Vacuum Definition and 1000 Threads

I have just a very general question regarding the idea of vacuum energy. It seems that it exists it would have to occur such that it would be the same in every reference frame to satisfy the principle of relativity, yes? Would that suggest it would be part of a stress-energy tensor which is...

Why is the speed of light slower in certain substances than in a vacuum. Since most of the atoms is empty, shouldn't the speed be the same? Is it because photons bounce off the nucleus, or because they get re-emitted?

At atmospheric pressure of 14.2 psi, if I had a 1 ft square hole through a 5 foot thick wall into an endless space vacuum, I am trying to find out the the final maximum volumetric flow rate that our atmospheric pressure would push air through the hole. I tried using Poiseuille's Equation...

"Energy is borrowed from the vacuum"/Virtual Particles I know that there are countless threads on virtual particles (some of which I have participated in), but I don't think that this issue has been adressed yet. One common handwaving argument for the existence of virtual particles is the...

Would a piece of metal suspended between two magnets in a vacuum-sealed jar be in a situation of frictionless vacuum? If yes, could such a situation be exploited to build a perpetual motion machine? If no, would the friction be enough to result in an appreciable loss of energy if the piece of...

Anybody know this one? I need to know for an evaporator design. Because there's no buoyancy from air, I'd think it would sink (this answer was given on Yahoo), but if it sank then there would be a low pressure area left above, and so the vapor should rise to fill it, hence evenly distributing...

I am doing a senior design project for a mechanical engineering degree. The project I am doing hinges on my teams ability to create a stable platform capable of adhering to a vertical, semi-permeable surface. Presently our greatest challenge is sorting out the mathematical proof of concept for...

It just occurred to me what if the vacuum state is not normalizable? We usually have the normalization \langle0|0\rangle=1, it's acceptable if we are sure the norm of vacuum state is always finite. However, we know states with definite momenta are normalized to delta functions, then how can we...

Hi this is probably very easy for you guys, but I can't figure this out. Heated air rises right? Then why is it that when I put a bowl of soup in the microwave and heat it in a plactic Tupperware-like container, then remove and cover it -- does a vacuum like effect occur? It would seem to me...

Could we harness energy from Earth movement relative to physical vacuum? Earth is moving around Sun with speed of 30 km/sec. Also there exist force of Casimir and similar effects. If we have some body (for example a ball) which is moving in some media (for example water) then to harness...

I'm doing work in microfluidics, and need help selecting a vacuum pump as I have no experience in creating or controlling a vacuum. Let me simplify my device: I have water confined between two plates. One of the plates has a hole, covered with a small patch of material that let's gas through...

Hi Friends! Consider an Ideal condition. suppose, I prepared a device which can generate and vary the frequency of a wave (you can consider the wave to be electromagnic wave). Using this device I studied following two scenarios: 1. I created a wave having frequency between 1014 to 1015 Hz...

125 GeV Higgs and "Vacuum Instability" So the Higgs has been http://press.web.cern.ch/press/pressreleases/Releases2011/PR25.11E.html (maybe). Nothing "beyond the standard model" about that of course; the Higgs is standard model. Except-- in the leadup to the LHC announcement, I repeatedly saw...

I understand that the the Higgs field has a vacuum expectation value of 246 GeV. I think that means that the expectation of the Hamiltonian energy operator applied to the vacuum state is 246 GeV. What does this imply for the energy density of the Higgs field in the vacuum (i.e. in Joules /...

I am curious if there is a terminal velocity for an object in free fall in a gravitational field based on the strength of that field. If I was falling to Earth and there was no atmosphere, and I had infinite time to fall(Meaning I'd never actually reach the surface) would the strength of Earth's...

when we fill a container with water so as to leave some space above the surface of water. And we close the container. When we turn the tube upside down. The air which which was above the surface of water transfers to the other side. How does this happen. Does air penetrate water? And suppose...

Hello, I'm having problems solving this problem I got in class. I want to learn the concept and how to approach the solution. Here it is: Consider the metric ds=dx^2+dy^2-dudv+2H(x,y,u)du^2 What form must the function H have for this metric to represent a plane gravitational wave...

Would there be any energy loss at all from a beam of light traveling in a vacuum?

can a liquid exist in vacuum? Wouldn't it vaporize to gaseous form?

I'm doing a thermodynamics project on possible future energy sources. I've decided to try and find out if you can extract heat from vacuum energy. My initial hypothesis was that by placing to plates close together creates a magnetic attraction due to the casimir effect, which would create heat...

Hello, I have a little problem I'm thinking about for work. We are considering a design that moves heat across a contact interface between 2 heat exchangers, each made of copper, in a high vacuum environment. There will be one fixed heat exchanger, maintained at 25 C by coolant flow. This...

How can we calculate the vacuum fields corresponding to certain frequencies?

Homework Statement A sphere is enclosed in a bell jar half filled with water. The sphere floats. Air is pumped out to create a vacuum above the water inside the bell jar. Will the sphere float in the same way, float better or will it sink? Homework Equations - The Attempt at a...

Is it possible to derive the value for vacuum permittivity(εo) without using the speed of light.?

Hello, I have read that vacuum cleaner makes 70 dBa and earplugs can easily go beyond this. The problem I have is that I can hear my neighbor's vacuum cleaner thru wall easily. But if I set my mp3 player at max (should be around 100dBa according to manufacturer) I can heard this at few...

Hello It seems we refer to the outer space as "the absolute vacuum." I read recently that the deepest vacuum man reached on the Earth is about 1000 molecules per cm3. To obtain this there was needed energy sufficient to reach a pressure of 400 billions Bars. Why space ships do not burst like...

In GR there is made a clear distinction between a vacuum region and a non-vacuum region as one is handled by the Ricci tensor and the other by the Weyl tensor. But is reality so black and white? And when do we realistically talk about dust and when about fluid? So the inside of an average...

What is the formula to calculate gas (air) density at negative pressures, as well as water content ? For instance, a vessel with air with volume of 1 m3, density 1 kg/m3, and water content 10g /m3 get vacuumed from 1BarA to 0.1BarA isothermally.

Ok guys, I need help. I work for a Contract Manufacturer that is working to solve a problem for a customer of ours. The customer has designed a snowglobe (it's actually in a jar) with a cool little Christmas tree inside it. It's a great idea, but there are a ton of nooks and crannies that...

I want to find a book that explain how the different grids affect the operating characteristic of the power pentodes. Most just give the optimal setup and states what is the output and most designer never vary away from this. I want to be able to play around with the different grid voltage to...

Think about it. If space was a vacuum how would energy from the sun (which has a mass equivalency) be radiated. Supposedly devoid of matter this is still energy which makes matter and almost every day we see the sun as something in our physical realm. Are there experiments detailing what happens...

How are internal lines with no free ends of Feynman diagrams of the perturbative expansion of QFT related to the quantum tunnelling barrier's negative kinetic energy and the HUP of QM? (if they are related at all)

Can this work?? Moving in a vacuum Okay, so i have been bugged by this idea for about a week now. And unfortunately it has been quite some time since I took any real in depth science classes. I am wondering if this idea is even plausible. In the vacuum of space, would you be able to have...

This question is really out of curiosity, and also due to my very limited knowledge of basic physics(biomed sciences tend to not teach you this). Say I wanted to create a vacuum inside a metal cubic casing with the following parameters: -The case is a cube, that measure 1x1x1m, so has a...

the pressure inside a 2 lit container has to be maintained at 0.01 bar. For this purpose, a vacuum pump will be used to pump the air outside. Also, air from atmosphere is leaking back into the container at 1 lit/min. one of the following pumps has to be selected. A. pumps out 10 lit/min...

Googled it and I was getting the vacuum pressure is 29.921 in of HG (Gage). Corresponding conversion for the other units are zero, from here http://www.engineeringtoolbox.com/vacuum-converter-d_460.html" Can anyone please tel what's the vacuum pressure in psia and psig? Any comment will be...

Everyone knows that particle-antiparticle pairs are supposed to be able to spontaneously pop into existence from "nothing", exist whilst the uncertainty principle allows it, then recombine and annihilate. Is it really spontaneous though, or has any thought been given towards whether this is...

Usually when studying thermodynamics and statistical mechanics of a macroscopic body one uses a "heat bath model" to define a temperature. In quantum mechanics one can assume that the heat bath has arbitrary low temperature. When studying quantum electrodynamics one has vacuum fluctuations...

Hello, sorry for bad english. I have probably a very stupid question :) Let's place two magnets in vacuum (empty space) How does one magnet "know" of the other one, if there is "nothing" between them? How "nothing" that exists between them can interact with magnets? I know of course...

would a baloon or a barrel 'filled' with vacuum act as a hellium balloon and float in air? of curse that would require hard shell balloon... density of air at sea level is 1.22521 kg/m3. so if we could make a vacuum chamber one m3 big that would weigh 1.22 kg it would float right...

As the usual argument goes, as I understand it, everything can be expressed in units of G, h and c. (though this argument exclude the particle masses from consideration.) The permittivity of the vacuum seems to be independent of G,h,c. Am I wrong?

I would like to know if there is a formula or a way to determine the amount of insulation a vacuum of 1 bar can produce. please note I am not talking about vacuum insulated panels.

Homework Statement Homework question for a graduate level atmospheric science course: A mercury barometer of height h has an imperfect vacuum above its mercury column so that it measures a surface pressure of 29.80 inches Hg when the true surface pressure is 29.90 inches Hg, and it...

I have a venturi tube and downstream of it, there is a small secondary opening at the end of the throat. This is where the local vacuum is created as the velocity increases and the pressure decreases. This difference between this pressure and the atmospheric pressure will induce air into the...

If an attenuated laser pulse (with expected number of photons <1) is incident on a perfectly efficient detector, and the detector does not click, does it mean we know the |n=0> state was realized, and does it imply that all subsequent detectors measuring this pulse will also not click?

Hi guys! I searchead a lot for this but i couldn't find in anywhere: what calculation is made to esimate the vacuum energy of a scalar field?? I red that it starts considering the Hamiltonian in the form \hat H=\frac{1}{2}\int d^{n-1}k[\hat n_k+\frac{1}{2}\delta^{n-1}(0)]\omega and...

According to Weinberg's logic, quantum fields are just convenient building blocks of constructing a Hamiltonian which can give a lorentz invariant S-matrix, then why must we consider vacuum filled with quantum fields and say there's no true vacuum since there's always fluctuations of quantum...

Air weighs about 800 times less than water, 1 litre of water weighs 1000 gms approx. while 1 litre of air weighs 1.25 gms approx. So theoretically it should need less energy ( in fact a lot less) to create a rough vacuum in a given volume than it would need to remove a liquid (water) from the...

If one had a high enough electric field could one pull electrons and positrons into existence out of the vacuum? The field needs to be high enough to accelerate the virtual particles away from each other strongly enough so they don't get a chance to recombine. If a particle has...

Hello all ! Help me please. I can not understand – which particles are entangled in this case http://prl.aps.org/abstract/PRL/v106/i11/e110404 Full text here http://arxiv.org/PS_cache/arxiv/pdf/1003/1003.0720v1.pdf