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. A

    Falling Feather and ball in vacuum

    I saw some of these videos showing feather and some balls falling with the same speed in vacuum. But on normal atmospheric pressure they fall depending on their weight. This is just blowing my mind, WHY is this ? Does this prove Newtons Law of Gravity is wrong ? Then how is Einstein's...
  2. S

    Would current flow in a vacuum like space

    Would lightning work in space? I think it would but you wouldn't be able to see it? Let's say I have some sort of device that creates a lightning bolt, if I shot it at a watermelon in a vacuum or another target would it hit the target, or nothing happen because of the vacuum?
  3. C

    Balloon Vacuum: Pressure Calculation w/ R0, σ

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  4. P

    I Maximizing Solar Heat Output with Vacuum Tubes: A Temperature Comparison

    Solar vacuum tubes are tubes covered with a vacuum jacket so that no heat can be dissipated by conduction and convection of air. By this process, we can get pretty high temperature even at very cold temperature. In this video, you can see how very temperature water can be produced by using such...
  5. R

    I How does nucleation work in cosmology?

    In this article https://en.wikipedia.org/wiki/False_vacuum#Bubble_nucleation it says that "In the theoretical physics of the false vacuum, the system moves to a lower energy state – either the true vacuum, or another, lower energy vacuum – through a process known as bubble nucleation." What is...
  6. A

    I Lamb shift and the QFT vacuum....

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  7. mesa

    B What is the vacuum at the Karman line?

    Hey guys, what is the vacuum at the Karman line (100km straight up). I found conflicting sources on this. Wikipedia links to a calculator that states it is ~2.4*10^(-4)T, while another chart I found says it is in between 1.09 and .0075 Torr...
  8. A

    I Vacuum cutoff, normal ordering, Planck scale and 10^120....

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  9. M

    B GR vs quantum vacuum Lorentz invariance

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  10. newjerseyrunner

    B Why is vacuum energy assumed to be uniform?

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  11. R

    Vacuum infusion bag - can external pressure help?

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  12. Lacplesis

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  13. C

    Hole size given the leak rate

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  14. duhuhu

    Can Resistive Heaters Fail in Vacuum Due to Reasons Other Than Temperature?

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  15. Mordred

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  16. A. Neumaier

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  17. wolram

    B Physicists study the quantum vacuum

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  18. C

    B Does gravity change the permittivity/ permeability of vacuum?

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  19. Carlos PdL SdT

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  20. A

    I Lorentz violation, multiple preferred frames, vacuum energy

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  21. O

    B Exploring the Quantum Vacuum: Its Effect on Matter and Fundamental Interactions

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  22. O

    B False Vacuum: Understanding its Impact on the Stability of the Universe

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  23. O

    Vacuum as the low energy limit of....

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  24. A

    I Lorentz violation and the physical vacuum....

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  25. Andreas C

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  26. Andreas C

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  27. fires21

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  28. A

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  29. ShayanJ

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  30. George Argyrou

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  31. Low-Q

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  32. Plat

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  33. Delta2

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  34. wolram

    B Cosmological constant vis-a-vis dynamical vacuum: bold challenging the ΛCDM

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  35. B

    Min Vacuum Pressure in Pipe

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  36. industria77

    How do you run vacuum pumps in series?

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  37. L

    Pendulum in vacuum vs with air resistance

    If a pendulum consisting of a string and a bob is allowed to swing in a vacuum vs in air, which has larger period?
  38. A

    Can hydrocarbons in oil wells move to vacuum zones?

    if we have a vacuumed tube inserted into a reservoir of 10,000psi will the oil rise up in the vacuum tube of will it stay in place because there is no Δp?
  39. Marylaax

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    Homework Statement [/B] Q = A / V Bernollis therom → γH = P+γZ+ρ.v2 /2 Air Flow Speed = 0.058 m3/s A = Section Area of the tube = π.r2 r = 19.65 mm ρ =1000 kg/m3 g =9.8 m/s2 P=pressure energy of water = 2.338 Homework Equations Find : V= Fluid Velocity = ? H=Energy Denisty = ? Z= Geodesic...
  40. Y

    Sound Pressure in Partial Vacuum

    Is there a good description or formula regarding how the sound pressure from a constant source depends upon ambient pressure? That is, if I were to conduct an experiment where I put a source and a microphone in a container, and then change the pressure in that container with a pump, assuming...
  41. P

    Thermodynamics: questions about vacuum engines

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  42. dreens

    What is the world's lowest vacuum pressure achieved?

    I'm trying to track down the best (lowest) vacuum pressure ever achieved. I'm talking about absolute pressures, not relative, so I wouldn't call the environment in a submarine the winner even though it achieves a very large magnitude negative pressure differential relative to the high ambient...
  43. J

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  44. mesa

    Looking for a high vacuum 8" conlfat, any suggestions?

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  45. M

    B How long can a virtual particles exist in a vacuum state?

    As much as I have understood, virtual particles keep appearing and disappearing in a vacuum state. This leads to zero-point energy, Casimir effect etc. Now, I want to know if there is a lifetime (i.e. a time limit) for which these virtual particles can exist before disappearing. Also can there...
  46. J

    A Vacuum pair creations on the light-cone

    When a field is quantized on the light front, there is no possible pair creation from the vacuum energy. This is because kinematic operator P^+ generates only a positive spectrum ( https://en.wikipedia.org/wiki/Light_front_quantization#Spectral_condition ). So there is no "particles popping out...
  47. A. Neumaier

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  48. T

    I Vacuum fluctuations - possible stupid question

    My background is in Health Physics and as such, I have had only rudimentary instruction in quantum mechanics, so my understanding (such as it is) is largely conceptual. With that in mind, this may be a very ignorant question, so I apologize in advance. I understand the theoretical basis for...
  49. A

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  50. oobgular

    Rocket engine operating in a vacuum

    Homework Statement So suppose there is a chemical rocket operating in the vacuum of space (assume it's a perfect vacuum). It generates a hot gas with a total enthalpy of h. What's the final speed of the rocket exhaust, in terms of h? Homework Equations The energy equation seems to be useful...
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