics, then logic and mathematics will have to change.

It's difficult to make experiments in cosmology, particularly concerning the BB, so we have to fall back on observations and mathematics. Ideally all the information should match. But I don't see how we can exclude logic - you mean we don't have to think straight?

The main problem with your argument is that you seem to be ignoring the necessity to interpret the results of experiments, as if they all lead to obvious conclusions. Quite apart from quality problems in the execution in some cases.

.
 
  • #41
Johninch said:
It's difficult to make experiments in cosmology, particularly concerning the BB, so we have to fall back on observations and mathematics. Ideally all the information should match. But I don't see how we can exclude logic - you mean we don't have to think straight?

You seem to be equation logic with thinking straight. Logic is a mathematical discipline with a very specific meaning.Furthermore, the current accepted logical system in mathematics is classical logic. This has already been shown not to model reality. So we already had to abandon (classical) logic and find a new kind of logic.

The main problem with your argument is that you seem to be ignoring the necessity to interpret the results of experiments, as if they all lead to obvious conclusions. Quite apart from quality problems in the execution in some cases.

I don't see how I ignored anything. In science, you make experiments and observations to test your theories. If eventually they seem to contradict the established theory (and if there are no errors), then the theory is wrong. This includes logic and mathematics. I see no a priori reasons why mathematics should be able to model this world. In fact, I speculate that it probably doesn't (but this is just a guess, I have no single shred of proof or evidence for it).
 
  • #42
marcus said:
When inflation was first proposed, folks couldn't think of what might have caused it so they came up with all sorts of ideas like "quantum fluctuation" and "eternal" and "anthropic" (to explain why a quantum fluctuation would produce the right amount of inflation which would then conveniently stop). It was a large exercise of the imagination, which is certainly fine up to a point.
Guth strikes me as coming from an earlier era. But maybe he defines inflation for the general pubic. A lot has changed though. Guth, Hawking, Vilenkin, Linde don't write so much any more, or their papers don't get quite the same amount of attention. Here are some recent papers where inflation comes from *something*. There's growing interest in this (which again does not prove it's right.)

As stated I went and looked into the history of developments on the various inflationary/expansion models. After some extensive searching I realize what your saying in your previous post.

Here is what I've found out.

false vacuum became old inflation later replaced by new inflation. Due to problems in new inflation it later became chaotic eternal inflation. There are other models that derived from the original false vaccuum. However all these models failed to solve one key problem that of pocket/multi universe formation.
As far as I can tell string theory is currently working with Guth I can't recall what string theory model is representative in this line of research DQ something lol. I don't follow string theory it makes my teeth ache.

This paper is the latest I could find that involved false vacuum
http://arxiv.org/abs/1112.3005

At first I thought of starting a new thread on it however I quickly realized that there are aspects in it that I don't quite agree with. However that's another topic.
 
  • #43
Chronos said:
I notice you go to great lengths to avoid addressing real science issues by imposing logical constraints amenable with your world view, rbj.

Johninch said:
I don’t know if the logical constraints which you say rbj seeks to impose are biased by his world view.

besides that, i would like to know what real science issues i am going to great lengths to avoid. what are they? certainly not that "science" is about what is material and empirical. that real science issue is something that i push relentlessly.

perhaps it's that i don't afford "science" the totality of reality in my worldview. (i.e. i do not subscribe to the belief system of "Materialism" or "Physicalism". and, BTW, neither do John Polkinghorne, Freeman Dyson, or Owen Gingerich as best as i understand what they say and write.) is that it, Chronos?

However, I do think that it is very necessary that we impose rational and logical constraints when we are addressing science issues, otherwise we get these accusations of witches and fairies.
Scientific theories and hypotheses have to stand the test of logic as well as mathematics.

it looks like PF Mentor micromass has weighed in on this issue on the other side. and, from previous experience, i have to be careful not to say something that whoever admin doesn't like (Greg seems to be fine, but it's the captains under him).

anyway, having done work in science (only in acoustics - totally classical physics), engineering mathematics, and in logic, i must dispute a few things said here:

logic is not a sub-discipline of mathematics but it is the other way around.

i would disagree with this:

micromass said:
Scientific theories must only stand the test of experiment. If it turns out that experiment is incompatible with logic and mathematics, then logic and mathematics will have to change.

even when the experimenter is hallucinating? when the astronomer is peaking into his telescope and sees teapots or spaghetti monsters or even the same guy with a beard in Michelangelo's Sistine Chapel painting, he might need to question the empirical outcome of the experiment.

micromass said:
You seem to be equati[ng] logic with thinking straight.

he's not the only one. so did Aristotle (and quite a few others of his descent). might want to look up "logic" and "term logic" in wikipedia. (again, not to say that wikipedia is accurate in all things, but this looks reasonably decent.)

these formal rules of logic are solely about thinking straight. it's about applying consistency and about being clear about what a premise says and what it does not say.

Logic is a mathematical discipline with a very specific meaning.

perhaps logic in mathematics is a mathematical discipline, but otherwise that statement is false in that it is not sufficiently broad.

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.
 
  • #44
rbj said:
real "nothing" would be no physical quantity (what i like to call "stuff") and no relationships or law of interaction either. and no one around to behold it.

The link below is including so many physical quantities that exist in universe .
Can you prove these quantities came from energy ? or came from another quantity ?
If you can not , that mean they came from real "nothing" .

http://en.wikipedia.org/wiki/List_of_physical_quantities
 
  • #45
This is what happens when you abandon a mathematical discussion and start arguing metaphysics and philosophy which are disciplines that go nowhere and terminate in pointless non mathematical / non empirical arguments and frankly Chalnoth hit the nail on the head many posts ago when he said "We don't know" as of now.
 
  • #46
big_bounce said:
The link below is including so many physical quantities that exist in universe .
Can you prove these quantities came from energy ?
This statement makes no sense whatsoever. Energy is a physical property of matter (pedantically, it is a property of every quantum-mechanical field).

big_bounce said:
or came from another quantity ?
If you can not , that mean they came from real "nothing" .
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.
 
  • #47
WannabeNewton said:
This is what happens when you abandon a mathematical discussion and start arguing metaphysics and philosophy which are disciplines that go nowhere and terminate in pointless non mathematical / non empirical arguments and frankly Chalnoth hit the nail on the head many posts ago when he said "We don't know" as of now.

Well said I for one, like many others have gotten tired of the pointless bickering going on.
Debating is one thing, provided supporting articles, mathematics or reasonable analysis is included is one thing.
Personal based arguments is quite another.
If you have a problem with a model, then take the time to provide supporting evidence or problems with THAT given model.
If you look at this thread carefully enough some of the problems of false energy has been stated. The one that stands out the most is the problem of stopping the inflation.
That lead to a multiple of alternate modifications. Some of which I listed.
If I as NON scientist can spend the time looking for problems in a given model AND supply supporting material. Then so can anyone else.
 
  • #48
Chalnoth posted:

...These fluctuations are the ones that started the initial density perturbations which eventually grew to be the galaxy clusters and voids in our universe today. These are not the fluctuations which might have gotten inflation started, but rather the ones that were occurring as inflation was progressing...

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...


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


The pre-inflationary dynamics of loop quantum cosmology:

Confronting quantum gravity with observations
Ivan Agullo, Abhay Ashtekar, and William Nelson

...Using techniques from loop quantum gravity, the standard theory of cosmological perturbations was recently generalized to encompass the Planck era. We now apply this framework to explore pre-inflationary dynamics. The framework enables us to isolate and resolve the true trans-Planckian difficulties, with interesting lessons both for theory and observations. Specifically, for a large class of initial conditions at the bounce, we are led to a self consistent extension of the inflationary paradigm over the 11 orders of magnitude in density and curvature, from the big bounce to the onset of slow roll.
 
  • #49
Certainly. Anything with "Nothing/create" are good catch phrases. Zero/uncertainty to entropy to universe. Might want to check "The information as absolute" by S.V. Shevchenko, V.V. Tokarevsky.

http://arxiv.org/abs/1004.3712.

In informational conception the unique fundamental essence that exists is absolutely infinite Set “Information”, which include, for example, subset “Matter”; all what one sees is/are “words”.
Any element of the Set contains the Set totally because of to define the element is necessary to point out all differences of given element from every other element in the Set. The element “nothing” is only one of the Set’s elements –i.e. dynamical null set.

'Nothing' is fairly complicated stuff. You have to define nothing in specific way. The idea of "nothing" stems from this notion of a collection and analogous to empty set. So we can think of "nothing" as a term describing the set itself and not a necessity of zero in mathematical language. The universe might came from uncertainty. Nothing can only make sense if given limitations but can be use in both accounts.

Nothing is our imaginative construct to make sense of specific order in a specific task. It is associated with the mathematicians new concept of "zero" (as a number without any magnitude). It is a formal "nothing", like zero, but made up of +1 and -1, or equal amounts of positive and negative charges, or even completely balanced forces which give the appearance of zero activity, and, of course, many others of similar ilk.

To say that the universe came from nothing is a "fair assumption" relative to what we 'currently' know to a certain (v) degree of confidence.
 
  • #50
WannabeNewton said:
... and frankly Chalnoth hit the nail on the head many posts ago when he said "We don't know" as of now.

it hadn't been the instances when Chalnoth says "We don't know" that i had ever disputed what he/she said.

it was, in fact, the instances when he should have said "We don't know", and said something quite different (and virtually diametrically opposite) that i took issue with what he said. at least in the other multiverse thread.
 
  • #51
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
 
  • #52
Chalnoth said:
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 ?
 
  • #53
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!...
 
  • #54
Thanks Naty that thread you posted is a great help
 
  • #55
Naty1 said:
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.


Naty1 said:
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).
 
  • #56
big_bounce said:
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.
 
  • #57
From a quantum point of view, 'nothing' would be unstable because it would be a pure state.
 
  • #58
Chronos said:
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.
 
  • #59
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.
 
  • #60
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?
 
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  • #61
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
 
  • #62
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.
 
  • #63
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?
 
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  • #65
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.
 
  • #66
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 ?
 
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  • #67
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.
 
  • #68
Chalnoth said:
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.
 
  • #69
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.
 
  • #70
Chronos said:
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".
 

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