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. Omega0

    Is zero of nothing nothing? If so, would you write units for nothing?

    I stumbled over a datasheet of an old pentode where it says, in the english translation: I thought, wow, I am not sure if I wouldn't have written Ug3=0V instead. I am a theoretician in physics but work more as an engineer and teacher. What happens inside of me seems to be the following: The...
  2. kaare_t

    I Pressure delta 1.0 bar: 0.0 to 1.0 vs 1.0 to 2.0

    Hi, New member here. I have no higher education, please excuse me if I'm asking an obvious question, and feel free to reply with more questions if my post is unclear! And please feel free to correct me if I'm using wrong term(s), or wrong assumptions. My question is related to pressure, and...
  3. L

    Do they have powerful battery packs that can run a vacuum?

    For those that have to vacuum large spaces often have to use many different outlets and worry about running over their own cord. Is there a battery pack one can strap to their back to power a vacuum cleaner? Or would that amount of power tide to a person be dangerous?
  4. UnreliableObserver

    A Asymptotic states in the Heisenberg and Schrödinger pictures

    In scattering theory, the quantity of interest is the amplitude for the system—initially prepared as a collection of (approximate) momentum eigenstates—to evolve into some other collection of momentum eigenstates. For example, for ##m\to n## scattering, the amplitude we're interested in is...
  5. paulb203

    B Velocity of freefalling bodies after 1s, 2s, 3s, etc

    On many websites etc the velocity of a freefalling object in a vacuum is shown as follows. After 1,2,3 and 4 seconds respectively; 9.8m/s; 19.6m/s; 29.4m/s; 39.2m/s I worked out the distance travelled by a freefalling object in a vacuum using d = at^2/2, or, d = 0.5gt^2 and got, for after...
  6. E

    A Tunneling to a false vacuum

    Could the Higgs field in a true vacuum tunnel to a false one? How much time would that process require?
  7. S

    B Homopolar motor rotation in Vacuum

    Hi again, I've found interesting video. Roller homopolar motor : Roller Motor Do you think the motor from 1:08 min Will self rotate in Vacuum/Space (No other forces : Gravitational or Other type.) Thank you in advance.
  8. D

    Magdeburg hemispheres - safety precautions

    I would like to show students the Magdeburg hemispheres and ask for two volunteers to try to separate the hemispheres. In doing so, however, I am concerned that if the students actually succeed, they may fly off to the back and possibly injure themselves. How would you avoid this - for example...
  9. geraldoon

    Building a Robotic Vacuum Cleaner

    I need to build a robotic vacuum cleaner that requires minimally 20kPa suction pressure, and is able to clean a 1000sqft area within a single charge of the battery. How do I first calculate the motor specs required to produce that suction pressure and the battery that is able to last the entire...
  10. T

    B Atmospheric pressure, vacuum, etc.

    The value of the atmospheric pressure does not seem to me to be correct 1013 HPa and can be recalculated as approx. 1kg/cm2 (is it true?), but it does not seem that such a pressure would be manifested by any resistance or any deformations, for example on a folded sheet of paper. It is possible...
  11. C

    Homemade vacuum chamber construction

    I hope you folks can help. I want to be able to pour a liquid from one container into two others in the absence of air. So I was thinking of making some sort of vacuum chamber out of 1/2" polycarbonate and some heavy duty plastic sleeving into which to place my hands and arms. Or am I being...
  12. nicolas1409

    B Question about a vacuum ejector (vacuum pump using the Venturi effect)

    I have a vacuum ejector and with a suction cup that drops items. think maybe it could be a pressure drop. but what happens if a vacuum ejector gets less pressure, does it suck less? know it's something with bernoulis
  13. J

    Optimal Size of Rocket Engine Nozzle for Vacuum Performance

    I'm interested in how rocket engines perform in a vacuum. My first impression is that an atmosphere is needed for the action/reaction to push against in order to get forward movement. I saw a demonstration using a long balloon attached to a long length of string stretched across a room. When the...
  14. S

    Using a Jar for vacuum storage

    I am wanting to start powder coating small items on my projects I am always working on around the house. To keep the small quantities of powder paint useable for as long as possible, I had thought about storing the paint in zip lock bags inside of a mason jar. I would install a rubber tire...
  15. V

    I Uncertainty Principle in QFT & Early Universe Conditions

    I have a question related to the uncertainty principle in QFT and if it is related to the early universe conditions. Do we still have four-vector momentum and position uncertainty relation in relativistic quantum theory? I have been following the argument related to the early universe and the...
  16. ravindrar

    I Vacuum Drying Vegetables w/ IR Heaters: Investigating Increased Batch Time

    I am working on a project on vacuum drying vegetables using IR heaters. Before winter batch time was around 3 to 4 hours now it has increased to 6 hours. Any logic behind this as though the temperature drops and RH also drop so why has the time increased?
  17. S

    I Exploring the Potential of Vacuum Energy & Gravity

    I was reading this, but am confused: https://nautil.us/the-remarkable-emptiness-of-existence-256323/
  18. D

    Opening a door between a vacuum and atmosphere

    I work as part of the engineering team running an incinerator. When the ash is removed from our furnace, it creates an open system between the furnace (which is close to being a vacuum) and the atmosphere. For many reasons, this is not ideal. We are looking to add a second door to this ash...
  19. R

    I Vacuum force factors (vacuum created by a "flow through" liquid)

    Greetings all, I'm new here and hope I'm asking this in the correct thread. So, the question is; where you have a vacuum created by a "flow through" liquid witin a large diameter container exerting suction force upon a smaller diameter input tube submerged in a liquid, does the surface area of...
  20. C

    Determine pump spec necessary to overcome leak

    A vacuum pump is mounted at ground level. The pump is connected to a tree of overhead pipework at a height of 20ft, connected to the pipework are 12 hose reels that can be attached to oil drain tanks. The client requests that the pump be sized so that sufficient vacuum can be achieved to suck...
  21. mpross

    B Dark Energy, Dark Matter and the Speed of Light

    Quote from NASA: My understanding of dark energy is based on NASA's report: https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy; were NASA state as follows: "It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27%. The rest - everything on...
  22. P

    B GTR Vacuum vs Quantum Theory Vacuum: Speed of Light

    What is the difference between the GTR vacuum and the vacuum of quantum theory? What is the speed of light in the vacuums, specifically what can be predicted and what must be measured?
  23. K

    A Is it possible for variable speed of light in a vacuum?

    <unacceptable reference deleted> As our universe is expanding, that is, our vacuum is becoming more and more sparse, I believe it is possible that some key characterics of our vacuum is also variable.
  24. Faisal Moshiur

    The diffusion coefficient in a vacuum

    J = Φ.n, where n is a unit vector normal to the flow of flux.
  25. S

    Engineering Looking for calculations I could apply to a vacuum-forming machine

    So far I have determined the evacuation time, a basic heat transfer between the heating element and plastic sheet, and a hold down force of the forming bed.
  26. J

    I Field fluctuations in the vacuum

    How does relativistic qft predict quantum fluctuations in the vacuum? We see this in the experiment proving the Casimir Effect so we know it's physical, but why?
  27. F

    I Weighing gas in a vacuum?

    Is it possible to weight a gas in a container surrounded by a vacum? I am arguing with flat-earthers on how gas weight is determined. I just assumed that you can weigh a gas by placing it in a container on a scale inside a vacum. I think this was wrong. Can you do this or must you weight gas...
  28. Dangoe

    B No vacuum anywhere vs the measurement of "c"

    Hi to the community! Glad to be able to ask 1-2 questions here so signed up. As an interested layman with some autodidactic efforts, still can’t see how this happened or got to the value: Question: We defined the second and hence the meter by the speed of light in vacuum, but there isn’t...
  29. Elizabeth111

    Uses of vacuum pumps in labs

    Summary: Research about the different vacuums used in labs and their applications. Hello, I am currently seeking assistance from people who work in labs. I am researching about the the different types of vacuums used in labs and their applications. Any information that you may have, please...
  30. JandeWandelaar

    A Has a calculation of the vacuum energy density been done with strings?

    The calculation of the vacuum energy density gives us a discrepancy with reality. There should be a mass equivalent of about $10^{96}$ kilograms. I'm wondering if the assumed point-like "structure" of particles could be the cause of this wrong value. Since string theory doesn't assume a...
  31. D

    I The Casimir effect and Quantum vacuum fluctuations

    The Casimir effect is a small attractive force that acts between two close parallel uncharged conducting plates. That force is caused by quantum vacuum fluctuations of the electromagnetic field. What is the cause of the fluctuations? Or, they are uncaused (random)? At least, what are the...
  32. LarryS

    I Speed of individual photons in a vacuum?

    Is there experimental evidence that confirms that the speed of individual photons in a vacuum never varies, even slightly? Thanks in advance.
  33. D

    I Questions about Negative Pressure and Vacuum Energy

    Currently, dark energy is described as a being that exerts a negative pressure while having a positive energy density. {\rho _\Lambda } + 3{P_\Lambda } = {\rho _\Lambda } + 3( - {\rho _\Lambda }) = - 2{\rho _\Lambda } However, there seems to be a problem with the negative pressure assertion...
  34. J

    Exploring the Potential of Vacuum Airships

    I was thinking about the vacuum airship concept that was conceived a long time ago. For example: I think the main problem is the required structural strength of the container, and also being light weight. I have not run any numbers, what do you think the potential issues with the following...
  35. Delta2

    B EM waves in vacuum analogy

    So, is water for water waves, what is the vacuum for EM waves traveling in vacuum. I know the analogy can't be exactly perfect because water molecules oscillate in the presence of water waves, but in vacuum nothing seems to oscillate? Or the vacuum oscillates in some way? And no I am not trying...
  36. LarryS

    I Is E/B = c for spherical EM Wave in Vacuum?

    In classical EM, consider an EM plane wave traveling in free space. The ratio of the amplitude of the electric field to the amplitude of the magnetic field is the velocity of the wave, the speed of light. Is the above also true if the wave is spherical, expanding from a point source, as in a...
  37. S

    A Vacuum Transitions and Lorentz Symmetry Breaking

    There are several "bumblebee" models [1], [2] where Lorentz invariance is violated usually resulting from a local vector or tensor field acquiring a nonzero vacuum expectation value We do not know whether we are in the true vacuum state or in a "false"/metastable vacuum state that could decay...
  38. D

    I Experimenting with a vacuum pump

    Hello, I would like to carry out a few experiments with a vacuum pump under a vacuum bell jar. However, I have no experience with this and the operating instructions could only help me to a limited extent. Specifically, I am interested in the sequence for switching off the pump: When I have...
  39. S

    I From a false vacuum to a true vacuum?

    In theory (please correct me if I am wrong in any point), if our vacuum were metastable (i.e. in a "false vacuum" state), it could go through a phase transition into a stable state (a "true vacuum" state). Depending on the properties of the new vacuum, fundamental forces and particles could...
  40. S

    I Could the Lorentz symmetry be theoretically broken in vacuum?

    In this paper [1] which considers the possibility that the Lorentz symmetry could be broken, at page 4-5 the author says: "We now introduce a Higgs sector into the Lagrangian density such that the gravitational vacuum symmetry, which we set equal to the Lagrangian symmetry at low temperatures...
  41. Ben_the_Druid

    I Vacuum pump operating at high altitude

    Hi I live in a high Altitude around 2500 meter over sealevel. I have a vacuum pump, at max my vacuum meter shows 21 inHG inside the vacuum chamber . my vacuum pump(welch 2014B) has a max of 40 torr it say the technical datasheet. What is now my endpressure in torr in my vacuumchamber?It's...
  42. S

    Anyone interested in Unidentified Aerial Phenomena (UAP) and how they work?

    Just wondering if anyone here finds these video/picture leaks about UAP's (Unidentified Aerial Phenomenon) interesting and inspiring enough to try and figure out how they work? Pretty big game changer of technology and would be fun to discuss. I'm hoping at least someone agrees.
  43. S

    I Is it a fact that vacuum energy exists?

    I have always read that vacuum energy and zero point energy are established facts of physics supported by various observations of their effects both indirectly and even directly. But I have also read some comments from various physics discussion sites where they say that it is not a fact that...
  44. J

    I Reflectivity of Pure Metals in Vacuum

    All data I see online about reflectivity of metals is about aluminum in the atmosphere meaning oxidized aluminum, but pure aluminum in vacuum in case of the James Webb telescope would also be extremely reflective but building it on Earth means it's going to get oxidized, similarly there are a...
  45. microatx

    B Does the quantum vacuum have information?

    Hey everyone, My question is simple. Has quantum vacuum information ? And can we measure it with Shannon Entropy and the other ways. By the way I just started to learn english so ı have any grammer mistake please tell me. I know this is out of subject but thank you.
  46. J

    I Possibility of PCB Oils in old Diffusion Pumps?

    I recently found three old vintage diffusion pumps left over by the previous lab owners: 1. Veeco EP 2A 2. Veeco EP 2A-1 3. Edwards Speedivac F203 Is there a possibility that these pumps have PCB based oil inside? I do not have access to PCB oil testing at the moment. Also any further...
  47. S

    B Light Speed in Vacuum: Does It Reach Cosmic Limit?

    As we all know, light itself is the fastest thing in the universe, and the cosmic speed limit, basically. That said, it is said to go at 299,792,458 meters per second in a vacuum. That is pretty fast. However, I have a question I want to ask... Does light really go that fast in a vacuum? I ask...
  48. ektov_konstantin

    Vacuum heating calculation

    Hello, everyone! I am calculating the time of substrates' heating in the vacuum chamber. It is a simple mathematical model to calculate roughly how much time does it take to heat polycor substrates in the vacuum chamber. At least all the tube heater`s power heats the substrates (this is...
  49. P

    A Vacuum Flask Thermodynamic Equation

    Im trying to find an advanced thermodynamic equation for a vacuum flask. I am looking for an equation to find the temperature of a liquid at time t as it cools down. Ignore the cap and bottom section; assume there is no heat loss in those areas. I'm just interested in the cylindrical...