A region of space devoid of any fluid molecules resulting in a zero pressure in ideal cases. In practice, even space has a small but finite number of molecules. In QFT, it signifies the ground state devoid of excitations/particles.

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possible x-ray production, low pressure discharge

What is the maximum pressure at which a high voltage discharge can produce x-ray radiation? I am experimenting with plasma in the form of ionized air in my vacuum chamber, maximum vacuum possible is ...
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1answer
36 views

Perfect vacuum in experiment [closed]

When conducting experiments to determine the speed of light in a perfect vacuum does that vacuum(?) replicate outer space?
3
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0answers
57 views

sound propagation at low pressure

I am curious about the properties of sound at low atmospheric pressure. Not the speed of sound, I want to know how lower pressure will affect the distance sound will carry and the frequency range. For ...
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30 views

Superheating Water Demonstration with a Vacuum

There are many Youtube videos which place a cup of water into a vacuum chamber and cause boiling around 0.020 atm, but I can't find any which show a vacuum-only "superheating" effect (to be clear, I ...
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1answer
46 views

Behaviour of gases in a vacuum

I have a doubt related to the behaviour of gases in a vacuum. In the following figure: The grey part is the vacuum and the green part is the gas, let the gas be Carbon Monoxide. The following are ...
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0answers
27 views

Vacuum marks on windows

I'm sure everyone one day or another has spotted some vacuum marks on their windows, usually when the windows are covered in steam, then the marks become quite obvious. i.e. the leftover circles from ...
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1answer
47 views

Single fluid simulation algorithm

Every fluid simulation I've seen implicitly involves a fluid that isn't mentioned, usually air. This is clear because the simulation usually has an ambient temperature, and always an ambient velocity. ...
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2answers
79 views

Keeping low pressure inside a bottle

will the pressure inside a bottle remain low if I attach the bottle with a vaccum pump via a one way check valve like th following picture and then take the vacuum pump?and why?
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0answers
89 views

Can you be your own space suit? [closed]

A few days ago a question was asked on Reddit whether or not a human could survive in space with "just enough" of a spacesuit to plug all the important holes, e.g. a face mask to plug the eyes, ears, ...
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1answer
145 views

Why, in quantum field theory, is $\hat{a}(p)|0\rangle=0$?

My Quantum Field Theory lecturer just said that $\hat{a}(p)|0\rangle=0$ because the vacuum state contains no particles. Now, according to Wikipedia, "according to quantum mechanics, the vacuum ...
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2answers
311 views

What's the difference between vacuum pump and vacuum cleaner? [closed]

I think vacuum pump and vacumm cleaner's structure is almost same.Isn't it?
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3answers
57 views

Sound wave in a Vacuum

If a Tuning fork was Struck in a Vacuum what happens to the resonant frequency of the fork and the potential sound wave. Does the wave leave the fork?
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1answer
113 views

Does a Tesla coil work in space?

If I took a Tesla coil into space, and then turned it on near, but not touching metal objects- would charge jump to the metal objects? It's my understanding I wouldn't see a flash, since the lightning ...
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3answers
133 views

The temperature in space is about 3K, however there are almost no atoms in space. How can there be residual heat?

My understanding is that heat is essentially atomic vibrations. If there are almost no atoms, how can there be residual heat? Also, as I understand in space there is no heat transfer via convection ...
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2answers
315 views

Could a bladeless “Tesla Turbine” type air compressor be used as a high vacuum pump?

I have a wacky idea for a new vacuum pump, I'm trying to figure out why it shouldn't work. I'm interested in learning about Tesla Turbines, specifically when used in reverse as compressors or vacuum ...
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1answer
267 views

What affect does pipe diameter have on a manometer? [closed]

I am building a DIY hoover and want to test different technical configurations of the device (hose diameter, hose length, motor RPM, motor voltage, cavity size, etc). My objective for testing these ...
2
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0answers
36 views

In what situation will a conformal transformation leave the vacuum invariant

Recently I am reading Francesco's CFT. In section 5.4.2, it considers a generic CFT living on the entire complex plane and maps this theory on a cylinder of circumference L by the transformation: $$ ...
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1answer
79 views

Where does the kinetic energy come from if galaxys are moving apart due to the expansion of the universe?

We know the universe is expanding because of the red shift of far away galaxies, the further away the galaxies are the faster they recede. We also know that the energy in the universe (mass and other ...
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2answers
117 views

Light always particle in vacuum because it has no medium

My physics teacher told me that light in a vacuum is always in the particle form. So what happens if you perform the double slit experiment in vacuum? Will the light spread like a wave or will it have ...
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0answers
222 views

Does the “luk” space suit in Seveneves make sense?

Tiny spoiler of the book Seveneves ahead. Early in the book, the Russian space agency develops an onion-like space suit called the "luk" (the Russian word for onion). It works like this: A ...
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1answer
45 views

Questions regarding Vacuum in space [duplicate]

The mention of vacuum has always created questions in my mind. In space isn't there near complete vacuum. If there is then why don't the oxygen travel from the suit to space (because of large ...
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0answers
85 views

Suction from flowing water

My memory from physics says yes but I want to check. Our pool is dirty and our vacuum is broken. If I were to stick the vacuum hose into the pool drain, would the flow of water going into the drain ...
3
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2answers
215 views

Is the vacuum empty? Are virtual particles in the vacuum? Is the vacuum non-zero? [duplicate]

I have read a lot about this stuff. Is the vacuum empty? How is it not-empty? But nobody can it explain serious and simple that I can fully understand it. Some physicists tell may that virtual ...
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1answer
42 views

Can you record sound through vacuum? Like this: (object)(vacuum)(object)

There are these videos on youtube that play sound of Jupiter for example: http://www.youtube.com/watch?v=e3fqE01YYWs Does anyone know if this is real at all? How can you record sound through vacuum ...
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4answers
251 views

Speed of sound in vacuum

I am not a scientist but I have a question about speed of sound in vacuum. All I know is that the speed of sound $v$ in a medium is given by formula $$v= \sqrt{\frac E\rho},$$ where $E$ is elasticity ...
3
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1answer
40 views

Why vacuuming an air chamber is much slower than vacuuming an argon chamber?

When pumping a chamber full of air down to a certain level of vacuum, it takes a while. However, when that same chamber is full with argon, reaching the same level of vacuum is much faster. What makes ...
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34 views

Difference between vacuum and pseudovacuum vector?

What exactly is the difference between the vacuum and pseudovacuum vector? In my case the ground state of a system is the vacuum vector and by letting operators act on that vacuum vector magnons are ...
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2answers
120 views

Does the density of virtual particles decrease when space expands due to dark energy? [closed]

I understand that vacuum (i.e. QED vacuum) is theorized to contain spontaneously appearing and annihilating pairs of virtual particles. Suppose the average density of those particles at a given moment ...
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2answers
182 views

How to calculate planar window's buckling pressure in vacuum chamber wall

I can't find the formula, I can see some formulas for circular windows are given here [1] (thanks CERN!). For example with a circular (flat/dome?) window, buckling pressure ($p_\text{CL}$) and max ...
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1answer
109 views

How does the fluid's vapor pressure in aspirator (pump) relate to strength of vacuum?

From wikipedia: If a liquid is used as the working fluid, the strength of the vacuum produced is limited by the vapor pressure of the liquid (for water, 3.2 kPa or 32mbar at 25 °C). ...
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1answer
289 views

Is empty space made of energy?

GR says that matter bends space around it, QM says even empty space must contain something. Is empty space a form of energy?
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3answers
296 views

Virtual Particles real? Virtual particles create a universe?

I am reading the book of Lawrence Krauss "A universe out of nothing", where he explained that the vacuum is not empty. It is a boiling brew of virtual particles that come out of their existence. And ...
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1answer
202 views

Why does very cold water in a thermos cause there to be strong suction on the cap?

After putting ice-cold water in a thermos, the cap is strongly held on by what feels like suction. I assume the cold water condenses the air, thus lowers the pressure inside, but can someone explain ...
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1answer
74 views

Can I say that the two-body problem is also a vacuum solution for the special case of two orbiting black holes?

A two body system is one where two bodies orbit each other. In the case of two orbiting black holes, since an individual black hole is described by a vacuum solution, can I say that the two-body ...
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4answers
4k views

Why is space a vacuum? Also, why doesn't air from the Earth escape into space? [duplicate]

Why is space a vacuum? Also, why isn't the air from the Earth escaping due to the vacuum in space? The ozone layer is only gas and a magnetic field, so why doesn't the air escape from Earth into ...
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1answer
109 views

What's the difference between vacuum particle-antiparticle annhiliation and regular annihilation?

Why does vacuum particle-antiparticle creation and annihilation result in nothing rather than photons? What is the difference between that and regular annihilation that does result in photons.
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2answers
237 views

Nothing cannot possibly exist, right? [closed]

A few things about this question. I am aware that people have written papers describing total nothingness, and even something from nothing type of scenarios. I have no idea how this is possible. If ...
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2answers
90 views

Infinite Accelatation

Before I ask my question, let me just say, I know very little about particle physics and general relativity, so I may ask a obvious question or a question that makes little or no sense. Now, what ...
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0answers
48 views

Can a pure vacuum with 0% gas be created? [duplicate]

If we were to create a vacuum room with no air in it to avoid air resistance can it be done?
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0answers
182 views

Vacuum pressure equivalent in a siphon hose filled with water?

So, I was thinking about how siphons worked today, and no matter how high or low the tube goes, as long as the end is lower than the start, water will flow. So, if you took a hose, ran it up 50 ...
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2answers
110 views

Is it easy to create a vacuum in space?

Say for example you have a closed, empty, and air-tight plastic bag, then you can't grip it from each side and pull the sides apart because for that to work a vacuum would need to be created inside ...
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0answers
15 views

Cosmological constant in General Relativity [duplicate]

According to my GR notes the cosmological constant can be thought of as a vacuum energy much in the same way as the ground state of the harmonic oscillator. The notes claim that the regularised energy ...
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2answers
107 views

How do EM waves travel in a vacuum? [duplicate]

Apart from that electric and magnetic field variation thing, is there any other explanation? Can photons simply pass through vacuum?
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1answer
72 views

Quantum gravity- Vacuum catastrophe

Why does the predicted mass of the quantum vacuum have a very little effect on the expansion of the universe?
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1answer
100 views

Difference between Cosmologial Constant and Quantum Vacuum State

Hello I am very new to cosmology and quantum physics. I need some basic understanding (in Layman's term) of the Difference between Cosmological Constant and Quantum Vacuum. Cosmological Constant is, ...
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2answers
60 views

Can high speed moving hydrogen atoms drive turbines?

We know that hydrogen is a part of air so if we accelerate hydrogen atoms in a circular vacuum tube as done in a particle accelerator, can the high speed moving atoms of hydrogen drive a turbine if we ...
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1answer
74 views

If you brought a hollow one-inch cube of steel filled with air into space, would the air exert a pressure of 14.7 psi on the cube?

In my thought experiment, since air exerts $14.7$ psi at sea level, the air within the cube of steel should exert the same pressure outward, $14.7$ psi. Right? The whole thing about balanced air ...
6
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1answer
1k views

Could a vacuum airship be possible? [duplicate]

According to Wikipedia, a vacuum airship is a hypothetical airship that is evacuated instead of using a lighter gas. Really, once I first saw this, I thought, "Why did I never think about this ...
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1answer
45 views

Can we spin a top in vacuum?

What happens to a top if we spin it in vacuum. Will it have any difference to rotating in a normal surface to a surface in vacuum.
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0answers
43 views

Slow sustained liquid movement in a vacuum

Can water or any other liquid be made to “simmer” or “low boil” (slow sustained liquid movement) in a vacuum as opposed to go from liquid to all out boil when the vapor pressure is equal to the ...