Vacuum Definition and 1000 Threads

Hi all, I have a vacuum chamber which is consistently pumped out by a mechanical pump at the downstream end and is fed nitrogen at the upstream end. The path of the nitrogen is as follows: A mass flow controller regulates 150 SCCM flowing at all times. The N2 flows through several feet of 1/4...

OK the atmosphere by definition envelopes the earth.The force keeping it here is solely gravity. The "force" opposing this is diffusion across a pressure gradient into the vacuum of space. Assuming that is correct how could I prove this other than looking out the window. Newton's law of...

First Question on this forum, here goes... IF you have a large syringe(no needle), and put your finger over the tip of the syringe, then pull back on the plunger, you will feel a resistance on the plunger due to the VIOD your are trying to create. In essence there is NOTHING in the void... SO...

If I induce vacuum in a glass tube and then I open the lid of the glass tube, air rushes into fill in the vacuum. Can vacuum be regarded as a sort of potential energy, able to exert a force? Can a vacuum tube be considered as a potential storage device for energy, just like a container filled...

Hello to everyone. My first question on this forum (it was quite tricky thinking of a heading and prefix for this thread!): Imagine for a moment that there is a hot air balloon which has a strong shell forming the balloons shape rather than one made from material and it weighs the same as a...

Hi, I'm wondering if a vacuum pump outlet air could be used as a blower? I have a small open-type wind tunnel that have been used with the vacuum pump by sucking the surrounding air. Could I use the outlet air from the pump to work as a blow-down wind tunnel? Thanks

klotza submitted a new PF Insights post Explosion-Generated Collapsing Vacuum Bubbles Reach 20,000 Kelvin Continue reading the Original PF Insights Post.

Hi everyone I was wondering, why is vacuum energy related to the zero point energy of an harmonic oscillator? The hamiltonian of an harmonic oscillator is $H= \frac{p^{2}}{2m} + \frac{1}{2} \omega x^{2}$. Where does the harmonic potential term come from in the vacuum?

Ok I heard that a very fast spinning top, in a perfect vacuum, on Earth, would stay spinning forever, and I suppose it would in the middle of the vacuum without falling, because spinning at lightspeed means it can't move 1 down, so if the speed in this top stays in it, then it could avoid...

I guess the question is also when. If you have some food or liquid to store. If you use a low quality cooler bag with 200mL to 300mL Ice pack at what point will a Vacuum seal with no Ice beat the cooler bag? I guess at the 10 hour mark or 24 hour mark or at some very long period of time.

Having trouble at a plant where the vacuum has increased to the point where a pump has been put on the end of the air ejector condenser to maintain vacuum, without it the limits would be too high and trip the Steam Turbine. The question is, does the air ejector condenser continuously drain...

It's my understanding that matter holds charge on Earth from the insulation of the atmosphere, since the atmosphere is a bad conductor and essentially blocks current due to the gaseous molecules' atomic structure and their covalent bonds. Does this mean it's impossible for matter to hold charge...

Hi, I am studying the Metal-Semiconductor junction. I cannot find any clear explanation of the continuity of the vacuum level at the interface. Can someone help me? My reference book provides me with the following: When two different materials are brought into contact, they must share the...

Hi, The Hamiltonian for the free scalar field, expressed in terms of the creation/annihilation operators, is H = \int d^{3}p [\omega_p a^{\dagger}_p a_p + \frac{1}{2}\omega_p \delta^{3}(0)] \hspace{3mm} I thought: \omega_p is a function of p as \omega^{2}_p = |p|^{2} + m^2 and so the...

Hi there, I have recently observed a strange effect regarding a fan and was wondering if someone could explain what's going on. I have a 22cm computer case fan which I am using in a project. For my purposes, I had to partially tape over the back of the fan. I also put a large plastic jar lid...

I don't recall where I saw this...but the author said that the Casimir effect experimentally proved that vacuum fluctuations exist. Does the Casimir effect really prove that or is it consistent with vacuum fluctuations? Thanks for any comments you care to make.

In the canonical formulation of QFT (to which I've been exposed), it is always argued that only differences in energy are physically observable and so we can deal with the fact that the vacuum energy is infinite by redefining the vacuum such that its energy is zero and we subsequently measure...

As far as I understand it gravity is sensitive to absolute energies, as seen directly through Einstein's equation G_{\mu\nu}=8\pi GT_{\mu\nu} Thus the local geometry of spacetime is directly affected by the local energy density (and not just differences in energy). So whenever gravity is taken...

Is space actually a vacuum or it is so large that any matter is negligible?

Why the kink (\phi(x)=tanh(\frac{x}{\xi})), can not tunnel into vacuum +v or -v (Spontaneous symmetry breaking vacuum). From the boundary condition(x\rightarrow \pm\infty, \phi(x)\rightarrow \pm v), it is self-evident. but the book states: Due to the infinite high energy barrier, the kink...

Do we know if the instantaneous/observed acceleration due to the vacuum is directly proportional to distance or possibly? (ignore any gravitational effects) A~D ? A~D^2 ? A~D^(1/2) ? A~D^(-2) A~D^(Other) ? OR A= constant (edited as I forgot this one) If not, is there a best guess/fit or...

Hi all, I have a question about the ground state of an interacting quantum field theory. The state space in non-interacting QFT is a space where each field mode (with specified momentum p) has some occupation number n. These modes are interpreted as n particles with momentum p. The vacuum is...

I want to ask a question about the Quantum Vacuum, but I want to make a few statements about my understanding of the Classical concept of a vacuum to act as a background. 1.)As I understand it, the classical vacuum is a place where there is nothing. 2.)Two attributes of the classical vacuum are...

So I've been wanting to build a particle accelerator for a while, and have kind of been brain storming ideas to make it work. I've been recently trying to figure out how to get the actual acceleration to happen. I have a few ideas, but the one that I like (assuming it's possible) is using a...

I have no qualifications in science but find it fascinating in general. Could anyone answer the following for me? Imagine an immensely strong pipe closed at one end with an airtight piston pressed tightly against the closed end. (a) Is it possible to pull the piston any distance along the...

I have read that freeze drying is the best way to salvage wet books (http://www.ccaha.org/uploads/media_items/technical-bulletin-salvaging-books.original.pdf). However, freeze dryers run in the thousands of dollars, and I don't know anyone who has one I can borrow. Solution: make my own! I...

Homework Statement A monochromatic plane wave with frequency ##\omega## and real amplitude ##E_0## passes from medium 1 to medium 2 orthogonally with the surface between the 2 media. Both media are semi-infinite; the indices of refraction are ##n_1=\sqrt{\mu_0 \varepsilon _0}## and...

For instance our quantum vacuum has a certain Cosmological constant and the question is can there be other vacuums with different values and if so where's the evidence for this I would like to read it. How do you derive the Cosmological Constant through something like Quantum field theory or...

http://arxiv.org/abs/1507.05760 Higgs boson cosmology Ian G. Moss (Submitted on 21 Jul 2015) The discovery of the Standard Model Higgs boson opens up a range of speculative cosmological scenarios, from the formation of structure in the early universe immediately after the big bang, to relics...

I want to build high voltage feedthroughs (vacuum) from epoxying pieces of alumina together, and then epoxying alumina strips on the outside to cover the spaces between. Can I use JB weld, as far as things go electrically? People have reported that JB weld is unexpectedly wonderful for vacuum...

I understand mild steel is very bad at out gassing so is never usually considered for hard vacuum applications. But if the decision was constrained by other factors would it be possible to apply a surface treatment or coating to the internal walls of the vessel - am I correct in assuming that as...

I have two tanks next to each other, first needs to be kept at 200 mmHg vacuum & the second at 500 mmHg. Both are attached to a vacuum header which can achieve a 600 mmHg vacuum by means of a water jet ejector. What is the best way to maintain the vacuum levels? Would a set of globe valves...

The speed of light is constant in all frame of reference... So the relative motion of the source of light and the frame of reference from which you are making measurement does not matter... Is it an Axiom in relativity ? I understand that they are experimentally proved concepts... But is it an...

Hi everybody! Why we don't have to prove Lorentz invariance of the Vacuum state in QFT? This fact is quite obvious in QED and follows from Lorentz invariance of electric charges. But in general case? I don't know, but it seems to me this fact is not so obvious as it treated.

According to Maxwell's Equations, the classical vacuum permittivity and permeability have a very important role: They determine the speed of light. But it seems like these two important concepts are not as precisely defined in the quantum world. Are there rigorous analogs of these two...

I've read in a set of lecture notes that the requirement of locality and unitarity in QFT imply that the vacuum must have a non-zero energy associated with it (http://arxiv.org/pdf/1502.05296v1.pdf , top of page 3 under heading "What is the problem?"). My question is, why does the locality and...

As we known, the force applied to the plane that fly in the atmosphere is to keep plane moving forward. The force given is to against the pressure of the air. If a space aircraft flies in the vacuum, the force given to it will accelerate aircraft because there is no friction caused by air...

Hello, I need to figure out the max water depth a motor will operate without water ingress. The plan is to use a vacuum pump to create differential pressure and correlate that to water depth. My issue is the correlation between the vacuum and pressure. Can someone please provide a formula for...

I have found this paper, it seems interesting although i haven't read it all yet arXiv:1507.00460 [pdf] Dark matter, Mach's ether and the QCD vacuum Gilles Cohen-Tannoudji Subjects: History and Philosophy of Physics (physics.hist-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Hello all, I have a Varian M4 diffusion pump that has a 6 inch diameter opening at the top, is it okay for me to connect that to a reduced size opening like just 2 or 3 inches diameter so that I can use a smaller valve? I am only trying to pump down a cubic foot or two sized chamber. I am...

I'm relatively new to QFT and was wondering how the QED vacuum has a dormant zero average-field condition if there is a zero-point energy of the field as well? How is there a zero average and a zero point energy?

The Purcell effect is when an atom placed inside a high finesse cavity with a very small mode volume gets an increase in the spontaneous emission rate. I've tried to find correct explanation for this effect, but it seems hard to find, except that it comes from an increase in the vacuum density...

I've just learned that work is done when a force moves something, and it's measured in joules. I've also learned that work = force x distance, but what significance does distance have? The force itself is what's being measured. In other words, if an object weighing 1kg was accelerated to...

Hello my first post :) I was wondering if it could be possible to achieve forever boiling of water in room temperature in vacuum. I understand that as water evaporates pressure increase and when equilibrium is reached, water stops boiling. But could it be possible to do that vapor in vacuum...

What is the correct value for the vacuum Debye screening length?

I'm trying to solve the exercise below in a book I'm reading. I inverted equation 1.3 to get ## \phi_{\mathbf k}(t)=\int \frac{e^{-i \mathbf k \cdot \mathbf x}}{(2\pi)^{\frac 3 2}} \phi(\mathbf x,t) d^3 \mathbf x ##. Then I put it in I to get: ## I=\int \int d^3 \mathbf x d^3 \mathbf y...

I've been reading up about vacuum tubes and (more specifically) the Audion, and how they were used for instruments/amplifiers. This isn't anything I'm learning about on my degree, just things I'm reading up on myself so forgive me if I'm a little slow to grasp some parts. I understand how the...

Assuming a spacetime with zero Weyl curvature and an Einstein tensor proportional to the metric, is it true that in a finite neighborhood of any point, that spacetime must be isometric to a de Sitter vacuum, or are there other possible solutions, and if so how are they classified? Thanks

I bought a new home AC (split; 1.5 ton) and the tech the company sent to install it didn't seem to have neither a vacuum pump nor a N2 cylinder in his kit. I am leery. Is it really possible to install an AC without these items? Can he do a reasonable job evacuating the lines & leak testing any...

So just to clear things up before we start, does vacuum polarization occur randomly, or does it just occur when an electromagnetic field is present? Also, how would vacuum polarization conserve energy - does it take energy from the field or does it emit negative energy gravity waves or...