Something and Nothing of Universe

xantox

It is true that it is less used, I did not oppose that. But note that the originators did not apparently consider it a misnomer at all, as Vilenkin considers it literally nothing, such as in "nothing is nothing". While it is true that this choice of term was also a way to emphasize the provocative character of the new proposal, it should also be carefully considered that "vanishing of classical fields" is a rather good physical definition of "no-existing-thing", "things" being implicitly classical entities in spacetime and unless we can try to come up with an even better physical statement roughly corresponding to the everyday word "nothing" which however I don't know of. There is a respectable western philosophical tradition, which you're in fact following, believing to be able to define more absolute notions of 'nothing' on purely logical terms but which I consider profoundly misguided.

Thank you, but it's not xantox' definition but Vilenkin'. Note that I'm not arguing to affirm my personal views or to contradict yours but to restate those historical facts which originated the expression discussed in this thread. Also, no final word has been spoken on tunnelling theories which remain extremely attractive and it would seem likely that they will also at some point get restated as approximations of newer theories.

Anyway, concerning LQC, there is a theoretical reason preventing to say the universe "came from nothing", since in Bojowald's theory there is a deterministically evolved transitory bounce at nonzero volume from a pre-big bang classical state. This reason is however not present for example in Loll's CDT, where the scale factor vanishing dynamics behaves quite similarly to Vilenkin theory (even if it has some essential differences in respect to a tunnelling scenario). It is perhaps not entirely semantically random that Loll wrote an article in 2007 and gave a conference in 2002 on the theme "Spacetime from nothing".

Note that there are also other more extreme possibilities, such as a completely vanishing wavefunction in the forbidden classical state.

marcus

Pretty nearly semantically meaningless. Loll's simulations do not start from nothing. They start from a minimal set of simplices. I forget how many, a dozen maybe. This continues along for a while and then takes off. At no point in the simulation are there zero simplices.

I think when Loll says "universe from scratch" she means that she gets something like a classical spacetime to emerge from very minimal fundamental elements. This doesnt refer to emergence in time but from a minimal ground---the simplest logical components.

What is the 2007 article where she says 'emerged from nothing'?

marcus

Good, that was the point I was trying to make.

There has been a change in language among professional researchers.
It was fashionable to say 'nothing' in the 1980s and 1990s. (When Vilenkin was doing what he's mostly known for.)

It has gone out of fashion.

Penrose pointed out the change in fashion in 2005 in a very pronounced way about the time he began presenting his own version of the "something" before the bang started.
It is good for lay people, I think, to realize that the prevailing professionals no longer refer to pre-bigbang conditions as 'nothing'.

marcus

Thomas, I agree wholeheartedly! A lot of boring rubbish can come about when apparently educated folks keep on misappropriating an ordinary language term to mean something entirely different. Especially when it stimulates laymen and they seize on the misunderstood idea. I see that Hurk also agrees with you.

Vakkim, that is beautiful poetry! I really like it as poetry. So let's not disparage it.
The only error or dishonesty is when religious mystics, christian and other, pretend that science supports the idea of an origin out of a mysterious nothing.

Scientists are against that idea and are working very hard on geometrical models that will not break down at t=0 and will go back and describe earlier conditions. It is an exciting time in what is called quantum cosmology.
The cosmology of the extreme conditions around the start of expansion.
If you want to get perspective on what the leading ideas are since 2005, you can do a search on the physics database at Stanford. It is called Spires.
http://www.slac.stanford.edu/spires/...tecount%28d%29
The leading ideas are the ones that show up in the top-cited 30 or 40 papers, when you search with keyword "quantum cosmology" date >2005 and have the hits ranked by number of citations (how often other scholars have referenced the given publication)

xantox

Here you use "nothing" in a purely logical definition applied to the theory itself. The point I was trying to make is that the only meaningful use of "nothing" in physical terms is here actually the one corresponding to Vilenkin' definition.

So, the confusion in the use of this terminology (and I agree there is a confusion, so better avoiding it so everyone will be happy, but disagreement is always good as it can usually lead to more fine-grained concepts) is not originating from Vilenkin' physical definition, as you believe. The confusion is originating, to the opposite, from the false philosophical belief that concepts like "nothing" or "exist" could possibly receive an absolute physical meaning. Don't hesitate to followup if you think this is not clear.

Quantum Raumzeit aus dem "Nichts", Spektrum der Wissenschaft 3/2007.

marcus

That's not a scientific journal. Spek der Wiss is a pop-sci magazine! It's like Scientific American only it can even get more sensationalist and inaccurate.
I don't think there is any professional publication by Loll in the past 5 years that suggests the universe arose from nothing--according to CDT.
I think you mislead people when you suggest that CDT has this feature.

I think you are way off base, Xantox.
You are the only person clinging to what you call "Vilenkin's definition". It is obsolete. To find an actual quote from Vilenkin defining nothing the way you like, you'd prob'ly have to go back before 2000.
What it comes down to is you are repetitiously arguing for your own preferred definition of a word. The professional research community has moved on.

xantox

That's where it was published. The conference was for a specialist audience however, so possibly in both cases the title was her choice, in which case I don't believe she would choose entirely misguided and inaccurate terms even when addressing to non-technical readers. Anyway, that's not so important. The interesting point here was that CDT and unlike LQC has some very similar features to Vilenkin's wavefunction.

There must be hundreds of papers even after 2000 quoting this term when referring to the tunnelling theories and their related variants up to string cosmology, for obvious historical reasons. But what should be understood here, is that Vilenkin and Hawking chose on purpose to refer to a state devoid of classical spacetime as 'nothing', and that's a subtle and provocative choice of term which deserves discussion, unless you consider they were so intellectually confused that they did not notice that the wavefunction in the forbidden classical state "is something". Fashions, LQC or Penrose have nothing to do with this.

That your personal dislike of this term leads you to dismiss the historical track of its use as being misguided in your original reply to the OP surprised me. I'm not especially fond of this term either, and I don't consider a big deal to call it whatever we like. But what once was philosophical speculation can become physics, and there is something to learn with these discussions on the use of language. The whole misconception here is residing in one's ill-defined expectations of what "nothing" -should- mean physically. This discussion can be a good occasion to clear that up, as moreover this is also at the root of innumerable other debates on physical existence/nonexistence such as, whether virtual particles exist or not, and so on – debates which cannot be solved by just side-stepping.

In short, when the OP asked "Many people say that the Universe essentially arose from nothing. Is it possible for nothing to be created?", I consider most fecund to first go back to Vilenkin and Hawking (who are the common source of all those sayings) and explain what they -exactly- meant, and then analyze in finer detail what do we expect the word "nothing" -should- mean physically, and compare.

Carid

I think there is a problem here; "nothing" is "no thing". "Thing" is something we can stick a mental label on; this allows us to categorise. This "thing" is different from/the same as that "thing". "Nothing" is too slippery to accept a label. The mind seeks to gain intellectual purchase and can't.

In Buddhism, and probably some other schools of thought, the approach to "nothingness" is via direct experience. Certain meditation techniques can lead with time to a certainty on the part of the practitioner that he or she has had direct contact with nothingness.

In my own experience, which is by no means of any great consequence, it has provoked a most terrifying feeling. More experienced people tell me that if you overcome that fear the experience is liberating.

What has all this got to do with physics. Nothing! Or maybe not for a century or three.

hurk4

Excluding believers, ID people and creationists, I think the conclusion can be: “finally we may be glad”. Glad that by now science (cosmology) is finding a way out of being stopped at a certain t=0 'hidden' in a Big Bang and that physics now is continuing its job of thinking about and discovering how things from past, present and future are related back and forward and that we are going beyond the BB. I think it is really a pity that a misleading and confusing word as “nothing” was slipped into physics, even if some well known scientists tried to give it a meaning, a notice which could have done very well if another word could have been chosen for "something" we are curious about, something we do not yet understand at a level we are happy with. May be it would be good to have a general accepted list for physicists where one could find misguiding, confusing or eventually forbidden words like “nothing”, “singularity” etc. I realise that some of these words sometimes are well fitting in other disciplines as there are mathematics, philosophy etc. I am waiting for the book that will come out this summer as Marcus mentioned.
Kind regards
Hurk4

xantox

Your focus on "things" and categories is appropriate. Being able to label physical objects with a name is in fact a consequence of them having independent properties, a physical feature only available in the classical regime – which can be abstractly modeled by set theory. In the purely quantum regime this feature is fundamentally lost, so it makes no sense whatsoever to call a physical generic quantum state a "thing" for example. It is in this sense a fundamentally meaningless language to say that a pre big-bang state devoid of spacetime is "something" (unless "something" refers to the equations on the sheet of paper, but of course we want to refer to nature instead).

We may follow Zurek in considering "existing" quantum states as essentially those persistent and predictable states ultimately coinciding with the classical behavior. It is only once we recognize that traditional "ontologic" concepts referred to the physical world, such as "existence", "thing", "no-thing", are purely relative and derived concepts, only having a meaning within the classical regime and emerging from the epistemic behavior of quantum states, that it should start to become clear how there can be proper descriptions of classical "things" and "no-things" conditions, and how the "universe tunnelling from nothing" expression may have an appropriate technical meaning, while the expression "absolute nothing" must be nonsense.