Vacuum Definition and 1000 Threads

Hi all, I've recently been reading about the Unruh effect, and there are a few things that I'm not very clear on: 1) An accelerating observer will see a vacuum filled with particles in thermal equilibrium (a warm gas) where an inertial observer would see zone. I'd originally read that...

I am examining various models of eternal inflation and I want to double check one of my assumptions, which is that space always expands when the space has vacuum energy and zero mass. Is this correct? Will space always expand when the space has vacuum energy and zero mass? Thank you.

We all know the trick of holding water in a drinking straw by holding your thumb over the top creating a vacuum I know its also to do with air pressure below. I managed this on a bigger scale using a 2inch pipe, a water pump and a valve i could close at the top of the pipe to replicate the...

Let us assume that harmonic oscilator has the lowest energy level equals 0, (and next one \hbar \omega and so on). Does this harmonic oscilator violates the principle of uncertainty? Let us assume that energy of vacuum equals 0 and not \hbar \omega/2. Does such vacuum violates the principle...

What happens when we send in a vacuum pulsed electron beam with a frequency 1e9Hz and power 1e6MeV? Thanks.

Hello. Here joined is the schematic of a small deflection amplifier. Outputs H0 & H1 are connected to electrodes placed in a vacuum volume. These outputs are protected by varistors. High voltage to collectors is 200 V DC. Sometimes, not very often, the head Op-Amp (LM324) is burnt. The only...

Hi all, I have a bit of a variation of a question I asked some time ago. Webb et al. continue to publish results which suggest that the fine structure constant may vary over space and time. I realize the results are controversial - what I'm wondering: If the fine structure constant...

Going uphill with no friction, think maglev, what forces would the mass/vehicle only have to overcome its weight... and gravity? I used the 'search' function but yielded no results. Please feel free to discuss or to simply put me in the right direction. Just to put things in context, I am...

Hello, This is my first post, so I believe, that you understand and help for me. So I have a task to design vacuum vessel, precisely, my task names "Training stand to measure the height of the flight fuel pump". Height will be simulated by vacuum in fuel tank, which will create a vacuum pump...

How is this for a perhaps unconventional, but I think accurate, description of the 'empty' vacuum: Without the vacuum we would be nothing...it contributes to everything around us, our very existence:The 'empty' vacuum has: ...spacetime, from which curvature arises and gives us gravity...

In a conductor suspended in an external electric field, in a vacuum, what holds the conducting electrons inside the conductor? Why don't they just fly off into space, under the influence of the field? If they are free enough to move between the atoms of the conductor, this means the force from...

Let's say there is a chamber with 1000 O2 molecules. According to wikipedia, a perfect vacuum is an arbitrary space in which there is an absence of matter. Of course, the space that consists of the entire volume inside the chamber isn't a vacuum because of those 1000 molecules, but then isn't it...

I've read that permittivity is resistance offered to flow of field lines,But vacuum does not have anything in it to resist or alternatively to get polarized.but we've seen that vacuum has permittivity constant..How's this possible??

Could a balloon be filled with vacuum - in a vacuum? And if a balloon was filled with any other gas and put in a vacuum, it would just expand until it popped, no doubt?

Homework Statement A tank is equally divided into two equal halves, one a vacuum and one filled with argon gas at 298K and 700 bar. The divider bursts and the gas equally disperses throughout the tank. What is the new T and P of the gas assuming argon is an ideal gas? Homework Equations...

Hi, What is vacuum level? I browsed internet and came across different definitions like 1. Threshold energy with which electron leave the atom. 2. Energy of electron outside the crystal. Can you please explain in detail what is vacuum level? At the same time, pls clarify why and how...

I don't know if its daylight savings or what, but I just can't seem to wrap my head around this analysis. There is a polycarbonate hemispherical head with 8 psi in a near vacuum environment (2.8 torr) Im trying to figure out what the minimum thickness is for the head. The shell is super...

If I have two, 10 kg objects, 10 meters apart, in a vacuum, How long will it take for the gravitational force between them to pull them together so that there is no room between? Please help I have been trying to figure how to do this math forever! I know the physics formula for the...

Before Higgs symmetry breaking of SU(2)xU(1) electroweak unified force or even before that, when strong and electroweak were unified as GUT theories propose, the vacuum was different from today's universe. What effects had these different vacua on the evolution of the universe? thanks

Homework Statement Okay, so the problem given is that there is a rigid tank with a partition down the middle. For partition A, the specific volume, the temperature, and therefore the pressure is known. The mass, or total volume is not known. Partition B is a vacuum for which the total volume is...

In the thread https://www.physicsforums.com/showthread.php?t=343049 Science Advisor Born2bwire mentioned: "Since the vacuum state has infinite energy, it has infinite photons. Everytime we add energy into the electromagnetic fields, we just pull a photon out of the vacuum state." How many...

Does anyone have an explanation for why kinetic energy carried by electromagnetic radiation travels at the speed of light? My understanding of the speed of sound is that the denser the medium, the faster the wave velocity. Since this is just kinetic energy propagating through a medium, how is...

I've been reading about what happens to water when exposed to vacuum, but can't seem to find a definitive answer concerning a few details in the step-by-step process. I read that water will quickly boil in the vacuum of space due to very low pressure, and then freeze. But roughly how long does...

The QCD vacuum condensate which breaks chiral symmetry in qcd, also break the SU(2) electoweak gauge symmtery, right? The operator which gets a vacuum expectation value isn't SU(2) invariant since it is built out of left handed quarks and right handed quarks which are in different...

I apologize for my lack of mechanical term knowledge. I'm looking for a type of screw I could use in a project. Sorry if the thing is unrealistic or if the part is obvious. I attached a sketch of what I'm looking for. The screw would never be completely out of the hole like the sketch...

I know the default library of LTspice don't have vacuum tube model. Does anyone know where I can get one. If not, any other free spice program have vacuum tube models? The only one I find so far is: http://www.duncanamps.com/technical/ltspice.html I tried to follow the instruction and...

Does electricity travel through vacuum?If so ,is it a good conductor?What is its resistance.

If a bullet is fired from a gun in vacuum(assume no gravity, no resistance). why is it that the bullet accelerates 0 to v inside the barrel but as it exit the muzzle it stop accelerating. Isn't when the bullet exit , it exit with some force which give it a initial velocity v.

I'm uneducated in Physics so I'm not sure where to begin with this. I want to build a vacuum chamber that is rectangular and fairly flat. It will measure 48"X96"X8" I plan on constructing it from clear polycarbonate sheet on one face (would clear acrylic be a better choice?) and aluminum sheet...

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...

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?