Vacuum Definition and 1000 Threads

According to http://tinyurl.com/2cfghd5", an Australian physicist has discovered that The Oxford dictionary's definition of "siphon" is incorrect, attributing its effect to atmospheric pressure, rather than gravity, which is what he maintains causes it a siphon work. This seems to me to come...

The Oxford dictionary is about to change its definition of a siphon to remove the reference to air pressure as being required. Will a siphon work in a vacuum?

This is a question about solving Einstein's Field Equations for some simple cases, but I'm not sure how to explain this without analogy. So bear with me for a brief discussion. Consider the electrostatic equation: \nabla^2 V = \rho / \epsilon_0 which show explicitly how the charges source the...

Boiling point in a vacuum... Gidday, I am as new here as it gets, and I have a question to post. I have been having a (heated) discussion with regards to the temperature that water boils in a vacumm. Given: @ 10in Hg water will boil at 192F. If you had a pressure reading of 29.7in of...

Need a vacuum cleaner? My wife just brought home a new Miele and test-drove it. She loves it. We have bought and maintained lots of vacuums over the past ~30 years, and none of them performed all that well - even the top-end Electroluxes. A co-worker of hers used to sell and service Mieles...

I'm studying (relativistic) quantum field theory and have a very simple question. Take for example the real scalar field. My notes simply state that <0|0>=1 is a very natural normalisation. If I'm not mistaken, then this implies that the probability of measuring the vacuum state is 1. How is...

Hi, Even though it is called 'vacuum energy'... do we know or do we have some theory on... whether the activities of virtual particle pairs is the same whether in the relative vacuum of space or... with in ther Earth's atmosphere (where tests confirmed it) or... say inside a rock? Rusty

Old CRT tv's use vacuum tubes and they get hot, but how does the glass get hot when the inside is under a vacuum and therefore shouldn't transfer any heat?

Can any dry pump be reused for evacuating a chamber? Ie: I have a 2hp compressor, can I use it to make a vacuum chamber. -lamonster

If light travels at constant velocity c in vacuum and constantly relative to any inertial reference body, then does that not mean all bodies and space are perforated, or rather filled in, with vacuum within which light can travel?

I've read ZapperZ's thread on the speed of photons through a solid and am still confused. If you imagine an experiment where two emitters A and B are set up to emit one photon each simultaneously towards two receptors (also A and B)in a vacuum 558,000 miles away. The receptors will sense the...

Hello PF, If the the interacting field (phi^4 theory or QED) vacuum corresponds to bubbles for example: photon goes into electron-positron pair and then vice versa.. etc... etc... To what does the free (non-interacting) field vacuum correspond? 10x

Are there any substances that are liquid in a vacuum? It seems mercury should be liquid. If so, what forces keep it from solidifying, yet not disipating into a gas?

Homework Statement A space capsule, which may be treated as a sphere of radius 10m, is hit by a micrometeorite which makes a hole of diameter 2mm in its skin. Estimate how long it will take for the air pressure to drop by 30%. Avogadro's number is about 6 \times 10^{23} Homework Equations...

Hey, Can anyone help me with my imaginary experiment? In a large glass tank I place air-filled balls of thin rubber (like a balloon but perfectly spherical). I fill the tank to the top with the rubber balls, seal the lid and evacuate the tank of air. The internal pressure difference...

The maxwell's equations in vacuum are satisfied by a non trivial solution involving \vec E (t,\vec x) and \vec B (t, \vec x). Correct me if I'm wrong. I don't really understand the physical interpretation of the solution. I know that if I'm given an initial condition then I can know the...

Is the space between the electron shell and nucleus a perfect vacuum?

Hey guys, I have a question; I was in a Physics lesson at school today, me and my teacher got into a discussion about space and vacuums. Somehow we managed to get marsh mellows into te convosation, and my mind wondered until I came up with this question - If a Marshe Mellow is traveling...

We all know that if you accelerate at 1g in a vacuum, you'd be pressed into the floor/wall of your spaceship in the same way that you're pressed into the ground on Earth; that is, you would have "Earth Gravity". I got into a discussion with some people about the structural integrity of a...

I have a powerful vacuum motor and wanted to put it to use. I would hate for a great functional motor to go to waste. Any project ideas, excluding vacuum cleaners?

Does the process of pair production mean that the quantum vacuum fluctuations can produce atoms(given enough time) as the following quote on wikipedia seems to suggest? Has it been experimentally confirmed that atoms can be formed in the seething with virtual particles zero-point energy state of...

Difference between "Nothing" & Vacuum Could you please tell me what is the difference between "Nothing" an a "theoretical perfect vacuum" ? The question is serious. Regards

I want to know the mechanism behind this. I folded a paper cloth (may of been of the bounty kind), and put my wet cups on there mouth down. I heard a hissing, and I thought I may have left the stove on. I followed the noise to the cup, and noticed it was hissing like crazy. I tilted the cups...

Okay, these questions aren't completely about the Higgs, but it is a good starting point / explicit example. After spontaneous symmetry breaking occurs, such that the vacuum state itself no longer has the symmetry of the Lagrangian, will there always be something equivalent to a Higgs (a...

Hi, I am reading Introduction to Statistical Physics by Kerson Huang. On chapter 10 about Bose Gas, a statement intrigued me. He explains Photons. "Photons are the quanta of the Electromagnetic field. They are bosons whose number is not conserved, for they may be created and absorbed singly...

If you put a piece of very hot metal in cold water the heat in the metal will transfer to the water until both are the same temperature. So the system water-metal still has the same initial energy. So my question is how does the piece of metal cool if it is put on a perfect vacuum. Is it...

Vacuum Physics? I would like some clarity on a problem I think is attributed to a vacuum space. This is what happened...I have a small room that is 7' x 10', there are two metal doors directly across from each other on opposites sides of the room. It seems that when I want to close the door...

Homework Statement If two protons start out at rest relative to each other, separated by 0.1 nanometers in vacuum, and then they are released, calculate their relative positions after 10 seconds. Homework Equations F = (kq^2)/r^2 = m*a The Attempt at a Solution I am fairly...

Hello friends, I am now interested in Einstein scalar field equations with a very little knowledge about Physics. I would like to ask why vacuum Einstein equations are hyperbolic equations? As far as I know that for 3+1-dimensional manifold V, we can convert the vacuum Einstein equations as a...

Homework Statement I'm having hard time seeing that from this picture: Follows that: \phi(\vect{r})=\frac{q}{4\pi\varepsilon_0}\cdot\frac{1}{|\vec{x}|} The thing that puzzles me isn't the equation but this...

Today in class we started talking about waves. I understand waves to be energy. This makes sense to me when thinking about sound waves, because the energy can travel from one particle to the next to travel; but I don't understand how things like electromagnetic waves can travel through a...

So, I've been wondering about this lately and wanted to know if anyone could provide me with a straightforward answer on what the theory behind this phenomenon currently is?

Homework Statement Hello. I am trying to calculate the minimum vacuum force required to keep a climbing robot attached to a ceiling. The robot body consists of a cuboid with two vacuum cups attached at either end. The robot will move using inchworm-style motion, attaching one of the cups...

Let's say I have a 5m3 cube of air and right next to it a 5m3 vacuum. Does the cube of air have potential energy? According to that, the potential energy would be converted into kinetic energy when the cube of air and the vacuum were joined. Would vacuum energy be the initial potential energy of...

Suppose you have an absolute vacuum, with zero particles, and its container is made of a conductive material, like a metal or something, which is heated. What happens inside the vacuum? Does heat need the medium of air, or will it heat the vacuum? I reason that heat needs a medium (like...

Vacuum polarization is when an EM field causes the virtual particle pairs around it to become polarized like a dipole. The most common example is with an electron in vacuum, but a transmitting radio antenna could do it as well. But, if this was with an oscillating signal, it would create waves...

Hi, I'm curious about how vacuum systems work... I was advised to try posting this here, hopefully it's the right place. So if you're designing a high vacuum system, how do you actually operate it? For example if you have a chamber connected to an oil diffusion pump connected to a rotary...

Homework Statement I'm doing a project where I have to design a high vacuum system (just on paper). I think I've figured out how all the parts hook up together, but I'm not sure how to operate the vacuum. Homework Equations The Attempt at a Solution So I have a chamber...

I only studied basis quantum physics as a graduate, my main focus was on light technology and I didn't carry it much further from there. But the passion for understanding how the world works remains. Basically, I was wondering what would happen if one were to explain quantum phenomena not so...

Having a Lorentzian 4-manifold, the Einstein vacuum equations of general relativity read \overline R_{\alpha \beta} - \frac{1}{2}\overline g_{\alpha\beta}\overline R=0 where \overline R the scalar curvature, \overline g_{\alpha\beta} the metric tensor and \overline R_{\alpha\beta} the Ricci...

What is the speed of free electrons in vacuum, plasma and superconductors? Can we 'slow down' free electrons? Just how slow can we make electrons go?

Homework Statement What is the uncertainty in the life time of an electron and positron produced in a vacuum?Homework Equations \Delta E\Delta t=\frac{\hbar}{2}The Attempt at a Solution \Delta E\approx1.6\times10^{-13}J \Delta t\geq\frac{\hbar}{2\Delta E}\approx 3ps (edited for Tex) This...

Isn't the distance between two atoms where nothing exists, no atoms or subatomic particles, absolute vacuum? a place where nothing exists?? I am not too educated in such physics, so please do explain what you say

I need to discharge a lot of current into an inductive load from a large capacitive bank. Ideally the current waveform would be as close to a flat-top as possible. Typically this seems to be done either by switching many caps in sequence using SCRs into a filter network to remove ripple or by...

If you were to destroy all the air around an object, would that give you a temporary vacuum or would the air be replaced so quickly that it wouldn't make a difference?

I've been thinking about this. I don't know a whole lot about physics so I'm sorry if I ask something stupid. If there are two particles in a vacuum, according to the theory of gravity, the two particles will be attracted to each other and collide. But, how does this one particle know that there...

How would a curious young gentleman like myself go about supplying power to a Mullard vacuum tube? I have several different types of Mullard tubes, but no idea as to how I can generate the electron beam. P.S. If side-effects of solution include death, injury or Hannah Montana please do not post.

"In this study, it is shown with reasons that superposition principle does not work in vacuum. This case can be observed by Young type double slit experiment to be carried out. Since field-field interaction is carried through charged particles, in the absence of charged particles linear...

My question is a relatively short one. Simply put it is: "Will an electron oscillating in a vacuum lose energy?" My thought comes from does the presence of the moving charge create electromagnetic fields. I have no idea how you could get the charge to oscillate but perhaps in the neutral...

vacuum vessel / distiller correct wall thickness?? Hello! I have a vacuum vessel / distiller type of vessel with following:- Temperature inside the vessel max. 200°C [Celcius] and a Vacuum at max. -80kPa = -0.8bar Material: SS-304 = Stainless Steel Volume = 0.654m³ My main question...