Something and Nothing of Universe

  • Thread starter redhedkangaro
  • Start date
  • Tags
    Universe
In summary: A very interesting one is R. Bousso, "Holographic Probabilities in Eternal Inflation", Physical Rev. Lett., 97-19, (2006).A very interesting one is R. Bousso, "Holographic Probabilities in Eternal Inflation", Physical Rev. Lett., 97-19, (2006).
  • #1
redhedkangaro
45
0
Many people say that the Universe essentially arose from nothing. Does anyone know if it is possible for "nothing" to be created?
 
Space news on Phys.org
  • #2
redhedkangaro said:
Many people say that the Universe essentially arose from nothing...

Do any professional cosmologists say this? I wouldn't go by what "many people" say, or by what was written 5 or 10 years ago.
Above all don't go by what you read in popularization books, mass media magazines etc.
What do cosmologists actually say in their technical journal articles (not for pop media consumption.)

I don't know any who say the universe arose from nothing.
If you do, could you find us an article where there is some quote to that effect?

It would surprise me and would be quite interesting, if you could find some reputable person really saying that :biggrin:
because the standard cosmo model that they pretty much all use does NOT say that about "arose from nothing."
My impression is that "arose from nothing" is popular BS or some kind of infectious misconception. But I'd be glad to
see some recent professional article that confirms what you say.

In case you would like some non-technical reading to bring you up to date, try the Einstein Online cosmology pages.
http://www.einstein-online.info/en/spotlights/cosmology/index.html
I've got the link in my signature as well.
One of their webpages is about confusions people have about what is meant by the Big Bang, astronomers mean two different things by it
and they clear up some of the misunderstanding that this causes.
http://www.einstein-online.info/en/spotlights/big_bangs/index.html
This is popularization writing, part of the Einstein Institute's outreach program. I suggest it for what it's worth in case it could be helpful.
 
Last edited:
  • #3
marcus said:
I don't know any who say the universe arose from nothing.
If you do, could you find us an article where there is some quote to that effect?
It would surprise me and would be quite interesting, if you could find some reputable person really saying that :biggrin:
because the standard cosmo model that they pretty much all use does NOT say that about "arose from nothing."
My impression is that "arose from nothing" is popular BS or some kind of infectious misconception. But I'd be glad to
see some recent professional article that confirms what you say.

A famous one is:
A. Vilenkin, "Creation of universe from nothing", Phys. Lett. B, 117B, 25-28 (1982).

But see also, using other words but with similar meaning:
S. W. Hawking, N. Turok, "Open inflation without false vacua", Phys. Lett. B, 425, 25 (1998).

The meaning of "nothing" is here extremely characterised, eg it means that the classical 3-geometry and matter vanishes entirely. This should be taken not as a way open towards cheap philosophy, but quite to the opposite, as an opportunity to doubt that the very concept of "nothing" may have an absolute physical scope.
 
Last edited:
  • #4
marcus said:
Do any professional cosmologists say this? I wouldn't go ... by what was written 5 or 10 years ago...
...

xantox said:
A famous one is:
A. Vilenkin, "Creation of universe from nothing", Phys. Lett. B, 117B, 25-28 (1982).

But see also, using other words but with similar meaning:
S. W. Hawking, N. Turok, "Open inflation without false vacua", Phys. Lett. B, 425, 25 (1998).

The meaning of "nothing" is here extremely qualified, eg it means that the classical 3-geometry and matter vanishes entirely. This should be taken not as a way open towards cheap philosophy, but quite to the opposite, as an opportunity to doubt that the very concept of "nothing" may have an absolute physical scope.

I know about the way people speculated back in 1980s and 1990s.
What I'd like is something more recent than that, preferably > 2004 or 2005.

My impression is all that "universe from nothing" stuff went out the window by 2005.
(It's a date Roger Penrose gave in a lecture at Cambridge where he was talking about ideas of before the big bang.)

Anything professional from > 2004?
I'd be interested!
 
Last edited:
  • #5
marcus said:
Anything professional from > 2004?
I'd be interested!

A very interesting one is R. Bousso, "Holographic Probabilities in Eternal Inflation", Physical Rev. Lett., 97-19, (2006).
 
Last edited:
  • #6
xantox said:
A very interesting one is R. Bousso, "Holographic Probabilities in Eternal Inflation", Physical Rev. Lett., 97-19, (2006).

And that is an example of where our expansion episode arises from something, an occurrence in some other part of of the universe.

I checked the paper and Raphael Bousso never says that our big bang expansion arose from nothing. That would be misleading language. It would not convey what he is trying to say, and he doesn't use the word. Bousso is proposing a definite condition leading up to BB. In fact Bousso is one of the authors to be included in a new book about conditions prior to the big bang which is supposed to come out in August of this year. You may know the book, it is edited by Ruediger Vaas and is called Beyond the Big Bang.

I repeat my request. Please anyone come up with a recent professional cosmo article where the author says our bigbang expansion arose from nothing.
 
Last edited:
  • #7
marcus said:
And that is an example of where our expansion episode arises from something, an occurrence in some other part of of the universe.
Actually, not. It really describes several disconnected regions nucleating "from nothing". If you really need the quoted term here, it appears briefly in a related paper by R. Bousso, B. Freivogel, I-S. Yang, "Eternal Inflation: The Inside Story", Phys. Rev. D74-10 (2006), but even if it is not spelled out as such in that and in several other papers, that is what the equations mean essentially. Note that Bousso has worked closely with Hawking and then Linde who both strongly supported such ideas. This is just one example, variants of this beautiful approach have in fact become rather common.

Again, "nothing" is there perfectly soundly defined as meaning "vanishing classical spacetime and matter".
 
Last edited:
  • #8
xantox said:
Again, "nothing" is here perfectly soundly defined as meaning "vanishing classical spacetime and matter".

Physics is living by theory, observations and experiments.
I can't see how or where "nothing" fits in. No experiments or observations of "vanishing" ever noticed.! Or who did?
 
  • #9
xantox said:
If you really need the quoted term here, it appears briefly in a related paper by R. Bousso, B. Freivogel, I-S. Yang, "Eternal Inflation: The Inside Story", Phys. Rev. D74-10 (2006),...

Where? I looked thru the whole article and could not find anywhere they say the universe arose from nothing.

The whole article is about a very definite idea of the something from which they think the universe could have arisen!

Hi Hurk,
here is the link to the article that Xantox thinks we should look at:
http://arxiv.org/pdf/hep-th/0606114v2
I find it is typical of a lot of current research that delves into what conditions might have been like before the big bang episode.
Many of the different approaches will be collected in a forthcoming book called "Beyond the Big Bang: Prospects for an Eternal Universe"
scheduled to come out this year. Loop cosmology bounce will feature in several of the chapters, and (Bousso and others') eternal inflation ideas will also be included. Before the big bang topics are becoming a lively research area!
 
Last edited:
  • #10
marcus said:
Where? I looked thru the whole article and could not find anywhere they say the universe arose from nothing.
Here some quotes at random, it is a frequently used term in the literature.
  • Bousso and Freivogel, Yang: "If one imagines that the universe was created, perhaps by 'tunneling from nothing' [..]"
  • Bousso and Linde: "Alternatively, one may consider the quantum creation from nothing of a closed inflationary universe [..]"
  • Bousso and Chamblin: "It may be interpreted to describe the semiclassical creation from nothing of two open universes [..]"
  • Vilenkin: "A cosmological model is proposed in which the universe is created by quantum tunneling from literally nothing into a de Sitter space."
  • Hawking and Hartle: "In other words, the ground state is the amplitude for the universe to appear from nothing".
  • Zel'dovich: "Spontaneous creation from nothing does not contradict the laws of conservation".
  • Linde: "The most natural way to realize inflationary scenario in this theory is to assume that the universe was created 'from nothing'".
  • Carroll: "This might be the case, for example, if the universe were created 'from nothing' [..]"
  • Polchinski: "The states of positive ρV would also be populated by any sort of tunneling from nothing [..]"
  • Garriga: "An inflating brane-world can be created from 'nothing'".

marcus said:
The whole article is about a very definite idea of the something from which they think the universe could have arisen!
I must insist on the physical definition of the word "nothing" in all the above quotes as meaning the vanishing of classical spacetime and matter.
 
Last edited:
  • #11
The point I made earlier was that people used to talk this way particularly in the 1980s and 1990s, but it seems to have gone out of fashion. And I think for good reason! In order to use your quotes to check my impression, I need dates.

Links to the papers would be helpful. I need to see things in context to know what they are actually saying.

I'm not interested in stuff before 2005. The Bousso Chamblin paper and the Bousso Linde paper are from 1998. No need to bother with those.
Hawking and Hartle would be their 1983 paper I expect. If so we can ignore that one.
Zel'dovich died in 1987.
Your Vilenkin quote is from 1982.

Turning to more recent stuff, notice that Carroll (presumably a more recent example) uses inverted comma scare quotes and considers a hypothetical case--"if the universe were created 'from nothing.'"
Bousso Freivogel and Yang also use scare quotes in an iffy imaginative statement "if one imagines that...perhaps by 'tunneling from nothing.' "
Inverted commas used like that means not really but in a manner of speaking.

I'm afraid I can't accept these quotes, out of context, without links and page references so I can see what they are talking about, as evidence that the professionals are claiming that the universe arose from nothing.

When one looks at what they actually say one sees that there is a lot of structure postulated in the pre-bigbang state. Very much something.
I think what you present as THE definition of nothing is your own private definition :biggrin:. Simply the absence of ordinary matter and the failure of spacetime to be classical is not what many experts would call nothing.
 
Last edited:
  • #12
marcus said:
When one looks at what they actually say one sees that there is a lot of structure postulated in the pre-bigbang state. Very much something.
I think what you present as THE definition of nothing is your own private definition :biggrin:. Simply the absence of ordinary matter and the failure of spacetime to be classical is not what many experts would call nothing.
This is also the way I've learned to think about "the universe came from nothing" or "spontaneous particle generation" statements. There's always some sort of 'nonclassical' mathematical model that "nothing" or "spontaneous" refers to -- and those models are, as you point out, "very much something".

Regarding redhedkangaro's question -- "Does anyone know if it is possible for 'nothing' to be created? -- would it be acceptable to entertain the idea that, at least wrt some universal evolutionary scenarios, our universe is in the process of becoming nonexistent (ie., literally nothing)?

Edit: On second thought, maybe it's just a nonsensical question.
 
Last edited:
  • #13
marcus said:
The point I made earlier was that people used to talk this way particularly in the 1980s and 1990s, but it seems to have gone out of fashion. [..] Inverted commas used like that means not really but in a manner of speaking [..]

There are two aspects that you're addressing here, 1) terminology, 2) theory. Let's see each separately.

1) Terminology. About the use of the word "nothing" in theoretical cosmology. You said that "When one looks at what they actually say one sees that there is a lot of structure postulated in the pre-bigbang state. Very much something."

Your argument seems to be that since there are some equations describing some kind of state, we can call that "something" and so it is fundamentally wrong to use the term "nothing". But here you clearly use the words "something" and "nothing" in the inappropriate definitions of a dictionary or traditional philosophy. These definitions are of course forbidden in the context of physical theories. It would be like for cosmological "quintessence" starting to debate that the term is incorrect since it is not really a fifth essence, or like for a "black hole" starting to debate that the term is incorrect since quantumly it is not totally black, or like for quantum field theoretical "vacuum" starting to debate that the term is incorrect since that vacuum is very much non-empty.

This is exactly what I warned against in my first comment above, that we should avoid entering speculations based on philosophical definitions. When "vacuum" is a term clearly defined in a physical theory, that is all we need, and even if some authors would start calling it differently tomorrow but with the same underlining definitions we would know we're talking about the same and so the specific choice of term used remains purely anecdotical and irrelevant. Thus, the same applies to "nothing", once it is a term clearly defined in the literature, and since it is, we can agree on the definition and that can be more than enough. As per where is defined, the following is a primary and sufficient source (other scholars use the exact same definition): "In this paper, I shall discuss a model in which the universe is created by quantum tunneling from 'nothing', where by 'nothing' I mean a state with no classical space time" [1].

You could still object that it is better when the terms used in a physical theory are chosen so as not to be confusing or contradicting with everyday meanings. Such as, why call "vacuum" a state which is not really empty and "nothing" a state which is not really nothing so that we have just "a manner of speaking" with "scare quotes". This objection is thus purely philosophical, but I shall reject it on the following basis. For classical observers, vanishing of classical fields is the best possible definition of classical nothingness. Trying to consider that the word "nothing" must refer to some kind of "absolute physical nothingess" (which you do by considering that those models are "very much something") is however meaningless: the philosophical idea of "absolute nothing" is pure nonsense, it is a classical concept which cannot have an absolute physical meaning.

The above definition from Vilenkin (who also use the expression "literally nothing" without quotes) is thus also appropriate on this aspect. "Nothing" is here classical nothingness, and any theory of quantum gravity which can describe spacetime as an emerging entity -can- describe such "nothing" in terms of a quantum wavefunction, and there is no contradiction.

2) Theory. Let's now turn very briefly on the underlining theoretical frameworks of the "universe from nothing" approaches instead than on the word "nothing". The idea that the universe can be originated with a quantum fluctuation from a state devoid of classical spacetime is of course one amongst many others but it is perhaps the most well-known one. The line of research was originated by Tryon [2] and then culminated with Vilenkin [3], Hawking and Hartle [4], Moss and Wright [5] and Linde [6]. It is based on the euclideanized path integral to define the tunnelling amplitude of the universal quantum wavefunction into classical spacetime. The transition can be described with a specific kind of instanton for different initial conditions, such as the de Sitter instanton, the Hawking-Moss instanton for closed FRW universes, or the Hawking-Turok instanton for open FRW universes.

Further developments have been made in string cosmology, where the "nothing" can be identified with the string perturbative vacuum itself (so that the approach is particularly significant to find a selection mechanism out of the exceedingly big landscape of vacua). In particular there is the generalization to the brane world scenario by Hawking, Hertog and Reall [7] and Garriga and Sasaki [8].

But there are other completely different lines of research which are generally similar on this aspect of picturing a transition from a classically forbidden region. You said "you're not interested in stuff before 2005". But on one hand, we should not be quite interested in dates at all, as it is not the freshness of research that determines its interest and the newest ideas are not always a progress. The scientific method works well enough to exclude by itself the dead paths and to identify the weaker paths, that we do not need to focus only on the newest ideas. But on the other hand, even those latest approaches such as Loll's CDT, which you may consider more fashionable, can be considered a kind of "universe from nothing" theories as well, since spacetime is emerging from a non-classical region of the wavefunction (in that specific case there is also a difference that only the scale factor is vanishing).

______
[1] A. Vilenkin, "Quantum origin of the universe", Nuclear Physics B 252, 141-152 (1985).
[2] E. P. Tryon, "Is the Universe a quantum fluctuation?", Nature 246, 396-397 (1973).
[3] A. Vilenkin "Creation of universes from nothing", Phys. Lett. B, 117 B, 25-28 (1982).
[4] J. B. Hartle and S. W. Hawking, "http://prola.aps.org/abstract/PRD/v28/i12/p2960_1", Phys. Rev. D 28, 2960-2975 (1983).
[5] I. G. Moss and W. A. Wright, "http://prola.aps.org/abstract/PRD/v29/i6/p1067_1", Phys. Rev. D 29, 1067-1075 (1984).
[6] A. D. Linde, "Quantum creation of an inflationary universe", Sov. Phys.-JETP 60:2401-405 (1984).
[7] S. W. Hawking, T. Hertog, and H. S. Reall, "http://prola.aps.org/abstract/PRD/v62/i4/e043501", Phys. Rev. D 62:4, (2000).
[8] J. Garriga, M. Sasaki, "Brane-world creation and black holes", Phys. Rev. D 62:4 (2000).
 
Last edited:
  • #14
xantox, I think your points are well taken. However, I also think that it's a good thing (ie., confusion and obfuscation is minimized) when physicists, cosmologists, etc. avoid appropriating (or misappropriating) ordinary language terms to refer to theoretical inventions (even though the practice usually serves some mnemonic purpose).
 
  • #15
ThomasT said:
... I also think that it's a good thing (ie., confusion and obfuscation is minimized) when physicists, cosmologists, etc. avoid appropriating (or misappropriating) ordinary language terms to refer to theoretical inventions (even though the practice usually serves some mnemonic purpose).

Yes Thomas,
I agree, it would be better if ordinary people were not annoyed by inventions by scientists, inventions they define or mention “nothing”. In fact the discussion here is about reality whatever that means. Personally I find myself confronted with an autonomous reality which can never fully understood by whatever theory and its underlying models. By the way what did redhedkangaro mean with his understanding of his "nothing"?
Kind regards
Hurk4
 
  • #16
I enjoyed reading posts -- thanks. One of my christian friend said, the initial state of big bang is the soul of God. And I think there can be many even infinite number of universes, but simple they do not interfere. However I like to think of the origin of my universe.
 
  • #17
ThomasT said:
... There's always some sort of 'nonclassical' mathematical model that "nothing" or "spontaneous" refers to -- and those models are, as you point out, "very much something".

Hi Thomas,
thanks for the reply. I think we all realize that the prebigbang conditions people postulate are indeed "very much something!"

The main point I've been making is that since 2000 (and especially since 2005) there has been a change in how scientists talk about it. In the 1980s and 1990s it was fashionable to call these nonclassical conditions "nothing".

But since 2000 they do that less and less. Since 2005, as far as I know, not at all. And I think with good reason. Calling such conditions "nothing" is a misnomer and misleads people.

Regarding redhedkangaro's question -- "Does anyone know if it is possible for 'nothing' to be created? --

If we were to take the definition seriously that was proposed earlier, that 'nothing' (by which I mean xantoxian 'nothing') is merely a period when vintage-1915 classical spacetime doesn't apply and there's no ordinary matter, then the answer is YES!

In Loop cosmology there is a collapsing prior universe (conventional classical spacetime and ordinary matter) which then undergoes a big crunch, which causes a high density state in which there is momentarily no ordinary matter and no classical geometry. This then begins to expand and becomes what we see.

The Loop people call this a quantum regime---a brief period when geometry is not governed by classical GR but functions according to a quantum version of GR. They don't call it 'nothing' even tho it satisfies xantox' definition! This is only one example, and is well known.

My point is that the Loop researchers do not call this brief bounce episode 'nothing'!
If they would use the xantoxian definition (which apparently very few people do nowadays) they would say there was a classical universe collapse, which caused a 'nothing', which then in turn caused the expansion that we see. They don't talk this way, and neither do other researchers studying other pre-big bang models. As a somewhat misleading figure of speech it is going out of style.

One reason people don't call these conditions 'nothing' any more (except for a few like xantox) is precisely because they want to study these conditions.
They want to model them, and if possible derive predictions of things to look for in the CMB--some models may have distinctive signatures which we can detect or not detect, providing a way to test.
 
Last edited:
  • #18
marcus said:
But since 2000 they do that less and less. Since 2005, as far as I know, not at all. And I think with good reason. Calling such conditions "nothing" is a misnomer and misleads people.
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.

marcus said:
The Loop people call this a quantum regime---a brief period when geometry is not governed by classical GR but functions according to a quantum version of GR. They don't call it 'nothing' even tho it satisfies xantox' definition! This is only one example, and is well known.
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.
 
Last edited:
  • #19
xantox said:
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".
...

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 doesn't 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'?
 
  • #20
xantox said:
It is true that it is less used, .

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'.
 
  • #21
ThomasT said:
... it's a good thing (ie., confusion and obfuscation is minimized) when physicists, cosmologists, etc. avoid appropriating (or misappropriating) ordinary language terms to refer to theoretical inventions...

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.

hurk4 said:
Yes Thomas,
I agree, it would be better if ordinary people were not annoyed by inventions by scientists, inventions they define or mention “nothing”. ... By the way what did redhedkangaro mean with his understanding of his "nothing"?

v2kkim said:
... One of my christian friend said, the initial state of big bang is the soul of God...

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/find/hep/www?rawcmd=FIND+DK+QUANTUM+COSMOLOGY+and+DATE+%3E+2005&FORMAT=www&SEQUENCE=citecount%28d%29 [Broken]
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)
 
Last edited by a moderator:
  • #22
marcus said:
Loll's simulations do not start from nothing.
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.

What is the 2007 article where she says 'emerged from nothing'?
Quantum Raumzeit aus dem "Nichts", Spektrum der Wissenschaft 3/2007.
 
Last edited:
  • #23
xantox said:
Quantum Raumzeit aus dem "Nichts", Spektrum der Wissenschaft 3/2007.

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.
 
Last edited:
  • #24
marcus said:
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.
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.

marcus said:
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.
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.
 
Last edited:
  • #25
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.
 
  • #26
xantox said:
....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. ...

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 realize 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
 
  • #27
Carid said:
"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".

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.
 
Last edited:

What is the Universe made of?

The Universe is made up of both something and nothing. Something refers to matter, energy, and all the visible objects in the Universe such as stars, planets, and galaxies. Nothing refers to the vast expanse of empty space between these objects.

How did the Universe begin?

The current leading theory is the Big Bang theory, which states that the Universe began as a singularity - a point of infinite density and temperature. This singularity then expanded and cooled, leading to the formation of galaxies and other structures we see today.

What is the role of dark matter and dark energy in the Universe?

Dark matter and dark energy are two mysterious substances that make up a large portion of the Universe. Dark matter is believed to make up about 27% of the Universe and is responsible for the structure and formation of galaxies. Dark energy, on the other hand, makes up about 68% of the Universe and is responsible for the observed accelerated expansion of the Universe.

Is the Universe infinite?

It is currently unknown whether the Universe is infinite or finite. According to the leading inflationary theory, the observable Universe is finite but the entire Universe may be infinite. However, this is still a topic of ongoing research and debate among scientists.

What is the ultimate fate of the Universe?

Based on current observations and theories, it is predicted that the Universe will continue to expand indefinitely, with the galaxies moving further and further apart until they are no longer visible from each other. This is known as the "heat death" of the Universe, where all matter and energy is evenly distributed and the Universe reaches a state of maximum entropy.

Similar threads

Replies
5
Views
1K
Replies
3
Views
1K
Replies
20
Views
1K
Replies
2
Views
1K
  • Cosmology
Replies
11
Views
1K
  • Cosmology
Replies
5
Views
1K
Replies
26
Views
4K
Replies
13
Views
456
Replies
4
Views
1K
  • Cosmology
2
Replies
57
Views
3K
Back
Top