Vacuum Definition and 1000 Threads

I saw some of these videos showing feather and some balls falling with the same speed in vacuum. But on normal atmospheric pressure they fall depending on their weight. This is just blowing my mind, WHY is this ? Does this prove Newtons Law of Gravity is wrong ? Then how is Einstein's...

Would lightning work in space? I think it would but you wouldn't be able to see it? Let's say I have some sort of device that creates a lightning bolt, if I shot it at a watermelon in a vacuum or another target would it hit the target, or nothing happen because of the vacuum?

Homework Statement Balloon in vacuum, radius R0 = 5,0 cm, surface tension σ = 25 N/m. a/ the pressure in the balloon p in,0 by radius R0………. pin,0 = ? b/ relation to the pressure inside the balloon pin, depending on its radius R…? c/relation to the pressure inside the balloon pin , depending...

Solar vacuum tubes are tubes covered with a vacuum jacket so that no heat can be dissipated by conduction and convection of air. By this process, we can get pretty high temperature even at very cold temperature. In this video, you can see how very temperature water can be produced by using such...

In this article https://en.wikipedia.org/wiki/False_vacuum#Bubble_nucleation it says that "In the theoretical physics of the false vacuum, the system moves to a lower energy state – either the true vacuum, or another, lower energy vacuum – through a process known as bubble nucleation." What is...

I think I already know the answer to this, but I'm looking for a source: Can the Lamb shift be explained entirely in terms of radiative corrections due to the self-interaction of the hydrogen's electron with its own EM field? That is, is it necessary to reference vacuum polarization or related...

Hey guys, what is the vacuum at the Karman line (100km straight up). I found conflicting sources on this. Wikipedia links to a calculator that states it is ~2.4*10^(-4)T, while another chart I found says it is in between 1.09 and .0075 Torr...

Hi all, This is a followup to a question from a couple of months ago regarding vacuum energy and cutoffs, basically to clarify some ideas. Given the usual picture of the vacuum as containing quantized harmonic oscillators at every point, it is not possible to apply a 'fixed' energy cutoff (at...

is spacetime Lorentz invariant like the quantum vacuum? They say the quantum vacuum is Lorentz invariant.. you can't locate it at any place.. but if spacetime manifold is also Lorentz invariant and you can't locate it at any place.. how come the Earth can curve the spacetime around the Earth...

Considering that all energy gravitates, why is it assumed that the vacuum energy that we measure inside the gravity well of the Milky Way is consistent throughout space? Is there any real way to know? Would it make any difference in the problem that QM and GR differ in the vacuum energy...

Vacuum bags are used to infuse various things with liquid resins such as fiberglass or carbon fiber. It seems that the higher the vacuum the better (and possibly faster) the infusion works. Could it be more effective to use a vacuum bag and also have the entire bag in a pressure chamber to get...

I know that in a sphere or other geometric conducting objects there is no E field inside because all the charge resides on the outside of the object canceling any inside field , although if I were to focus an electron gas in a vacuum chamber in some circular shape , all the electrons would want...

Hey everyone!Here's my first post in the forum!You probably usually discuss more substantial issues, but I'm having troubles and I'm sure you can help me!I'm trying to calculate the size of an ideal circular hole in a vacuum vessel given the measured leak rate in mbar l/s (helium spray leak test...

I am working on a project for a cube-sat to go up on a balloon to 40 km. My team has been talking to some other groups who have worked on other cube-sats who say that our resistive heaters need to be Kapton heaters rather than 1D heaters like what we have designed for. They claim that our...

Evidence for vacuum birefringence from the rst optical polarimetry measurement of the isolated neutron star RX J1856.5−3754...

A. Neumaier submitted a new PF Insights post Vacuum Fluctuations in Experimental Practice Continue reading the Original PF Insights Post.

https://www.sciencedaily.com/releases/2017/01/170118132244.htm I read this with a degree of skepticism, can we manipulate the quantum back ground? An important step towards a completely new experimental access to quantum physics has been made by researchers in Germany. The team of scientists...

For example if you send a light beam towards a massive object the propagation speed will reduce if μ and ε are increasing, but the spacetime curvature will compensate for that reduction.

I have a weird question here. At what speed does air flow from a pressurized container at one atm into vacuum (rupture in ISS for example). I was watching the Martian and I wanted to see how much deltaV Mark Wattney can get by puncturing his suit, so I did my homework and saw that the spacesuit...

Hi all - hope I'm not beating a dead horse here, but I'm following up on at least two other threads (made sense to consolidate): There are theories of quantum gravity (or the Standard Model Extension) that allow for local Lorentz violation. So, my first question: is there any reason why there...

We know an interaction exists between the quantum vacuum and physical matter. It is this fundamental interaction that determines the ground state energies of all the atoms and thus all the molecules and all the condensed matter present in the universe. Is the value of the ground state random...

According to wiki reference. If our vacuum was a false vacuum, things can be destroyed when the true vacuum appears. But is there no way or exception for true vacuum to exist that would still have stable things? For example. if the true vacuum were negative (what else is there?).. why would it...

It is said that the physical vacuum, is by definition a state with no "physical particles" -- more precisely, it is the ground state (state of lowest energy) of the field. Is there any beyond standard model where the vacuum is a lower energy limit of another theory or stuff... like the...

Posting as this was buried in another thread - If Lorentz invariance is broken in, e.g., whatever theory of quantum gravity turns out to be correct, what effect would this have (if one can speculate) on the physical vacuum? That is, for two observers, let's say, moving at different, constant...

I posted this question again in a different way, but it was a mess, and people were not satisfied, so it was closed down. I hope this time it's ok. Let's say humanity could concentrate all of its resources to create a perfect vacuum (neutrinos, photons etc don't count, it only has to be devoid...

Suppose a green alien came down to Earth in his big spaceship. Suppose that alien was the alien who brought life on Earth and created humanity. Suppose that alien is a bit dissatisfied with us. So basically God, if you're a christian (only green instead). So, what does he do? He asks us to...

We have all seen the marshmallow peep inside a vacuum chamber grow and them shrink. I want to convey the importance of Space suits and protecting the human body by creating a sort of "space suit" for a peep to wear or get placed inside of while in a vacuum chamber, so it is protected from the...

One more question before Santa comes. There are a number of different related threads, so hopefully I'm not repeating this - however, I haven't found a crisp answer yet. If one introduces a UV cutoff in the vacuum energy (in an attempt to avoid having infinite vacuum energy), is it possible at...

I'm reading the path integral chapter of Schwartz's "Quantum Field theory and the Standard model". Something seems wrong! He starts by putting complete sets of states(field eigenstates) in between the vacuum to vacuum amplitude: ## \displaystyle \langle 0;t_f|0;t_i \rangle=\int D\Phi_1(x)\dots...

[EDIT] I am of the opinion that putting a noisy motor in a vacuum would make it more efficient, as it is not losing energy by sound anymore. Does this make sense? Or am I just confusing myself?

Hello, I have a somewhat dumb question. It is based on the fact that I can create a small vacuum in my mouth to move that "string" of spagetti into my mouth. I know it is possible, but I do not understand how spaghetti is possible to suck in if the shape is even and round like a "piston". I...

I am working on a barometer that will operate t-ed into an experimental vacuum chamber. The fluid column is composed of vacuum oil so it doesn't boil. I have calculated that given the oil's density of 0.92g/cm3, each cm of oil height indicates 90 pascals of pressure. The oil has a vapor pressure...

First of all I want to say that I am a *scrub* in relativity so when people say things like that the universe expands and/or inflates I still don't get the full grasp of it. Here is my question. When we refer to a vacuum I would expect it to be a region of space that has absolutely no...

I have read this paper, but i do not understand the consequences in the broadest sense.arXiv:1612.02449 [pdf, ps, other] Cosmological constant vis-a-vis dynamical vacuum: bold challenging the ΛCDM Joan Sola Comments: 31 pages, 2 tables, 9 figures. arXiv admin note: text overlap with...

I have a length of pipe where air is being pulled through by a high powered fan at one end. The pipe is stainless steel, outer diameter is 100 inches. the thickness is 0.125 inches. I need to know what is the minimum vacuum pressure inside the pipe can be before the atmospheric pressure will...

can anyone refer me to a graphical representation of how this works so i can build one?

If a pendulum consisting of a string and a bob is allowed to swing in a vacuum vs in air, which has larger period?

if we have a vacuumed tube inserted into a reservoir of 10,000psi will the oil rise up in the vacuum tube of will it stay in place because there is no Δp?

Homework Statement [/B] Q = A / V Bernollis therom → γH = P+γZ+ρ.v2 /2 Air Flow Speed = 0.058 m3/s A = Section Area of the tube = π.r2 r = 19.65 mm ρ =1000 kg/m3 g =9.8 m/s2 P=pressure energy of water = 2.338 Homework Equations Find : V= Fluid Velocity = ? H=Energy Denisty = ? Z= Geodesic...

Is there a good description or formula regarding how the sound pressure from a constant source depends upon ambient pressure? That is, if I were to conduct an experiment where I put a source and a microphone in a container, and then change the pressure in that container with a pump, assuming...

Hi, I am trying to understand which thermodynamics process or processes could model a vacuum engine (mostly known by the name "flamelickers") and similar engines.. In a vacuum engine you have a cylinder and piston system that draws hot air from a heat source, cools it and mechanical work is...

I'm trying to track down the best (lowest) vacuum pressure ever achieved. I'm talking about absolute pressures, not relative, so I wouldn't call the environment in a submarine the winner even though it achieves a very large magnitude negative pressure differential relative to the high ambient...

Hi all. New to PFs. I deal in (exotic) human biology, which happens to have put me at the intersection of fields and, in this instance, conceptually more challenging physics. I'm presently involved in a comparative analysis of biological versus physical time contraction-dilation. I happen to...

Hey guys, I have had a lot of success finding what I need on campus for an experimental setup, but for some reason this piece has been alluding me. I am trying to source an 8" HV conflat with 5.75" ID. It can have fixed or rotatable holes, be threaded or un-threaded so long as it has at least a...

As much as I have understood, virtual particles keep appearing and disappearing in a vacuum state. This leads to zero-point energy, Casimir effect etc. Now, I want to know if there is a lifetime (i.e. a time limit) for which these virtual particles can exist before disappearing. Also can there...

When a field is quantized on the light front, there is no possible pair creation from the vacuum energy. This is because kinematic operator P^+ generates only a positive spectrum ( https://en.wikipedia.org/wiki/Light_front_quantization#Spectral_condition ). So there is no "particles popping out...

A. Neumaier submitted a new PF Insights post The Vacuum Fluctuation Myth Continue reading the Original PF Insights Post.

My background is in Health Physics and as such, I have had only rudimentary instruction in quantum mechanics, so my understanding (such as it is) is largely conceptual. With that in mind, this may be a very ignorant question, so I apologize in advance. I understand the theoretical basis for...

Hello I needed to know a logical answer to the question that whether the time of flight of the objects in air increases or decreases as compared to vacuum? Why?

Homework Statement So suppose there is a chemical rocket operating in the vacuum of space (assume it's a perfect vacuum). It generates a hot gas with a total enthalpy of h. What's the final speed of the rocket exhaust, in terms of h? Homework Equations The energy equation seems to be useful...