What is Vacuum: Definition and 1000 Discussions

A vacuum is a space devoid of matter. The word is derived from the Latin adjective vacuus for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often discuss ideal test results that would occur in a perfect vacuum, which they sometimes simply call "vacuum" or free space, and use the term partial vacuum to refer to an actual imperfect vacuum as one might have in a laboratory or in space. In engineering and applied physics on the other hand, vacuum refers to any space in which the pressure is considerably lower than atmospheric pressure. The Latin term in vacuo is used to describe an object that is surrounded by a vacuum.
The quality of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum. For example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. But higher-quality vacuums are possible. Ultra-high vacuum chambers, common in chemistry, physics, and engineering, operate below one trillionth (10−12) of atmospheric pressure (100 nPa), and can reach around 100 particles/cm3. Outer space is an even higher-quality vacuum, with the equivalent of just a few hydrogen atoms per cubic meter on average in intergalactic space.Vacuum has been a frequent topic of philosophical debate since ancient Greek times, but was not studied empirically until the 17th century. Evangelista Torricelli produced the first laboratory vacuum in 1643, and other experimental techniques were developed as a result of his theories of atmospheric pressure. A Torricellian vacuum is created by filling a tall glass container closed at one end with mercury, and then inverting it in a bowl to contain the mercury (see below).Vacuum became a valuable industrial tool in the 20th century with the introduction of incandescent light bulbs and vacuum tubes, and a wide array of vacuum technologies has since become available. The development of human spaceflight has raised interest in the impact of vacuum on human health, and on life forms in general.

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  1. H

    A long rod being pushed in zero g vacuum

    Homework Statement Lets take a long rod of length l and mass m in a zero g vacuum. If a force F acts upon the center of mass of the rod then the rods linear accelaration will be F/m. If the force acts on a distence of d then the work done by the force is F*d. If the force acts off of the...
  2. G

    Boundary layer thickness in partial air vacuum

    How does low ambient pressure effect on the thickness of the boundary layer for given flow conditions of gas? In absolute vacuum the thickness of the boundary layer is 0 of course, but it seems that all the boundary layer thickness correlations use the Reynolds number, which doesn’t change much...
  3. T

    A Free Simulator Software for Vacuum Field BVPs | Tom

    Hi, I am interested in simulating the vacuum field equations, but solving a full boundary value problem rather than the initial value problem. i.e. I might have boundary conditions in all spatial and temporal extents/extremes, rather than just an initial 3D surface. Does anyone know any free...
  4. K

    I Exploring the Optimal Dimensions and Materials for High Vacuum Transparent Tubes

    Hello For the purpose of the experiment, I wonder what the maximum dimensions can have a transparent tube, I thought over a diameter of 30cm and a length of 1-1,5m and from what material should such a pipe be made. I would like to get a high vacuum (about 0,2-2Pa)
  5. M

    What is the top velocity of an object with a certain force applied in a vacuum?

    ok i have a simple enough scenario that i need a hand with solving. first off just to say, i don't know how to do the math for it so maybe someone here could help me out. basically has to do with finding the top velocity of an object with a certain force applied. all in a vacuum and without any...
  6. V

    A Mystery of Einstein's Relativity Solved with Classical Physics

    https://curiosity.com/topics/a-mystery-of-einsteins-relativity-has-been-explained-using-classical-physics-curiosity?utm_source=androidapp If anybody understands what the author is trying to say, kindly elaborate. I haven't read the paper
  7. S

    No sublimation for human body in vacuum? [Thermodynamics]

    In my Thermodynamics course, we recently learned about the saturation pressure and saturation temperature of different substances -mainly water. As you know, the saturation temperature at which a substance begins to boil is specific to a fixed saturation pressure. Water only boils at 100...
  8. J

    I Evaporation under vacuum; surface area

    I run a vacuum distillation unit that is used to distill ethylene glycol. The old glycol is subjected to 25Hg of vacuum at a temp of 275 degrees F. There are burner tubes submerged in the glycol to heat it up. The vessel has a diameter of 36 inches and is 124 inches long. We fill the vessel...
  9. J

    I Trouble with Humboldt H12090 aspirator vacuum pump

    I've been in the process of doing experiments requiring 28- 30 Hg vacuum. For the last couple of weeks, everything seemed to be going well with a glass aspirator I acquired as it would pull the necessary vacuum, when hooked up to the tap, in about 45 seconds. Then, as luck would have it, while...
  10. T

    I Shape of Vacuum Space: Constant Spatial Volume with Time

    If we have a small 4-volume of empty spacetime of boxlike dimensions t, x, y, z, then according to the vacuum field equations the change of the shape of this box with respect to time is (I think): \frac{d (xyz)}{dt}=0 or equally: yz\frac{dx}{dt}+xz\frac{dy}{dt}+xy\frac{dz}{dt}=0 in other words...
  11. davidge

    I So, do vacuum fluctuations exist?

    I'd like to know the reasons many physicists support the existence of quantum vacuum fluctuations. It seems that QED doesn't predict such phenomenum, nor any experiment has undoubtedly confirmed it, at least on the grounds of QED.
  12. V

    Rewriting neutral gauge bosons (EW) for vacuum with Y=-1

    Homework Statement So, my textbook proposes a to check what will change in mass and mass eigenvectors of Z and photon in terms of ##W_{3}## and ##B_{\mu}## fields in Higgs mechanism for EW if we choose a vacuum hypercharge to be -1 and compare results to SM (where we know that photon is...
  13. J

    Cheap, suitable one way valve for aspirator vacuum pump?

    I have a glass aspirator vacuum pump that has a built in one way check valve, but after a week of use, it no longer functions and when input water is turned off, there is a sudden backflow of water into the vacuum line. I'd like to add a one way valve inline to allow the vacuum pull but not...
  14. T

    I Comparing Vacuum Solutions to Topologies of Einstein Space

    Hi, Wikipedia lists about 10 vacuum solutions of the Einstein Field Equations. However, if I look for topologies of Einstein space, there are many different families, which include Calabi-Yau manifolds, of which abelian, Enriques, Hyperelliptic and K3 surfaces are subsets. Within K3 surfaces...
  15. C

    Variable Space Vacuum Tank - Pump question help

    This process and mechanism is very difficult to explain via the computer and even during presentations many people simply do not grasp the concept so I am trying my best to explain it easily and ask my questions as best as I can so that you guys understand me. I really need help with these few...
  16. J

    Vacuum system connections question

    I am making a device like this for the purpose of freeze drying insects. I am basically following along the same guidelines as the author. However, I am wondering about something. For his aspirator valve, he elected to save costs and use what I believe is a brass or copper 1/4" valve like is...
  17. C

    I Does moisture escaping from powders decrease chamber vacuum?

    I'm drying some wet powders using vacuum oven and start seeing some condensation on the window after few minutes. The vacuum level stays pretty constant which puzzles me as i thought that the moisture escapes from the powder into the air will increase the chamber pressure or decrease the vacuum...
  18. B

    Making mirrors parallel in a vacuum using charge

    Two identical front surface mirrors are hung in a vacuum chamber with a high vacuum with a bit of bias of their mass wanting to lean into each other so they don't separate on their own. The metal surface is connected to a variable high voltage source. Both mirrors are connected to the same...
  19. redtree

    I Metric for Lambdavacuum EFE - Radial Coordinates

    I am having trouble finding the equation for the metric for the Lambdavacuum solution to the EFE in radial coordinates. Any suggestions?
  20. G

    B How is a Vaccum mathmatically described?

    Anyone know what books and astrophysicist has this knowledge? Thank you, Greg
  21. SchroedingersLion

    A Enhancing Spontaneous emission in a vacuum standing wave

    Hi, it is well known that spontaneous emission of an atom can be enhanced, if the atom sits at a node of the vacuum standing wave field in a cavity. My question is, why is it the node? At a node of a standing wave, there is zero intensity, so there should be no interaction between the atom and...
  22. M

    A Quantum fluctuations of the metastable false vacuum

    I have been trying so hard to get some answers to a few questions I have in regard to this paper: https://arxiv.org/abs/1404.1207 I think those questions can best be summarized this way: 1) A metastable false vacuum is a field and fields are just the changing value of a parameter in...
  23. A

    Will a Ball Thrown in a Vacuum Move Forever Without Gravity?

    if I throw ball in vacuum and there is no gravity ,is the ball will be moving for ever or will move for just a time and stop? And thanks.
  24. R

    Would a straw work in a vacuum?

    If the liquid in a soda straw moves up because the outside air pressure is greater than the pressure in the lungs, it seems that a straw wouldn't work in a vacuum. Is this the case?
  25. E

    How to pump liquid from vacuum to atmosphere

    Greetings, The application is a wiped film evaporator (~1.2-1.5 kg/hr throughput). The concentrate and the distillate gravity feed round bottom flasks. I'm not worried about the cold-trap waste. The evaporator volume is under vacuum (~0.003Torr). I want to pump the liquid from the...
  26. F

    I Timelike Killing vectors & defining a vacuum state

    I've read that if a given spacetime possesses a timelike Killing vector, then it is possible to define a unique vacuum state by constructing positive and negative frequency modes with respect to this timelike Killing vector. My question is, what does this mean? Explicitly, how does one use a...
  27. C

    Two materials heated in vacuum

    Homework Statement This isn't a homework question but something I'm working on that I thought should be simple. Two disks (area ##A## and thickness ##d##) are joined together and placed under a radiation heater in vacuum, so that one side of the top disk is heated with a constant power. Assume...
  28. R

    Acceleration of a gas into a vacuum

    Set up: Gas on one side of a divider and an infinite vacuum on the other. Question: When you remove the divider, over time, does the gas increase in acceleration, does it peak and then decrease or does it remain the same as the gas enters the vacuum/ leaves the side opposite the vacuum?f Thanks
  29. G

    Difference between Steam and Vacuum Distillation

    Hello Guys... I know this is simple but this two concepts confuse me a lot. Like in vacuum distillation Pressure is reduced to increase the difference in boiling point between two components and steam distillation is where steam is introduced in the mixture to reduce the vapor pressure. So what...
  30. S

    Is the speed of light always constant in nature?

    When I read the speed of light in vacuum is c, does it imply that light doesn't actually travel at this speed in nature? My guess is no, light always travels at c, it's just that in the definition, we're trying to ignore the affects on light from other stuff like the comological constant and the...
  31. B

    Vacuum / Electron Tubes and X-rays

    I've read that if you apply enough voltage to the plate of certain types of tubes, they will generate a fairly good amount of X-rays (even more so if the cathode is hot) -- I even read about a guy who managed to take relatively detailed radiographs of random objects using a standard...
  32. L

    Show that the vacuum polarization is transverse

    Homework Statement Show that the vacuum polarization \Pi^{\mu\nu}_2(p) in 1-loop is transverse. Decide whether you want to use Ward's identity and prove this to be true in all orders or only prove for 1-loop. Homework Equations Ward's identity q_\mu \mathcal{M}^{\mu}=0 which must hold where...
  33. SonnetsAndMath

    I Effective Mass-to-Charge Ratio of Electroweak or QED Vacuum

    Apologies if my question is confused, because I'm beginner in field theory: adding up all corrections, can we talk about an effective (at least approximate) overall mass-to-charge ratio for the electroweak or QED vacuums? Suppose we want to talk about the relative strength of...
  34. c704710

    B Light Beams Attraction: e=mc^2 & Asymmetry

    Appearently, two beams of light in a vacuum are attracted to each other. Photons have no Newtonian mass, but their relativistic mass (e=mc^2 or mass-energy equivalence) causes this (as is my understanding). So will a 10^4 Hz beam bend more towards a 10^20 Hz beam than the 10^20 Hz bends towards...
  35. D

    B Can the vacuum density produce only normal matter?

    Without knowing whether WIMPs or axions or something else are what dark matter is composed of, can we speculate about the vacuum density creating only normal matter, and by what mechanism?
  36. K

    Vacuum created or suction created when we use peristaltic pump

    Hi All, How to find vacuum created or suction created when we use peristaltic pump?
  37. nomadreid

    Newtonian vacuum: what to call it in thought experiment

    Suppose you wanted a thought experiment about a variation on the vacuum (i.e., the spatial slice of spacetime) in which the quantum effects were absent or negligible, and the vacuum energy was zero . What would you call it? You can't call it the vacuum, because this Newtonian version of the...
  38. R

    Why are ice chests not vacuum insulated?

    Aside from vacuum flasks and vacuum insulated panels, there doesn't seem much else vacuum insulated. Why are there no ice chests vacuum insulated? My uneducated guesses as to why ice chests are not vacuum insulated: 1. Cost to vacuum insulate. 2. The cylindrical shape of a flask offers...
  39. D

    Electroscope experiment in vacuum

    Hi I am running the electroscope experiment in vacuum. This is shown in (a) in the uploaded figure . Once the aluminum leafs are charged the chamber is pump down (b). As soon the pressure decrease low enough (around relative pressure of 30 inHg) the leafs collapse to each other abruptly. Here...
  40. Lmlodninja

    Vacuum & Sound: What Happens to Energy?

    What happens to sound when it hits a vacuum? Because there is nothing for the sound wave to vibrate against, what happens to the energy?
  41. davidge

    I Relativity Matter & Vacuum Energy: Stress-Energy Tensor

    Matter is responsible for the stress-energy tensor. What is included in "matter"? Does vacuum energy contributes somewhat to the stress-energy tensor? Would it be correct to include all forms of energy in the stress-energy tensor, through the mass-energy equivalence?
  42. S

    I Do the vacuum states created by soft photons have vacuum flu

    Putting a soft photon in vacuum will result in a zero energy vacuum state. Despite the zero energy, has this state vacuum fluctuations? Putting more of these photons will result in more vacuum states. Would they have vacuum fluctuations as well resulting in more vacuum flctuations? A total...
  43. F

    A Vacuum polarization at intermediate distances

    using the references below, the effective charge and the potentials are derived for either r >> 1/m or r << 1/m, so what happens between these two distances. Thanks https://en.wikipedia.org/wiki/Vacuum_polarization https://en.wikipedia.org/wiki/Uehling_potential...
  44. G

    Cooling a gas by releasing it into vacuum: Entropy?

    Hi. I just read an article where following cooling method is described. Apparently it's very common, but I don't know what it's called: A gas under pressure is released into a vacuum through a small hole. The average particle speed in this beam of gas is the same as before, but the...
  45. olgkd123

    Designing a rectangular vacuum chamber -- Help please

    Hello everyone! I want to design a rectangle vacuum chamber (12x12x72) out of 1/2 steel. I would be welding the sides together to form a seal. Would this work? any suggestions on what I could do? Thx! (I not great at this stuff so your help is much appreciated!)
  46. N

    I Common interaction vacuum for QED + QCD?

    Hello, I know QED and QCD as isolated theories but now I thought about particle interactions with QED and QCD processes (like fpr proton-antiproton scattering). But I'm not sure how to interpret this mathematically. As I understood my Feynman diagrams are nothing more like pictures for the...
  47. Anton Zhyzhyn

    Column of water, vacuum pressure and a one-way valve problem

    A conceptual problem related to a design I'm working on: If I use a pump to suck air out of the top of a vertical pipe, with the bottom of the pipe in water, I can only make the water rise around 10 metres inside the pipe, if I produce a perfect vacuum. Now let's say the pipe was 100m long and...
  48. J

    Can cold air become water in a vacuum cylinder?

    can cold air become water in a vacuum cylinder?
  49. D

    How to avoid boiling/bubbling effect under vacuum?

    I have a process problem where my product is mixed with water and needs to be separated under low temperature range 5-10 deg C. I hope evaporation under vacuum is the only solution but the boiling effect is creating splash and want to avoid it. Prefreezing or lyophilization is not an option...
  50. S

    A Decay of false vacuum in new inflation

    In new inflation, the time scale for the decay of the false vacuum is controlled by ##- m^{2} = \frac{\partial^{2}V}{\partial\phi^{2}}\bigg|_{\phi=0}.## This is the negative mass-squared of the scalar field when it is at the top of the hill in the potential diagram. This is an adjustable...
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