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The quality of a vacuum is measured in relation to how closely it approaches a perfect vacuum. The residual gas pressure is the primary indicator of quality, and is most commonly measured in units called torr, even in metric contexts. Lower pressures indicate higher quality, although other variables must also be taken into account. Quantum mechanics sets limits on the best possible quality of vacuum. Outer space is a natural high quality vacuum, mostly of much higher quality than what can be created artificially with current technology. Low quality artificial vacuums have been used for suction for millennia. This article is about pressure in the physical sciences. ... The torr (symbol: Torr) or millimeter of mercury (mmHg) is a non-SI unit of pressure. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... Layers of Atmosphere - not to scale (NOAA)[1] Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ... Suction is the creation of a partial vacuum, or region of low pressure. ...

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 artifical vacuum in 1643, and other experimental techniques were developed as a result of his theories of atmospheric pressure. 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 technology has since become available. The recent development of human spaceflight has raised interest in the impact of vacuum on human health, and on life forms in general. Philosophy (from the Greek words philos and sophia meaning love of wisdom) is understood in different ways historically and by different philosophers. ... Note: This article contains special characters. ... (16th century - 17th century - 18th century - more centuries) As a means of recording the passage of time, the 17th century was that century which lasted from 1601-1700. ... Evangelista Torricelli portrayed on the frontpage of Lezioni dEvangelista Torricelli. ... // Events January 21 - Abel Tasman discovers Tonga February 6 - Abel Tasman discovers the Fiji islands. ... Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901&#8211;2000 in the sense of the Gregorian calendar (1900&#8211;1999... Light bulb redirects here. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... Edward White on a spacewalk during the Gemini 4 mission. ...

Photo of a vacuum chamber being opened by an engineer. ... Photo of a vacuum chamber being opened by an engineer. ... A large vacuum chamber. ...

## Uses

Light bulbs contain a partial vacuum because the tungsten reaches such high temperatures that it would combust any oxygen molecules, usually backfilled with argon, which protects the tungsten filament

High to ultra-high vacuum is used in thin film deposition and surface science. High vacuum allows for contamination-free material deposition. Ultra-high vacuum is used in the study of atomically clean substrates, as only a very good vacuum preserves atomic-scale clean surfaces for a reasonably long time (on the order of minutes to days). Thin-film deposition is any technique for depositing a thin film of material onto a substrate or onto previously deposited layers. ... Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid-liquid interfaces, solid-gas interfaces, solid-vacuum interfaces, and liquid-gas interfaces. ... Ultra high vacuum (UHV) is the regime of characterised by pressures lower than about 10-7 Pascal or 100 nanopascals (~10-9 torr). ...

Suction is used in a wide variety of applications. The Newcomen steam engine used vacuum instead of pressure to drive a piston. In the 19th century, vacuum was used for traction on Isambard Kingdom Brunel's experimental atmospheric railway. Suction is the creation of a partial vacuum, or region of low pressure. ... Animation of a schematic Newcomen steam engine. ... Alternative meaning: Nineteenth Century (periodical) (18th century &#8212; 19th century &#8212; 20th century &#8212; more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... Isambard Kingdom Brunel, FRS (9 April 1806 â€“ 15 September 1859) (IPA: ), was a British engineer. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

## Outer space

Main article: Outer space
Outer space is not a perfect vacuum, but a tenuous plasma awash with charged particles, electromagnetic fields, and the occasional star.

Stars, planets and moons keep their atmospheres by gravitational attraction, and as such, atmospheres have no clearly delineated boundary: the density of atmospheric gas simply decreases with distance from the object. In low earth orbit (about 300 km or 185 miles altitude) the atmospheric density is about 100 nPa (10-9 Torr), still sufficient to produce significant drag on satellites. Most artificial satellites operate in this region, and must fire their engines every few days to maintain orbit. For other uses, see Atmosphere (disambiguation). ... A low Earth orbit (LEO) is an orbit in which objects such as satellites are below intermediate circular orbit (ICO) and far below geostationary orbit, but typically around 350 - 1400 km above the Earths surface. ... Look up Drag in Wiktionary, the free dictionary. ... For other uses, see Satellite (disambiguation). ...

Beyond planetary atmospheres, the pressure of photons and other particles from the sun becomes significant. Spacecraft can be buffeted by solar winds, but planets are too massive to be affected. The idea of using this wind with a solar sail has been proposed for interplanetary travel. Sol redirects here. ... The Space Shuttle Discovery as seen from the International Space Station. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... Solar sails (also called light sails or photon sails, especially when they use light sources other than the Sun) are a proposed form of spacecraft propulsion using large membrane mirrors. ...

All of the observable universe is filled with large numbers of photons, the so-called cosmic background radiation, and quite likely a correspondingly large number of neutrinos. The current temperature of this radiation is about 3 K, or -270 degrees Celsius or -454 degrees Fahrenheit. For other uses, see Universe (disambiguation). ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... When any patch of the sky is observed where no individual sources can be discerned, and the effects of interplanetary dust, and interstellar matter are taken into account, there is still radiation. ... For other uses, see Neutrino (disambiguation). ... For other uses, see Temperature (disambiguation). ... For other uses, see Kelvin (disambiguation). ...

## Effects on humans and animals

This painting, An Experiment on a Bird in the Air Pump by Joseph Wright of Derby, 1768, depicts an experiment performed by Robert Boyle in 1660.

Vacuum is primarily an asphyxiant. Humans exposed to vacuum will lose consciousness after a few seconds and die within minutes, but the symptoms are not nearly as graphic as commonly shown in pop culture. Robert Boyle was the first to show that vacuum is lethal to small animals. Blood and other body fluids do boil (the medical term for this condition is ebullism), and the vapour pressure may bloat the body to twice its normal size and slow circulation, but tissues are elastic and porous enough to prevent rupture. Ebullism is slowed by the pressure containment of blood vessels, so some blood remains liquid.[1][2] Swelling and ebullism can be reduced by containment in a flight suit. Shuttle astronauts wear a fitted elastic garment called the Crew Altitude Protection Suit (CAPS) which prevents ebullism at pressures as low as 15 Torr (2 kPa).[3] However, even if ebullism is prevented, simple evaporation of blood can cause decompression sickness and gas embolisms. Rapid evaporative cooling of the skin will create frost, particularly in the mouth, but this is not a significant hazard. Human physiological adaptation to the conditions of space is a challenge faced in the development of human spaceflight. ... Image File history File links Download high resolution version (2024x1491, 228 KB) Summary An Experiment on a Bird in an Air Pump by Joseph Wright of Derby, 1768. ... Image File history File links Download high resolution version (2024x1491, 228 KB) Summary An Experiment on a Bird in an Air Pump by Joseph Wright of Derby, 1768. ... An Experiment on a Bird in the Air Pump is a 1768 oil-on-canvas painting by Joseph Wright of Derby, part of a series of candlelit scenes that Wright painted during the 1760s. ... An Experiment on a Bird in an Air Pump (1768). ... Robert Boyle (Irish: Robaird Ã“ Bhaoill) (25 January 1627 â€“ 30 December 1691) was an Irish natural philosopher, chemist, physicist, inventor, and early gentleman scientist, noted for his work in physics and chemistry. ... Asphyxia is a condition of severely deficient supply of oxygen to the body. ... Consciousness is a quality of the mind generally regarded to comprise qualities such as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and ones environment. ... Robert Boyle (Irish: Robaird Ã“ Bhaoill) (25 January 1627 â€“ 30 December 1691) was an Irish natural philosopher, chemist, physicist, inventor, and early gentleman scientist, noted for his work in physics and chemistry. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... Ebullism describes the formation of gas bubbles in bodily fluids at reduced environmental pressure. ... The vapor pressure is the pressure (if the vapor is mixed with other gases, the partial pressure) of a vapor. ... A flight suit worn by an SR-71 Blackbird pilot, now in an Air Force museum. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ... â€œVaporizationâ€ redirects here. ... Decompression sickness (DCS), the diverâ€™s disease, the bends, or caisson disease is the name given to a variety of symptoms suffered by a person exposed to a decrease (nearly always after a big increase) in the pressure around his body. ... An air embolism, or more WITCH generally gas embolism, is a medical condition caused by gas bubbles in the bloodstream (embolism in a medical context refers to any large moving mass or defect in the blood stream). ...

Animal experiments show that rapid and complete recovery is the norm for exposures of fewer than 90 seconds, while longer full-body exposures are fatal and resuscitation has never been successful.[4] There is only a limited amount of data available from human accidents, but it is consistent with animal data. Limbs may be exposed for much longer if breathing is not impaired. Rapid decompression can be much more dangerous than vacuum exposure itself. If the victim holds his breath during decompression, the delicate internal structures of the lungs can be ruptured, causing death. Eardrums may be ruptured by rapid decompression, soft tissues may bruise and seep blood, and the stress of shock will accelerate oxygen consumption leading to asphyxiation.[5] Decompresion has several meanings: in physics, decompression is the release of pressure and is the opposition of compression in medicine, scuba diving and aviation, decompression can refer to a sickness in scuba diving, decompression can refer to a stop, a chamber, a buoy, a trapeze, tables or a computer in... Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ... The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. ...

In 1942, in one of a series of experiments on human subjects for the Luftwaffe, the Nazi regime tortured Dachau concentration camp prisoners by exposing them to vacuum in order to determine the human body's capacity to survive high-altitude conditions. Year 1942 (MCMXLII) was a common year starting on Thursday (the link will display the full 1942 calendar) of the Gregorian calendar. ... Nazism in history Nazi ideology Nazism and race Outside Germany Related subjects Lists Politics Portal         Nazi human experimentation was medical experimentation on large numbers of people by the German Nazi regime in its concentration camps during World War II. // According to the indictment at the Subsequent Nuremberg Trials, these experiments... The Deutsche Luftwaffe or   (German: air force, literally Air Weapon, pronounced lufft-va-fa, IPA: ) is the commonly used term for the German air force. ... Nazism in history Nazi ideology Nazism and race Outside Germany Related subjects Lists Politics Portal         Nazism or National Socialism (German: Nationalsozialismus), refers primarily to the ideology and practices of the Nazi Party (National Socialist German Workers Party, German: Nationalsozialistische Deutsche Arbeiterpartei or NSDAP) under Adolf Hitler. ... The main entrance just after the liberation Memorial at the camp, 1997. ...

Some extremophile microrganisms, such as Tardigrades, can survive vacuum for a period of years. An extremophile is an organism, usually unicellular, which thrives in or requires extreme conditions that would exceed optimal conditions for growth and reproduction in the majority of mesophilic terrestrial organisms. ... Classes [2] Heterotardigrada Mesotardigrada Eutardigrada Tardigrades (commonly known as moss piglets or water bears) comprise the phylum Tardigrada. ...

## Historical interpretation

Historically, there has been much dispute over whether such a thing as a vacuum can exist. Ancient Greek philosophers did not like to admit the existence of a vacuum, asking themselves "how can 'nothing' be something?". Plato found the idea of a vacuum inconceivable. He believed that all physical things were instantiations of an abstract Platonic ideal, and he could not conceive of an "ideal" form of a vacuum. Similarly, Aristotle considered the creation of a vacuum impossible — nothing could not be something. Later Greek philosophers thought that a vacuum could exist outside the cosmos, but not within it. The term ancient Greece refers to the periods of Greek history in Classical Antiquity, lasting ca. ... For other uses, see Philosophy (disambiguation). ... For other uses, see Plato (disambiguation). ... Platonic idealism is the theory that the substantive reality around us is only a reflection of a higher truth. ... For other uses, see Aristotle (disambiguation). ... The Ancient and Medieval cosmos as depicted in Peter Apians Cosmographia (Antwerp, 1539). ...

The philosopher Al-Farabi (850 - 970 CE) appears to have carried out the first recorded experiments concerning the existence of vacuum, in which he investigated handheld plungers in water.[6] He concluded that air's volume can expand to fill available space, and he suggested that the concept of perfect vacuum was incoherent.[7] A philosopher is a person who thinks deeply regarding people, society, the world, and/or the universe. ... Al Farabi (870-950) was born of a Turkish family and educated by a Christian physician in Baghdad, and was himself later considered a teacher on par with Aristotle. ... BCE redirects here. ...

Torricelli's mercury barometer produced the first sustained vacuum in a laboratory.

The Crookes tube, used to discover and study cathode rays, was an evolution of the Geissler tube.

In the 17th century, theories of the nature of light relied upon the existence of an aethereal medium which would be the medium to convey waves of light (Newton relied on this idea to explain refraction and radiated heat). This evolved into the luminiferous aether of the 19th century, but the idea was known to have significant shortcomings - specifically that if the Earth were moving through a material medium, the medium would have to be both extremely tenuous (because the Earth is not detectably slowed in its orbit), and extremely rigid (because vibrations propagate so rapidly). For other uses, see Light (disambiguation). ... Look up aether, ether in Wiktionary, the free dictionary. ... For other uses, see Newton (disambiguation). ... For the property of metals, see refraction (metallurgy). ... The luminiferous aether: it was hypothesised that the Earth moves through a medium of aether that carries light In the late 19th century luminiferous aether (light-bearing aether) was the term used to describe a medium for the propagation of light. ...

While outer space has been likened to a vacuum, early physicists postulated that an invisible luminiferous aether existed as a medium to carry light waves, or an "ether which fills the interstellar space".[9] An 1891 article by William Crookes noted: "the [freeing of] occluded gases into the vacuum of space".[10] Even up until 1912, astronomer Henry Pickering commented: "While the interstellar absorbing medium may be simply the ether, [it] is characteristic of a gas, and free gaseous molecules are certainly there".[11] The luminiferous aether: it was hypothesised that the Earth moves through a medium of aether that carries light In the late 19th century luminiferous aether (light-bearing aether) was the term used to describe a medium for the propagation of light. ... Look up aether, ether in Wiktionary, the free dictionary. ... Year 1891 (MDCCCXCI) was a common year starting on Thursday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Saturday of the 12-day slower Julian calendar). ... Sir William Crookes, OM, FRS (17 June 1832 â€“ 4 April 1919) was an English chemist and physicist. ... 1912 (MCMXII) was a leap year starting on Monday in the Gregorian calendar (or a leap year starting on Tuesday in the 13-day-slower Julian calendar). ... An astronomer or astrophysicist is a person whose area of interest is astronomy or astrophysics. ... William Henry Pickering (February 15, 1858 &#8211; January 17, 1938) was an American astronomer, brother of Edward Charles Pickering. ...

Einstein argued that physical objects are not located in space, but rather have a spatial extent. Seen this way, the concept of empty space loses its meaning.[12] Rather, space is an abstraction, based on the relationships between local objects. Nevertheless, the general theory of relativity admits a pervasive gravitational field, which, in Einstein's words[13], may be regarded as an "aether", with properties varying from one location to another. One must take care, though, to not ascribe to it material properties such as velocity and so on. General relativity (GR) or general relativity theory (GRT) is the theory of gravitation published by Albert Einstein in 1915. ...

In 1930, Paul Dirac proposed a model of vacuum as an infinite sea of particles possessing negative energy, called the Dirac sea. This theory helped refine the predictions of his earlier formulated Dirac equation, and successfully predicted the existence of the positron, discovered two years later in 1932. Despite this early success, the idea was soon abandoned in favour of the more elegant quantum field theory. Paul Adrien Maurice Dirac, OM, FRS (IPA: [dÉªrÃ¦k]) (August 8, 1902 â€“ October 20, 1984) was a British theoretical physicist and a founder of the field of quantum physics. ... The Dirac sea is a theoretical model of the vacuum as an infinite sea of particles possessing negative energy. ... In physics, the Dirac equation is a relativistic quantum mechanical wave equation formulated by British physicist Paul Dirac in 1928 and provides a description of elementary spin-Â½ particles, such as electrons, consistent with both the principles of quantum mechanics and the theory of special relativity. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... Year 1932 (MCMXXXII) was a leap year starting on Friday (the link will display full 1932 calendar) of the Gregorian calendar. ... Quantum field theory (QFT) is the quantum theory of fields. ...

## Quantum-mechanical definition

For more details on this topic, see vacuum state.

In quantum mechanics, the vacuum is defined as the state (i.e. solution to the equations of the theory) with the lowest energy. To first approximation, this is simply a state with no particles, hence the name. In quantum field theory, the vacuum state, usually denoted , is the element of the Hilbert space with the lowest possible energy, and therefore containing no physical particles. ...

Even an ideal vacuum, thought of as the complete absence of anything, will not in practice remain empty. Consider a vacuum chamber that has been completely evacuated, so that the (classical) particle concentration is zero. The walls of the chamber will emit light in the form of black body radiation. This light carries momentum, so the vacuum does have a radiation pressure. This limitation applies even to the vacuum of interstellar space. Even if a region of space contains no particles, the Cosmic Microwave Background fills the entire universe with black body radiation. As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... WMAP image of the CMB anisotropy,Cosmic microwave background radiation(June 2003) The cosmic microwave background radiation (CMB) is a form of electromagnetic radiation that fills the whole of the universe. ...

An ideal vacuum cannot exist even inside of a molecule. Each atom in the molecule exists as a probability function of space, which has a certain non-zero value everywhere in a given volume. Thus, even "between" the atoms there is a certain probability of finding a particle, so the space cannot be said to be a vacuum.

More fundamentally, quantum mechanics predicts that vacuum energy will be different from its naive, classical value. The quantum correction to the energy is called the zero-point energy and consists of energies of virtual particles that have a brief existence. This is called vacuum fluctuation. Vacuum fluctuations may also be related to the so-called cosmological constant in cosmology. The best evidence for vacuum fluctuations is the Casimir effect and the Lamb shift.[8] For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... Vacuum energy is an underlying background energy that exists in space even when devoid of matter (known as free space). ... In physics, the zero-point energy is the lowest possible energy that a quantum mechanical physical system may possess and is the energy of the ground state of the system. ... In physics, a virtual particle is a particle which exists for such a short time and space that its energy and momentum do not have to obey the usual relationship. ... In the description of the interaction between elementary particles in quantum field theory, a virtual particle is a temporary elementary particle, used to describe an intermediate stage in the interaction. ... In physical cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Î›) was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. ... This article is about the physics subject. ... In physics, the Casimir effect is a physical force exerted between separate objects, which is due to neither charge, gravity, nor the exchange of particles, but instead is due to resonance of all-pervasive energy fields in the intervening space between the objects. ... In physics, the Lamb shift, named after Willis Lamb, is a small difference in energy between two energy levels and of the hydrogen atom in quantum mechanics. ...

In quantum field theory and string theory, the term "vacuum" is used to represent the ground state in the Hilbert space, that is, the state with the lowest possible energy. In free (non-interacting) quantum field theories, this state is analogous to the ground state of a quantum harmonic oscillator. If the theory is obtained by quantization of a classical theory, each stationary point of the energy in the configuration space gives rise to a single vacuum. String theory is believed to have a huge number of vacua - the so-called string theory landscape. Quantum field theory (QFT) is the quantum theory of fields. ... Interaction in the subatomic world: world lines of pointlike particles in the Standard Model or a world sheet swept up by closed strings in string theory String theory is a model of fundamental physics, whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point... In physics, the ground state of a quantum mechanical system is its lowest-energy state. ... The mathematical concept of a Hilbert space (named after the German mathematician David Hilbert) generalizes the notion of Euclidean space in a way that extends methods of vector algebra from the plane and three-dimensional space to spaces of functions. ... The quantum harmonic oscillator is the quantum mechanical analogue of the classical harmonic oscillator. ... Stationary points (red pluses) and inflection points (green circles). ... In mathematics, a function space is a set of functions of a given kind from a set X to a set Y. It is called a space because in most applications, it is a topological space or/and a vector space. ... Interaction in the subatomic world: world lines of pointlike particles in the Standard Model or a world sheet swept up by closed strings in string theory String theory is a model of fundamental physics, whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point... The string theory landscape or anthropic landscape refers to the large number of different false vacua in string theory. ...

## Pumping

The manual water pump draws water up from a well by creating a vacuum that water rushes in to fill. In a sense, it acts to evacuate the well, although the high leakage rate of dirt prevents a high quality vacuum from being maintained for any length of time.
Main article: Vacuum pump

Fluids cannot be pulled, so it is technically impossible to create a vacuum by suction. Suction is the movement of fluids into a vacuum under the effect of a higher external pressure, but the vacuum has to be created first. The easiest way to create an artificial vacuum is to expand the volume of a container. For example, the diaphragm muscle expands the chest cavity, which causes the volume of the lungs to increase. This expansion reduces the pressure and creates a partial vacuum, which is soon filled by air pushed in by atmospheric pressure. Image File history File links L-Pumpe2. ... Image File history File links L-Pumpe2. ... The Roots blower is one example of a vacuum pump A vacuum pump is a pump that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. ... In the anatomy of mammals, the diaphragm is a shelf of muscle extending across the bottom of the ribcage. ...

To continue evacuating a chamber indefinitely without requiring infinite growth, a compartment of the vacuum can be repeatedly closed off, exhausted, and expanded again. This is the principle behind positive displacement pumps, like the manual water pump for example. Inside the pump, a mechanism expands a small sealed cavity to create a deep vacuum. Because of the pressure differential, some fluid from the chamber (or the well, in our example) is pushed into the pump's small cavity. The pump's cavity is then sealed from the chamber, opened to the atmosphere, and squeezed back to a minute size. The Roots blower is one example of a vacuum pump A vacuum pump is a pump that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. ...

A cutaway view of a turbomolecular pump, a momentum transfer pump used to achieve high vacuum

The above explanation is merely a simple introduction to vacuum pumping, and is not representative of the entire range of pumps in use. Many variations of the positive displacement pump have been developed, and many other pump designs rely on fundamentally different principles. Momentum transfer pumps, which bear some similarities to dynamic pumps used at higher pressures, can achieve much higher quality vacuums than positive displacement pumps. Entrapment pumps can capture gases in a solid or absorbed state, often with no moving parts, no seals and no vibration. None of these pumps are universal; each type has important performance limitations. They all share a difficulty in pumping low molecular weight gases, especially hydrogen, helium, and neon. Image File history File links Cut_through_turbomolecular_pump. ... Image File history File links Cut_through_turbomolecular_pump. ... Interior view of a turbomolecular pump Turbomolecular pumps is a form of turbopump used to obtain and maintain high vacuum. ... The Roots blower is one example of a vacuum pump A vacuum pump is a pump that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. ... The Roots blower is one example of a vacuum pump A vacuum pump is a pump that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. ... This article is about the chemistry of hydrogen. ... For other uses, see Helium (disambiguation). ... For other uses, see Neon (disambiguation). ...

The lowest pressure that can be attained in a system is also dependent on many things other than the nature of the pumps. Multiple pumps may be connected in series, called stages, to achieve higher vacuums. The choice of seals, chamber geometry, materials, and pump-down procedures will all have an impact. Collectively, these are called vacuum technique. And sometimes, the final pressure is not the only relevant characteristic. Pumping systems differ in oil contamination, vibration, preferential pumping of certain gases, pump-down speeds, intermittent duty cycle, reliability, or tolerance to high leakage rates.

In ultra high vacuum systems, some very odd leakage paths and outgassing sources must be considered. The water absorption of aluminium and palladium becomes an unacceptable source of outgassing, and even the adsorptivity of hard metals such as stainless steel or titanium must be considered. Some oils and greases will boil off in extreme vacuums. The porosity of the metallic chamber walls may have to be considered, and the grain direction of the metallic flanges should be parallel to the flange face. Ultra high vacuum (UHV) is the regime characterised by pressures lower than about 10âˆ’7 pascal or 100 nanopascals (~10âˆ’9 torr). ... Aluminum redirects here. ... For other uses, see Palladium (disambiguation). ... General Name, symbol, number titanium, Ti, 22 Chemical series transition metals Group, period, block 4, 4, d Appearance silvery metallic Standard atomic weight 47. ...

The lowest pressures currently achievable in laboratory are about 10-13 Torr.[14] The torr (symbol: Torr) or millimeter of mercury (mmHg) is a non-SI unit of pressure. ...

## Outgassing

Main article: Outgassing

Evaporation and sublimation into a vacuum is called outgassing. All materials, solid or liquid, have a small vapour pressure, and their outgassing becomes important when the vacuum pressure falls below this vapour pressure. In man-made systems, outgassing has the same effect as a leak and can limit the achievable vacuum. Outgassing products may condense on nearby colder surfaces, which can be troublesome if they obscure optical instruments or react with other materials. This is of great concern to space missions, where an obscured telescope or solar cell can ruin an expensive mission. Outgassing (sometimes called Offgassing, particularly when in reference to indoor air quality) is the slow release of a gas that was trapped, frozen, absorbed or adsorbed in some material. ... â€œVaporizationâ€ redirects here. ... This article does not cite any references or sources. ... Outgassing (sometimes called Offgassing, particularly when in reference to indoor air quality) is the slow release of a gas that was trapped, frozen, absorbed or adsorbed in some material. ... The vapor pressure is the pressure (if the vapor is mixed with other gases, the partial pressure) of a vapor. ...

The most prevalent outgassing product in man-made vacuum systems is water absorbed by chamber materials. It can be reduced by desiccating or baking the chamber, and removing absorbent materials. Outgassed water can condense in the oil of rotary vane pumps and reduce their net speed drastically if gas ballasting is not used. High vacuum systems must be clean and free of organic matter to minimize outgassing. A rotary vane pump is a positive displacement pump that consists of variable-length, tensioned vanes mounted to a rotor that rotates inside of a cavity. ...

Ultra-high vacuum systems are usually baked, preferably under vacuum, to temporarily raise the vapour pressure of all outgassing materials and boil them off. Once the bulk of the outgassing materials are boiled off and evacuated, the system may be cooled to lower vapour pressures and minimize residual outgassing during actual operation. Some systems are cooled well below room temperature by liquid nitrogen to shut down residual outgassing and simultaneously cryopump the system. A tank of liquid nitrogen, used to supply a cryogenic freezer (for storing laboratory samples at a temperature of about -150 Celsius). ... A cryopump is a vacuum pump that traps gases and vapours by condensing them on a cold surface. ...

## Quality

The quality of a vacuum is indicated by the amount of matter remaining in the system. Vacuum is primarily measured by its absolute pressure, but a complete characterization requires further parameters, such as temperature and chemical composition. One of the most important parameters is the mean free path (MFP) of residual gases, which indicates the average distance that molecules will travel between collisions with each other. As the gas density decreases, the MFP increases, and when the MFP is longer than the chamber, pump, spacecraft, or other objects present, the continuum assumptions of fluid mechanics do not apply. This vacuum state is called high vacuum, and the study of fluid flows in this regime is called particle gas dynamics. The MFP of air at atmospheric pressure is very short, 70 nm, but at 100 mPa (~1×10-3 Torr) the MFP of room temperature air is roughly 100 mm, which is on the order of everyday objects such as vacuum tubes. The Crookes radiometer turns when the MFP is larger than the size of the vanes. Pressure (symbol: p or P) is the measure of the force that acts on a unit area. ... For other uses, see Temperature (disambiguation). ... For sound waves in an enclosure, the mean free path is the average distance the wave travels between reflections off of the enclosures walls. ... This box:      Fluid mechanics is the study of how fluids move and the forces on them. ... A nanometre (American spelling: nanometer) is 1. ... The pascal (symbol: Pa) is the SI unit of pressure. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... The Crookes radiometer, also known as the light mill or solar engine, consists of an airtight glass bulb, containing a partial vacuum. ...

Deep space is generally much more empty than any artificial vacuum that we can create, although many laboratories can reach lower vacuum than that of low earth orbit. In interplanetary and interstellar space, isotropic gas pressure is insignificant when compared to solar pressure, solar wind, and dynamic pressure, so the definition of pressure becomes difficult to interpret. Astrophysicists prefer to use number density to describe these environments, in units of particles per cubic centimetre. The average density of interstellar gas is about 1 atom per cubic centimeter.[15] A low Earth orbit (LEO) is an orbit in which objects such as satellites are below intermediate circular orbit (ICO) and far below geostationary orbit, but typically around 350 - 1400 km above the Earths surface. ... Existing or occurring between planets. ... The interstellar medium (or ISM) is a term used in astronomy to describe the rarefied gas and dust that exists between the stars (or their immediate circumstellar environment) within a galaxy. ... The number density, in physics, refers to the number of entities (often of particles, but it could be of sound waves, galaxies, etc. ...

Vacuum quality is subdivided into ranges according to the technology required to achieve it or measure it. These ranges do not have universally agreed definitions (hence the gaps below), but a typical distribution is as follows:[16][17]

 Atmospheric pressure 760 Torr 101 kPa Low vacuum 760 to 25 Torr 100 to 3 kPa Medium vacuum 25 to 1×10-3 Torr 3 kPa to 100 mPa High vacuum 1×10-3 to 1×10-9 Torr 100 mPa to 100 nPa Ultra high vacuum 1×10-9 to 1×10-12 Torr 100 nPa to 100 pPa Extremely high vacuum <1×10-12 Torr <100 pPa Outer Space 1×10-6 to <3×10-17 Torr 100 µPa to <3fPa Perfect vacuum 0 Torr 0 Pa
• Atmospheric pressure is variable but standardized at 101.325 kPa (760 Torr)
• Low vacuum, also called rough vacuum or coarse vacuum, is vacuum that can be achieved or measured with rudimentary equipment such as a vacuum cleaner and a liquid column manometer.
• Medium vacuum is vacuum that can be achieved with a single pump, but is too low to measure with a liquid or mechanical manometer. It can be measured with a McLeod gauge, thermal gauge or a capacitive gauge.
• High vacuum is vacuum where the MFP of residual gases is longer than the size of the chamber or of the object under test. High vacuum usually requires multi-stage pumping and ion gauge measurement. Some texts differentiate between high vacuum and very high vacuum.
• Ultra high vacuum requires baking the chamber to remove trace gases, and other special procedures.
• Deep space is generally much more empty than any artificial vacuum that we can create. However, it is not High Vacuum with respect to the above definition, since the MFP of the molecules is smaller than the (infinite) size of the chamber.
• Perfect vacuum is an ideal state that cannot be obtained in a laboratory, nor can it be found in outer space.

Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ... The torr (symbol: Torr) or millimeter of mercury (mmHg) is a non-SI unit of pressure. ... Ultra high vacuum (UHV) is the regime characterised by pressures lower than about 10âˆ’7 pascal or 100 nanopascals (~10âˆ’9 torr). ... Layers of Atmosphere - not to scale (NOAA)[1] Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ... In physics, free space is a concept of electromagnetic theory, corresponding roughly to the vacuum, the baseline state of the electromagnetic field, or the replacement for the electromagnetic aether. ... Regular canister vacuum cleaner for home use. ... A manometer is a pressure measuring instrument, often also called pressure gauge. ... For sound waves in an enclosure, the mean free path is the average distance the wave travels between reflections off of the enclosures walls. ... This article does not cite any references or sources. ...

### Examples

pressure in Pa pressure in Torr mean free path molecules per cm2
Vacuum cleaner approximately 80 kPa 600 Torr 70 nm 1019
liquid ring vacuum pump approximately 3.2 kPa 24 Torr
freeze drying 100 to 10 Pa 1 to 0.1 Torr
rotary vane pump 100 Pa to 100 mPa 1 Torr to 10−3 Torr
Incandescent light bulb 10 to 1 Pa 0.1 to 0.01 Torr
Thermos bottle 1 to 0.1 Pa 10−2 to 10−3 Torr
Near earth outer space approximately 100 µPa 10−6 Torr
Vacuum tube 10 µPa to 10 nPa 10−7 to 10−10 Torr
Cryopumped MBE chamber 100 nPa to 1 nPa 10−9 to 10−11 Torr 1..105 km 109..104
Pressure on the Moon approximately 1 nPa 10−11 Torr
Interstellar space approximately 1 fPa 10−17 Torr 1

Regular canister vacuum cleaner for home use. ... A liquid ring pump is a rotating positive displacement pump. ... The Roots blower is one example of a vacuum pump A vacuum pump is a pump that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. ... Freeze drying (also known as Lyophilization) is a dehydration process typically used to preserve a perishable material, or to make the material more convenient for transport. ... A rotary vane pump is a positive displacement pump that consists of variable-length, tensioned vanes mounted to a rotor that rotates inside of a cavity. ... Light bulb redirects here. ... Lunchbox and vacuum bottle owned by Harry S. Truman A vacuum flask or Thermos flask is a bottle that reduces heat transfer from the inside to the outside and conversely to a minimum, and therefore keeps warm drinks warm and refrigerated drinks cold. ... Layers of Atmosphere - not to scale (NOAA)[1] Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... A cryopump is a vacuum pump that traps gases and vapours by condensing them on a cold surface. ... Molecular beam epitaxy, abbreviated MBE, is the deposition of one or more pure materials onto a single crystal wafer, one layer of atoms at a time, under ultra-high vacuum, forming a perfect crystal. ... This article is about Earths moon. ... The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. ...

## Measurement

Main article: Pressure measurement

Vacuum is measured in units of pressure. The SI unit of pressure is the pascal (symbol Pa), but vacuum is usually measured in torrs (symbol Torr), named for Torricelli, an early Italian physicist (1608 - 1647). A torr is equal to the displacement of a millimeter of mercury (mmHg) in a manometer with 1 torr equaling 133.3223684 pascals above absolute zero pressure. Vacuum is often also measured using inches of mercury on the barometric scale or as a percentage of atmospheric pressure in bars or atmospheres. Low vacuum is often measured in inches of mercury (inHg), millimeters of mercury (mmHg) or kilopascals (kPa) below atmospheric pressure. "Below atmospheric" means that the absolute pressure is equal to the current atmospheric pressure (e.g. 29.92 inHg) minus the vacuum pressure in the same units. Thus a vacuum of 26 inHg is equivalent to an absolute pressure of 4 inHg (29.92 inHg - 26 inHg). The construction of manometer, construction elements are made of brass Many techniques have been developed for the measurement of pressure and vacuum. ... This article is about pressure in the physical sciences. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... For other uses, see Pascal. ... The torr (symbol: Torr) or millimeter of mercury (mmHg) is a non-SI unit of pressure. ... One way of defining pressure is in terms of the height of a column of fluid that may be supported by that pressure; or the height of a column of fluid that exerts that pressure at its base. ... A manometer is a pressure measuring instrument, often also called pressure gauge. ... Pressure is the application of force to a surface, and the concentration of that force in a given area. ... A barometer is an instrument used to measure atmospheric pressure. ... Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ... The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. ... Standard atmosphere (symbol: atm) is a unit of pressure. ... Pressure is the application of force to a surface, and the concentration of that force in a given area. ... The torr (symbol: Torr) or millimeter of mercury (mmHg) is a non-SI unit of pressure. ...

A glass McLeod gauge, drained of mercury

Many devices are used to measure the pressure in a vacuum, depending on what range of vacuum is needed.[18] Image File history File linksMetadata Download high resolution version (1712x2288, 546 KB) Summary An old McLeod gauge used for high precision measurement of vacuum. ... Image File history File linksMetadata Download high resolution version (1712x2288, 546 KB) Summary An old McLeod gauge used for high precision measurement of vacuum. ...

Hydrostatic gauges (such as the mercury column manometer) consist of a vertical column of liquid in a tube whose ends are exposed to different pressures. The column will rise or fall until its weight is in equilibrium with the pressure differential between the two ends of the tube. The simplest design is a closed-end U-shaped tube, one side of which is connected to the region of interest. Any fluid can be used, but mercury is preferred for its high density and low vapour pressure. Simple hydrostatic gauges can measure pressures ranging from 1 Torr (100 Pa) to above atmospheric. An important variation is the McLeod gauge which isolates a known volume of vacuum and compresses it to multiply the height variation of the liquid column. The McLeod gauge can measure vacuums as high as 10−6 Torr (0.1 mPa), which is the lowest direct measurement of pressure that is possible with current technology. Other vacuum gauges can measure lower pressures, but only indirectly by measurement of other pressure-controlled properties. These indirect measurements must be calibrated via a direct measurement, most commonly a McLeod gauge.[19] A manometer is a pressure measuring instrument, often also called pressure gauge. ... General Name, Symbol, Number mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12, 6, d Appearance silvery Standard atomic weight 200. ... A McLeod gauge is a scientific instrument to measure very low pressures, down to 10-7 Torr. ...

Mechanical or elastic gauges depend on a Bourdon tube, diaphragm, or capsule, usually made of metal, which will change shape in response to the pressure of the region in question. A variation on this idea is the capacitance manometer, in which the diaphragm makes up a part of a capacitor. A change in pressure leads to the flexure of the diaphragm, which results in a change in capacitance. These gauges are effective from 10−3 Torr to 10−4 Torr.

Thermal conductivity gauges rely on the fact that the ability of a gas to conduct heat decreases with pressure. In this type of gauge, a wire filament is heated by running current through it. A thermocouple or Resistance Temperature Detector (RTD) can then be used to measure the temperature of the filament. This temperature is dependent on the rate at which the filament loses heat to the surrounding gas, and therefore on the thermal conductivity. A common variant is the Pirani gauge which uses a single platimum filament as both the heated element and RTD. These gauges are accurate from 10 Torr to 10−3 Torr, but they are sensitive to the chemical composition of the gases being measured. In electronics, thermocouples are a widely used type of temperature sensor and can also be used as a means to convert thermal potential difference into electric potential difference. ... A resistance temperature detector measures the relationship between electrical resistance and temperature. ...

Ion gauges are used in ultrahigh vacuum. They come in two types: hot cathode and cold cathode. In the hot cathode version an electrically heated filament produces an electron beam. The electrons travel through the gauge and ionize gas molecules around them. The resulting ions are collected at a negative electrode. The current depends on the number of ions, which depends on the pressure in the gauge. Hot cathode gauges are accurate from 10−3 Torr to 10−10 Torr. The principle behind cold cathode version is the same, except that electrons are produced in a discharge created by a high voltage electrical discharge. Cold cathode gauges are accurate from 10−2 Torr to 10−9 Torr. Ionization gauge calibration is very sensitive to construction geometry, chemical composition of gases being measured, corrosion and surface deposits. Their calibration can be invalidated by activation at atmospheric pressure or low vacuum. The composition of gases at high vacuums will usually be unpredictable, so a mass spectrometer must be used in conjunction with the ionization gauge for accurate measurement.[20] An ionization gauge, or ion gauge, is a manometer that is used to measure the negative pressure of vacuum, high vacuum, and ultra-high vacuum (UHV). ... Note: Principals are mostly the same for hot cathode ion sources in particle accelerators to create electrons The Hot filament ionization gauge sometimes called a hot filament and hot cathode , is the most widely used vacuum (negative pressure) measuring device for the region from 10-1 to 10-9 pascals. ... Note: Principles are mostly the same for cold cathode ion sources as in particle accelerators to create electrons. ...

## Properties

Many properties of space approach non-zero values in a vacuum that approaches perfection. These ideal physical constants are often called free space constants. Some of the common ones are as follows:

The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic radiation, including visible light, in a vacuum. ... The refractive index of a material is the factor by which electromagnetic radiation is slowed down (relative to vacuum) when it travels inside the material. ... Permittivity is a physical quantity that describes how an electric field affects and is affected by a medium. ... Examples of various types of capacitors. ... The metre, or meter (symbol: m) is the SI base unit of length. ... This article is in need of attention. ... The characteristic impedance of a uniform transmission line is the ratio of the amplitudes of a single pair of voltage and current waves propagating along the line in the absence of reflections. ...

## Notes

1. ^ Billings, Charles E. (1973). "Barometric Pressure", in edited by James F. Parker and Vita R. West: Bioastronautics Data Book, Second Edition, NASA. NASA SP-3006.
2. ^ Human Exposure to Vacuum. Retrieved on 2006-03-25.
3. ^ Webb P. (1968). "The Space Activity Suit: An Elastic Leotard for Extravehicular Activity". Aerospace Medicine 39: 376–383.
4. ^ Cooke JP, RW Bancroft (1966). "Some Cardiovascular Responses in Anesthetized Dogs During Repeated Decompressions to a Near-Vacuum". Aerospace Medicine 37: 1148–1152.
5. ^ Czarnik, Tamarack R.. EBULLISM AT 1 MILLION FEET: Surviving Rapid/Explosive Decompression. Retrieved on 2006-03-25.
6. ^ Zahoor. Muslim History.
7. ^ http://plato.stanford.edu/entries/arabic-islamic-natural/
8. ^ a b Barrow, John D. (2000). The book of nothing : vacuums, voids, and the latest ideas about the origins of the universe, 1st American Ed., New York: Pantheon Books. ISBN 0-09-928845-1.
9. ^ R. H. Patterson, Ess. Hist. & Art 10 1862
10. ^ William Crookes, The Chemical News and Journal of Industrial Science; with which is Incorporated the "Chemical Gazette." (1932)
11. ^ Pickering, W. H., "Solar system, the motion of the, relatively to the intersteller absorbing medium" (1912) Monthly Notices of the Royal Astronomical Society 72: 740
12. ^ French Wikipedia article on Vacuum, citing appendix 5 of Relativity - the Special and General Theory, translated to French by Robert Lawson, 1961. (Please replace this with a more direct reference.)
13. ^ Einstein, A., Naturwissenschaften 6, 697-702 (1918)
14. ^ Ishimaru, H (1989). "Ultimate Pressure of the Order of 10-13 Torr in an Aluminum Alloy Vacuum Chamber". J. Vac. Sci. Technol. 7 (3-II): 2439–2442.
15. ^ University of New Hampshire Experimental Space Plasma Group. What is the Interstellar Medium. The Interstellar Medium, an online tutorial. Retrieved on 2006-03-15.
16. ^ American Vacuum Society. Glossary. AVS Reference Guide. Retrieved on 2006-03-15.
17. ^ National Physical Laboratory, UK. FAQ on Pressure and Vacuum. Retrieved on 2006-03-25.
18. ^ John H., Moore; Christopher Davis, Michael A. Coplan and Sandra Greer (2002). Building Scientific Apparatus. Boulder, CO: Westview Press. ISBN 0-8133-4007-1.
19. ^ Beckwith, Thomas G.; Roy D. Marangoni and John H. Lienhard V (1993). "Measurement of Low Pressures", Mechanical Measurements, Fifth Edition, Reading, MA: Addison-Wesley, 591-595. ISBN 0-201-56947-7.
20. ^ "Vacuum Techniques". The Encyclopedia of Physics (3rd edition). (1990). Ed. Robert M. Besançon. Van Nostrand Reinhold, New York. pp. 1278-1284. ISBN 0-442-00522-9.

Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 84th day of the year (85th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 84th day of the year (85th in leap years) in the Gregorian calendar. ... John David Barrow FRS (born November 29, 1952, London) is an English cosmologist, theoretical physicist, and mathematician. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 74th day of the year (75th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 74th day of the year (75th in leap years) in the Gregorian calendar. ... The National Physical Laboratory (NPL) is the national measurement standards laboratory for the United Kingdom, based at Bushy Park in Teddington in the London Borough of Richmond upon Thames. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 84th day of the year (85th in leap years) in the Gregorian calendar. ...

Pair production refers to the creation of an elementary particle and its antiparticle, usually from a photon (or neutral bosonic fields). ... Pair production refers to the creation of an elementary particle and its antiparticle, usually from a photon (or another neutral boson). ... A Helium mass spectrometer (often called a leak detector) or sniffer, is a scientific instrument, used to detect very small leaks, typically using a vacuum and injecting helium around a chamber or cavity. ... Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engines intake manifold and Earths atmosphere. ... For sound waves in an enclosure, the mean free path is the average distance the wave travels between reflections off of the enclosures walls. ... Pressure is defined in terms of a force applied over an area. ... Rarefaction is the reduction of a mediums density, or the opposite of compression. ... Suction is the creation of a partial vacuum, or region of low pressure. ... Vacuum cementing (also called vacuum welding) is the natural process of solidifying small objects in a hard vacuum. ... Vacuum engineering deals with technological processes and equipment that use vacuum to achieve better results than those run under atmospheric pressure. ... In quantum gauge theories, in the Hamiltonian formulation, the wave function is a functional of the gauge connection A and matter fields Ï†. Being a quantum gauge theory, we have to impose first class constraints in the form of functional differential equations. ... A vacuum flange is a flange at the end of a tube used to connect vacuum containing vessels, tubing and vacuum pumps to each other. ...

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