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
273 views

String theory landscape and false vacua

What is the multiverse of string theory? I always thought it would be from brane cosmology where there's chances for multiple collisions of the branes that can make a universe. So this "multiverse" ...
0
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1answer
167 views

Understanding particle's space travel

Before the discovery of dark matter, the prevailing popular understanding of Space content is that of celestial bodies (planets, stars..etc) floating in 'void' and emitting particles and waves ...
9
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3answers
2k views

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 ...
2
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1answer
351 views

Calculating spacecraft water leak flow rate

A large container of heated water is floating in space. How can I calculate leak rate if a small puncture is opened? I'm assuming the water is kept at 298K and in the liquid state inside the chamber. ...
2
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1answer
206 views

Asynchronous generator run in vacuum chamber

what will be happen if we put asynchronous generator in vacuum chamber & run it above its synchronous speed. After reaching its over synchronous speed we will cut off electrical supply. Can it run ...
3
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5answers
179 views

Will a warm body naturally slowdown?

Suppose a warm body moving in an empty space with high speed. The body emits radiation based on its temperature. The protons emitted forwards of the body will have higher energy due to Doppler shift ...
4
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0answers
242 views

Stability of the vacuum state of interacting quantum fields

"Stability" is generally taken to be the justification for requiring that the spectrum of the Hamiltonian should be bounded below. The spectrum of the Hamiltonian is not bounded below for thermal ...
2
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1answer
283 views

Why dynamic Casimir effect does not appear in static gravity field?

Dynamic Casimir effect tells us that a constantly-accelerated mirror should emit radiation due to interaction with vacuum. Following principle of equivalence, a similar mirror placed in static ...
3
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3answers
89 views

What's in my box?

Let's say that I have a box which is 100% empty. I fly into the vacuum of space, open the box and close it after a certain time. Then I go back to earth and my question is.. What's in my box? ...
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2answers
426 views

Effect of coarse vacuum on consumer electronics?

What is the long-term effects of storing materials in consumer electronics in a vacuum? Ie, plastics, electronic circuits and optical glasses?
17
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2answers
3k 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 ...
2
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1answer
1k views

Would a high-explosive in a vacuum be less harmful?

Putting aside shrapnel effects, I believe that high-explosives cause damage by producing a shockwave. How do shockwaves work in space? I've managed to convince myself that a high-explosive shockwave ...
6
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1answer
358 views

Defining the ground state energy of a QFT

I would like to hear of some general discussion on how is the ground state and its energy defined in QFT and how does one go about finding it. (..at least in some simple cases I have seen the use of ...
11
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1answer
1k views

How to interpret vacuum instability of Higgs potential

If the Higgs mass is in a certain range, the quartic self-coupling of the Higgs field becomes negative after renormalization group flow to a high energy scale, signalling an instability of the vacuum ...
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2answers
784 views

Who first realized the uncertainty principle allows for virtual particle pair production?

For all I've read about Quantum Field Theory I've never seen the concept of the living vacuum accredited to someone in particular. Given the importance of this very application of the uncertainty ...
0
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1answer
104 views

Difference between $|0\rangle$ and $0$ in the context of isospin

I know this has been asked before, but I am confused having read it in the context of isospin, where the creation operators act on the "vacuum" state (representing no particles) $$a^\dagger_m|0\rangle ...
3
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0answers
271 views

good and reasonably cheap way of connecting glass and metal in a vacuum setup [closed]

Sorry for this very technical question, but we suffer from this problem at work and I do not know any other place to ask. Its about a good and cheap way of connecting a glass tube with a metal tube ...
0
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1answer
2k views

Would a generator in vacuum/space provide electricity endlessly?

At it's simplest, electricity generation is achieved by induced voltage due to a changing magnetic field. In a vacuum in the absence of friction, would the initial spin imparted to the rotor of a ...
0
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4answers
978 views

Atoms pop out of nothing/vacuum/pre-big-bang?

I saw a great documentary last night about 'nothing'. It's about vacuums, and how if you have a total vacuum atoms will pop out of nowhere! Pretty crazy stuff. Atoms literally coming out of ...
4
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3answers
663 views

Vacuum and repulsive gravity

How can one show from General Relativity that gravity is attractive force, and under which conditions it becomes repulsive, also why positive energy vacuum drives repulsive gravity?
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0answers
271 views

Gravitation and the QFT vacuum

I'm asking this to get yet another lessson in the inability of QFT and GR to cohabit. Many people believe GR must yield to quantization. The question here is as to why the activity of the vacuum ...
12
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7answers
1k views

Can energy be taken out of the QFT vacuum?

There have been recent questions about the vacuum. In my simplified knowledge the vacuum is like a ground state energy level, and also that there might even exist other lower energy levels than the ...
2
votes
5answers
426 views

Can computers survive bubble nucleations?

According to string landscape theory, our vacua with a cosmological constant of $10^{-123}$ is a metastable vacua which can decay to a supersymmetric vacua with either a zero or negative cosmological ...
8
votes
4answers
278 views

Direct exposure to the vacuum of space

I was watching a few sci-fi movies and was wondering the real science explaining what would happen if you were to be subject to the conditions of outerspace. I read the wikipedia article on space ...
2
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4answers
2k views

Can heat be transfered via magnetic field in a vacuum?

Say you want to store hot coffee in a container surrounded by a vacuum. To remove all sources of conductive energy loss the container is suspended in the vacuum by a magnetic field and does not have a ...
1
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1answer
166 views

In a low pressure (near vacuum), -20°C vessel, would sublimated moisture rise to the top or fall to the bottom?

If I have a strong vessel that I've cooled to say -20°C, and lowered the pressure below 0.006 atmospheres, the water in food placed inside will sublimate and freeze dry the food. But what happens to ...
3
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2answers
407 views

Effect of spacetime curvature on the sea of virtual particles

Does the nature of the assortment of virtual particles depend upon the warping of spacetime in a direct manner ?
3
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1answer
234 views

The vacuum as trigger

Do the apperance in the atomic nucleus of virtual matter-antimatter particle pairs play a role in the random nature of radioactive decay?
0
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1answer
575 views

Lawrence Krauss' Theory of Origin

I don't understand how a vacuum, the absence of matter, can hold energy. How can it hold energy when Einstein proved that matter is energy? And a second related question; how does the energy in a ...
4
votes
2answers
942 views

If I put a ping pong ball in a vacuum, would it pop?

If I put a ping pong ball in a vacuum, would it pop? If so, at what point would it happen? Any standard table ping pong ball is acceptable.
9
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3answers
400 views

What is the difference between $|0\rangle $ and $0$?

What is the difference between $|0\rangle $ and $0$ in the context of $$a_- |0\rangle =0~?$$
3
votes
1answer
714 views

Effects on a tree exposed to the vacuum of Space

My wife's kindergarten class asked, "What would happen to a tree planted on the moon?" Aside from the obvious that it would die from lack of water/air, what physical effects would happen to a tree ...
2
votes
2answers
295 views

Will physic object in a perfect environment last/exist forever?

We know,i.e. wood/steel tables in earth will completely broken or disappear in a very future day. If we put the table in a perfect/ideal environment (maybe in vacuum), will the disappear/broken still ...
1
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6answers
6k views

Does vacuum (empty space) exist? [closed]

Added: 5 times down vote for now! Down voter is this religion or physics, please try to explain your decision. I'm confused about this. In physics we know for a vacuum, but I think that there is a ...
1
vote
0answers
283 views

Creating the proper suction

I'm a bit rusty on my fluid dynamics. I'm experimenting with creating my own leaf vacuum. How would I determine how much suction a fan creates? Bernoulli's equation would apply correct? I would ...
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votes
3answers
840 views

Anti-laser: How sure we are that energy is transported?

Reading this PE question can-we-transport-energy-over-infinite-distances-through-vacuum-using-light, a related question arises naturally: Is energy transported (by light)? -- (I did believed in this ...
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1answer
484 views

The difference between free energy and perpetual motion [closed]

What is the difference between free energy (over unity) and perpetual motion? Please provide some examples, both real world and theoretical.
4
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1answer
292 views

What are the current (popular(ish)) approaches to modelling the quantum nature of spacetime at the Planck scale?

My guess at a list of them would be: spin foams, casual sets, non-commutative geometry, Machian theories, twistor theory or strings and membranes existing in some higher-dimensional geometry... ...
12
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2answers
2k views

Are we living in a false vacuum? Is there any way to tell?

I was thinking of the noted 1980 paper by Sidney Coleman and Frank de Luccia--"Gravitational effects of and on vacuum decay"-- about metastable vacuum states that could tunnel to a lower energy "true ...
0
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1answer
285 views

Volume of Matter in the Universe [closed]

What would the size of the universe be if it were physically possible to remove all of the empty space, leaving only matter?
16
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6answers
997 views

Do all massive bodies emit Hawking radiation?

It is known that any accelerated observer is subject to a heat bath due to Unruh radiation. The principle of equivalence suggests that any stationary observer on the surface of a massive body should ...
6
votes
2answers
849 views

Wheeler-Feynman theory, QED without fields, vacuum polarization

Initially Wheeler and Feynman postulated that, the electromagnetic field is just a set of bookkeeping variables required in a Hamiltonian description. This is very neat because makes the point of ...
6
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2answers
560 views

“Space” in General Relativity and “vacuum” in Standard Model, is it the same thing?

And expansion of space is equal to expansion of vacuum?
9
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6answers
2k views

Does anything exist in the intergalactic space?

I am a part time physics enthusiast and I seldom wonder about the intergalactic space. First, it is my perception that all(almost all) the objects in the universe are organized in the forms of ...