Talk:Vacuum/Archive 2

Units

Ytrottier/Yannick, who talks on the archived pages about "torr" being some "industry standard", and who phrases the choices above as between "SI units" and "Torrs", maybe ought to get out more, see a bit of the rest of the world.

At least, you might venture out as far as your local Canadian Tire store, where you might see if they have their Pro Vacuum-Pressure Tester on hand.[1]

Scales in two sets of units—but neither of them torrs.

Part of my point, of course, is that Yannick is using a weird notion of the existence of an "industry standard" for a concept, a physical property, that is quite general in nature and which crops up in many different fields of activity.

BTW, Torrs shouldn't be capitalized if it has an "s" at the end; "Torr" (uppercase T) is the symbol for "torr" (lowercase t), and symbols aren't changed in the plural. Gene Nygaard 15:20, 15 April 2006 (UTC)

Hi, Gene. Thanks for your comments, but please stay polite. I am well aware that the automotive world uses psi's and pascals rather than torrs, but cars are a very small and low-tech fringe of the world of vacuum. I realize that the debate over units is not over, and that's why I was careful to leave a note about it on the main talk page when archiving the discussion. But I have worked with a wide variety of industrial and scientific vacuum equipment and I've done my research for this article - most of those footnotes are from me. The standard unit I saw pretty much everywhere is the torr. And yes, I am Canadian, and I've taken apart my motorcycle engine and put it back together a couple of times with Mastercraft tools.--Yannick 01:16, 16 April 2006 (UTC)

What about the Marine Engineering world? I'm quite aware the practical side of such a use is quite low-tech, but ever since ships used steam engines with condensing turbines, they more or less operated with the condenser at a vacuum (measured in inches of mercury, often with the use of steam "air ejectors", basically eductor pumps with the working fluid being saturated steam). On the more modern diesel engines, the engine crankcases are kept at a slight vacuum due to blowers, designed to prevent crankcase explosions, and such a vacuum is usually measured in inches of water (using a manometer). I know I'm really only discussing American ships, but British ships were built this way as well. --Hengineer 21:36, 16 July 2006 (UTC)

Vacuum - nothing to show for it

After months of arduous work, we have nothing to show for it. Seriously folks, I think we've done a good job on this page, it's quite stable, and nearly ready to go for FAC. Your constructive criticism would be appreciated.--Yannick 04:11, 4 April 2006 (UTC)

Lead can be safely doubled or tripled in size, at the moment it's pretty light. MoS is rather strict when it comes to bolding: unbold things like 'perfect vacumm' and turn them into ilinks. I'd recommend moving 'Historical interpretation' section to the begining - history often goes first and the current 'Vacuum Quality' section is rather to technical and can scare away people. I'd recommend expanding 'Uses' section - it is quite short now. Keep up the good work :)--Piotr Konieczny aka Prokonsul Piotrus ^Talk 21:49, 4 April 2006 (UTC)

:) Yes, I think, the lead section should be expanded and probably reworded, e.g. a reference in it seems to be inappropriate to me. Some of the sections should not just list characteristics with numerical values, but rather be description-style, in particular "Properties" section doesn't look good for me. But as concerns comprehensiveness, I see the article to be very good and helpful. Cmapm 13:57, 5 April 2006 (UTC)

Comment Techy stuff should go down the bottom, move Vacuum Quality / Measurement / Properties to the end, just before notes. --PopUpPirate 22:57, 6 April 2006 (UTC)

Thank you for your comments, all of you. I've working up close with this article for a few months, and had lost track of some of the wider perspective.

• I agree with your general comments to expand the lead and move technical details to the end, but I disagree on some of the specifics. I don't really want to move 'Historical interpretation' to the begining because I have concerns about its completeness and accuracy in its current form. The philosophical debates about vacuum were much more complicated than is currently represented. However, maybe 'Uses' and 'Vacuum pumping' would be suitable first sections? I had placed 'Vacuum quality' and 'Measurement' at the top to explain the quantification of partial vacuum early on, but this can probably be done in the expanded lead section.
• A minor edit war and arguments on the discussion page indicate that many users have trouble understanding the physical impossibility of perfect vacuum, despite explanations in the article. That's why I put a reference in the lead section. I'm not sure how best to deal with that. Your suggestions are appreciated.
• I reviewed the Wikipedia:Manual of Style and did not find it so strict regarding bolding. In fact, it seems to require bolding of alternate article titles such as "perfect vacuum". The legibility section says "Make judicious use of devices such as bulleted lists and bolding," but then it points to an outside article that seems to recommend bolding of the kind used in the Vacuum article.

--Yannick 02:47, 10 April 2006 (UTC)

OK, I just tripled the size of the lead section per your suggestions, and I think this should allow the restructuring you have recommended.--Yannick 03:57, 12 April 2006 (UTC)

I reordered the sections to try to meet suggestions. Please comment.--Yannick 03:17, 25 April 2006 (UTC)

Electrical properties of vacuum

Hi, the article at present discusses the electrical properties of vacuum which make "electron microscopes and vacuum tubes possible". This is true, and results from the fact that it there is nothing (or at least less) to impede the flow of electrons fired from one end of a device to the other. There is another electrical property of vacuum as well, and this is its ability to withstand a high electric field without electrical breakdown. In fact, the electrical insulating property (or dielectric strength) of high vacuum is only limited to the point where electrons are literally pulled out of the conductors. It is therefore used in several specialised high voltage applications. Not sure if I am explaining myself too clearly here, but this is an electrical property of vacuum that is separate from its ability to form electron guns, and so on. --BillC 20:40, 8 May 2006 (UTC)

There's a discussion about the insulating quality of vacuums on Talk:Electrical insulation DMacks 21:20, 8 May 2006 (UTC)

Historical interpretation

The article states that "Plato was right". Plato may have been right and may have been wrong. Are we forgetting that all of science, including quantum mechanics, is based on theory? It is at best an approximation of reality, and it is certainly not correct. I feel this sentence should be removed from the article as it implies we know the quantum mechanical interpretation of the vacuum to be the correct one - we don't, it is only our current theory. —The preceding unsigned comment was added by Corp1117 (talk • contribs) .

Perfect vaccuum exists or not?

"space can never be perfectly empty. A perfect vacuum with a gaseous pressure of absolute zero is a philosophical concept with no physical reality, not least because quantum theory predicts that no volume of space is perfectly empty in this way." -- This is probably a quibble, but any volume of space between atoms of gas has a gaseous pressure of zero, right? Although particles are produced by the decay of the vacuum, they aren't technically "a gas". -- 201.51.236.252 14:51, 7 November 2006 (UTC)

No. Read the Vacuum#Quantum-mechanical definition section for a full explanation. The "gaseous pressure between atoms" may be undefined, depending on your definitions, but it is not zero.--Yannick 23:42, 7 November 2006 (UTC)

Vacuum Graphs

I am a young and inexperienced Mechanical engineer. I would like to know if anyone out there could tell me where I can find a vacuum graph (if it exists). I know that when creating a vacuum, flow rate out of the pump is high initially and it slowly decreases as the pressure inside the control volume decreases. I think that this is exponential. I would like to see a graph that links Pressure, Time, and flowrate within a system under that process of decompression (vacuum). Greatly appreciate all your help. Cheers, --203.94.168.206

The relationship between pressure, time, and flowrate is different for every pump, chamber, and contents under vacuum, so you will have to develop your own graph for your own system. However, if you just want some examples, go to any vacuum pump manufacturer and lookup their specifications. Most of them provide graphs of pumping speed versus pressure. (example) You can learn a bit more about the math and how to relate time to these by looking at our vacuum pump article.--Yannick 14:16, 12 November 2006 (UTC)

pressures as low as 5×10-17 Torr have been indirectly measured in a 4 K cryogenic vacuum system. I think if you put one of these things in space you might get a lot closer to a perfict vacuum! {jason.d.c} —Preceding unsigned comment added by 68.90.159.37 (talk) 12:39, 22 September 2008 (UTC)

Solar Sails

"The idea of using this wind with a solar sail has been proposed for interplanetary travel." I believe that to be incorrect. Also contrary to what it says on the Solar sail page. "Another false claim is that solar sails capture energy primarily from the "solar wind": high speed charged particles emitted from the sun. These particles would impart a small amount of momentum upon striking the sail, but this effect would be small compared to the force due to radiation pressure from light reflected from the sail. The force due to light pressure is about 100 times as strong as that due to solar wind."

A solar sail uses the momentum of photons by reflecting them off its surface rather than the energy captured when a charged particle collides with it. Underlord 22:54, 10 December 2006 (UTC)

Density of intergalactic space

What is it? This article says: "But no vacuum is perfect, not even in interstellar space, where there are a few hydrogen atoms per cubic centimeter"

Whilst the Intergalactic Space article(http://en.wikipedia.org/wiki/Intergalactic_space) says: "The average density of the Universe is less than one atom per cubic meter."

Are these contradictory or is there some explanation that accounts for both statements? Even if there is, doesn't it seem more reasonable to quote the lower number ie "one atom per cubic meter"(assuming that is correct) when making a comparison to a perfect vacuum? —The preceding unsigned comment was added by 220.239.143.19 (talk) 14:01, 11 January 2007 (UTC).

I don't think there's any contradiction here. Interstellar space is much denser than intergalactic space. Possibly it would be more comprehensive to say "But no vacuum is perfect, not even in intergalactic space, where there are a few hydrogen atoms per cubic meter," but the word "intergalactic" is not as well known to a general audience as "interstellar."--Yannick 01:45, 14 April 2007 (UTC)

NEITHER of these states would be logical to include as an example of an exceptionally vacuous environment, since even the lower number represents the _average_ density. Therefore, there must be some region(s) of the Universe that are substantially lower in density, since stars (etc...) are much higher, and those regions and numbers would be the appropriate example.

BTW: Sorry if this is already addressed. What about energy, such as light (e.g. solar pressure)? And the degree to which it is dispersed it may be virtually pervasive (e.g. background microwave radiation)?

~KC

Interstellar space intergalactic space vacuum density. Kasaalan (talk) 20:21, 11 December 2009 (UTC)

Home Vacuum Power

I was just wondering, does anyone have an idea of how much of a vacuum a home vacuum could create? Like a shop vacuum with .5 or 1 horsepower? (Anser in microns or atmospheres please, seeing as I don't know any of the other measurements) Also, do they make gauges to measure how many atmospheres/microns you have in something. Like a vacuum gauge?? Lastly, how many horsepower does a super vacuum have? Like one that will pump down to 1 micron and stuff like that? Thanks —The preceding unsigned comment was added by 67.86.150.183 (talk) 01:51, 9 May 2007 (UTC).

Well, we're on the vacuum page, so let's look there...seems that the "Examples" section gives a household vacuum cleaner pulling down to about 80 kPa (600 Torr). A torr is equivalent to mm Hg (760 torr is 1 atmosphere), so you can't really get a very good vacuum at all that way, only 6/7 atm or so. You're on an encyclopedia website, so I assume you tried searching for the t erm "vacuum gauge"? So you found the vacuum gauge page, which indicates that there are many different types of them, each tailored to specific pressure ranges. Horsepower isn't really a useful term here, since different types of vacuum pumps operate by different mechanisms entirely...the strongest and fastest blower motor in the world can move a lot of air, but it can't produce a very good vacuum. DMacks 02:10, 9 May 2007 (UTC)

Would it be good to present a graduated scale from 1 Atm to 0 showing the following:

Human sucking on straw

Home vacuum cleaner

Vapor pressure of Hg.

Pressure in light bulb

Pressure in TV CRT

...

and so on, you get the idea. This is a research project, would probably answer many questions John (talk) 02:14, 23 March 2008 (UTC)

Heisenberg Uncertainty Principle

In the "Quantum-mechanical definition" section: "Another reason that perfect vacuum is impossible is the Heisenberg uncertainty principle which states that no particle can ever have an exact position." This is a partial statement of the uncertainty principle. As the full page explains, the position of a particle can be known to arbitrary accuracy, at the expense of knowledge of the momentum. Moreover, this incarnation of the uncertainty principle does not seem to be responsible for vacuum fluctuations. According to the Virtual Particle and Casimir Effect pages, the energy/time (not position/momentum) uncertainty principle gives rise to the creation of virtual particles which affect the idea of "perfect vacuum." I don't think that in the context of an astrophysical vacuum (or even a laboratory vacuum) the issue is the spreading of the wave function. Since the wave functions die off over long distances (they have to for the wave functions to be normalized), it seems like this effect is not really what impacts the "perfect vacuum." Does this jive with other people's understanding of this issue? —Preceding unsigned comment added by Jack.m.gill (talk • contribs) 22:39, 29 October 2007 (UTC)

Some people claim there is a perfect vacuum between molecules. (You can find an example of this higher up on this page.) My understanding is that this is incorrect, since particles are not point entities but rather spread out and overlapping wave functions. That's the point I was trying to make. I'm not sure that energy/time and position/momentum uncertainty are really distinct principles, and I thought that the wave function just tended towards zero over distance, with no finite boundary. But I confess that I flunked out of quantum, feel free to rewrite this if you think you understand it better.--Yannick 01:05, 30 October 2007 (UTC)

How's this for a rewrite of the second paragraph, splitting it into two paragraphs:

Even an ideal vacuum, thought of as the complete absence of anything, will not in practice remain empty. Consider a vacuum chamber that has been completely evacuated, so that the (classical) particle concentration is zero. The walls of the chamber will emit light in the form of black body radiation. This light carries momentum, so the vacuum does have a radiation pressure. This limitation applies even to the vacuum of interstellar space. Even if a region of space contains no particles, the Cosmic Microwave Background fills the entire universe with black body radiation.

An ideal vacuum cannot exist even inside of a molecule. Each atom in the molecule exists as a probability function of space, which has a certain non-zero value everywhere in a given volume. Thus, even "between" the atoms there is a certain probability of finding a particle, so the space cannot be said to be a vacuum.

I think this makes the distinction between the different phenomena more clear. It also side steps the issue about the Heisenberg Uncertainty Principle, which is really a subtle point probably best discussed elsewhere. Thoughts?

--Jack.m.gill 23:03, 30 October 2007 (UTC)

I think it's better than what we have now, so please be bold and put it in. Welcome to Wikipedia, by the way! I'll leave some good introductory links on your talk page so you can learn a bit more about how Wikipedia works.--Yannick 00:45, 31 October 2007 (UTC)

NO! I disagree. There certainly ARE definite regions of the Schrödinger wave function that are equal to zero. These are forbidden regions where the probability of finding an electron is zero. This is why, in the simplest case of a hydrogen atom for example, the available energy levels are discreet with regions disallowed. The electrons jump from one allowed orbital to the next available orbital in discreet (NOT CONTINUOUS) steps, without every existing in the interstial space (i.e. quantum tunneling). For a hydrogen atom, this includes the region from the nucleus up to 13.6eV (s1, or first orbital) then another region from the first to the second orbital etc... for an isolated hydrogen atom, most of the space around it is a true vacuum. These discreet levels for atoms split into bands for molecules and atoms in bulk, so while the available regions (N or density of available states), increase, forbidden regions remain. For molecules, this includes the regions in semiconductors between the valence and conductions bands (or HOMO and LUMO levels) which are a forbidden zone for electrons (zero probability distribution)and DO represent (as far as science knows at this point) a true ideal vacuum! I refer those interested in knowing more to "Solid State Electronics" (Streetman, Bannerjay), "Solid State Physics" (Ashcroft and Meriman), "Quantum Mechanics" (Merzbacher) and/or "Quantum Mechanics, concepts and applications" (Zetilli).

I think the confusion here comes from the fact that the wave-function is continuous in that it is assumed not to have any points of discontinuity, but that is not the same as having a finite and positive probability everywhere (which it DOES NOT). If it did have a continuous, positive (non zero) distribution everywhere, we would lose the "Quantum" part of quantum mechanics. Therefore, mathematically, and as far as we know, really, a true vacuum exists everywhere the probability distributions (Chi squared) for all particles is zero. These regions are real and significant (not a trivial theoretical anomaly). This is a lay explanation. The true answer forbids not only energy level regions, but also sets of solutions of momentum vectors in k-space (for example). But the point is, there are spacial regions where the probability of finding a particle is zero, and that's, by definition, a vacuum. BTW: regarding the points made above about normalization of the wavefunction, even functions with everlasting expoential decays which approach zero at inifinity (at the limits), can be integrated to finite areas (for convergent functions/Taylor series); as counter-intuitive as it seems, an infinite series CAN have a finite sum. [David Keith Chambers] Dec. 13, 2007. —Preceding unsigned comment added by 74.193.250.232 (talk) 04:59, 14 December 2007 (UTC)

As I understand it, electrons do jump between discreet discrete energy steps, but it's exactly that precision in energy level that makes spatial position infinitely diffuse. Atomic orbitals are clouds with no real boundary. The orbital shapes normally drawn are actually a probability envelopes, e.g. 90% chance of finding an electron within this envelope at any given instant in time. It's true that outside of atoms there are always lots of free electrons with highly uncertain energy state whose wave is excluded from certain spatial regions. But each electron whose energy is precisely known has a wave function that permeates the entire universe.--Yannick (talk) 01:58, 17 December 2007 (UTC)

Quantum Tunneling does not involve a particle moving through a region in which it has no probability of existing. On the contrary, quantum tunneling exists BECAUSE a particle's probability function only decreases exponentially, not instantly, when it reaches a region of greater potential than its kinetic energy. So on the other side of the region, a finite probability for the particle will always still remain. That's why tunneling is only practically observable across very small distances -- because the probability is exponentially decreasing throughout the barrier. Erikmartin (talk) 19:10, 8 October 2008 (UTC)

Yannick, I think you are confusion momentum and energy. If you know the exact position, you know nothing about the MOMENTUM (not the same as energy). [DKC]

OK, my wording was inexact. But if you know the energy and mass of an electron precisely, then you know its momentum precisely, and that makes spatial position infinitely diffuse. I don't think you've addressed the core of my argument.--Yannick (talk) 20:22, 23 December 2007 (UTC)

Light bulb filaments

The metal filament bulb we know today is a 20th century invention. 19th century lamps were carbon filament. There were also 19th century metal filament lamps, but they were very different to the type we use today, and not practical for general lighting use.

The confusion seems to be very common. Tabby (talk) 06:08, 5 January 2008 (UTC)

True enough, but this information is already in the incandescent light bulb article. The tungsten light bulb was the one that put a vacuum in every household for the first time, and I think that's the point that's important to this article.--Yannick (talk) 14:13, 23 March 2008 (UTC)

Irving Langmuir worked out that a low-pressure inert gas fill is better than hard vacuum in a light bulb. Material that boils off the filament sticks to the glass envelope, and rapidly forms a dark coating if the pressure is too low. A bit of inert gas won't stop the material from boiling off or, the filament from eventually rupturing, but it does prevent the stuff from darkening the glass. —Preceding unsigned comment added by 71.199.121.113 (talk) 14:58, 24 February 2010 (UTC)

Crook's Tube Photo (Isn't)

The photo caption is wrong, the photo shows an early X-Ray tube. Do we want a "real" Crooks tube photo or do we want to fix the caption. Anybody care? John (talk) 02:08, 23 March 2008 (UTC)

Sure, I care. But isn't the only difference between a Crookes tube and an X-ray tube the nature of the target? We can't really see it in this photo, so how can you tell it's not a Crookes tube? Do you have a picture of a "real" Crookes tube to offer instead?--Yannick (talk) 12:42, 23 March 2008 (UTC)

Vacuum is a singularity

A vacuum is not a volume of space. A vacuum is a singularity. Spacetime is altered by a vacuum singularity. The single point affects matter, pulling on the walls of a canister that contains the vacuum, evenly. -BPL —Preceding unsigned comment added by 75.162.45.212 (talk) 20:35, 13 June 2008 (UTC)

partial vacuum

"The first suction pump, a device which sucks fluids into a partial vacuum, was invented in 1206 by the Arabian engineer and inventor, Al-Jazari. The suction pump later appeared in Europe from the 15th century."

-i have deleted this from that page because it contains factually inaccurate material, which is not backed up the sources listed. Neither of your source state that Al-Jazari's suction pumps created partial vacuum. You are correct in saying that a suction pipe can create a partial vacuum, but that just modern suction pumps, and even many modern cannot create one. Most importantly neither if your sources make that claim, so there is no reason to believe Al-Jazari's did, you are going to require a respectable source to back that up, you can't just assume because your making the assumption that his suction pipes resembled modern ones. -lastly, the creation of a partial vacuum is not something all entirely knew, they can be created by a syringe without a design alter, follow this link: http://www.exo.net/~pauld/activities/boylingwater/boylingwater.html. In fact most suction devices can create a partial vacuum. Heron invented the first syringe, follow this link:http://en.wikipedia.org/wiki/Hero_of_Alexandria#Inventions_and_achievements Your free to list the fact that Al-Jazari invented a suction pipe, but not a partial vacuum since you don't have a source to back that claim up Tomasz Prochownik (talk) 06:25, 27 July 2008 (UTC)

Etymology

Why is vacuum is spelled that way: its not in this page. Something should be done. there is no other word spelled with two u's. its a cryin' shame information like this is not at my fingertims. —Preceding unsigned comment added by 71.193.226.225 (talk) 03:41, 23 August 2008 (UTC)

• Residuum and continuum come to mind. The words come from particular neuter forms of latin transitive verbs - 'be empty', 'contain', 'remain', etc. The information seems a little beyond the scope of the article (a simple etymology is already given) but is at home in wiktionary. Moreover, menstruum, carduus, equus and derivatives also have a double 'u' so this spelling is by no means unique, just a bit rare. Eutactic (talk) 04:49, 7 September 2009 (UTC)

The Vacuum Gluon Field / Animated GIF

It seems to me that something should be added discussing that even in a theoretical vacuum of zero gaseous pressure, zero matter, and zero light, current understanding of physics (quantum chromodynamics) describes a dynamic and pervasive gluon field. If possible, I think this animated gif[2] should be added to the article. It shows the dynamic topological vacuum color charge, from a computer simulation of the vacuum gluon field. However, I don't really know about the usage considerations, or whether permission would have to be obtained in order to use it. It's from Derek Leinweber of the University of Adelaide[3], and was used in Frank Wilczek's 2004 Nobel Prize Lecture. Erikmartin (talk) 16:52, 7 October 2008 (UTC)

Mean free path of cryopumped MBE chamber?

it says 1.10^5 meters.. wouldnt it be easier to put 1.61 meters? —Preceding unsigned comment added by 96.18.35.35 (talk) 23:05, 6 December 2008 (UTC)