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.

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1answer
319 views

What is the difference between quantum fluctuations and thermal fluctuations?

Start with a simple scalar field Lagrangian $\mathcal{L}(\phi)$ at zero temperature $T = 0$, which has a hidden symmetry and spontaneously break it. By the standard procedure a field $\phi$ is ...
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1answer
41 views

Pressure - How much fluid can void support?

Please refer to the attached (terrible) drawing while reading the post ! After watching some videos about the U-tube effect in drilling, a question came to me. Imagine one fluid of heavy density ...
7
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1answer
335 views

Is a venturi pump feasible at very low pressure?

I need assistance (or experience feedback) in estimating if a Venturi pump would work at low pressure. A boiler under vacuum (10% atmosphere) will produce steam (at a given speed depending on the ...
3
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1answer
49 views

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

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 ...
0
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1answer
19 views

Pressure and humidity

Does pressure/vacuum affect water vapor differently than other gases and hence humidity? For example, imagine I have a vacuum bell at atmospheric (mean sea level) pressure and the air in it is 50% ...
-1
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3answers
732 views

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 ...
4
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1answer
489 views

Child-Langmuir Space Charge Law for Non-Zero Cathode Potential (Non-Zero Initial Electron Velocity)

I'm trying to reconcile some conflicting results that I've found in publications that address the idea of the current in a vacuum diode in the case where the cathode has a non-zero potential, in other ...
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0answers
45 views
2
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1answer
338 views

What happens to the total volume of a chunk of space that is being sucked into a black hole?

Does it increased, decrease, or stay the same? Maybe it explodes to infinity... Here is a similar question: Do black holes have infinite areas and volumes? But it's different because it asks how to ...
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4answers
4k 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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0answers
25 views

What would happen to me, if a human left in space without any special suits? [duplicate]

What would happen to the human body, If I left in space without any suits? like in the pic from "Guardians of the galaxy" Will the human body explode, because of pressure? Or will blood circulate ...
0
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0answers
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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3answers
2k views

How can there be heat in a vacuum?

I keep reading in the Physics World focus issue on vacuum technology about scientists creating high temperatures in the vacuums etc. If heat is caused by thermal energy being radiated from particles ...
17
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2answers
4k views

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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0answers
50 views

Virtual particles, electrons and quantum foam [duplicate]

Do quantum foam, electrons and virtual particles pop in and out of existence without a cause? If so, aren't they violating the laws of cause and effect and the 1st law of thermodynamics? is the 1st ...
0
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0answers
30 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 ...
3
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2answers
105 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} ...
6
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2answers
188 views

Do virtual particles actually physically exist?

I have heard virtual particles pop in and out of existence all the time, most notable being the pairs that pop out beside black holes and while one gets pulled away. But wouldn't this actually violate ...
-1
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2answers
29 views

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. ...
2
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1answer
62 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 ...
2
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2answers
94 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 ...
8
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1answer
1k 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 ...
5
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0answers
642 views

Is the double-slit experiment typically carried out in a vacuum?

It is my understanding of the double-slit experiment that when a measuring device is activated, to measure which of the two slits a particle is travelling through, this measuring is responsible for a ...
3
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1answer
879 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 ...
2
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0answers
47 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 ...
2
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4answers
229 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 ...
56
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6answers
10k views

What is the speed of sound in space?

Given that space is not a perfect vacuum, what is the speed of sound therein? Google was not very helpful in this regard, as the only answer I found was 300 km/s, from Astronomy Cafe, which is not a ...
3
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4answers
203 views

Can electricity flow through vacuum?

People say yes, and give a wonderful example of vacuum tubes, CRTs. But can we really say that vacuum (..as in space) is a good conductor of electricity in a very basic sense?
54
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7answers
10k views

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
754 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, ...
5
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1answer
80 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 ...
1
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1answer
132 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 ...
2
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3answers
66 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 ...
2
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3answers
266 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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3answers
144 views

Why is it impossible to have a perfect vacuum?

In another question someone mentioned that it couldn't happen. Why not? For example I asked about the speed an object would have to move at sea level to create a vacuum behind it; in the comments ...
3
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0answers
52 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 ...
17
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5answers
3k views

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 ...
1
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1answer
39 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?
0
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0answers
21 views

Vacuum Systems, Vapor Pressure, and Machine Damage

When operating a vacuum pump, after we have pumped it to its (almost) limit, and want to pump it back down, we normally Turn off the Turbomolecular Pump first Turn off the rotary vane pump next ...
12
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7answers
3k views

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 ...
0
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2answers
69 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?
2
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1answer
78 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 ...
1
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1answer
46 views

Can Impossible Vacuum balloon be possible with this idea?

As it is well known, a vacuum balloon using the materials we have at our disposal is not possible, because of the sheer force they have to resist from the air outside. I have an idea and I want to ...
0
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0answers
54 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?
2
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2answers
131 views

Propagation speed of photons when taking higher-order QFT corrections into account

In our group of experimental physicist who have nothing to do with and know very little about quantum field theory, we recently had a question concerning the propagation speed of photons in vacuum: ...
7
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2answers
1k views

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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2answers
154 views

Can I blow soap bubbles (of air) inside a vacuum chamber?

When I blow soap bubbles from a liquid dish soap mixed with distilled water at atmospheric pressure at ground level both internal and external air pressure nullify and the tension of the bubbles ...
0
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1answer
52 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 ...
5
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3answers
2k views

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: ...
0
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1answer
44 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?