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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129 views

How far could one fire a charged particle in space?

I've wondered how far would be able to send a concentrated beam of electrons in space. The reason is would we be able to launch a magnetic ring with an electron absorbing material on one side and just ...
3
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3answers
4k views

How does blood/saliva boil in outer space?

Why would the blood boil? Is it because of the temperature or pressure? Because I really can't figure it out. I thought space didn't have a temperature above freezing unless close to a star or the ...
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1answer
115 views

are there any “known unknowns” that could affect the possibility of a false vacuum?

(Although Donald Rumsfeld was mocked for talking about "known unknowns" and "unknown unknowns", I think it's an truly important distinction.) Periodically, I hear about how the universe might be in a ...
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1answer
807 views

Will the “Vacuum Wine Saver” suck the bubbles out of Champagne?

The "Vacuum Wine Saver" comes with the following "warning": Not for sparkling wines Intuitively and naively, I imagine that the bubbles (or the "bubble-potential"—my made-up terminology) will be ...
3
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1answer
906 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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1answer
73 views

Attraction of a Bullet due to Gravity in a Perfect Vaccum

I realise that this might be conventially very difficult to answer because there's no KG or Newtons in space, only particles. As far as I understand, every object creates a 'pull' due to the forces ...
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1answer
60 views

Does photons undergo the process of cyclic absorption and re-emission by virtual particles in vacuum?

The process of cyclic absorption and re-emission by electrons in a medium is an explanation for the fact that light appears to slow down in mediums relative to vacuum. But, does light undergo this ...
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0answers
222 views

Is false vacuum bubble nucleation possible in our universe?

Is it possible that a false vacuum bubble to nucleate into our universe rather than a true vacuum one ? If yes,it will expand at speed of light within our spacetime or what ?
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0answers
63 views

Conservation laws in vacuum phase transition

Let's consider a bubble nucleation phase transition between different vacua via quantum tunnelling .For my understanding a particle must penetrate the potential barrier and find herself in an another ...
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1answer
164 views

Particle Spacing in a Vacuum

Four questions: (To start off, I know very little about physics it isn't even funny (I probably use a ton of wrong terms here and leave out vital information, if so I will try to edit it in as you ...
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2answers
250 views

Why Goldstone Bosons? (A Question about VEVs)

I understand how the mechanism of spontaneous symmetry breaking works, and why it produces Goldstone bosons (for global symmetries) and massive gauge bosons (for local ones). However, I'm confused as ...
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2answers
200 views

Do siphons really require air pressure to function?

Can the siphon mechanism work in vacuums? There seems to have been experiments where exotic liquids (low vapor pressure) were used in siphons mounted in vacuum chambers. The idea is that the falling ...
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0answers
138 views

What does $\text{VAC}$ mean in Weinberg's QFT?

Hopefully Weinberg is sufficiently popular that this question isn't too localized. I'm reading Volume II (16.1, p. 63) and he refers to the state $\lvert\text{VAC}\rangle$ quite a lot. Does this mean ...
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2answers
274 views

From which side should I solder electrical feedthroughs into a vacuum flange?

I work on an experiment that requires electrical connections to a vacuum vessel, which is submerged in liquid helium (LHe). For sending the signals into the vessel, we use a feedthrough flange. I am ...
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3answers
760 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 ...
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1answer
104 views

Does time pass fastest in isolated, resting space?

While it is fairly established that both fast movement and the presence of gravity make time pass slower as compared to a system at rest / free of gravity, does that mean that there is no way for time ...
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3answers
156 views

Can the vacuum be filled with virtual micro-black holes?

Since the vacuum is thought to be virtual particles, is it possible that there might be virtual micro-black holes with virtual horizons and virtual hawking radiation which form and evaporate at a rate ...
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2answers
1k views

Why does vaccum have a nonzero characteristic impedance towards electromagnetic radiation

OK, so the characteristic impedance is calculated "as square root of the ratio of the permeability of free space (µ o ) in henrys per meter ( H/m ) to the permittivity of free space ( o ) in farads ...
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2answers
410 views

Vacuum to hold an object

How can i check and calculate if a certain vacuum pump can hold an object that weights X kg? By "hold" I mean not let that object fall to the floor due to gravity
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0answers
53 views

Question on “pocket” universes

I recently heard about the possibility of the creation of a "baby" universe or "pocket" universe from our space time,the theory says that concentrating enough mass into a tiny volume of space (like in ...
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1answer
69 views

What is vacuum to DC flow?

I know how an air gap behaves: for lower voltages the resistance is extremely high, until spark voltage is achieved, at which point resistance rapidly drops, creating electric arc. Now, how does that ...
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1answer
235 views

Are dark energy and zero-point energy the same thing?

According to Quantum Mechanics is it possible that the famous "dark energy" and "zero-point energy" are the same thing that drives the accelerated expansion of the universe or maybe related to each ...
2
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1answer
292 views

Symmetry Breaking and Vacuum Expectation Values

Consider a real scalar field $\phi$ in a theory with a Lagrangian $$ \mathcal{L}:=-\frac{1}{2}\partial _\mu \phi \partial ^\mu \phi -V(\phi ), $$ where $$ V(\phi ):= -\mu ^2\phi ...
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1answer
103 views

What does electroweak vacuum lifetime refer to?

I just read an article about the correlation between the Higgs boson mass and the stability (or metastability) of vacuum, so I want to ask to someone this: When someone is talking about the ...
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0answers
246 views

How fast is a true vacuum bubble going to expand?

If a true vacuum bubble will occur in our universe, how fast is it going to expand?
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2answers
490 views

Vacuum Expectation Value and the Minima of the Potential

Often times in quantum field theory, you will hear people using the term "vacuum expectation value" when referring to the minimum of the potential $V(\phi )$ in the Lagrangian (I'm pretty sure every ...
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1answer
663 views

The vacuum in quantum field theories: what is it?

In Section 10.1 of his textbook Quantum Field Theory for Mathematicians, Ticciati writes Assuming that the background field or classical source $j(x)$ is zero at space-time infinity, the presence ...
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1answer
186 views

Vacuum energy extraction: What happens to the cosmological constant?

If the vacuum energy is extracted, then what will happen to the cosmological constant? Will it remain the same? .
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1answer
80 views

Is the “pressure” as we know a kind of “instantaneous action at a distance”?

This may be a very simple question, but I still dont know how that work in the essence (quantic/atomic level) Consider the image bellow: How the "pressure (air atoms) " known that in the other ...
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1answer
98 views

Does an antiDeSitter space compensate the vacuum energy?

Sometimes I read here or there that a problem with the electroweak vacuum is that it implies a huge positive cosmological constant. On other side, I also read that AdS spaces are not useful anymore ...
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1answer
486 views

What would stop a pendulum swinging forever in vacuum? What kind of friction is in vacuum? [duplicate]

Suppose I put a pendulum of metal ball and very thin rope in highest achievable vacuum. What would keep it from not swinging forever?
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0answers
95 views

Could Elon Musk's proposed Hyperloop transportation system reach 760 mph? [closed]

Hyperloop is a proposed mode of High speed transportation by Elon Musk. Theoretically it's speed is about 760 mph. Can 760 mph speed be achieved with this project ? Hyperloop - Alpha - ...
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1answer
187 views

Vacuum as a physical/chemical/material substance

Can the vacuum be understood as a physical/chemical/material substance? Remark: Vacuum has a density energy (so it has a density "mass" equivalence due to $E=mc^2$). Vacuum is quantum (but not ...
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4answers
1k views

Is it possible to create a vacuum ballon using concentric partially pressured spheres?

The old saying goes, nature abhors a vacuum, but that isn't exactly true. The universe is full of vacuum; what nature abhors large energy differentials. So for example, a vacuum chamber has to be ...
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3answers
11k views

What is meant by Vacuum?

What is the exact meaning of the word vacuum? Is it just a state of very low pressure or is it nothingness (as in there is nothing)? Also, when we say space is vacuum - it must be referring to ...
2
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1answer
240 views

Vacuum polarization in QCD and gluon bubbles

In analogy to QED, the following Feynman diagram is a diagram contributing to the vacuum polarization effect, leading to anti-screening, asymptotic freedom and running of the strong coupling constant. ...
0
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1answer
364 views

How could vacuum energy cause the expansion of the universe? [duplicate]

Is it by gravity? How could gravity produce a repulsive force?
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3answers
1k views

How should I clean a part before installing it in a vacuum system?

What are proven procedures for preparing a part that comes fresh out of the workshop for ultra-high vacuum (UHV) and extremely-high vacuum (XUV)?
22
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4answers
4k views

Is space “real”, or is it some sort of accepted postulate?

What is space? It seems to be everywhere in the equations of physics, as some sort of postulate or hidden hypothesis. We also have a direct experience of it, but is it "real"? The fact that we ...
7
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1answer
348 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 ...
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5answers
3k views

Nothing vs. empty space

This question quotes Hawking saying: [...] you enter a world where conjuring something out of nothing is possible (at least, for a short while). That's because at this scale particles, such as ...
1
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2answers
2k views

Are quantum fluctuations completely uncaused events?

I read here that particles/antiparticles appear and annihilate each other spontaneously in empty space. Since particles appear and disappear in empty space, it would seem that empty space has some ...
7
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1answer
300 views

Understanding multiple instanton contributions to vacuum tunneling in a double potential well

I'm trying to understand the method of calculating the transition probability of one vacuum state to another in a double well potential, using instantons. The reference I am following is Sidney ...
4
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1answer
304 views

de Sitter versus Minkowski QFT and cosmological constant

WMAP/Planck results confirm than we live in a de Sitter-like phase, i.e., a Universe with positive acceleration or positive cosmological constant! Therefore, I believe that a way to solve the ...
10
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5answers
3k views

What causes the permittivity and permeability of vacuum?

When light travels through a material, it gets "slowed down" (at least its net speed decreases). The atoms in the material "disturb" the light in some way which causes it to make stops on its path. ...
4
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2answers
140 views

How does a pierced vacuum move?

If a can of compressed air is pierced on the right, air pushes out, and the can moves to the left. If a vacuum container is pierced on the right, which way does it move? Right? Left? Not at all? ...
4
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1answer
199 views

How important is it, really, to clean vacuum parts?

In every lab I've seen, people are quite meticulous about cleaning parts that are to be used in ultrahigh vacuum, as well as the components of the chamber itself. The parts may be put in an ultrasonic ...
12
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1answer
491 views

How is it possible the speed of light is not constant?

I was reading this article recently, which summarizes a couple of new studies into the speed of light. In one paper, Marcel Urban from the University of Paris-Sud, located in Orsay, France and his ...
0
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1answer
956 views

How does the radius and length of a pipe affect vacuum performance?

Can I use Poiseuille's equation? Also If I have a vacuum pump which says that its performance is 30 cubic feet per minutes and I have two pipes (one is radius R1 and L1, the other one is 2*R1 and ...
3
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1answer
74 views

What would happen if a piece of matter, in our atmosphere, were to suddenly vanish?

What would happen if an object were to suddenly disappear? I mean actually disappear, as in, the space occupied by that object were now completely empty- and a vacuum was left. If I was holding a ...