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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Using reflective optics concepts to focus gas pressure in a vacuum

At very low vacuum pressures the bulk behaviour of molecules can be approximated by non interacting particles bouncing off of the chamber walls: For an monotonic molecule such as He with perfect ...
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112 views

Temperature of planets without atmosphere

I am wondering how come a planet without atmoshhere loses heat in space when the space around it is a vacuum. In my understanding for one object to lose heat it must have contact with another ...
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Locality, unitarity & vacuum energy

I've read in a set of lecture notes that the requirement of locality and unitarity in QFT imply that the vacuum must have a non-zero energy associated with it (http://arxiv.org/abs/1502.05296 , top of ...
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31 views

Partitioning a single vacuum chamber to isolate out-gassing components?

Planning a DIY vacuume chamber that would contain motors and electronics for manipulating in random experiments My thought is to section the chamber into two parts: clean and dirty - the dirty part ...
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152 views

Ground state for interacting field thoeries

Are there references where the ground state of an interacting quantum field theory is explicitly written in terms of states of the underlying free theory? For example, let us suppose to have a self ...
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1answer
127 views

Forces of suction in WIllie Wonka's Chocolate Factory (filmed 2005 starring Johnny Depp) [closed]

Before I begin the question: I am in no way judging this movie, just happened to be casually watching it and saw the scene (referred to below) and thought to post this question. The scene: Boy falls ...
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In truth, only atoms and the void

I have a question about this motto used by Sean Carroll in his blog: In truth, only atoms and the void. Can you explain what this sentence means? My interpretation is that the sentence does ...
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14k views

How do electromagnetic waves travel in a vacuum?

This is perhaps a total newbie question, and I will try to formulate it the best I can, so here it goes. How does an electromagnetic wave travel through for example, the vacumm of space? I usually ...
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20 views

How abruptly would you have to brake to form an almost complete vacuum in the back seat? [duplicate]

Suppose you brake with a car (or any other moving object). As the air inside will rush forward, won't there be a relative dearth of air molecules in the back? So, how strong does the acceleration have ...
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How does space affect the human body (no space suit, no space craft)

How does "outer space" affect the human body? Some movies show it as the body exploding, imploding or even freezing solid. I know space is essentially a vacuum with 0 pressure and the dispersion of ...
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37 views

Virtual Particles and Causation [duplicate]

Sometimes when people debate what type of cause a universe with a beginning may have Virtual Particles has been used as an example of a thing that can arise without a cause. So my question would be ...
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2answers
129 views

Functional integral in spontaneous symmetry breaking

So, functional integral is defined to be (with $\lvert\Omega\rangle$ is the vacuum state): $$\frac{\langle\Omega\rvert ... \lvert\Omega\rangle}{\langle\Omega\vert\Omega\rangle} = \int \mathcal{D} ...
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Speculative experiment: A golf ball at the frontier of the universe

Consider a golf ball in the center of an empty sphere (maybe a GR vacuum, I'm not so sure). Consider this empty sphere as being the only space available to the golf ball, it is surrounded by nether. ...
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91 views

How is possible to hear mechanical sounds in space?

In the footage taken by U.S. astronaut Terry Virts during spacewalk (EVA) on the International Space Station on 25.02.2015, sounds can be heard while in space. I can understand "shaking" sounds while ...
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2answers
118 views

Can the vacuum energy be made finite with quantized space

From what I know the reason we have infinite vacuum energy is because according to Quantum Field Theory at every point in space we have something analogous to a harmonic oscillator but since the Zero ...
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1answer
2k views

Water in a vacuum sealed jar?

I recently purchased a Vacmaster VP215C chamber sealer, and have noticed that when I place a small container of water into the chamber, and pull a vacuum for just over 25 seconds, the water begins to ...
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1answer
1k views

Why does Hauksbee's electrostatic machine produce light?

I'm reading on the history of the discovery of electricity and the electron, and I've went from reading about Rutherford's gold leaf experiment all the way back to Francis Hauksbee's spinning glass ...
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93 views

Why does Hauksbee orb or a similar device produce light?

This essentially fits well to the question asked earlier but had to placed as a separate question... An interesting and detailed answer was provided. However, there are few points, originating from my ...
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4answers
312 views

If a bell is rung in a perfect vacuum and is suspended by opposing magnets will it ever stop ringing?

As far as I am aware a bell rung in a perfect vacuum would only lose energy and stop ringing due to friction between the bell and the hanging mechanism (due to the lack of air resistance). Therefore ...
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7answers
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Does gravity exist in a vacuum?

My understanding has always been that it does from conventional science courses, but really thinking about it, I was wondering if this is really the case. To my limited understanding there is a ...
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2answers
1k views

What is space made of?

General Relativity posits that matter curves spacetime, such that geodesics point towards the object in question, hence, gravity. Now, how does matter do this? What is spacetime "made of", anyway, ...
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1answer
163 views

If we go to space why isn't the temperature high? [duplicate]

We know that the temperature in space (which has vacuum) is low. If I go to space will I feel sweaty and hot or chilly? I think I will feel sweaty and hot because the radiation (UV, IR, etc) of the ...
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3answers
158 views

Why stars are white? According to Rayleigh Scattering

According to Rayleigh Scattering, the red waves are capable of travelling a long distance, so that only we are seeing the Sun as reddish during Sunset and Sunrise. If this was true then all other ...
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459 views

Vacuum-ether and spacetime

In the past you could not give an explanation for various phenomena in which there was an action at a distance, like magnetism or gravity, that occurred in a vacuum; For this reason, ether was ...
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59 views

Is a “Perfect” Vacuum theoretically possible [duplicate]

I came across this answer to another stack exchange question and wondered about how true the claim was. http://physics.stackexchange.com/a/174683/42787 It starts with a disclaimer that claims that ...
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5answers
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Is speed of propeller-driven airplane limited by the speed of sound?

Mine line of thoughts goes like this: A propeller is effectively pushing itself away from molecules of air. The best any propeller can do is to create total vacuum in the front of itself. The ...
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82 views

Why metals fused in vacuum? [duplicate]

On Earth when two pieces of metal comes into direct contact with each other, nothing amazing happens. In a complete vacuum condition the two metals fused permanently, how and why?
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Drying clothes with the sun's heat, without any air

Will my wet clothes dry if I hang them under the sun, and if there is no air around the clothes? In other words, do I need both air and heat to dry wet clothes, or is heat alone (in the imagined ...
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2answers
167 views

Negative pressure

How is negative pressure created in a fluid system?Isn't it counter intuitive that we are reducing the pressure of a system containing no molecules(zero pressure) to a lower value?
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1answer
98 views

Meaning of “vacuum state”?

I just learned about $|0\rangle$ and siblings $|0_\gamma\rangle$ and $|0_\infty\rangle$ while studying coherent and squeezed states in a QM class, and I have a question about the meaning of ...
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183 views

What properties does the vacuum have?

Once upon a time the vacuum was defined as "nothing". We now know it has all kinds of properties such as permeability, dimensionality etc. Is there a list of such properties anywhere?
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What happens to a body, initially at 300K, kept in isolated space? Will it's temperature drop to 0k?

With regards to Thermal Radiation, given a stable body initially at 300 Kelvin placed in isolation, after continuous Thermal Radiation will it's temperature gradually reduce to 0 kelvin ...
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1answer
108 views

Can we generate electric current by injecting electrons into a copper panel

Suppose I take a vacuum tube and accelerate electrons in it by electric fields then collide it on a copper plate. Will the electrons then go inside it and generate an electric current by putting a ...
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What if you opened a door in a spaceship without a spacesuit?

In movies/cartoons you see astronauts and people in spaceships opening doors and closing them again with no suits on. Is it possible in "real life" or would you die immediately? Because consider this: ...
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53 views

Temperature in a vacuum made in the lab

Is the thermal energy of a vacuum 0? And, how close to a perfect vacuum can we make in the lab?
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Can a volume of N2 be more negative than -14.7 psi?

Ok. I’m getting -30 PSI on a gauge calibrated at 0 for 1 ATM. Let’s say I have a chamber with a volume of 20L of N2 at 1 ATM. A vacuum pump that can pump to absolute vacuum let’s say 1X10^-10mTORR. ...
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60 views

What happens if a free radical is placed in absolute vacuum?

I'd like to know what happens if a free radical has no material around to interact with. I have asked many people but I am not satisfied with their answer. I know there is nothing like absolute ...
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266 views

What is the meaning of Einstein's field equation in terms of source and its effects on curvature?

The Einstein's Field Equation is $$R_{\mu\nu}-(1/2)g_{\mu\nu}R=-8\pi T_{\mu\nu},$$ where the left hand side is the curvature term and the right hand side is the source term (see, Hartle). Now, in the ...
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65 views

Repulsion of electric charges

If a take a vacuum tube and put electrons in it and put a negative ion strip or something like that outside the tube will the electrons inside the tube start moving due to the repulsion of charges of ...
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Proving and demonstrating vacuum in container without breaking it

Let there be a hollow container made of glass or some other transparent material, roughly the size and shape of an apple. Let the walls be of sufficient thickness for the container to be safely ...
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1answer
97 views

Time in a perfect vacuum? [duplicate]

If we were able to make a perfect vacuum with no forms of energy in, including all forms of light would time still go on in that vacuum and if it doesn't how would we tell that it doesn't? Then if we ...
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Creating vacuum in a glass by acceleration

Suppose we have a cylindrical glass at atmospheric pressure. The glass is put in a horizontal position such that the bottom of it (the closed end) is at the right side and the open side is on the ...
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3answers
381 views

Are vacuum fluctuations really happening all the time?

In popular physics articles and even some physics classes I've been to, the vacuum of space is described as being constantly full of quantum fluctuations. Supposedly, all sorts of ...
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What is the relationship between the Young's modulus of a material and the elasticity of a free fall collision

I'm coding a 2D physics simulator based around the Newtonian physics principles with some alterations due to computation limits and I am at the stage of creating a collision event between a planetary ...
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4answers
2k views

Is there an intuitive description of vacuum entanglement?

People often refer to the fact that the vacuum is an entangled state (It's even described as a maximally entangled state). I was trying to get a feeling for what that really means. The problem is ...
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2answers
164 views

Moving frames - a blow on “virtual particles”?

There is a polemic about whether virtual particles EXIST, or are only a tool for making our calculi easier. Here is a doubt about their existence, and on the other hand, an argument in support of ...
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4answers
972 views

Why do we theorize that the Big Bang created space? [duplicate]

I just asked this astronomy question about how far away the light is that would show us the beginning of time, the Big Bang. Some answers claim that the light I ask about doesn't exist, because "The ...
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What are the calculations for Vacuum Energy?

In wiki the Vacuum Energy in a cubic meter of free space ranges from $10^{-9}$ from the cosmological constant to $10^{113}$ due to calculations in Quantum Electrodynamics (QED) and Stochastic ...
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How does air in a water balloon act in space?

I was making an analogy with gravity and water and it went like this. When air is trapped in water as a bubble, water is pushing towards the inside and like Newton's law equal and negative forces ...