Vacuum Definition and 1000 Threads

I was reading a book about cosmolgy.And there wrotes vacuum energy must be higher than cosmological constant 10100 times to satisfy (It may just the opposite ) observations. Is that true ?

Hi all, I'd like to ask about " the vacuum saturation approximation " in a calculation as the decay width of ## B \to l \nu ## [hep-ph/0306037v2] equ. 1 till equ. 4, that why ## < 0 | \bar{u} \gamma_\mu b | B > ~ and ~ < 0 | \bar{u} b | B > = 0 ## ? and for ## [ \bar{l} \gamma^\mu...

Hey guys I was wondering what would happen if: took a ball neo magnet, balanced it on a few other magnets to basically make it a frictionless bearing. Then spin the ball magnet to 10k rpm. But do all this in a box that's a vacuum. Would the neo ball magnet spin basically for a VERY long...

Is it possible to pump out water from three tanks all under a different vacuum level using a common pump and common suction header? Or would this arrangement cause problems? The destination is a single tank at atmospheric pressure. See Sketch below. I'm trying to intuitively figure how the...

Trying to build a vacuum kiln using an old shipping container. Internal dimensions. 19'3"x7'7"x7'9". The space inside will be about half full trying to figure out how big of a vacuum pump I need. About 565 cubic feet.

The measured energy density of the vacuum has a disturbing discrepance with the one theorized by imposig Poincare invariance in QFT, usually referred to as the "vacuum catastrophe". On the other hand the Heisenberg indeterminacy principle leads to a nonzero vacuum expectation value for the...

I'm a little confused as to how to figure out the pressure exerted on a material pressed between two solid "press plates" Let's say we have 2 .5" thick x 12" x 24" hardened steel plates. I have a 1" thick layer of cloth (say 50+ layers) of 8" x 18" (1ft^2). The fabric is placed between the...

I have a theoretical question for physicists. For reference, see attached image. Suppose you have two perfectly flat plates aligned laying adjacent to each other. The plates are parallel to gravity. (perpendicular to the ground). Between the plates are perfect seals (no leaking). The seals...

Suppose two people, A and B, are pulling on a rope of mass ##M_r## in space. The force exerted by B is ##F_B## and the force exerted by A is ##F_A## (in magnitude). Suppose B pulls harder than A, we now have the equation of motion: $$F_B - F_A = Ma_{rope}$$ We also have a constraint; since A, B...

This metric ##ds^2=\frac{K}{r}\left(-dt^2+dr^2+r^2d\phi^2+r^2\sin(\theta)^2d\theta^2 \right)## (obviously in a spherical polar chart) gives an Einstein tensor (in the comoving frame field) ##\kappa T_{00}=\frac{3\,K}{4\,r},\ \kappa T_{11}=-\frac{5\,K}{4\,r}, \ \kappa T_{22}=\frac{K}{4\,r}, \...

Hi, even though it seems so simple; I can't solve this since a few days and it's driving me crazy. Flow gets inside the tube from point 1, it will create a vacuum, which will let a secondary flow inlet from point 2. Both flows will mix inside the tube, and get out of the junction from point...

Hi friends, this is my third post of my curiosity. :woot: First of all a photonic vacuum (as defined by me) is a region of space where there doesn't exist any type of photons or EM radiations ( those too which are beyond the detection of our present tech... i.e. including each and every...

Hi Members, As described above, I am making a prototype of a vacuum and compression chamber and I could use some help calculating the wall thickness/support structure that is needed to make sure things don’t go boom. After a fair amount of research I discovered that a few people did post...

When calculating the dynamics of a particle, we can use Feynman's path integral to determine the observables involved. This integrates over every possible path that the particle can take. We can even use it to calculate the vacuum energy of empty space. Now what happens to that vacuum energy...

Hi, I'm doing a 1D thermal conduction simulation on Comsol Multiphysics 4.4 and my first component is vacuum. I did'nt found the vacuum in the material list. Should I create a new component with a null thermal conductivity ? Thanks

Hello, I have seen in various places in the literature the expression for the spectral energy of the vacuum, but I don't seem to find a book/article where the derivation of this expression is shown. Also sometimes people state at its dependence on the third power of frequency is the only form...

I was wondering what might happen If we for instant, Rotated a ball around an axis in a vacuum chamber. First, If the initial speed was 20m/s would it remain like that forever, hypotheticaly saying No friction exists and that Air Resistance does not exist as the Ball rotates in vacuum. Also...

Hi everybody, I want to design two industrial vacuum distillation systems. The dimension of my distillation tanks are as follow: (1) A Horizontal Cylinder Tank with 200 cm length and 200cm diameter (total volume = 6300 liter) (2) A Horizontal Cylinder Tank with 400 cm length and 290cm diameter...

I am trying to find references for the the Wikipedia article Frost line (astrophysics) I am having a hard time finding a reference for the "Sublimation temperature of water in vacuum" that is used for calculation of the current snow line. E.g.: I have found 150K in several places, without any...

I am wondering if there is an existing hypothesis that suggests the most fundamental building block of energy being vacuum pockets rather than waves, or solid particles? Are there any equations that describe time as a differential? What are the current methods for calculating the mass of a...

If we put cathode rod with enormouse voltage in vacuum between strong magnetic fields pointing down parallel to rod end then put electron in it with initial speed equal to speed of light and begin circling around cathode, Will electron make gamma -rays according to synchrotron radiation?

In the text I'm looking at, the Schwarzschild metric derivation, and it argues to the form ## ds^{2}= -e^{2\alpha(r)} dt^{2} + e^{\beta(r)}+r^{2}d\Omega^{2} ## [1]. Up to this point some of the ##R_{uv}=0## components have been used, not all. It then says we have proven any spherically symmetric...

Can I make diffusion pumps from aluminum? I am going to create parallel connected diffusion pumps for many UHV purposes. I see that aluminum that is treated to prevent outgassing is used for UHV valves, chambers, and reactors. I'd like to know what temperature diffusion pumps boil their...

If using diffusion pumps (2 or 3 in series) to achieve ultra high vacuum, how do you hook them up together, for example adding them onto a system like in the provided picture? Would you use T-connectors to put them all on the same input and output valves or would you have valves for each pump?

Hello fellow engineers. I'm looking for a little direction as to the terminology and/or suppliers of some parts I need to build a Langmuir Probe. I'm unsure as to what some of these parts are called. They are all controlled by a stepping motor. Attached is a picture of the device I'm trying...

Homework Statement Take an elastic balloon of volume V in vacuum. The surface of the balloon has tension T. Find the pressure inside the balloon in terms of V and T, then combine this to the ideal gas law to find an expression for V. Homework Equations See below The Attempt at a Solution I...

UV catastrophe didn't occur because em are quantized.. so the higher frequency modes were not there. In vacuum.. if you compute the contribution of the em modes, it is 120 magnitude greater than observed.. the mystery is why it is not and they theorize it is just canceled out. But why didn't...

What factors determine the anode plate-to-grid capacitance? I know that the capacitance of a regular capacitor is determined by the surface area of the plates and is inversely proportional to the distance between them. Does this hold for vacuum tube grids and anode plates? The reason I'm asking...

how do I calculate the time when matter pressure and vacuum pressure add to 0 in the evolution of the universe. I have an exam of gravitation and cosmology coming Monday but have no clue where to start from. I can find nothing on weinberg and kolb and Turner textbooks

There is a metal cube that is any size desired. the contents of the cube is a vacuum of space. there is a tube that is also a vacuum of space that also can be any size desired. The third item is a ball that fits air tight in the tube perfectly at the furthest point from the ball. The ball can...

(like the wavefront that is photographed when it travels through air)

Electron can scatter off virtual photon of Coulomb field (or even emit real photon). But why it cannot do the same off virtual photons of vacuum fluctuations without external field?

Need to move some concrete powder, would like to use compressed air or a blower. I will need it to vacuum and convey the product, the storage vessel is broken and there is no way to gravity or manually feed it. The vertical distance is 8-10' and no more then 20' horizontal. I have played around...

Hi! I've been experimenting in my kitchen (much to wife's amusement) with vacuum pressure. Basically, I have been trying to understand...if I have a container (2 ltr soda bottle size/type) that is at low pressure (e.g. 1/2 atm) and I put a small hole on one side...will the soda bottle move in...

Velocity of phase wave in vacuum is grater than light velocty. This contradict the princles of relativity,so how this can be possible.

Hello everybody, I am working on some tests on materials and structures in a vacuum chamber. I noted that during the final moments of the pressure rising (when I open the valve to let the air in), temperature sensors installed in the chamber record the temperature rising more than ten degrees...

I've a hot-liquid filled tank (approx. 5000 Litres) at ground level within which there's a considerably good vacuum. Approx. 100 mmHg abs pressure. Is it possible to pump out liquid from this tank using a pump (any kind) without destroying the vacuum in the tank? What kind of pump would work...

I am interested specifically in the rate of formation of particle-antiparticle pairs in the empty void of vacuum space according to Quantum Theory? For example: for any given cubic centimeter of empty vacuum space, the rate of formation of electron-positrons is X pairs per second; the rate of...

As all of us know that in a vacuum the particle antiparticle pairs or the virtual particles are created violating the law of conservation of energy. So even near an Event Horizon of a Black Hole virtual particles are formed. One of the particles gets sucked into the black hole but the other...

Homework Statement I was doing an experiment containing gas or vacuum tubes "type 884 tube". It contains argon gas but when reading about triodes and cathode ray tubes, they are generally referred to as vacuum tubes - the type 884 tube is a triode, so does that mean it is a gas filled triode...

I haven't learned about this yet in school but I'm assuming as the atoms condense down to a single wavelength the volume of the liquid would be very small. If this condensate was instantly released out of a vacuum and into normal atmospheric pressure, would the volume rapidly expand? Secondly...

Lets take a simple water molecule for example. You can use the photoelectric effect to remove electrons from a molecule. As a thought experiment, let's say you have a contained single water molecule in a vacuum with no impurities. Perfect Vacuum. If you use the Photoelectric effect and beam...

If an object is in a vacuum and it is constantly increasing its velocity, since it would need to use energy to do so it would create a waste. Since it is the largest mass in the vacuum would the waste created be pulled towards the mass causing it never to reach the speed of light?

What would happen under these circumstances: A sealed container of water in a vacuum chamber. Since water doesn't expand like air, I assume that there would be no extra pressure within the sealed container once the air was evacuated around it. Since there would be no, or very little air...

The force in the Casimir effect can be "explained" by two causes, see, http://en.wikipedia.org/wiki/Casimir_effect#Possible_causes In some optics experiments we must account for the fluctuations of the quantum vacuum to get the right experimental results. See, Vacuum noise...

I'v been troubled by something. Einstein's second postulate determines the speed of light in empty space to be a constant c, measured by all observers to be the same. So I was thinking, it is possible to slow light by making it pass through a dense medium like water or glass. If we imagine such...

It is my understanding that on earth, a hotter object surrounded by colder air will decrease in temperature because the faster moving atoms in the hotter object are repelled by the slower moving atoms in the colder air. This isn't worded very well, I hope you know what I mean. By what mechanism...

I put helium in a balloon (with a maximum pressure of 1.5-1.7 atm), but I do not want changes in the volume, so I have to use a rigid material (non-elastic). To make sure that there is only helium in the balloon, I have to create a "strong vacuum." My fear 'that, in the material can break or...

Hello everyone, I am thinking of a thought experiment about a so-called "space tower" but don't have enough information to estimate the numbers. I understand the material strength needed for such high structures is huge, because of the weight of the structure. But what if the "tower" would be...

Hi I have been thinking about this idea and i'we come to the conclusion that i need to discuss this with someone who has a better understanding of physics than i have. First off, let me help you visualize it: You put pieces of hardware that generate heat inside of a container, the container...