Vacuum Definition and 1000 Threads

Has there been any theories proposed that model Dark Matter as just the pressure from vacuum fluctuations? It would be just a big cosmological-scale version of the Casimir Effect, where instead of using a couple of plates separated by microns, we're using the gravity wells of galaxies to create...

Hello ! A few days ago, I came across this article http://www.bbc.com/news/uk-scotland-glasgow-west-30944584 And I was wondering if it has any consequences with the relativity ? I mean, in my mind, light velocity is supposed to be constant in vaccum, c0 = 3e08 [m/s] approximatively... What...

Derive Vacuum permittivity and permeability using Quantum Field theory or String theory! If QFT or String theory is real fundamental theory, it can be derived the permittivity and permeability of vacuum. << Moderator's note: personal contact details deleted>>

Is it me, or the overall problem in CED is not addressed anywhere? Statement of the problem: Let there be two massive electrically charged particles of invariant masses m1 and m2 and electric charges q1 and q2, respectively. They are free to move arbitrarily in Minkowski spacetime endowed with...

http://arxiv.org/abs/1603.04170 Effective cosmological constant induced by stochastic fluctuations of Newton's constant Marco de Cesare, Fedele Lizzi, Mairi Sakellariadou (Submitted on 14 Mar 2016) We consider implications of the microscopic dynamics of spacetime for the evolution of...

I've been trying to learn about cosmological expansion (some weeks ago), I think I understand as much as any lay-person could, regarding why everything is moving away from our galaxy. However I still don't understand what spacetime is. The fact that space can deform indicates to me that...

If you had a generator in a vacuum with a magnetically levitated rotor and power was drawn from the system by induction, use your imagination on the design of the device, but my question is: Where are the flaws in this concept? (Since perpetual machines are theoretically impossible). In other...

Hi friends. What is difference between true vacuum and false vacuum. And what is metastability? I read these words said by Stephen Hawking saying about Higgs Boson may destroy our universe. So please explain this terms, anyone!

From reading about the permeation of gasses through polymer seals, I am led to believe that given two identical sealed chambers, one containing a vacuum and the other pressurized perfectly dry nitrogen, water vapor would permeate through the seals and into the chambers at the same rate. This...

I may be in the dark here but many of the media-dependent constants like permeability, permittivity and even the speed of light are ALMOST identical in both media ie. vacuum and the atmosphere of the Earth. This exists even though the 2 are very different because one is almost empty and the...

I recently got an older tube amplifier , since ti was dirty from being left for a long time in an old shed i took the covers off and cleaned it , now I am listening it also with the covers off , everything works etc. Now I wonder do tubes at lower voltages and lower frequencies such as in the...

Quantum particles are not localized before they are observed, as shown with the Young double slit experiments and those with entangled particles. On the other side, vacuum is filled with virtual particles. Are the non-localized particles responsible for the virtual particles? or only for a part...

Hi Guys, I am having issues trying to repair this amp. http://www.tangible-technology.com/schematics/fender/HR-Deville/Hot%20Rod%20DeVille.pdf A little history is in order I guess. I have not been working on guitar amps for too long, several months now. I have repaired perhaps fifty or so...

If I have a volume of gas in a sealed container with a special one way valve in it, and I heat the gas inside the container, the pressure increases and some gas escapes through the valve to the outside. I now have less atoms of gas inside the container, which, when cooled back to the starting...

Homework Statement In a region of empty space, the magnetic field is described by ##\vec{B} = B_0e^{ax}\sin{(ky-\omega t)} \hat{z}##. Find the speed of propagation ##\vec{v}## of this field. Homework Equations ##\Delta \vec{B} = \frac{1}{v^2}\frac{d^2\vec{B}}{dt^2}## , ##k=\frac{\omega }{...

Moved this question from the quantum physics section to this section, since... Well it fits this section better since electrons apparently do obey conservation of momentum in the 'classical' sense. Why not produce thrust in microgravity with electrons? Plenty of harnessable electricity in...

Given that no assumption is of a point energy is necessary to derive the vacuum (Schwarzschild) solution to the EFE, why is the solution assumed to apply to spacetime surrounding a point energy?

Hey everyone, I found this video on Youtube of this guy boiling water by reducing the pressure: I'm not sure how the gauge he's looking at works but I think this is the vacuum instrument he's using: https://us.vwr.com/store/catalog/product.jsp?product_id=4789427 ^It says that it provides...

If an object is in a large vacuum chamber and is dropped, what is to stop it from accelerating to the point that it passes the speed of light, because there would be no air resistance to stop it from constantly accelerating?

Hello Everyone, I have a question regarding the diffusion of a gas (or mixture of gases) into an evacuated space. The situation I am picturing is one where you have two vessels of equal volume, one contains a gas at room temperature, some known pressure (say ~760torr), and the other at static...

I'm building a vacuum kiln to dry wood and have some questions that may be rhetoric, since I am fairly certain I know the answers. I don't see a need to describe the project in great detail so I'll stick with the basics. The biggest challenge is applying heat to the wood. I believe I will have...

The top and Higgs mass determination arose the old discussion about electroweak vacuum metastablity. There is an interesting fact that with available data the universe places in the edge of stable and meta-stable zone tends to be inside the meta-stable region. This conclusion confirms up to...

Light being emitted from a source in vacuum, can photons accelerate ?

Precisely how does a vacuum pump take the gas, let's just assume air, out of a container?

How to understand QCD vacuum? What is the model independent expectation value for it? Looking for some basic literature on it. Thanks in advance!

We use lasers containing various elements in vacuums on Earth all the time. Is it possible to use lasers in the dirty vacuum of space to take pics and transmit at near the speed of light?

I have learned that temperature is defined as the vibration of particles. However, in vacuum, there is no particles. In reality, no absolute vacuum can be done, so I can't find answer online. Do you think the temperature (in Kelvin) is zero or undefined? Thank you.

What is the maximum practical or theoretical pressure at which x-rays can be produced, as in a Crookes tube or cathode ray tube? I know Crookes tubes operate at 0.1pa and lower, but I need to know if I am at risk of producing x-rays with high voltage (60kv+) discharges at medium vacuum, as low...

I have a thin gap between a disk shaped component (7.5"OD, 0.5" thick, let's call it the "mount") and a long pipe serving as a vacuum chamber. I'd like to fill this gap with something to reduce the conduction between the two volumes on either side of the mount. The mount already has a sizeable...

I did a experiment. I made a vacuum chamber with a silo on the top. Also provided the butter fly valve between vacuum chamber & silo. Filled the silo with low density powder say 0.2 gm / cc. Created vacuum in silo having powder and vacuum chamber. When I dropped this powder in vacuum chamber...

If Hilbert space is just a mathematical tool like a column for an accountant and doesn't have factual existence. How about the quantum vacuum. Isn't it quantum vacuum is just another tool? Is it like Hilbert space or does the quantum vacuum have more factual existence? If the quantum vacuum is...

Hi guys, I have a very very simple and naive question, which I hope I shouldn't be ashamed to ask, but I would like to clarify an issue in my mind. We hear everywhere that the value of the ew vacuum is v ~ 246GeV, fixed by the Fermi Constant G_F, v = (\sqrt(2)*G_F)^(-1/2). Now this is also the...

I understand that one would use a vacuum pump to evacuate a light bulb, but once a vacuum is created, how is the bulb sealed without air coming in?

http://postimg.org/image/p7sz481cv/ I now know what is effective distance Suppose you have two charges embedded in a dielectric medium with constant k (so instead of empty space there's a "sea" of dielectric media around them). They are separated by a distance d in the medium, so that Coulomb's...

Srednicki page 65 it says "Let us compute the vacuum expectation value of the field $$\phi(x)$$ which is given by $$\langle 0| \phi (x)|0 \rangle = \frac{\delta}{\delta J(x)} Z_{1}(J) |_{J=0}$$ This expression is then the sum of all diagrams that have a single source, with the source removed."...

Suppose that there is a positively charged particle and a negatively charged particle in free space. The electric field of the positive charge causes a difference in potential between the position of the negatively charged particle and the positively charged particle. This, causes the negatively...

Homework Statement Pressure in vacuum is 10^-3 Torr. External Pressure is 1atm and 300K. Pinhole of 10^-10cm^2 made in vacuum. Assuming all molecules striking hole pass through, how many molecules leak into vacuum in 1hour? Answer: 10^17 molecules Homework Equations Flux = <v>*N/4V Rate = Flux...

Hello! When a torricelli barometer is made there is a vacuum at the end of the top of the tube, does this vacuum exert a force to the water or mercury to go up? and how is that it can be a bigger vacuum depending on the air preassure? How does it exactly work? Thanks.

does rubbing your hands together in space make them warm? like if there is no air in a room will friction between your hands generate heat?

, the question was: if a elliptical shaped bulb , which was covered from outside and internally reflected light in the bulb itself . what would happen if it were placed in a vacuum ? would it emmit light for eternity ? hope someone would shed some light on the matter ?:) , and explain this...

Could someone please tell me the difference between tree diagrams and loop diagrams? If I'm thinking correctly tree diagrams are before contracting? Also how do vacuum diagrams fit into the picture? Thanks!

Is there such a thing? Wouldn't such a thing give ultimate protection for the eyes? I first thought i would post this in general engineering, b/c i have another question: How thick must the total eyepiece be if i need 2 semi-transparent sunglass material (of the size of a standard sunglass...

Chasing a ghost perhaps but in the process of pressure testing a simple propane furnace installation I installed a water Column pressure gauge. Over a period of 11 hours the pressure gauge reading will go from 10" WC to 0" WC. In the course of trying to understand this I installed a manometer...

This paper presents an unusually concrete hypothesis about the string theory landscape - that it is numerically dominated by "flux vacua" arising from a single compactification manifold. And our world could be one of them. http://arxiv.org/abs/1511.03209 The F-theory geometry with most flux...

So, assume you have a plasma in a vacuum made of an even distribution of 50% electrons and 50% protons all flowing in one direction with low collision frequency. Then you suddenly turn on an external magnetic field and watch what happens. How will the plasma react? Will the magnetic field...

Hi. I'm a first year Engineering student at QUT here in Brisbane. My problem is I come up with all these great ideas but lack the confidence and skills to carry them through to realization. I am currently taking 6 months deferment from my degree due to the difficulty of the maths. I have this...

Hi all This is a fairly basic QFT question but it's bothering me. And Peskin/Schroeder fails at explaining basic stuff, so here I am. After calculating Z for a particular theory I know this can be used to calculate all kinds of correlation functions. Itself, however, is the probability...

Why do we multiply permittivity of vacuum with relative permittivity? What does this calculation mean?

Hi all, A question about the vacuum energy density and spectrum. The only spectrum that is frame invariant involves the cube of the frequency. Is it also possible to have a constant offset term (which would also be frame invariant), to 'adjust' the energy density so it doesn't turn out to be...

Hi everyone, I had a related, more complicated post in another thread - I hope it's ok to post a simplified and slightly different question here (posting as a layman): Let's say I have an electron traveling alone in the vacuum, when a vacuum disturbance (fluctuation) occurs nearby. If the...