Vacuum Definition and 1000 Threads

Ok, this might seem like a silly question, but I just want to get it straight. Just tell me if anything I am saying is wrong, and answer the best you can. Ok, the moon has no air, because it has no atmosphere correct? And the reason for no atmosphere is because the moon is biologically...

Hi! I'm trying to model a vacuum pipe on Ansys. I've already modeled it using an isotropic material, assuming its a plane strain problem (infinate pipe), but now I want to use a laminate structure composed of an orthogonal material such as nomex (honeycomb) with a seal tight layer of Al or...

Following are some fascinating ideas (to me anyway) on the origin of mass and gravity from the quantum vacuum...have these ideas been dissected here in the forums before?? A superficial search did not turn up anything. Comments/criticisms? Other threads?? Tentative outline of a research...

The vacuum polarization result in QED seems to always be written in a "QED form". I would be interested in seeing it in an old-fashioned classical physics form. Without vacuum polarization the electric potential in a region containing a point charge is of course Q/r. So if the vacuum...

As I understand it, string theory only has one coupling constant, but there is a whole discrete landscape of false vacua, each of which gives different values to the quantities, such as coupling constants, that are taken to be fixed inputs to the standard model. Since the false vacua are...

I would like to have a conceptually better understanding of GR solutions in the absence of matter, and a little difficulty I usually run into is that seemingly since in these solutions we have both the Einstein and stress-energy tensors equal to zero (which is what it means to have no...

Homework Statement Calculate q, w, ΔH, ΔU, ΔS for the following problem: One mole of a monatomic ideal gas starting at 300K, and 10 atm, the gas freely expands into a vacuum to triple its volume. Homework Equations w = PΔV, ΔU = q - w or Cv dT, ΔH = ΔU + PΔV or Cp dT, ΔS =...

Is it possible for electricity to jump a vacuum gap? If so, what is it called when that happens?

Hello all. Another year has begun and yet again I'm stumped with all this stuff. If anyone can provide me with sources, articles, or any type of information to help me with this design process. I uploaded a word document with a pretty nice intro I wrote with all the formulas and a...

What would the moistue content be inside a cylinder where a vacuum is pulled 25-30HG? Could such a cylinder be used to "dry out" something?

Hey physics forum, My name is Lawrence and I have a crazy idea, i want to create a vacuum container (as close to space as POSSIBLE). then I want to fill it with equal parts of the pure elemental gases. I know this might be impossible but if anyone knows away to build a containment field...

I'm wondering if the speed of light in a medium other than vacuum is well defined. I explain myself: Say I am underwater and I create a laser pulse. I know that at any given time, the speed of the photons constituting the light is always c. However I also know that photons will get absorbed...

First off, I'm not in any way anti-LHC. Quite the opposite to be honest. Even so, this speculative disaster scenario (vacuum bubbles) have caught my attention latelly, and I haven't been able to let go off it. Mostly because I find the otherwise brilliant LSAG-report (both actually) to be quite...

I have small question computing vacuum expectation values here http://www.cns.gatech.edu/FieldTheory/extras/SrednickiQFT03.pdf" from Mark Srednicki. My problem is with equation 210 on the pdf page 69. In the second line of 210, where does the second term come from? Z(J) and W(J) are defined...

I had a idea while driving, I have some physics background from college but not much. If an object were to fall in a vacuum with a gravitational force there would be nothing from slowing it down and it would keep accelerating. If you were to drop an bowling ball in a vacuum with a extreme...

As the title states, if I go to space and detect several atoms per square meter of space, does this suggest that the space between these atoms is essentially void of all forms of matter? Thus is this a perfect vacuum?

When the LHC was starting up, there were some worries that a collision of two particles could form a bubble of "true vacuum", as opposed to the "metastable vacuum" that the universe is in today. This bubble would then expand outward at the speed of light, annihilating any matter that stood in...

Five years ago I posted this question. At the time it was difficult for me to understand almost all of what I was trying to learn and was very frustrated. I put it down and studied other stuff including math. I just looked at this question again and am finding myself still unable to derive...

I understand that there are 4 forces: Gravity, Electromagnetic and the two nuclear ones. So, which one is responsible for the force that pushes air (for example) into a vacuum? Am I correct in assuming its electromagnetic? Like... there is some sort of electromagnetic potential between the...

I wonder if there is any correlation between the weak coupling of a quantum field in the path integral and how it adds to or cancels out vacuum energy. If so, then how would weakly interacting dark matter effect the vacuum energy? Thanks.

"Vacuum Catastrophe" When looking at http://en.wikipedia.org/wiki/Vacuum_catastrophe I thought about my problem in understanding the question of virtual particles being real physical things or not. It appears to me that if the virtual particle pairs were actually real, always existing in high...

Hi, I was wondering about the G\tilde{G} term that can be added to the QCD Lagrangian. It seems clear that the analogous QED term can be left out because it is (just as the G\tilde{G} term) a total divergence and thus has no influence on the physics. But in the case of a non-abelian gauge...

I am trying to fit a vacuum pump at one end of a pipe system and a cylindrical container with a size that has minimal clearance with the inner pipe wall would be inserted at the inlet to the pipe system. The purpose of the vacuum pump is to create a pressure difference so that the lower...

I'm witnessing an argument elsewhere about whether a vacuum is a good insulator in space. Person 1 said this: Person 2 said this: I said this: what would really happen if the vacuum between us and the sun were replaced with steel?

Hi, I would like to learn to to design Vacuum Systems for typical materials processing. Pressures on the order of 1*10^-8 torr. I know there is an ASME standard, but I am looking something more introductory that goes about how the fabrication is done and what calculations are important. If...

Hello everybody, I have kind of a philosophical question about vacuum and piston. I know this does not work in the real world because, of imperfection in seals and lack of "real vacuum", but here it goes. If you have a tube which is closed in one end, open in the other end, and 100% rigid...

I need Help measuring central Vac low voltage circuit. I would like to put a relay in line if possible to trigger when the unit powers on. I measured 17.78 DC volts when off and then 0 when vacuum powers on. Seems like an odd voltage for the contacts that start the unit when you insert a hose.

I saw a science fiction movie in which some guys planted an atomic bomb in a cave in an asteroid which was headed toward Earth. The bomb blew the asceroid into a million meteroites which harmlessly burned up in the atmosphere. Is this possible ? An atomic bomb, detonated on Earth, creates...

According to http://tinyurl.com/2cfghd5", an Australian physicist has discovered that The Oxford dictionary's definition of "siphon" is incorrect, attributing its effect to atmospheric pressure, rather than gravity, which is what he maintains causes it a siphon work. This seems to me to come...

The Oxford dictionary is about to change its definition of a siphon to remove the reference to air pressure as being required. Will a siphon work in a vacuum?

This is a question about solving Einstein's Field Equations for some simple cases, but I'm not sure how to explain this without analogy. So bear with me for a brief discussion. Consider the electrostatic equation: \nabla^2 V = \rho / \epsilon_0 which show explicitly how the charges source the...

Boiling point in a vacuum... Gidday, I am as new here as it gets, and I have a question to post. I have been having a (heated) discussion with regards to the temperature that water boils in a vacumm. Given: @ 10in Hg water will boil at 192F. If you had a pressure reading of 29.7in of...

Need a vacuum cleaner? My wife just brought home a new Miele and test-drove it. She loves it. We have bought and maintained lots of vacuums over the past ~30 years, and none of them performed all that well - even the top-end Electroluxes. A co-worker of hers used to sell and service Mieles...

I'm studying (relativistic) quantum field theory and have a very simple question. Take for example the real scalar field. My notes simply state that <0|0>=1 is a very natural normalisation. If I'm not mistaken, then this implies that the probability of measuring the vacuum state is 1. How is...

Hi, Even though it is called 'vacuum energy'... do we know or do we have some theory on... whether the activities of virtual particle pairs is the same whether in the relative vacuum of space or... with in ther Earth's atmosphere (where tests confirmed it) or... say inside a rock? Rusty

Old CRT tv's use vacuum tubes and they get hot, but how does the glass get hot when the inside is under a vacuum and therefore shouldn't transfer any heat?

Can any dry pump be reused for evacuating a chamber? Ie: I have a 2hp compressor, can I use it to make a vacuum chamber. -lamonster

If light travels at constant velocity c in vacuum and constantly relative to any inertial reference body, then does that not mean all bodies and space are perforated, or rather filled in, with vacuum within which light can travel?

I've read ZapperZ's thread on the speed of photons through a solid and am still confused. If you imagine an experiment where two emitters A and B are set up to emit one photon each simultaneously towards two receptors (also A and B)in a vacuum 558,000 miles away. The receptors will sense the...

Hello PF, If the the interacting field (phi^4 theory or QED) vacuum corresponds to bubbles for example: photon goes into electron-positron pair and then vice versa.. etc... etc... To what does the free (non-interacting) field vacuum correspond? 10x

Are there any substances that are liquid in a vacuum? It seems mercury should be liquid. If so, what forces keep it from solidifying, yet not disipating into a gas?

Homework Statement A space capsule, which may be treated as a sphere of radius 10m, is hit by a micrometeorite which makes a hole of diameter 2mm in its skin. Estimate how long it will take for the air pressure to drop by 30%. Avogadro's number is about 6 \times 10^{23} Homework Equations...

Hey, Can anyone help me with my imaginary experiment? In a large glass tank I place air-filled balls of thin rubber (like a balloon but perfectly spherical). I fill the tank to the top with the rubber balls, seal the lid and evacuate the tank of air. The internal pressure difference...

The maxwell's equations in vacuum are satisfied by a non trivial solution involving \vec E (t,\vec x) and \vec B (t, \vec x). Correct me if I'm wrong. I don't really understand the physical interpretation of the solution. I know that if I'm given an initial condition then I can know the...

Is the space between the electron shell and nucleus a perfect vacuum?

Hey guys, I have a question; I was in a Physics lesson at school today, me and my teacher got into a discussion about space and vacuums. Somehow we managed to get marsh mellows into te convosation, and my mind wondered until I came up with this question - If a Marshe Mellow is traveling...

We all know that if you accelerate at 1g in a vacuum, you'd be pressed into the floor/wall of your spaceship in the same way that you're pressed into the ground on Earth; that is, you would have "Earth Gravity". I got into a discussion with some people about the structural integrity of a...

I have a powerful vacuum motor and wanted to put it to use. I would hate for a great functional motor to go to waste. Any project ideas, excluding vacuum cleaners?

Does the process of pair production mean that the quantum vacuum fluctuations can produce atoms(given enough time) as the following quote on wikipedia seems to suggest? Has it been experimentally confirmed that atoms can be formed in the seething with virtual particles zero-point energy state of...

Difference between "Nothing" & Vacuum Could you please tell me what is the difference between "Nothing" an a "theoretical perfect vacuum" ? The question is serious. Regards