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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104 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 ...
4
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1answer
50 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 ...
2
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0answers
30 views

Can we prevent metal corrosion by creating a vacuum around it? [migrated]

I have a device in a box which has parts of metal. So can I prevent corrosion by creating a vacuum around the metallic object?
2
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3answers
52 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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0answers
50 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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1answer
33 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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0answers
14 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 ...
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7answers
2k 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 ...
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1answer
62 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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2answers
47 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
35 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 ...
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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 ...
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0answers
36 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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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 ...
2
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2answers
113 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: ...
3
votes
2answers
70 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} ...
2
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2answers
113 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 ...
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1answer
35 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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votes
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
40 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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0answers
14 views

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. ...
8
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4answers
2k views

A cup of water in ZERO gravity

What will happen if I try to pour a cup of water in zero gravity, into another empty cup? Will the water come out of the cup? The adhesive force between the water molecules and the interior of the cup ...
0
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1answer
52 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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2answers
2k views

Bell in a vacuum, where does the sound energy go?

I'm not educated in physics, but I learned that a bell struck in a small vacuum chamber will not be heard by people around it (in a school science lab). If it had been surrounded by air, there would ...
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1answer
45 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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4answers
118 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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5answers
935 views

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
65 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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0answers
51 views

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 ...
0
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1answer
30 views

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 ...
2
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4answers
497 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 ...
28
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5answers
3k views

What physical evidence is there that subatomic particles pop in and out of existence?

What physical evidence shows that subatomic particles pop in and out of existence?
51
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5answers
9k 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 ...
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4answers
79 views

Can this container withstand a vacuum? [closed]

I am putting together a piece of equipment that will involve a vacuum pump pulling up to 10 Torr / 13 Mbar.  I need to use a container for liquid within the equipment and have found a stainless steel ...
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3answers
97 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
votes
1answer
213 views

How fast would an object have to move to create a vacuum behind it?

When an object moves, I assume that the air above it, instead of remaining at the same general height, is pulled downward as it is passed in order to fill the low-pressure area behind the object where ...
5
votes
2answers
2k 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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vote
2answers
171 views

Could a really tall tube suck garbage in to space?

When I was around 10 years old, I had this idea that was supposed to solve our waste problems; I imagined having tubes miles high that would stretch in to space. Every tube would have a door at the ...
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4answers
87 views

What happens when I place an object of certain temperature in space ? Does it loose its entire heat energy?

Can i obtain absolute zero temperature this way? And let's assume there is no cosmic microwave background and also assume that there is a way to shield the object from any heat source, such as the ...
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vote
2answers
191 views

Does spacetime have a “mass” value? or What is “Spacetime” made out of?

When measuring the MASS within the Universe, does "space" or "spacetime" have a value? I only ask, because when speaking of expansion, space is expanding. Could it be possible, to reverse the ...
0
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0answers
68 views

Spontaneous de-excitation of an atom

Consider the Hamiltonian for the process of spontaneous de-excitation on an excited atom, (an electron jumped to a higher energy level while a lower energy level is not complete). This Hamiltonian ...
0
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2answers
52 views

Can energy be “subtracted” from vacuum?

It probably sounds absurd, but I heard such expressions as "subtracting a particle from vacuum", or from squeezed vacuum, in the context of quantum experiments, or quantum optics, (not black holes). ...
10
votes
4answers
3k views

Why is space a vacuum? [duplicate]

Why is space a vacuum ? Why is space free from air molecules ? I heard that even space has a small but finite number of molecules. If so, won't there be a drag in space?
2
votes
1answer
59 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 something analogous to a harmonic oscillator but since the Zero Point ...
3
votes
1answer
81 views

Which assumption is less plausible, “action at a distance”, or that “virtual particles” can exist for a short time?

It is understood that virtual particle appear in Feynman diagrams as a tool of calculus. And it is understood that they are problematic about their mass, and cannot be detected (is that sure indeed?). ...
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0answers
74 views

Help with derivation of the Casimir Effect?

I am at the very last part of a relatively long derivation of the Casimir effect, and I just don't understand the final step D: So far, I have derived the ground state energy to be $$\langle 0| ...
0
votes
1answer
58 views

Why is the storage ring of a synchrotron a vacuum?

Why is the storage ring of a synchrotron a vacuum? I know that when the accelerated particles get to the storage ring they lose energy, releasing synchrotron radiation, but how does the vacuum make ...
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vote
3answers
123 views

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 ...
0
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0answers
57 views

Thermal conductivity in vacuum

It is my assumption that material objects preserve/gain heat via: 1) material contact (air or other touching material/object) and/or 2) absorbing radiation / electromagnetic waves So, imagine that ...
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2answers
147 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 ...