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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Max weight the lid of a vacuum can hold

I have a box with a lid that has a mass object inside of it. I will be creating a vacuum inside of it with a $4~\mathrm{HP}$ Shop Vac that has a sealed pressure of $59~\mathrm{psi}$ and an airflow of ...
2
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0answers
43 views

Drop of water in zero gravity [closed]

Suppose there is a drop of water in gravity-free space. A man slowly touches the drop and keeps his fingers touched. What happens? Does the drop change its shape? Or wet his fingers? Or there is no ...
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22 views

Can a 'Perfect Vacuum' Really exist? [duplicate]

By a perfect vacuum, I mean an area of space containing no particles. I have heard people talk about this, and I always think: 'If an area of space has no particles, wouldn't it cease to exist, ...
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42 views

Is the vacuum state of a quantum field necessarily zero temperature?

A statement in Quantum field theory: zero vs. finite temperature points to temperature as it relates to the vacuum as being a matter of definition. In that post, Will states By, "at zero ...
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6k views

If particles are points, then aren't atoms empty space?

Zero dimensional points do not take up space, so then wouldn't everything in the universe be literally empty? Or is there something that I'm missing?
2
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0answers
32 views

Do Thorlabs piezoelectric transducers s PAZ009 and PAZ015 wor in vacuum?

We have few closed loop piezoelectric transducers (stacked) from Thorlabs, part numbers PAZ009 and PAZ015. I have prepared all the required feed through. I want to use them under rough vacuum $\sim 10^...
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7answers
4k views

How can a vacuum implode a metal tank?

An interesting video: youtube video - Railroad tank car vacuum implosion But how is it possible for a metal tank to implode? Even if one can vacuum it, it is subject to 1 external atmospheric ...
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26 views

Does the vacuum have a zero Seebeck coefficient?

I was considering how at very high energies (e.g the Schwinger Limit) the vacuum starts having properties we would normally associate with "materials", such as non-linear polarizibility. The Seebeck ...
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39 views

Why must the Vacuum Manifold contain the quotient group?

For a symmetry breaking pattern $G \rightarrow H$, the vacuum manifold must contain the quotient space $G/H$. In most cases, we take the vacuum manifold to be the quotient space. My question is, Is ...
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34 views

Why is the Vacuum Expectation Value measured in GeV?

As I understood, the Higgs field has a non-zero vacuum expectation value (vev) on zero energy. For example, in the case of the non-quantized electric field, it would be measured in $\dfrac{J}{C}$, i....
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60 views

Could vacuum chambers lighten the load for space bound technology?

Would cavities of near vacuums in the head (or in the 6 x 6 blocks surrounding the rocket [for reentry temperatures]) of a rocket make it lighter so it can be sent out easier?
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17 views

When de-evacuation occurs, what provides energy?

When a syringe piston is pulled from its initial position to spray position by blocking the nozzle with a finger, creating a vacuum inside the syringe, the piston will probably get pulled back to ...
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2answers
56 views

If two pieces of the same type of metal touch in space, will they bond and be permanently stuck together? [duplicate]

Yesterday I was watching discovery channel, on a program they said that 'if two pieces of the same type of metal touch in space, they will be permanently stuck to each other.' Is it true..? If yes... ...
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45 views

Space vacuum power

How strong is the vacuum in space? If possible in mph, or other easy to understand measurements...as someone else asked, "if you took a bottle of air into space and opened it, where would it go?" I'm ...
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1answer
70 views

What are the problems in the idea that a person would freeze to death in outer space?

It is said that the body would freeze to death, if left in outer space, which is true, since the temperature is around $3$K. But what are the flaws in this theory, in terms of thermodynamics (if we ...
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1answer
57 views

How do we measure the temperature of vacuum?

Afaik. temperature is in relation with the kinetic energy of the individual molecules. In vacuum there are only a few molecules so measuring their kinetic energy is very hard, because vacuum has a ...
3
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1answer
70 views

Vacuum expectation value in presence of a source

If a vacuum is translationally invariant i.e., $P^\mu|0\rangle=0$ or $e^{(\pm ip\cdot x)}|0\rangle=0$, we can express the the vacuum expectation value of a field as $\langle 0|\phi(x)|0\rangle$ as $$\...
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1answer
118 views

Confusion in understanding of quantum fluctuations and vacuum energy

I'm having a bit of trouble understanding what exactly is meant by a quantum fluctuation of a quantum field and its relation to the vacuum energy attributed to such a field. Is the point, that due ...
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0answers
10 views

How long is the surface migration length of adatoms deposited by thermal evaporation in vacuum?

The deposition of metals through thermal evaporation involves the process of adatoms migrating on the substrate before its kinetic energy decreases to a certain point or before encountering a cluster. ...
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58 views

Classical Yang Mills vacuum

What is the vacuum of classical Yang Mills theory $$\mathcal{L} = - \frac14 F^{a \mu \nu} F^a_{\mu \nu}~?$$ Is it simply $A^a_\mu=0$ for all its components?
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56 views

Proof for fluctuations in vacuum

I'm not a physicist. My understanding of Heisenberg's uncertainty principle and its proof (that is given by an imaginary microscope) is that for example: at a specified time determining the exact ...
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0answers
35 views

Comparison of vacua and annihilation operators of Klein-Gordon theory and phi-fourth theory

The ground state or vacuum of an interacting theory is, in general, different from the ground state or vacuum of a free theory. In what cases are the two vacuums the same as each other? Can an ...
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31 views

How can we orient light in vacuum?

Let's consider the mirror clock used to show time dilation in special relativity: In the rest frame of the clock, the light pulse from the laser pen propagates in vertical direction down then up: ...
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2answers
48 views

Annihilation operator in harmonic oscillator

In Wikipedia's QHO page there is a moment when the following is stated: I don't know why "the ground state in the position representation is determined by $a|0\rangle=0$". I would say that the ...
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If we threw a baseball from the ISS, could we deorbit the ball?

Clearly this is a hypothetical question. Say we bring a star baseball player into NASA, prep them appropriately for a mission in space, and fly them up to the International Space Station. They go on ...
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23 views

The force of a vacuum on a breached environment in space

Screenwriter and Physics newbie, not looking for hard numbers, but sort of a general idea of what the force of a breach in a sealed environment in space would be. In films in space, often the ship or ...
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80 views

Why are there e.m. vacuüm fluctuations?

According to the rules of qft there are virtual photons in the vacuüm. But how can this be if for the production of photons you need an electric charge?
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88 views

Can the fact that the vacuum energy in curved spacetime is not boost invariant be explained without mathematics?

I read in an answer to a question if Hawking radiation can be explained without too much mathematics that this is impossible insofar the vacuum energy is not boost invariant in a curved spacetime. ...
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1answer
37 views

Would a literal Air ship (boat) work?

If a set of very large airtight pontoons were made in the vacuum of space, would they float on top of the upper atmosphere? I thought about this while watching the last season of Mythbusters when they ...
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545 views

An explanation of Hawking Radiation

Could someone please provide an explanation for the origin of Hawking Radiation? (Ideally someone who I have been speaking with on the h-bar) Any advanced maths beyond basic calculus will most ...
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1answer
54 views

What are the vacuum Einstein's equations? [closed]

I read on Wikipedia that if the Stress-Energy Tensor is set to zero in General Relativity's Field Equation that it makes the Vacuum Equations. What are these equations, and how are they used?
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46 views

Entropy and vacuums

If I have a vacuum (completely devoid of any particles; Q.M. effects aside), then turn a nozzle and let a gas freely expand into the vacuum, will I have increased the entropy of the vacuum? I get ...
3
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2answers
600 views

Producing gravitational waves in labs

Can gravitational waves be created on very small region of vacuum with quadruple movement of atom or subatomic particles?
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44 views

Why does the lack of pressure in outer space affect what's inside our bodies?

I have read multiple similar questions on this site, but none answer specifically the thing I am having trouble understanding. I have read repeatedly that a lack of pressure will cause the fluids ...
3
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1answer
56 views

Balloon of ideal gas pops in vacuo - K.E. per atom unchanged, velocities become locally correlated?

My question is: is the following thinking pretty much correct? I'm interested hearing about anything here that is fundamentally wrong. Of course there is a bit of hand waving and approximation. If a ...
11
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280 views

How is the ground state chosen in a spontaneous symmetry breaking process?

This question is about how the ground state is chosen in a spontaneous symmetry breaking process. Say we have a Mexican Hat potential (e.g. the one for the Higgs field) and are sitting at the unstable ...
2
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1answer
115 views

How does Bremsstrahlung occur in a vacuumized particle accelerator?

In our electrodynamics course we have learned that accelerating a charged particle will lead to a loss of energy in the particle due to Bremsstrahlung. The exact amount of power radiated away is given ...
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50 views

effect of opening the barrier between a tube with one side pressurized and the other side a vacuum

What would happen when a tube with an air space pressurized to 500 atm by the water exerted at 5 km below the surface was opened into a vacuum chamber rising up 5 km to the surface? The bottom of the ...
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2answers
17 views

How to quantify the spreadness of beam of air molecules as they escape from a capillary to a vacuum?

Consider a tube from an oxygen cylinder attached into a vacuum chamber. When the cylinder is opened, the molecules escape out into vacuum chamber. What makes the molecules spread out when they escape ...
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12 views

What is the growth mode of thermal-evaporated aluminum on organic subtrates?

Does aluminum grow in an island mode or layer-by-layer mode on organic substrates which is amorphous? For example, on PMMA, fullerene or surfactant thin films. Can I predict the mode by comparing the ...
3
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1answer
62 views

Helmet to helmet in vacuum - can we talk?

Usual SciFi scene. In a spacesuit, in vacuum, with the comms out for some reason. They want to talk, so the butt helmets together so sound can pass through. Questions are: a) Would it really work in ...
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47 views

Questions regarding space

A difficulty I face is when I think of space. I haven't studied GR or SR yet, but I really want to know what it is. What is space? Is it just the empty place where things are in reality, or something ...
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61 views

Rising glass in xkcd what if

In http://what-if.xkcd.com/6/, Around this time, the glass on the left starts to visibly lift into the air. The air pressure is trying to squeeze the glass and water together. This is the ...
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38 views

Backing pressure for a turbo-molecular pump

It is known that turbo-molecular pumps are to be operated at already low levels of pressure. So the turbo is always backed by another pump (usually a scroll, rotary pump) that ensures this. One should ...
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1answer
63 views

Probability of finding vacuum?

Consider a real scalar quantum field $\varphi (x)$, interacting with a classical real scalar field $J(x)$ : $$ \mathcal{L} = \frac{1}{2}(\partial \varphi)^2 - \frac{m^2}{2} \varphi^2 + \varphi J$$ ...
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1answer
57 views

The Space Between Atoms And Sub-Atomic Particles And More [closed]

I was wondering what the space between atoms or electrons is called. Is it Vacuum ? And what is in there ? Is it really free or empty space ? And if so, how can nothing exist ? It is a bit of an odd ...
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1answer
150 views

Is space really empty? [duplicate]

This guy here says space is not empty.. It explains how space inside nucleus is Full of fields. Does it mean to say gluons are present everywhere, even outside nucleus? Consider a region without any ...
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69 views

What is meant by a “change in volume of a system”?

I keep getting confused when my professor talks about the change in volume of a system. Sometimes it seems as though he's talking about the volume of the gas and at other times he might be talking ...
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2answers
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Does eq. of continuity hold in vacuum too?

When a streamlined flow of water flows down through an ordinary tap, it's cross-sectional area decreases according to eq. of continuity due to atmospheric pressure. If the same apparatus were to be ...
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Imaginary part of the stress-energy tensor

I just encountered in an article of D. G. Boulware ("Quantum Field Theory in Schwarzschild and Rindler Spaces", Phys. Rev. D 11, 1404, 1975, in the last paragraph of the Introduction) the statement ...