Vacuum Definition and 1000 Threads

Hi Everybody am using chemical vapour deposition unit for coating silver thin films. The pirani gauge is not showing readings, t he readings are fluctuating, but the penning gauge shows reading. am not able to make out where is the problem. 1. is the gauge needs to be cleaned due to...

I'm programming a simple physics engine that works with rockets in space. I haven't done any physics since high school and I'm embarrassingly lost on how to proceed. What I have is a constant mass (say 50,000kg for example), and a constant thrust (75,000N for example) on the mass. The mass is...

A plane electromagnetic wave[traveling in the x-direction in an inertial frame]in vacuum is usually represented by an equation of the form: {E}{=}{E_{0}}{exp{[}{i}{(}{k}{x}{-}{\omega}{t}{)}{]}} The wave velocity[phase velocity] is given by: {c}{=}{\frac{\omega}{k}} We can perform Lorentz...

Picture a 15' sailboat with a hull made of a sandwich (from the outside in) of gelcoat (relatively impermeable), resin-impregnated fiberglass, stiff closed-cell foam, then more resin-impregnated fiberglass (which you see looking into the boat). The foam is not one piece, but a grid of 2" x 4"...

Hello, I was hoping for some information on vacuum systems. There are two side channel blowers that produce -8kPa of pressure on the inlet. The outlet pressure in roughly the same. The two blowers are connected in series. Can some please refer me to some reading material so that I...

hi, does anyone know why vacuum energy has negative pressure? is it only experimental or it is theoretical too? i also wonder if the negative pressure of the Casimir effect is absolutely negative or if it is relatively negative relatively to the rest of the laboratory? i would be...

One of the proposed explanations for the Pioneer Anomaly is that the additional deceleration is caused by interaction with the vacuum energy. http://en.wikipedia.org/wiki/Pioneer_anomoly#Definition_of_inertia_modified This makes sense to me, given that some of the particles must actually...

hi, just to be sure, I believe that an electron in complete vacuum, that does not interact, carries an electromagnetic field, and that this electromagnetic field is mediated by virtual photons even when there is only one electron, in vacuum, that does not interact. is that statement correct?

Deviations from the vacuum energy bring about deviations from a Euclidean spatial geometry. Fine; I am not questioning this principle. I am wondering why a Euclidean metric is the base from which everything deviates? An answer that it is the limit of more general metrics only begs the question...

Hi, I've been reading about particle- and quantum physics and have seen some educational video's about it. But I do have a probably philosophical question about it. Most likely based on ignorance (but what question isn't) and false interpretations of what I think to know. This is what I...

This isn't a homework question but if it belongs in another thread please tell me so I can switch it. I was just wondering if there is an "agreed-upon" speed that an electron would travel in say a vacuum? I understand that one can continue adding energy until the electron reaches very nearly...

Hi, So this question might be a little simple, or not. But I was wondering about the exact nature of magnetic fields. Now obviously magnetic fields work in a vacuum(due to the fact that it's not a perfect vacuum), but would a magnetic field exist in a theoretical perfect vacuum? Now I think...

In a Vacuum, a coin and a feather fall equally, side by side. Would it be correct to say that equal forces of gravity act on both the coin and vacuum? Explain Id say they have equal forces acting on them. Gravity is the only force acting on them its just that there's no air resistance so they...

Homework Statement I have attached a diagram, for this question, I am stuck on how to calculate the flow rate. there is 70kg/h of feed going into the evaporator, of which 11% is solids, so that's 7.7kg/h of solids, and so 62.3kg/h of liquid in the feed. so now how do I calculate the...

What is the relation between a vacuum state in light-front quantization and a vacuum in the equal time formulation? For example, I quantize a free field at equal light-front time and make a mode expansion. The resulting creation and annihilation operators can then be used to define the...

Finding resistance in a vacuum (triode??) Homework Statement Suppose that we decided to provide the grid bias emf (-8volts) with a grid bias resistor, R(b), inserted between point B and the cathod. (E(c) is to be removed from the circuit, of course.) Assume that there is a negleigible current...

http://hackedgadgets.com/2006/06/03/vacuum-cannon/ I was wondering how this can possibly work. There's even instructions on how to make it but theoretically, i don't know how a vacuum can do this

Hi I'm trying to learn more about the Unruh effect, and was wondering if someone could comment on how exactly the lack of Poincare symmetry in a general curved space leads ambiguity in the notion of "particles". Why exactly do we associate particles in QFT with positive frequency modes...

Minkowski vacuum is Poincare invariant and quasi-free state. I wonder if these two conditions fully define it or there are more states which fulfill these conditions (or maybe Poincare invariance alone is sufficinet). Thanks for answers.

It is said that its not good for your computer to be cleaned with a vacuum cleaner (the inside) as long as the vacuum cleaner is on "intake" mod. If there is, however, an "output" mod, then its ok. I don't entirely understand this. I understand that the moving air can easily charge up the...

Homework Statement A rocket of initial mass m_{0} accelerates from rest in vacuum in the absence of gravity. As it uses up fuel, its mass decreases but its speed increases. For what value of m is its momentum p = mv maximum?Homework Equations Tsiolkovsky rocket equation: v(m) = v_e ln \left(...

hi the airy disk equation is d= 1.22 lambda / NA my question is: lambda is the wavelength in medium or in vacuum? thanks in advance

In QFT expressions such as these hold: real scalar: \Delta_F(x-x')\propto\langle 0| T\phi(x)\phi(x')|0\rangle 4-spinor S_F(x-x')]\propto\langle 0| T\psi(x)\bar{\psi}(x')|0\rangle where T is the time-ordering operation and the proportionality depends on the choice of normalization...

Ok I been trying to figure partially exactly what things in Quantum Mechanics, Quantum Field Theory, QED, or any physics that matter gave rise to concepts of things like hyperspace and multiverse and other theories that seem to have more of a fictional history and origin than the original...

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...

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'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...