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.

learn more… | top users | synonyms

1
vote
1answer
69 views

How does water height in a vacuum chamber effect pressure

I am testing for package leaks in non-porous packages. Quick details are: 1) Package is sealed at atmospheric pressure. There is some headspace inside the package which is just air. 2) A small hole is ...
3
votes
1answer
95 views

Vacuum has both zero four-momentum and nonzero vacuum energy?

I have heard that in QFT, the vacuum has zero four-momentum: $$P^\mu |\Omega \rangle = 0.$$ However, I also know that the vacuum has vacuum energy, i.e. $$ \langle \Omega | H | \Omega \rangle = E_0 \...
0
votes
1answer
51 views

Balloon in a vacuum

What arrangement will a mixture of low density gas and high density gas take inside a balloon (in a vacuum chamber) in zero gravity? FYI: water boil then freeze's in a vacuum. which one will stick to ...
-1
votes
2answers
33 views

Can we enhance a thermal gradient by combining a dark surface and a shiny surface with an external glass layer?

I refer to the article at this site: http://solarcooking.wikia.com/wiki/Solar_Kettle-Thermos_Flask As we know, dark surfaces absorb radiation (eg. solar water heater), while shiny surfaces reflect ...
0
votes
3answers
99 views

Thinking about the properties of 'nothing' [closed]

If a certain identifiable part of space that has no type of measurable energy fields manifesting 'in it' for a given duration ; is such a totally empty space the same as 'nothing'? Anything with any ...
0
votes
2answers
86 views

why is there no total vacuum condition on earth? [duplicate]

I know that Bell jars are often used in laboratories to form and contain a vacuum but not total vacuum like space.So i don't understand why can't human make vacuum bell jar a total vacuum state?
1
vote
2answers
48 views

what would happen to flowing electrons in a vacuum if they are not giving any exit point?

Lets say theoretically electron flow is captured in a vacuum and not allowed to exit then where would they go? I do not want to know the practical impossibilities of it. And also what would happen if ...
0
votes
1answer
20 views

HV Vacuum seals

I have a vacuum port that is 8.75" in diameter, it was attached to a block of aluminum. I am machining a piece of stainless steel to make a blank for it since it is a non-standard size. What are my ...
2
votes
2answers
82 views

Vacuum is not really empty

Vacuum should contain something in it. Because nothing is perfectly empty that's what I feel, but what is there left in it? Is there any matter or its just enegry. Can energy be pulled out of some ...
3
votes
3answers
95 views

Why would we freeze in space if there is no matter to conduct the heat away from us?

If a near perfect vacuum is assumed to be in space, how can heat leak around from our body for example? Although theoretically energy wishes to spread equally all around, it still needs a medium to ...
1
vote
3answers
66 views

Motion in vacuum [closed]

If we have a hollowed sphere in a vacuum, and its hallow space is filled with vacuum. In the center of the hollowed space inside the sphere is a ball. If we push the sphere does the ball move? (prior ...
1
vote
1answer
50 views

Methods to solve a vapor pressure equilibrium question with water on the moon? [closed]

"Imagine a tall column of water on the Moon, maintained at a temperature of 50°C and left to the open vacuum at the top. Up to what depth will the water continue to boil? The Moon's radius is 0.273 ...
1
vote
3answers
120 views

Is the empty space really empty? [duplicate]

I've come across another article in "list verse" which says that the empty space is not actually empty at least for a while. I've tried to find about this, so I googled it .It also quotes a word "...
3
votes
2answers
121 views

Gases Expanding and Bonding in the Vacuum? Frozen Clouds

Why do gasses expand in space rather than attract forming a liquid? Do some gasses attract or bond when they get colder and what would be the characteristics of it in space? Would it be like powder ...
1
vote
0answers
62 views

Could a perfect vacuum exist at the boundary of the universe?

Space is not truly a vacuum because of our observation of quantum foam, but if causality does not exist outside our universe, could that mean that quantum foam cannot exist outside our observable ...
0
votes
0answers
46 views

acrylic vacuum chamber design

I want to build a vacuum chamber for experimentation from acrylic sheets, ideally a cube $60~\textrm{cm}$ on each side. Assume that the chamber can be pumped down to theoretical perfect vacuum. How ...
-3
votes
1answer
140 views

Atoms, Gravity and Electrostatic Charge [closed]

How close do 2 atoms of any type the have can be together before gravity with an electrostatic charge that repulses?
0
votes
0answers
18 views

What result would I get from series-mounted vacuum assist? (hydraulic vacuum assist)

If I install two inline vacuum assist devices (such as VH44) on my clutch line, what will change in comparison to having a single boost? Will it decrease pedal travel? Tension? Both? Neither? Lest ...
2
votes
2answers
271 views

What happens with liquids in vacuum? [closed]

I am wondering what would happen in a situation where there is some liquid in a closed container A is vacuum and B is the liquid. I am also interested if there are any differences in behaviour ...
3
votes
0answers
90 views

Angular momentum of the vacuum

I'm studying quantum field theory from "An introduction to Quantum field theory" by Peskin and Schroeder and from "A modern introduction to quantum field theory" by Maggiore. I've read from "An ...
3
votes
0answers
30 views

Baryonic operators in ${\cal N}=1$ $U(N)$ SQCD in four dimensions

Seiberg's duality is usually considered as a duality for $SU(N_c)$ theories with $N_f$ flavors. In his case, the vacuum for $N_f \geq N_c$ is parameterized by mesons $M$ and baryons ${\bar B}$ and $B$....
5
votes
2answers
568 views

Why does the QCD vacuum have zero momentum?

Today in the hadron physics tutorial we were talking about the Fabri-Picasso theorem where one step in the proof involves $\hat P |0\rangle$ which is the four-momentum operator on the vacuum. And from ...
0
votes
0answers
20 views

How to Calculate Pressure From Earth up to Space at Certain Height? [duplicate]

https://en.wikipedia.org/wiki/Vacuum#Measurements_relative_to_1_atm https://en.wikipedia.org/wiki/Pressure_measurement#Thermal_conductivity I wonder if there's a clear equation for this calculation. ...
1
vote
1answer
42 views

Cryogenic (LN2) gas vs liquid for cooling

For cooling, would you recommend using gas over liquid or vice-versa? What is the temperature differential between gas and liquid? In other words, at standard volumes and pressures from a gas ...
1
vote
1answer
162 views

What happens to a sound wave going from air to vacuum?

Let's say you are in a space ship. The inside is filled with air, a medium in which sound waves can exist and travel. Then there's a wall, still a medium in which sound waves can exist and travel. And ...
1
vote
1answer
38 views

What is the temperature of a vacuum? [duplicate]

what is the temperature of Vacuum since temperature of a system is related to the average of the molecular kinetic energy and there is no molecule in a vacuum? i know there could be radiations but i ...
0
votes
0answers
24 views

Can we lock electric charges in dielectric cells?

Suppose next. We using Wimshurst machine and gathering charges in dielectric cells such as mica .Before discharge we put whole machine in vacuum chamber.Question is next. Can we storage those charges ...
0
votes
0answers
27 views

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 ...
0
votes
1answer
43 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
votes
0answers
67 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 ...
0
votes
0answers
34 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 ...
0
votes
1answer
63 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 ...
0
votes
0answers
31 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 ...
1
vote
1answer
48 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. ...
0
votes
2answers
99 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?
2
votes
0answers
95 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, ...
3
votes
1answer
146 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 ...
0
votes
2answers
576 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?
0
votes
3answers
66 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?
5
votes
1answer
145 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 ...
2
votes
3answers
149 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 ...
3
votes
2answers
539 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 ...
0
votes
1answer
436 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
votes
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: $$ z\...
1
vote
1answer
97 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 ...
1
vote
2answers
130 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 ...
1
vote
0answers
331 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 ...
0
votes
1answer
58 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 ...
2
votes
0answers
103 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
votes
2answers
288 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 ...