Vacuum Definition and 1000 Threads

Is it possible to make a liquid evaporate solely with vacuum? If you were to reduce the pressure in a container of liquid to 0, while also insulating it from any outside heat, would it remain a liquid or turn into a gas? If it turns into a gas via lack of pressure alone, does the...

Homework Statement We want to design a cylindrical vacuum capacitor of a given radius a for the outer cylindrical shell, which will be able to store the greatest amount of electrical energy, subject to the constraint that the electric field strength at the surface of the inner sphere may not...

I've heard that fire creates a vacuum due to the consumption of oxygen. Obviously, combustion results in other gases being released (CO2 and H2O vapor). Some have said that there is no vacuum; others have said there is in fact a partial vacuum. I assume that it depends on the relative...

I would like to find an easier way to build spice models from old data sheets. Normally one would have to tediously build spread sheet tables from curve traces of these old tubes. However, I was wondering if there is some sort of program that allows one to trace lines over the images, set...

As a radioactive sample decays in a glass vacuum container, and the released alpha particles collide with the glass, would it be correct to assume that the particles "bounce around?"

Okay the question is, given a plane electromagnetic wave in a vacuum given by E=(Ex,Ey,Ez)exp^{(i(k_{x}x+k_{y}y+k_{z}z-wt)} and B=(Bx,By,Bz)exp^{(i(k_{x}x+k_{y}y+k_{z}z-wt)} , where k = (kx,ky,kz), to show that kXE=wB. So I'm mainly fine with the method. I can see the maxwell's equaion...

Hi, here is something I can't understand: When you fill a 100% tube with Mercury, close it in one end (the top) and stick it into a bowl of mercury, vacuum forms in the top of the tube. Where does the vacuum come from if it was not there to begin with? The tube was full of mercury to begin...

Vacuum pressure for design of pipe Dear experts, I have a line pipe which internal design pressure is 98 bar,dia is 36: thickness is 13 mm,length is 12 mtr. I want to know that how much vacuum pressure sustain by this line pipe? Regards, Satish patel,

I want to create a mechanical vacuum (semi not necessarily complete), I've heard the easiest way to create one is by expansion (basically expanded a pump). But is this also the easiest way physically, as in takes the least amount of energy? Or is there any other 'mechanical' way possible for...

IMHO as amateur QG watcher, this paper has considerable potential importance. Really impressed. Could be a game-changer: http://arxiv.org/abs/1401.6441 A new vacuum for Loop Quantum Gravity Bianca Dittrich, Marc Geiller (Submitted on 24 Jan 2014) We construct a new vacuum for loop quantum...

Hi everyone, here's the situation: Everyone knows that you can simulate artificial gravity by rotating a space ship. Usually these scenarios include an atmosphere with regular air inside. I know that the inclusion of air has an influence on the effects inside by way of friction. How different...

Hi, Can someone give me some guidance on how to calculate the work or energy required to create a vacuum. For example, I would like to create a 2.5psi vacuum in a tube of a specific length and diameter using a pneumatic cylinder to remove the air. How would I go about calculating the...

Hi Folks, Could someone please help me?:blushing: I want to work out the power requirements for the torque or wattage required in an electric motor when evacuating a vacuum to a certain level. The tube to be evacuated is 200 mm x 50 mm and the evacuation would be done using a pneumatic...

I'm a home-scale experimenter/dabbler in the arts of distilling liqueurs/spirits and essential oils, and right now I'm trying to see what vacuum distillation(at very low temperatures) can add to the finished product as far as taste, aroma, and color go. For my initial experiments, I've been...

I have noticed that some of my tube amp power tubes are glowing slightly blueish. Why? It has been explained to me that this only means that the tube is ok. However, I find it fascinating! Because what is this blueish glow, really? To me it sounds like secondary emission of either the anode...

In chapter 10 of Robert D. Klauber's excellent QFT book, there's a nice overview of different concepts occurring in the context of vacuum fluctuations. Inspired by that chapter I ask: If one would state that there is no such thing as vacuum fluctuations, what counter arguments are there? In...

Homework Statement EM Waves propagating through vacuum towards the x-direction approaches a conducting surface at x = 0. Part (a): Prove the following relations. Find the boundary conditions for E and B if charge density σ and current density s exists on the surface. Part (b): Find B in...

Suppose we consider a proton where we set the electric charge of the three quarks towards zero. At this point I assume we still would have the three quarks bound together? Now reduce the strength of the strong force by say ten times. I was told in posts that the radius of the proton depends on...

I learned that work done by gas is zero when a gas expands in vacuum. But the volume and pressure of the gas change.Then how work done by gas is zero?

In various other threads we have been kicking around various equations for a spherical shell and discussing the implications. In this thread I would like to present what (I think) I have worked out about how the shell metric relates to the vacuum metric inside and outside the shell. I hope to...

So I was looking through the internet on how one could improve the efficiency of a vacuum system (with a diffusion pump). Lots of websites describe systems with, cold traps to remove condensable vapors such as water. If I am not mistaken, cold traps also help prevent back streaming, similar...

Hi, Similar to the position-momentum uncertainty principle, there is a time-energy uncertainty of the form $$\Delta E \Delta t \geq\frac{\hbar}{2}\enspace .$$ However, since time is not an observable, the derivation and interpretation of this inequality is somehow different compared to...

I'd like to understand better the connection between Hal Haggard's September ILQGS talk http://relativity.phys.lsu.edu/ilqgs/ http://relativity.phys.lsu.edu/ilqgs/haggard091713.pdf http://relativity.phys.lsu.edu/ilqgs/haggard091713.wav and the talk he gave at PI two days ago...

The quantum vacuum is said to be the ground state of the combination of all virtual particles contributions from all particles and forces. How about in deep space where there is only CMB... so the virtual particles present is only from contribution from the CMB or complete particles meaning the...

Let's say I have an unbreakable pole. Let's also say I'm in an infinite vacuum. This pole is 240,000,000 meters in length. You are at the other end of the pole. I move the pole to the right 1 meter over the course of 0.9 seconds. Does the other end of the pole move immediately? If so, does it...

Hi all, i was pottering away at work yesterday and realized just how little i truly understand about vacuum! So i have a question, i have a piston in a cylinder, the piston is fully in the cylinder so there is very little air space and the cylinder port is blocked off, the piston has an area of...

First of all, I understand that an EM wave is created by a charged particle that is moving. What I don't understand is how it propagates itself when traveling through a vacuum as there is no medium for it to interact with. Can this be explained by anything other than photon theory? I really...

Hi, If we took the blood of all people here on Earth and made a ball of it (r=200, T = 310 K) how long would it take for it to cool down to ~ 285 K in vacuum (absent of sunglight)? How long would it take to cool down in air, with reasonable conduction speeds?

Air typically has a very high but non zero resistance. Given that air is just a medium, and that space is also just a medium, does the vacuum of space have a fundamental constant of electrical resistance, or is the electrical resistance of space truly infinite? How is this proven one way or the...

It's a theoretical study. I would like to understand how the sum of forces can be at 0 if I put an object (vacuum in it) in a big liquid disk (disk is fulled with liquid), the disk is big enough for agglomerate liquid (like this works with a planet, matter is agglomarate with gravity). There is...

I did a demo for my students, using a simple vacuum pump and a vacuum chamber. I put a burning candle in the vacuum chamber. This generates numerous CCNs (cloud condensation nuclei) (I believe) and perhaps some larger-than-normal CCNs. A cloud forms in the vacuum chamber for a few seconds, then...

Why does Tesla coil detects vacuum leaks?

I have been interested in constructing a vacuum chamber for quite some time, but I am not completely certain on what the structural specifications need to be so that it can hold up to the immense external pressure. My main motivation for building a chamber like this is in the hope that I will...

I wish to design a two chamber stainless steel vacuum system where the two vacuum chambers are connected via a flexible tube with a valve. The system needs to be able to be pumped down to 6 torr and must be able to maintain that vacuum for at least a year without pumping. The size of the...

Homework Statement In 1654 Otto von Guericke, inventor of the air pump, gave a demonstration before the noblemen of the Holy Roman Empire in which two teams of eight horses could not pull apart two evacuated brass hemispheres. (a) Assuming the hemispheres have (strong) thin walls, so that...

What operator acting on the vacuum state (vacuum state of the box?) gives a m^3 box of cosmic background radiation at 2.7K? As the temperature 2.7K slowly drops (wait a million years) must our operator above change in time? Do photons scatter via gravitions so that their energy changes...

It could be possible for a driven vacuum bubble (like an Alcubierre drive,assuming that it could be possible to realize ) to travel not only many order of magnitude faster than light but even trough different vacuum phase ? like for example region of false vacuum ?

Why doesn't a mercury barometer containing vacuum get crushed by the atomospheric pressure? Here is what I think might be the reason. Although there is vacuum inside a mercury barometer, that vacuum is pressurized by the atmosphere that pushes mercury from the reservoir. That pressure is...

Greetings, I am thinking of ways to make a parabolic dish. If you apply vacuum to one side of a flat circular elastic sheet, will it make a parabolic or spherical shape? Thanks

I have a hand vacuum pump I'm using to evacuate air out of a container and hold the vacuum for a long period of time. This pump came with a valve that eventually failed. I bought a few more just like it and those failed as well. I guess the diaphragm inside the valve is too weak to hold a vacuum...

The general field equation for GR is Rab - 1/2 gab R = 8πTab where I am setting G = 1 and c = 1. Also, the vacuum solution is Rab = 0 But it seems to me that this "vacuum" solution must hold even when there is matter present. Pick a point within a planet. Then excavate an...

I was wondering on what parameters the vacuum generated by a fan in a vacuum cleaner depends. How can I calculate the vacuum created and the density of materials that it can suck in? Thanks

Hello forum members and thank you for letting me post. My question refers to how rocket thrust works in a vacuum. I know this question has been posted before, but I am still confused about how it works. My understanding is that rockets do not move by pushing against air but move by pushing...

I'm reading a paper by Art Hobson called "There are no particles, there are only fields" and had a question about something in there. (http://arxiv.org/abs/1204.4616) (Page 20-21) He basically says that since the vacuum in QFT has energy and non-vanishing expectation values, it is ultimately...

Would a piezoelectric crystal create a negative voltage if held within a vacuum? Perhaps it's my misunderstanding of the materials properties, but it seems that if there is zero net output within the "creation"(0) atmosphere, and any slight elastic deformation shows itself in the form of an...

My understanding is that when a fan begins spinning, a partial vacuum is created. Physically, what creates this partial vacuum? Does the motion of the blades create a void in which there are fewer air molecules than in the ambient air and thus the pressure is lower than the ambient pressure?

Consider the vacuum state that is hypothesised to precede the moment of inflation in classical inflationary theory. The theory assumes that quantum fluctuations in this vacuum are magnified because of the process of inflation and have gone on to form the real energy structures that we witness...

i understand why there can be no breakdown, however "arcing" is just the transfer of electrons. a breakdown in air just provides a path for the electrons to take. But if you have two sharp surfaces, like a needle, pointing towards each other, separated by some distance d, let's even say that d...

According to the third law of thermodynamics, one could argue that a vacuum has zero entropy, since it has only one ground state and a temperature at absolute zero. However, assuming the accelerated expansion of the universe to result in a 'heat death', i.e. a state of absolute thermal...

I'm a bit confused by vacuum "fluctuations" (I know there is nothing fluctuating since vacuum is lorentz invariant) and their interpretation/representation by Feynman diagrams. In a normal Feynman diagram, you have energy conservation at each vertex, so overall energy conservation is ensured...