Vacuum Definition and 1000 Threads

What sort of limits would be encountered if you tried to charge a magnetically levitating sphere to as high a voltage as possible in an ultra high vacuum by using an electron beam aimed at the sphere? Assume the sphere is highly spherical and polished. If electrons have sufficient energy to...

Assuming a completely clean and flat solid surface (metal and amorphous carbon as examples). The surrounding vacuum is contaminated with water vapour at very low pressure. In what orientation would the water molecules adsorb to the solid surface?

how high does a vacuum need to be for electron gun to work? for example, will 1 pascal work, will 1 tenth of a pascal work? is there a minimum vacuum for a electron gun to work?

A client asked me to look into designing a vacuum chamber for drying out lumber. I am a decent fabricator but sadly not so great at the physics side of things. I know the chamber I'm building will need pretty thick material and a lot of reinforcement. He wants it to be roughly 10'x3'x3' inside...

If we start with the Lagrangian \begin{equation} \begin{split} \mathcal{L} = & \frac{1}{2}(\partial_\mu \phi)^2 + \frac{1}{2}\mu^2 \phi^2 - \frac{1}{4}\lambda^2 \phi^4\\ \end{split} \end{equation} and give the scalar field a VEV so that we can define the field ##\eta##, where $$\eta = \phi...

Can I sum up the potential due to all positive line charges and all negative line charges separately, with the boundary condition being at the edge of my unit cell, the potential should be the same and inside the metal there is a contant potential?

If a medium with speed of light ##c_1## is considered, shall the Lorentz transformation be considered relative to it or to speed of light in the vacuum ? I don't know if we could send particles like muons through water for example, to check this with their life time.

I made experiment on "Free Fall". I made a conical hopper of 15 liter volume and a vacuum chamber of , installed hopper upon vacuum chamber of 65 liter volume. Fixed a 2.5" gate valve to discharge powder in vacuum chamber. Connected both, hopper and vacuum chamber to vacuum pump (63 cum/ hr) and...

Lorentz gauge: ∇⋅A = -μ0ε0∂V/∂t Gauss's law: -∇2V + μ0ε0∂2V/∂t2 = ρ/ε0 Ampere-Maxwell equation: -∇2A + μ0ε0∂2A/∂t2 = μ0J I started with the hint, E = -∇V - ∂A/∂t and set V = 0, and ended up with E0 ei(kz-ωt) x_hat = - ∂A/∂t mult. both sides by ∂t then integrate to get A = -i(E0/ω)ei(kz-ωt)...

The vacuum density, or the zero point energy, of a field, doesn't change as space expands, it remains constant. But, aren't particles and virtual particles just fluctuations of these fields? Meaning as space expands, more and more particles are being created, violating conservation of energy?

Summary: Vacuum pump help I need advice on what type of vacuum pump would create max negative pressure in a very small area ( a space no larger than your pinky finger I guess) ? Maybe some kinda high suction low cfm pump? I don't know enough about vacuum pumps to know which type to...

Hi all, Just had a look at the 2016 paper by Wang, Zhu, and Unruh, "How the huge energy of quantum vacuum gravitates to drive the slow accelerating expansion of the Universe," Qingdi Wang, Zhen Zhu, and William G. Unruh, Phys. Rev. D 95, 103504 – Published 11 May 2017 The paper states...

Hi folks, I think a lot about aeronautics and physics for the purposes of helping people. I stumbled across the idea of vacuum airships as a cheap method of transporting food and water to places where it's unsafe for vehicles, or where there are no roads. We all know it's unconventional and...

Recently I was thinking about the Hubble's constant (which, actually, is not Hubble's and not constant...) and wondering: if the universe is expanding at 70 km/s each Mpc, then there's possible to calculate some expansion of space, say from me to a person 1 meter away from me (theoretically)...

I am experimenting with using a radiometer as an approximate indicator of pressure in my homemade high vacuum system, running a small turbo pump. I am interested in the relationship between pressure and vane rotation speed, with light intensity being constant. I have only been able to find...

I am a student attending an HVAC program at a trade school. Today I recovered refrigerant out of a heat pump in order to debraze the compressor out of the heat pump. My instructor has taught me how to use a recovery machine to recover refrigerant out of an air-conditioner or heat pump before...

Does the real vacuum pressure/underpressure depends only on the amount of impurities? In the case of theoretical Torricelli vacuum test, when no purities left in the vacuum: Is the vacuum 0Pa at 1m height (with 760mm of Hg) and also the same at 10m height (also with 760mm of Hg) of the test...

Summary: Expansion of matter in the visible universe, total volume of space outside the visible universe, black hole mechanics, and general questions from an uneducated but extremely interested evolved monkey. Hello everyone! I do not know the rules of this forum, or any forum for that matter...

I've wondered what would happen to a particle if it could break through the 186,000 miles/second speed barrier and go faster than light. Would it go say 186,001 miles/second or would it go infinitely fast. I know Einsteins Special Relativity prohibits this but I have just wondered. Now if this...

Summary: I was reading that the most powerful gamma ray burst experienced a 'drag' due to quantum turbulence and wondered how this could effect a plasma. After reading this Wikipedia article https://en.wikipedia.org/wiki/GRB_080916C I noticed the part about how the light was slowed down by the...

In the functional integral approach to quantum field theory, we have W[J] = ⟨0+|0-⟩J = ∫ D[Φ] eiS + ∫ JΦ Can someone give me some insight into why this path integral is a vacuum-to-vacuum amplitude. How and also why does this path integral W[J] become a vev?

Hello, I'm trying to find the right wattage heater band for a cylindrical vacuum chamber that is stainless steel (304), ~2ft in length, ~0.5ft in diameter, and ~0.5 in thick. From a quick google search, I was able to calculate the required wattage for bring the chamber up to and constant at...

Hello, I've been studying electromagnetics, electromagnetic radiation, and bit of quantum electrodynamics for about 12 months, but I'm stumped on an issue.. This is what I understand so far: Charge consists of countless "vacuum fluctuations" (i.e., virtual particles). Accelerated charges...

Hi, I have a bottom plate resting on a table (see figure in attachment). On top of this bottom plate is are series of springs and on top of it rests a top plate. Between the bottom and top plate (inside the springs) is a seal to create a vacuum chamber. Question: what is the total force acting...

Hello, thanks in advance. I'm trying to make a near 100% solid carbon fiber wing. I'm vacuum bagging the top half of the wing and the bottom half of the wing separate. After making sure there is a thin 2mm gap b/w the center of both halves the goal is to put a very strong, thick epoxy between...

I have a vacuum tank at work that I am trying to determine the flow rate and pressure curve of when I open up the tank and I just cannot figure these equations out. Environment: average office space Atmospheric pressure: 29.92 inHg (per weather information) Temperature: 72°F Tank info...

Hi, I have been asked to identify the right vacuum pump to lift the object having 500 grams weight with one suction cup. I am going through lot of materials to identify correct formulas to calculate the lifting force. and now I am able to calculate the theoretical lifting force. But seems, I am...

In a vacuum the speed of light is a constant. What if its not in a vacuum? Okay, as always I'm confused. I'm very interested in physics but am a layman. Alright, so we know that time is relative to one's distance from a mass, so that as we go further from the Earth, let's say, time moves...

I have been reviewing potential methods for measuring Quantum Vacuum Fluctuations that I might be able to implement in a home hobbyist environment. Must be room temperature devices. I have seen that there are only a couple of possibilities: The Tunnel FET and the Single Electron Transistor. I...

According to Sean Carroll's The Cosmological constant(https://arxiv.org/pdf/astro-ph/0004075.pdf) (Eqn.20) cosmological observations imply that the magnitude of the vacuum energy density in natural units is given by $$|\rho^{(obs)}_\Lambda|\le (10^{-12}\ \rm{GeV})^4.$$ Does this imply that the...

Does the Friedmann vacuum equation have a linear solution rather than an exponential one? Using natural units one can write Friedmann's equation for the vacuum as $$ \begin{eqnarray*} \left(\frac{\dot a}{a}\right)^2 &=& \frac{8\pi G}{3}\rho_{vac}\\\tag{1} &=& L^2 \left(\frac{\rho_0}{L^4}\right)...

Hi all, I've been looking at de Broglie-Bohm theory and more recent attempts at Bohm-like models that are relativistic and attempt to reproduce QFT. What I'm not clear on (non-expert) is how the vacuum is modeled in these cases? If we have a set of infinite quantum harmonic oscillators...

Hi all, I would need an high dielectric strenght glue to fix PTFE or Hostaphan to the vacuum chamber wall in stainless steel, so the glue should be vacuum compatible. Force against the bonding direction would be 50N, so if the glue has already 100N it would be good but I don't think it is an...

In exploring the feasibility of constructing a vacuum chamber, I am trying to calculate the thickness of rectangular polycarbonate sheet needed to withstand 100kPa of pressure, given dimensions of 30.5cm by 61cm (12 by 24 inches) and clamped edges. I have found some calculators that will tell...

If you calculate the uncertainty of a scalar field in the vacuum state, i.e. ##\langle0\left| \phi^2\right|0\rangle##, you get a divergent integral that comes out to something like $$\frac{1}{4\pi^2}\int_0^\Lambda \frac{k^2 dk}{\sqrt{{m^2}+{k^2}}}$$ Where ##\Lambda## is some momentum cutoff...

A very basic level question. Two objects are floating in a vaccum, Object A and Object B. Then distance begins to grow between the two objects. Object A feels acceleration being exerted, Object B does not. What does this show? From a classical perspective, it would be my understanding...

im trying to jog my memory back 30years when I worked with vacuum tubes. I worked with manufacturing of image tubes. I remember the vacuum systems used vac-ion pumps to achieve -12 power torr. I alsoo remember first using a molecular seive for roughing,pumping to 10 microns. The seive was a...

I've been reading this book, in which the author expresses the vacuum projection operator ##\vert 0\rangle\langle 0\vert## in terms of the number operator ##\hat{N}=\hat{a}^{\dagger}\hat{a}##, where ##\hat{a}^{\dagger}## and ##\hat{a}## are the usual creation and annihilation operators...

The Schwarzschild solution of the Einstein Equation of GR is said to be the only time-independent matter-free solution of that equation. In this usage, does “matter-free solution” mean without matter everywhere except at the singularity of the solution? I thought that the only solutions of the...

Dear Sirs, After my theoretical post on vacuum diode electron flow, I decided to try and measure it physically. I didn't have a vacuum tube, so I improvised with some tungsten wire, aluminum sheets and some screws and the result was usable. Obviously the tungsten wire fails after some time due...

From the action ∫Ldt =∫ι√|g|d4x where |g| is the determinant of the metric .and ι the lagrangian density. For gravitational field why is this ι is replaced by the Ricci scaler R which yield field equations in vaccum.(Rij-1/2Rgij)=0 Is it that the lagrangian density corresponding to vacuum is the...

Dear Sirs I have been going through the "radiotron designers handbook", but I can't seem to find the answer to the doubt I have about the electron flow of the source Vp. Kindly consider the below two circuits, the difference is the polarity of Vf. Question: In both circuits, the electrons...

It is commonly said that the speed of light when traveling inside materials is lower than that of light in vacuum, but I don't understand how this can be true. It is the same light traveling, so how can it act differently? Does light appear to be slower in materials because it is not following a...

Hello all, as my final project to attain my bachelors, I have tasked myself with designing some sort of device to collect insects from the canopy of soybean plants that can be suspended under a UAS (quad copter/drone). What I am trying to do is essentially build some sort suction device. The...

The Casimir force is often explained in connection with the zero point energy of the quantized EM field, and the fact(?) that metal boundaries modify this spectrum in such a way that a force is created. However, other sources (including some discussions on this forum) say that this is not the...

Hello. Recently Scientific American magazine carried an article about the work of the authors of this paper. https://arxiv.org/abs/1502.04573 The Undecidability of the Spectral Gap. The SciAm article is linked to here -...

Hello all, I've been entrusted a project of developing a Vacuum Drying System for my company. This system will be used for instant drying of automotive parts after washing. Needless to say the parts will be wet and at an elevated temperature (approx 50 degree C). The requirement is to dry the...

I am planning a physical experiement under vacuum conditions. In this experiement, I want to detect ionizing rays, especially as broad band as possible, for instance including alpha radiation. Typically geiger tubes are filled with a certain gas, that gets ionized by the radiation to measure...

Hello! When calculating the Hamiltonian operator in QED, in terms of creation and annihilation operators, we obtain an infinite term, which is considered irrelevant for most part (beside some renormalization problems) because we usually care about the difference in energies, so that would be...