View Full Version : Does a pure vacuum exist?


zanket
01-02-04, 03:14 PM
Is there such a thing as a pure vacuum? Or is it thought that every portion of the universe no matter how small is completely full of energy, such as quantum foam, virtual particles or electromagnetic waves?

Crisp
01-02-04, 05:05 PM
Depends on how you define a vacuum.

Void of particles ? That surely exists.

Void of electromagnetic radiation ? That's quite a bit harder already. But in theory this can exist.

Void of virtual particles ? ... well, they say this does not exist. I am not sure what to think of it though, but appearantly this does not exist.

Bye!

Crisp

Quantum Quack
01-02-04, 07:17 PM
absolute vacuum = absolute nothing.

Like before the big bang?

zanket
01-03-04, 10:36 AM
Crisp – I define a pure vacuum as a space void of any energy. If every portion of space is taken up by virtual particles at least, how do the virtual particles move? Wouldn’t they be hemmed in on all sides by other virtual particles? The pictures I’ve seen show them moving some distance within an apparently pure vacuum before coalescing. Also, when they disappear, wouldn’t there be a void at that location for some moment of time?

Quantum Quack – No, just within any portion of the universe now, no matter how small. Like, does a pure vacuum exist anywhere within a donut?

lethe
01-03-04, 03:14 PM
Originally posted by zanket
Is there such a thing as a pure vacuum? Or is it thought that every portion of the universe no matter how small is completely full of energy, such as quantum foam, virtual particles or electromagnetic waves?

because of quantum mechanics, the vacuum should be filled with a zero point energy. there are some thorny issues with this stuff (like, it might be infinite, or at least the theory makes predictions many orders of magnitude too large), but there can be no doubt that it is real. it was measured with the Casimir effect.

it doesn t really make sense to talk about virtual particles in the vacuum, i think, since virtual particles are, even in principle, not observable. on the other hand, we know that whenever there is interacting matter present, the so called "vacuum bubbles" contribute to the interaction. it is as if the particles which would otherwise be travelling through a vacuum, are seeing pairs of virtual particles. but then again, its not a true vacuum, since i have real particles as well.

ScRaMbLe
01-03-04, 11:18 PM
What the hell is going on here?!!! I go to bed, wake up this morning and all of a sudden the more respected physics posters are acknowledging zero point energy?!! Did I fall into an alternate reality while I was sleeping? Don't get me wrong, I'm so glad you guys are accepting the concept, but WTF? What changed your minds?

Quantum Quack
01-04-04, 02:11 AM
Absolute nothing = absolute vacuum. Absolute vacuum is inverse energy therefore absolute vacuum is infinite energy.

Absolute nothing has absolute energy by simply being absolute vacuum.

The absence of pressure means that it has an incredably strong attraction to anything that has pressure and this I believe is gravity, the effect of the attraction ofabsolute vacuum or in other words absolute nothing.

In the centre of everything is absolute nothing ( vacuum ) which by default is extremely attractive.

lethe
01-04-04, 03:18 AM
Originally posted by ScRaMbLe
What the hell is going on here?!!! I go to bed, wake up this morning and all of a sudden the more respected physics posters are acknowledging zero point energy?!! Did I fall into an alternate reality while I was sleeping? Don't get me wrong, I'm so glad you guys are accepting the concept, but WTF? What changed your minds?

i didn t change my mind. as i said in the other thread: zero point energy is real, but it cannot be tapped to drive your car.

i am starting to wish i had not called it zero point energy, but instead called it vacuum energy, since the latter is not as often associated with crackpot schemes.

ScRaMbLe
01-04-04, 05:03 AM
See "zero point energy" thread for my explanation. I'll stop hi-jacking this thread.

zanket
01-04-04, 07:00 PM
So far the answer seems to be “no, arguably.” Are physicists really so divided about this or am I just misunderstanding what I’m reading here? When I read about vacuum energy, I see no mention of it being observed within an arbitrarily small volume, like that of a subatomic particle. It's more believable that it exists within larger volumes.

lethe
01-05-04, 07:35 AM
Originally posted by zanket
So far the answer seems to be “no, arguably.” Are physicists really so divided about this or am I just misunderstanding what I’m reading here? When I read about vacuum energy, I see no mention of it being observed within an arbitrarily small volume, like that of a subatomic particle. It's more believable that it exists within larger volumes.

if it exists in large volumes, then it must be found in small volumes as well. remember that the vacuum is Poincaré invariant

MacM
01-06-04, 02:51 AM
Zanket,


Crisp – I define a pure vacuum as a space void of any energy.

I suspect your definition is flawed in that while it is not a universal idea yet, a Cornell University paper (and others) believe that space is created by energy. No energy, no space.

Quantum Quack
01-06-04, 03:58 AM
Vacuum is energy without doubt......just inverse. (My thoughts)

rainman
08-25-09, 04:43 PM
I think there is a subtle difference between a "Pure Vacuum" and a "Perfect Vacuum". A perfect vacuum is more of a scientific concept that could be attainable given the right technology. A "Pure Vacuum" seems to be more of an artsy concept of simple nothingness. Does or can either one of these ideas/concepts exist in our Universe? That, to me, is the big question.

Rick
08-25-09, 07:32 PM
Quantum, you said something very interesting ... you said, "BEFORE" big bang; I remember that Space and time are connected (general theory of relativity I believe), so there CANNOT be any thing BEFORE big bang, because time is a conception tightly coupled with space; off course I am a noob to everything, so i could be completely wrong, if so; please excuse me.

Rick

Quantum Quack
08-25-09, 07:41 PM
Quantum, you said something very interesting ... you said, "BEFORE" big bang; I remember that Space and time are connected (general theory of relativity I believe), so there CANNOT be any thing BEFORE big bang, because time is a conception tightly coupled with space; off course I am a noob to everything, so i could be completely wrong, if so; please excuse me.

Rick
yes this is a correct view IMO. There can be no moment before time began. Nor can there be any moments after time ceases. So if the universe should end it will do so as if it never had existed in the first place as no historical remnant will remain to demonstrate it.
One can not separate time from substance nor substance from time as both are more or less the same thing described from differring perspectives. IMO [ time in this context is not the abstraction of clock time we humans utilise to measure with but the actual movement and change that the universe undergoes within itself which we use an abstraction called time to measure that change with. So time has too aspects to it that are often confused.IMO


Logically the advent of time is what created the universe from nothingness....however since this thread was posted too over 4 years ago much has been learned and thought about and I am still probably just as much a "noob" as you are...

AlphaNumeric
08-26-09, 03:05 AM
Absolute nothing = absolute vacuum. Absolute vacuum is inverse energy therefore absolute vacuum is infinite energy.And your logic for this is.....?


The absence of pressure means that it has an incredably strong attraction to anything that has pressure and this I believe is gravity, the effect of the attraction ofabsolute vacuum or in other words absolute nothing.

In the centre of everything is absolute nothing ( vacuum ) which by default is extremely attractive.Except that isn't how it works, a vacuum isn't attractive. If you opened the door on the Shuttle you aren't sucked out by the 'attractive' properties of the vacuum, you're blown out by the high pressure of the air in the Shuttle. The air is applying an outwards pressure and when you remove the constraint holding the air in (ie open a door) then it'll blast out. The same is true for your body, the fluid and gases are held in because there's an equalising pressure on the other side of your skin due to the atmosphere. If you removed that your blood and lung air wouldn't be sucked out of you, it'd be forcing its way out of you.

Obviously basic mechanics is another thing you didn't read up on in your twenty years of research. :rolleyes:

rainman
08-26-09, 02:51 PM
We shouldn't "hedge" when it comes to defining "Pure Vacuum". It should be nothing..period. If you observe energy of any kind within a fixed volume then you do not have a "Pure Vacuum". You have something else. You have a semi-perfect vacuum. Pure vacuum contains nothing. Maybe we could argue whether Pure Vacuum can be contained within a vessel? But the Universe is not a vessel. It is infinite. I like leaving "Pure Vacuum" as a completely empty volume and instead arguing about how pure it can be and still be observed by our rudimentary instruments.

thinking
08-26-09, 03:26 PM
[QUOTE=rainman;2353343]We shouldn't "hedge" when it comes to defining "Pure Vacuum". It should be nothing..period.

agreed , absolutely




If you observe energy of any kind within a fixed volume then you do not have a "Pure Vacuum". You have something else. You have a semi-perfect vacuum. Pure vacuum contains nothing. Maybe we could argue whether Pure Vacuum can be contained within a vessel? But the Universe is not a vessel. It is infinite. I like leaving "Pure Vacuum" as a completely empty volume and instead arguing about how pure it can be and still be observed by our rudimentary instruments.

agreed

thinking
08-26-09, 03:27 PM
Vacuum is energy without doubt......just inverse. (My thoughts)

what............................?

BenTheMan
08-26-09, 04:02 PM
It should be nothing..period. If you observe energy of any kind within a fixed volume then you do not have a "Pure Vacuum".

Then such a thing does not exist within the framework of physics as we know it.

\Delta E \Delta t \sim \hbar

1100f
08-26-09, 04:56 PM
This is pure vacuum: |0> .
Isn't it?

litewave
08-26-09, 05:02 PM
Then such a thing does not exist within the framework of physics as we know it.

\Delta E \Delta t \sim \hbar
Doesn't this mean that there is no defined energy within a zero time interval?

Also, is there any energy in an area smaller than Planck length?

thinking
08-26-09, 05:22 PM
lets not make this to complicated

as someone yrs ago suggested there is a chiral condensate , which means there is energy of some form in all of space

inotherwords there is no pure vacuum , at all

BenTheMan
08-26-09, 08:39 PM
Doesn't this mean that there is no defined energy within a zero time interval?

There's different ways to understand the uncertainty principle. The way I understand it in the context of a vacuum is that you can borrow some energy from the energy bank, but the more you borrow, the quicker you have to pay it back. The constant which dictates the size of how much you can borrow and how quickly you must repay is h-bar. So there are constantly particles popping into and out of existence in the vacuum.

Of course, this also means that there is not really such a thing as a classical ``vacuum'' in the full quantum theory.


Also, is there any energy in an area smaller than Planck length?

Sure, why wouldn't there be?

I should clarify, though---this is still an open question. Some research programs (loop quantum gravity, causal dynamical triangulation) do work by introducing a minimum length scale, but they do this at the cost of breaking lorentz invariance.


This is pure vacuum: |0> .
Isn't it?

That's good enough for me. Some people here, though, can't seem to accept the fact that quantum mechanics is weird :)

gfellow
08-26-09, 08:54 PM
Might I suggest that a vacuum is not an empty space, but a volume empty of space?

litewave
08-27-09, 03:07 AM
Also, is there any energy in an area smaller than Planck length?

Sure, why wouldn't there be?

I should clarify, though---this is still an open question. Some research programs (loop quantum gravity, causal dynamical triangulation) do work by introducing a minimum length scale, but they do this at the cost of breaking lorentz invariance.
Here is an article that seems to be saying that the region under the Planck scale is unphysical, that is there is no defined energy in this region. What do you think about it?

http://www.colorado.edu/philosophy/vstenger/Godless/Origin.pdf

Rav
08-27-09, 05:08 AM
Might I suggest that a vacuum is not an empty space, but a volume empty of space?

It really all depends on how one wants to define a vacuum. Paradoxically, in order for a vacuum to exist, it has to contain something. Just so we don't wander too far off into the realm of philosphical absurdity, being that this is a physics forum, let's say that it has to contain space.

Now, feel free to offer alternative perspectives on this, because I'd really like to hear some, but my position on the matter is that rather than being the absence of anything, space is something. Quantum foam, vacuum energy, whatever. The supporting evidence I prefer to use however is the idea that because nothing is absence of anything at all, it is impossible for nothing to exist.

In the end the idea of a vacuum is only useful so far as it relates to the absence of something in particular rather than the absence of absolutely everything.

1100f
08-27-09, 07:37 AM
Might I suggest that a vacuum is not an empty space, but a volume empty of space?
Can you please explain according to your definition what is a volume?

rainman
08-27-09, 12:06 PM
Then such a thing does not exist within the framework of physics as we know it.

\Delta E \Delta t \sim \hbar

Seems to be true but does this mean that "pure vacuum" or "nothing" does not exist or ever did exist...period...dead stop?

rainman
08-27-09, 12:17 PM
Then such a thing does not exist within the framework of physics as we know it.

\Delta E \Delta t \sim \hbar

[QUOTE=Rav;2353640]It really all depends on how one wants to define a vacuum. Paradoxically, in order for a vacuum to exist, it has to contain something. Just so we don't wander too far off into the realm of philosphical absurdity, being that this is a physics forum, let's say that it has to contain space.QUOTE]

This seems like one of the absurdities of physics...that in order for a "Pure Vacuum" to exist, it has to contain something??? Are you saying something smaller than a Planck Length? or are you just redefining the words "Pure Vacuum" to say that a pure vacuum does not mean simply "nothing"? To me it sounds like a Tautology to say something contains itself.

rainman
08-27-09, 12:19 PM
Can you please explain according to your definition what is a volume?

We have to be careful here to differentiate between a concept and something that exists. A volume is a concept..."Pure Vacuum" may or may not exist.

BenTheMan
08-27-09, 01:10 PM
Seems to be true but does this mean that "pure vacuum" or "nothing" does not exist or ever did exist...period...dead stop?

It means that the classical concept of a ``vacuum'' doesn't apply in a full quantum theory.

gfellow
09-03-09, 09:59 AM
Can you please explain according to your definition what is a volume?
Yes. Not only will I give you a definition, I can offer a performable laboratory experiment that will confirm my definition and a prediction based on solar neutrino data that will compliment the laboratory experiment.

I'll touch on these right away.
We know that the gravitational moment of gas, liquid and solid are inviolate, they always weigh the same and the gravitational attraction of two given masses is stable. But is the same true for a super-hot plasma?
The plasma experiment would consist of a high energy plasma discharge, coupled with an appropriate gravitational sensing device. I predict it will demonstrate a minute but measurable, momentary increase in the force of gravity towards the discharge and in doing so, demonstrate that gravity can be induced without a corresponding quantity of mass.
It will be demonstrated that there is a moment during a z-pinch when stripped electrons and protons organize into like camps and contribute their individual magnetic moment to the whole, unifying the plasma in a strong magnetic field. (This phenomenon cannot be studied for very long. Even constrained by strong magnetic fields in fusion reactors, the plasma's magnetic field rapidly 'escapes'.)
I believe the gravitational induction comes about at the moment an organized quantity of super-hot plasma strips protons from electrons.

Needless to say, a successful outcome of this experiment will have far-reaching implications, because it will confirm a direct link between the electric, magnetic and gravitational forces. Furthermore, gravitational induction will have fundamental implications upon the very foundation of contemporary physics, the experiment will demonstrate that the relationship between mass and gravity are not inviolate.

From the many inquiries I have made over the years, I am given to understand that this experiment has not as yet been performed, nor is anyone other than myself expecting this result.*
I liken it to Hans Christian Ørsted's chance experiment, when he happened to notice a compass needle jump when inducing a current through a wire.

*In a recent update, I have come across a Russian physicist who has submitted his paper based plasma experiments, "GRAVITATIONAL INTERACTION ON QUANTUM LEVEL AND CONSEQUENCES THEREOF" by S.I. Fisenko. He claims the paper is going to be published October in a peer reviewed journal, and that is the experiment I am seeking. The paper is beyond my capacity to make any judgment on it. It can be found on the arxiv.org site. I would be interested in opinions.

Next, the solar neutrinos prediction: A compilation of solar neutrino data will show that the angle of incidence of solar neutrinos emanating from the Sun will be expressed in a concave graph rather than a convex graph. A convex graph, is what one might expect from a standard model of the sun, with neutrinos emanating from the Sun's center.
The concave graph which is what I am predicting, will demonstrate that neutrinos are emanating from the shell and atmosphere of the Sun, and not from its core. To my knowledge, no one is expecting a concave graph. After consultation with several solar neutrino physicists, I am to believe that the angle of incidence data is too scattered at present, but better programming and the ever-accumulating amount of data (20 strikes a day) may make the observation possible in the foreseeable future.

If a concave graph is in evidence, the data will infer that the Sun is a magnetically constrained non-space volume. This volume is sustained by an exterior shell best described as a magnetically unified high energy plasma. The interior volume of non-space induces gravity, causing the Sun's shell to continually implode. This implosion of the Sun's mass releases energy, magnetically sustaining the Sun's interior volume of non-space.
I make no claim as to the particular nuclear chain reaction leading to solar energy output, merely that it is distributed in a shell, gravitationally crushing in on the Sun's interior non-space.

A few thoughts on the nature of 'non-space':
If you consider the black hole hypothesis, a scenario where matter has accumulated to such a degree that - depending what theory you subscribe to - even light has difficulty escaping. Non-space is on the other end of the spectrum.
The nature of absolute vacuum is significantly different from space. Because the standard definition of an absolute vacuum is 'a space with nothing in it', it is useful to re-coin the concept as we will be considering a 'volume with no space in it', hence, 'non-space'.
Non-space is a volume which has no time, no temperature. Space behaves gravitationally towards this volume, it crushes in on the boundary in an attempt to annihilate the non-space.

Wherever we look in the universe, absolute vacuums are nowhere to be observed. That is pretty astonishing because, for the longest time space was thought to be an absolute vacuum.
When Einstein produced his work on Relativity in the early part of the 20th century, he had no way of knowing that space was not a vacuum.
Even in the thinnest intergalactic space, any given cubic centimeter is awash in activity, virtual particles spontaneously come into existence then blink out again. Radiation permeates this thinnest of space. Whole atoms, unhindered, reach such high velocities that a plethora of them pass through a given cubic centimeter at any given time.
We know that light travels upon the fabric of space, but no observation has ever been made of light propagating through an absolute vacuum, so the "v" in E=MC2v (the speed of light in a vacuum) is incorrect. Light does not travel in a vacuum, it travels in space. I believe it will be demonstrated that the virtual particles that are associated with absolute vacuums can be crudely illustrated as a 'foam' on the non-space boundary.

I expect significant skepticism for these extraordinary claims, and I realize that the experiment and observation might well return a null result, rightfully condemning my contemplations to the historical trash-heap of absurd ideas.
Consider though, that the plasma experiment is achievable with our present technology, and I suspect at a relatively reasonable cost, and the solar neutrino data-collection ought to be feasible the foreseeable future.

It would be a great shame not to perform the plasma experiment, for if by the slimmest chance the experiment produces a positive result, is that not in itself enough incentive?
And, if the proposed experiment, with the potential seed of a positive result languishes, would history not condemn today's plasma physicists for their reticence? Would we have to wait, leaving the discovery to a future generation, a generation who would look back and mock us?

Eximus
09-07-09, 06:02 AM
This use of the number zero is dangerous.

I'm going to say "zero" does not occur in descriptions of things that exist, except as placeholders.

i.e. 0.00000000000001 grams per cubic beard-second

BenTheMan
09-08-09, 07:59 PM
This use of the number zero is dangerous.

Especially in quantum mechanics :)

Not only is there not a good definition of ``zero'' in a quantum theory, there's not even a good definition of particle number, or even of particle.

This thread hilights some of the prejudices that people have, and some of the dangers of imposing our classical intuitions on a quantum world.

noodler
09-08-09, 10:04 PM
The |0\rangle Dirac bracket is for the term that is "set to zero"; it has an expectation value and a real probability of "not being zero".
Another view is the "zero-bracket" is empty - a vacuum - until a wavefunction evolves and fills the vacuum; the other |1\rangle term has a coefficient which is the inner product or hidden phase of the wavefunction.

So the expectation is "zero" initially but QM says there is no real vacuum - the wavefunction will evolve in some real interval of time; when exactly or where, is the "quantum dilemma"

thinking
09-08-09, 10:21 PM
so the only way to have a pure vaccum is to have no energy/matter within that volume of space , however large or small

noodler
09-08-09, 10:32 PM
"No energy/matter" is a quid pro quo; no such thing exists in any QM theory.

The universe may exist because of an expectation value, in a "non-empty" vacuum.

thinking
09-08-09, 10:49 PM
"No energy/matter" is a quid pro quo; no such thing exists in any QM theory.


The universe may exist because of an expectation value, in a "non-empty" vacuum.

a value has nothing to do with the essence existence , since any value is based on energy/matter

the Universe exists because energy/matter is infinite in its existence

noodler
09-09-09, 05:24 PM
the Universe exists because energy/matter is infinite in its existence ??
The universe exists because it has a finite amount of energy; the density of this energy is assumed to have been nearly infinite in the past (so nearly, it was effectively infinite density).

If it was infinite, there wouldn't be any room for all the "low-energy" space we can see now.
Note, the space is getting bigger, which is impossible for infinite energy since this would mean infinite expansion and infinite space, but space "ends" at a finite distance, there's a boundary. Why is that?

Eximus
09-11-09, 11:52 PM
We cannot say that the universe has a definite boundary, outside of defining the universe as that which we can observe, keeping in mind that light can only travel so fast.