174-425: Helium (from Greek : ἥλιος , romanized : helios , lit. 'sun') is a chemical element ; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert , monatomic gas and the first in the noble gas group in the periodic table . Its boiling point is the lowest among all the elements , and it does not have a melting point at standard pressures. It
348-561: A Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the world's oldest recorded living language . Among the Indo-European languages, its date of earliest written attestation is matched only by the now-extinct Anatolian languages . The Greek language is conventionally divided into the following periods: In the modern era, the Greek language entered
522-446: A diamond anvil cell . The insulating electride Na 2 He has been shown to be thermodynamically stable at pressures above 113 GPa. It has a fluorite structure. Greek language Greek ( Modern Greek : Ελληνικά , romanized : Elliniká , [eliniˈka] ; Ancient Greek : Ἑλληνική , romanized : Hellēnikḗ ) is an Indo-European language, constituting an independent Hellenic branch within
696-540: A nuclear halo . Table of thermal and physical properties of helium gas at atmospheric pressure: Helium has a valence of zero and is chemically unreactive under all normal conditions. It is an electrical insulator unless ionized . As with the other noble gases, helium has metastable energy levels that allow it to remain ionized in an electrical discharge with a voltage below its ionization potential . Helium can form unstable compounds , known as excimers , with tungsten, iodine, fluorine, sulfur, and phosphorus when it
870-412: A nucleus of protons and neutrons , and a surrounding "cloud" of orbiting electrons which "take up space". However, this is only somewhat correct because subatomic particles and their properties are governed by their quantum nature , which means they do not act as everyday objects appear to act – they can act like waves as well as particles , and they do not have well-defined sizes or positions. In
1044-491: A quantity of matter . As such, there is no single universally agreed scientific meaning of the word "matter". Scientifically, the term "mass" is well-defined, but "matter" can be defined in several ways. Sometimes in the field of physics "matter" is simply equated with particles that exhibit rest mass (i.e., that cannot travel at the speed of light), such as quarks and leptons. However, in both physics and chemistry , matter exhibits both wave -like and particle -like properties,
1218-427: A solar eclipse in 1868 by Georges Rayet , Captain C. T. Haig, Norman R. Pogson , and Lieutenant John Herschel, and was subsequently confirmed by French astronomer Jules Janssen . Janssen is often jointly credited with detecting the element, along with Norman Lockyer . Janssen recorded the helium spectral line during the solar eclipse of 1868, while Lockyer observed it from Britain. However, only Lockyer proposed that
1392-439: A superfluid phase, but only at much lower temperatures; as a result, less is known about the properties of the isotope. Helium II is a superfluid, a quantum mechanical state of matter with strange properties. For example, when it flows through capillaries as thin as 10 to 100 nm it has no measurable viscosity . However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium
1566-430: A baryon, is given a baryon number of 1/3. So the net amount of matter, as measured by the number of quarks (minus the number of antiquarks, which each have a baryon number of −1/3), which is proportional to baryon number, and number of leptons (minus antileptons), which is called the lepton number, is practically impossible to change in any process. Even in a nuclear bomb, none of the baryons (protons and neutrons of which
1740-570: A basis for coinages: anthropology , photography , telephony , isomer , biomechanics , cinematography , etc. Together with Latin words , they form the foundation of international scientific and technical vocabulary ; for example, all words ending in -logy ('discourse'). There are many English words of Greek origin . Greek is an independent branch of the Indo-European language family. The ancient language most closely related to it may be ancient Macedonian , which, by most accounts,
1914-635: A charge of −1 e . They also carry colour charge , which is the equivalent of the electric charge for the strong interaction . Quarks also undergo radioactive decay , meaning that they are subject to the weak interaction . Baryons are strongly interacting fermions, and so are subject to Fermi–Dirac statistics. Amongst the baryons are the protons and neutrons, which occur in atomic nuclei, but many other unstable baryons exist as well. The term baryon usually refers to triquarks—particles made of three quarks. Also, "exotic" baryons made of four quarks and one antiquark are known as pentaquarks , but their existence
SECTION 10
#17330925782392088-623: A desired degree, the resulting substance is said to be chemically pure . Chemical substances can exist in several different physical states or phases (e.g. solids , liquids , gases , or plasma ) without changing their chemical composition. Substances transition between these phases of matter in response to changes in temperature or pressure . Some chemical substances can be combined or converted into new substances by means of chemical reactions . Chemicals that do not possess this ability are said to be inert . A definition of "matter" based on its physical and chemical structure is: matter
2262-441: A distance from other particles under everyday conditions; this creates the property of matter which appears to us as matter taking up space. For much of the history of the natural sciences , people have contemplated the exact nature of matter. The idea that matter was built of discrete building blocks, the so-called particulate theory of matter , appeared in both ancient Greece and ancient India . Early philosophers who proposed
2436-508: A faster, more convenient cursive writing style with the use of ink and quill . The Greek alphabet consists of 24 letters, each with an uppercase ( majuscule ) and lowercase ( minuscule ) form. The letter sigma has an additional lowercase form (ς) used in the final position of a word: In addition to the letters, the Greek alphabet features a number of diacritical signs : three different accent marks ( acute , grave , and circumflex ), originally denoting different shapes of pitch accent on
2610-417: A few millikelvins. It is possible to produce exotic helium isotopes , which rapidly decay into other substances. The shortest-lived heavy helium isotope is the unbound helium-10 with a half-life of 2.6(4) × 10 s . Helium-6 decays by emitting a beta particle and has a half-life of 0.8 second. Helium-7 and helium-8 are created in certain nuclear reactions . Helium-6 and helium-8 are known to exhibit
2784-443: A few of its theoretical properties. There is considerable speculation both in science and science fiction as to why the observable universe is apparently almost entirely matter (in the sense of quarks and leptons but not antiquarks or antileptons), and whether other places are almost entirely antimatter (antiquarks and antileptons) instead. In the early universe, it is thought that matter and antimatter were equally represented, and
2958-521: A gas-like index of refraction of 1.026 which makes its surface so hard to see that floats of Styrofoam are often used to show where the surface is. This colorless liquid has a very low viscosity and a density of 0.145–0.125 g/mL (between about 0 and 4 K), which is only one-fourth the value expected from classical physics . Quantum mechanics is needed to explain this property and thus both states of liquid helium (helium I and helium II) are called quantum fluids , meaning they display atomic properties on
3132-469: A helium-oxygen bond could be stable. Two new molecular species, predicted using theory, CsFHeO and N(CH 3 ) 4 FHeO, are derivatives of a metastable FHeO anion first theorized in 2005 by a group from Taiwan. Helium atoms have been inserted into the hollow carbon cage molecules (the fullerenes ) by heating under high pressure. The endohedral fullerene molecules formed are stable at high temperatures. When chemical derivatives of these fullerenes are formed,
3306-573: A lesser extent, in the Western Mediterranean in and around colonies such as Massalia , Monoikos , and Mainake . It was also used as the official language of government and religion in the Christian Nubian kingdoms , for most of their history. Greek, in its modern form, is the official language of Greece, where it is spoken by almost the entire population. It is also the official language of Cyprus (nominally alongside Turkish ) and
3480-400: A limited but productive system of compounding and a rich inflectional system. Although its morphological categories have been fairly stable over time, morphological changes are present throughout, particularly in the nominal and verbal systems. The major change in the nominal morphology since the classical stage was the disuse of the dative case (its functions being largely taken over by
3654-409: A lower boiling point, can achieve about 0.2 kelvin in a helium-3 refrigerator . Equal mixtures of liquid He and He below 0.8 K separate into two immiscible phases due to their dissimilarity (they follow different quantum statistics : helium-4 atoms are bosons while helium-3 atoms are fermions ). Dilution refrigerators use this immiscibility to achieve temperatures of
SECTION 20
#17330925782393828-433: A macroscopic scale. This may be an effect of its boiling point being so close to absolute zero, preventing random molecular motion ( thermal energy ) from masking the atomic properties. Liquid helium below its lambda point (called helium II ) exhibits very unusual characteristics. Due to its high thermal conductivity , when it boils, it does not bubble but rather evaporates directly from its surface. Helium-3 also has
4002-453: A mixed syllable structure, permitting complex syllabic onsets but very restricted codas. It has only oral vowels and a fairly stable set of consonantal contrasts . The main phonological changes occurred during the Hellenistic and Roman period (see Koine Greek phonology for details): In all its stages, the morphology of Greek shows an extensive set of productive derivational affixes ,
4176-458: A negative Joule–Thomson coefficient at normal ambient temperatures, meaning it heats up when allowed to freely expand. Only below its Joule–Thomson inversion temperature (of about 32 to 50 K at 1 atmosphere) does it cool upon free expansion. Once precooled below this temperature, helium can be liquefied through expansion cooling. Most extraterrestrial helium is plasma in stars, with properties quite different from those of atomic helium. In
4350-514: A phenomenon now called superfluidity . This phenomenon is related to Bose–Einstein condensation . In 1972, the same phenomenon was observed in helium-3 , but at temperatures much closer to absolute zero, by American physicists Douglas D. Osheroff , David M. Lee , and Robert C. Richardson . The phenomenon in helium-3 is thought to be related to pairing of helium-3 fermions to make bosons , in analogy to Cooper pairs of electrons producing superconductivity . In 1961, Vignos and Fairbank reported
4524-590: A plasma, helium's electrons are not bound to its nucleus, resulting in very high electrical conductivity, even when the gas is only partially ionized. The charged particles are highly influenced by magnetic and electric fields. For example, in the solar wind together with ionized hydrogen, the particles interact with the Earth's magnetosphere , giving rise to Birkeland currents and the aurora . Helium liquifies when cooled below 4.2 K at atmospheric pressure. Unlike any other element, however, helium remains liquid down to
4698-424: A rate three times that of air and around 65% that of hydrogen. Helium is the least water- soluble monatomic gas, and one of the least water-soluble of any gas ( CF 4 , SF 6 , and C 4 F 8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x 2 /10, respectively, versus helium's 0.70797 x 2 /10), and helium's index of refraction is closer to unity than that of any other gas. Helium has
4872-445: A result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, it is very difficult to confine. Unless the container is carefully constructed, the helium II will creep along the surfaces and through valves until it reaches somewhere warmer, where it will evaporate. Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity,
5046-516: A sea of degenerate electrons. At a microscopic level, the constituent "particles" of matter such as protons, neutrons, and electrons obey the laws of quantum mechanics and exhibit wave–particle duality. At an even deeper level, protons and neutrons are made up of quarks and the force fields ( gluons ) that bind them together, leading to the next definition. As seen in the above discussion, many early definitions of what can be called "ordinary matter" were based upon its structure or "building blocks". On
5220-456: A state of diglossia : the coexistence of vernacular and archaizing written forms of the language. What came to be known as the Greek language question was a polarization between two competing varieties of Modern Greek: Dimotiki , the vernacular form of Modern Greek proper, and Katharevousa , meaning 'purified', a compromise between Dimotiki and Ancient Greek developed in the early 19th century that
5394-426: A subclass of matter. A common or traditional definition of matter is "anything that has mass and volume (occupies space )". For example, a car would be said to be made of matter, as it has mass and volume (occupies space). The observation that matter occupies space goes back to antiquity. However, an explanation for why matter occupies space is recent, and is argued to be a result of the phenomenon described in
Helium - Misplaced Pages Continue
5568-460: A surface extends past the level of helium II, the helium II moves along the surface, against the force of gravity . Helium II will escape from a vessel that is not sealed by creeping along the sides until it reaches a warmer region where it evaporates. It moves in a 30 nm-thick film regardless of surface material. This film is called a Rollin film and is named after the man who first characterized this trait, Bernard V. Rollin . As
5742-472: A temperature near absolute zero. The Pauli exclusion principle requires that only two fermions can occupy a quantum state, one spin-up and the other spin-down. Hence, at zero temperature, the fermions fill up sufficient levels to accommodate all the available fermions—and in the case of many fermions, the maximum kinetic energy (called the Fermi energy ) and the pressure of the gas becomes very large, and depends on
5916-449: A temperature of absolute zero . This is a direct effect of quantum mechanics: specifically, the zero point energy of the system is too high to allow freezing. Pressures above about 25 atmospheres are required to freeze it. There are two liquid phases: Helium I is a conventional liquid, and Helium II, which occurs at a lower temperature, is a superfluid . Below its boiling point of 4.22 K (−268.93 °C; −452.07 °F) and above
6090-508: A total solar eclipse in Guntur , India. This line was initially assumed to be sodium . On October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in the solar spectrum, which he named the D 3 because it was near the known D 1 and D 2 Fraunhofer lines of sodium. He concluded that it was caused by an element in the Sun unknown on Earth. Lockyer named the element with
6264-462: A γ phase, which is body-centered cubic (bcc). There are nine known isotopes of helium of which two, helium-3 and helium-4 , are stable . In the Earth's atmosphere, one atom is He for every million that are He . Unlike most elements, helium's isotopic abundance varies greatly by origin, due to the different formation processes. The most common isotope, helium-4, is produced on Earth by alpha decay of heavier radioactive elements;
6438-400: Is 0.187 ± 0.009 g/cm . At higher temperatures, helium will solidify with sufficient pressure. At room temperature, this requires about 114,000 atm. Helium-4 and helium-3 both form several crystalline solid phases, all requiring at least 25 bar. They both form an α phase, which has a hexagonal close-packed (hcp) crystal structure, a β phase, which is face-centered cubic (fcc), and
6612-934: Is any substance that has mass and takes up space by having volume . All everyday objects that can be touched are ultimately composed of atoms , which are made up of interacting subatomic particles , and in everyday as well as scientific usage, matter generally includes atoms and anything made up of them, and any particles (or combination of particles ) that act as if they have both rest mass and volume . However it does not include massless particles such as photons , or other energy phenomena or waves such as light or heat . Matter exists in various states (also known as phases ). These include classical everyday phases such as solid , liquid , and gas – for example water exists as ice , liquid water, and gaseous steam – but other states are possible, including plasma , Bose–Einstein condensates , fermionic condensates , and quark–gluon plasma . Usually atoms can be imagined as
6786-405: Is approximately 12.5 MeV/ c , which is low compared to the mass of a nucleon (approximately 938 MeV/ c ). The bottom line is that most of the mass of everyday objects comes from the interaction energy of its elementary components. The Standard Model groups matter particles into three generations, where each generation consists of two quarks and two leptons. The first generation
6960-399: Is constructed which is connected to a reservoir of helium II by a sintered disc through which superfluid helium leaks easily but through which non-superfluid helium cannot pass. If the interior of the container is heated, the superfluid helium changes to non-superfluid helium. In order to maintain the equilibrium fraction of superfluid helium, superfluid helium leaks through and increases
7134-631: Is expected to be color superconducting . Strange matter is hypothesized to occur in the core of neutron stars , or, more speculatively, as isolated droplets that may vary in size from femtometers ( strangelets ) to kilometers ( quark stars ). In particle physics and astrophysics , the term is used in two ways, one broader and the other more specific. Leptons are particles of spin- 1 ⁄ 2 , meaning that they are fermions . They carry an electric charge of −1 e (charged leptons) or 0 e (neutrinos). Unlike quarks, leptons do not carry colour charge , meaning that they do not experience
Helium - Misplaced Pages Continue
7308-400: Is made up of atoms . Such atomic matter is also sometimes termed ordinary matter . As an example, deoxyribonucleic acid molecules (DNA) are matter under this definition because they are made of atoms. This definition can be extended to include charged atoms and molecules, so as to include plasmas (gases of ions) and electrolytes (ionic solutions), which are not obviously included in
7482-455: Is made up of neutron stars and white dwarfs. Strange matter is a particular form of quark matter , usually thought of as a liquid of up , down , and strange quarks. It is contrasted with nuclear matter , which is a liquid of neutrons and protons (which themselves are built out of up and down quarks), and with non-strange quark matter, which is a quark liquid that contains only up and down quarks. At high enough density, strange matter
7656-485: Is more subtle than it first appears. All the particles that make up ordinary matter (leptons and quarks) are elementary fermions, while all the force carriers are elementary bosons. The W and Z bosons that mediate the weak force are not made of quarks or leptons, and so are not ordinary matter, even if they have mass. In other words, mass is not something that is exclusive to ordinary matter. The quark–lepton definition of ordinary matter, however, identifies not only
7830-436: Is natural to phrase the definition as: "ordinary matter is anything that is made of the same things that atoms and molecules are made of". (However, notice that one also can make from these building blocks matter that is not atoms or molecules.) Then, because electrons are leptons, and protons and neutrons are made of quarks, this definition in turn leads to the definition of matter as being "quarks and leptons", which are two of
8004-412: Is no exception. Thus, numerical mathematical methods are required, even to solve the system of one nucleus and two electrons. Such computational chemistry methods have been used to create a quantum mechanical picture of helium electron binding which is accurate to within < 2% of the correct value, in a few computational steps. Such models show that each electron in helium partly screens the nucleus from
8178-429: Is no such thing as "anti-mass" or negative mass , so far as is known, although scientists do discuss the concept. Antimatter has the same (i.e. positive) mass property as its normal matter counterpart. Different fields of science use the term matter in different, and sometimes incompatible, ways. Some of these ways are based on loose historical meanings from a time when there was no reason to distinguish mass from simply
8352-480: Is not a substance but rather a quantitative property of matter and other substances or systems; various types of mass are defined within physics – including but not limited to rest mass , inertial mass , relativistic mass , mass–energy . While there are different views on what should be considered matter, the mass of a substance has exact scientific definitions. Another difference is that matter has an "opposite" called antimatter , but mass has no opposite—there
8526-429: Is not generally accepted. Baryonic matter is the part of the universe that is made of baryons (including all atoms). This part of the universe does not include dark energy , dark matter , black holes or various forms of degenerate matter, such as those that compose white dwarf stars and neutron stars . Microwave light seen by Wilkinson Microwave Anisotropy Probe (WMAP) suggests that only about 4.6% of that part of
8700-472: Is produced in fusion reactions from hydrogen, though its estimated abundance in the universe is about 10 relative to helium-4. The unusual stability of the helium-4 nucleus is also important cosmologically : it explains the fact that in the first few minutes after the Big Bang , as the "soup" of free protons and neutrons which had initially been created in about 6:1 ratio cooled to the point that nuclear binding
8874-800: Is sometimes called aljamiado , as when Romance languages are written in the Arabic alphabet. Article 1 of the Universal Declaration of Human Rights in Greek: Transcription of the example text into Latin alphabet : Article 1 of the Universal Declaration of Human Rights in English: Proto-Greek Mycenaean Ancient Koine Medieval Modern Matter In classical physics and general chemistry , matter
SECTION 50
#17330925782399048-758: Is still used internationally for the writing of Ancient Greek . In Greek, the question mark is written as the English semicolon, while the functions of the colon and semicolon are performed by a raised point (•), known as the ano teleia ( άνω τελεία ). In Greek the comma also functions as a silent letter in a handful of Greek words, principally distinguishing ό,τι ( ó,ti , 'whatever') from ότι ( óti , 'that'). Ancient Greek texts often used scriptio continua ('continuous writing'), which means that ancient authors and scribes would write word after word with no spaces or punctuation between words to differentiate or mark boundaries. Boustrophedon , or bi-directional text,
9222-518: Is subjected to a glow discharge , to electron bombardment, or reduced to plasma by other means. The molecular compounds HeNe, HgHe 10 , and WHe 2 , and the molecular ions He 2 , He 2 , HeH , and HeD have been created this way. HeH is also stable in its ground state but is extremely reactive—it is the strongest Brønsted acid known, and therefore can exist only in isolation, as it will protonate any molecule or counteranion it contacts. This technique has also produced
9396-403: Is the up and down quarks, the electron and the electron neutrino ; the second includes the charm and strange quarks, the muon and the muon neutrino ; the third generation consists of the top and bottom quarks and the tau and tau neutrino . The most natural explanation for this would be that quarks and leptons of higher generations are excited states of
9570-465: Is the second least reactive noble gas after neon , and thus the second least reactive of all elements. It is chemically inert and monatomic in all standard conditions. Because of helium's relatively low molar (atomic) mass, its thermal conductivity , specific heat , and sound speed in the gas phase are all greater than any other gas except hydrogen . For these reasons and the small size of helium monatomic molecules, helium diffuses through solids at
9744-444: Is the second-lightest and second most abundant element in the observable universe , after hydrogen . It is present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this in both the Sun and Jupiter , because of the very high nuclear binding energy (per nucleon ) of helium-4 , with respect to
9918-414: Is thus energetically extremely stable for all these particles and has astrophysical implications. Namely, adding another particle – proton, neutron, or alpha particle – would consume rather than release energy; all systems with mass number 5, as well as beryllium-8 (comprising two alpha particles), are unbound. For example, the stability and low energy of the electron cloud state in helium accounts for
10092-611: Is to modern spoken English ". Greek is spoken today by at least 13 million people, principally in Greece and Cyprus along with a sizable Greek-speaking minority in Albania near the Greek-Albanian border. A significant percentage of Albania's population has knowledge of the Greek language due in part to the Albanian wave of immigration to Greece in the 1980s and '90s and the Greek community in
10266-419: Is trapped with natural gas in concentrations as great as 7% by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation . Terrestrial helium is a non-renewable resource because once released into the atmosphere, it promptly escapes into space . Its supply is thought to be rapidly diminishing. However, some studies suggest that helium produced deep in
10440-399: The 2017 Qatar diplomatic crisis severely affected helium production there. 2014 was widely acknowledged to be a year of over-supply in the helium business, following years of renowned shortages. Nasdaq reported (2015) that for Air Products , an international corporation that sells gases for industrial use, helium volumes remain under economic pressure due to feedstock supply constraints. In
10614-524: The American Great Plains , available for extraction as a byproduct of natural gas . Following a suggestion by Sir Richard Threlfall , the United States Navy sponsored three small experimental helium plants during World War I. The goal was to supply barrage balloons with the non-flammable, lighter-than-air gas. A total of 5,700 m (200,000 cu ft) of 92% helium was produced in
SECTION 60
#173309257823910788-544: The British Overseas Territory of Akrotiri and Dhekelia (alongside English ). Because of the membership of Greece and Cyprus in the European Union, Greek is one of the organization's 24 official languages . Greek is recognized as a minority language in Albania, and used co-officially in some of its municipalities, in the districts of Gjirokastër and Sarandë . It is also an official minority language in
10962-637: The European canon . Greek is also the language in which many of the foundational texts in science and philosophy were originally composed. The New Testament of the Christian Bible was also originally written in Greek. Together with the Latin texts and traditions of the Roman world , the Greek texts and Greek societies of antiquity constitute the objects of study of the discipline of Classics . During antiquity , Greek
11136-654: The Hindenburg disaster . The helium market after World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen/hydrogen rocket fuel (among other uses) during the Space Race and Cold War . Helium use in the United States in 1965 was more than eight times the peak wartime consumption. After the Helium Acts Amendments of 1960 (Public Law 86–777),
11310-510: The Indo-Iranian languages (see Graeco-Aryan ), but little definitive evidence has been found. In addition, Albanian has also been considered somewhat related to Greek and Armenian, and it has been proposed that they all form a higher-order subgroup along with other extinct languages of the ancient Balkans; this higher-order subgroup is usually termed Palaeo-Balkan , and Greek has a central position in it. Linear B , attested as early as
11484-473: The Pauli exclusion principle , which applies to fermions . Two particular examples where the exclusion principle clearly relates matter to the occupation of space are white dwarf stars and neutron stars, discussed further below. Thus, matter can be defined as everything composed of elementary fermions. Although we do not encounter them in everyday life, antiquarks (such as the antiproton ) and antileptons (such as
11658-492: The Standard Model of particle physics , matter is not a fundamental concept because the elementary constituents of atoms are quantum entities which do not have an inherent "size" or " volume " in any everyday sense of the word. Due to the exclusion principle and other fundamental interactions , some " point particles " known as fermions ( quarks , leptons ), and many composites and atoms, are effectively forced to keep
11832-527: The U.S. Bureau of Mines arranged for five private plants to recover helium from natural gas. For this helium conservation program, the Bureau built a 425-mile (684 km) pipeline from Bushton, Kansas , to connect those plants with the government's partially depleted Cliffside gas field near Amarillo, Texas. This helium-nitrogen mixture was injected and stored in the Cliffside gas field until needed, at which time it
12006-747: The United Kingdom , and throughout the European Union , especially in Germany . Historically, significant Greek-speaking communities and regions were found throughout the Eastern Mediterranean , in what are today Southern Italy , Turkey , Cyprus , Syria , Lebanon , Israel , Palestine , Egypt , and Libya ; in the area of the Black Sea , in what are today Turkey, Bulgaria , Romania , Ukraine , Russia , Georgia , Armenia , and Azerbaijan ; and, to
12180-621: The beta decay of tritium . Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten, and these ratios can be used to investigate the origin of rocks and the composition of the Earth's mantle . He is much more abundant in stars as a product of nuclear fusion. Thus in the interstellar medium , the proportion of He to He is about 100 times higher than on Earth. Extraplanetary material, such as lunar and asteroid regolith , have trace amounts of helium-3 from being bombarded by solar winds . The Moon 's surface contains helium-3 at concentrations on
12354-570: The energy–momentum tensor that quantifies the amount of matter. This tensor gives the rest mass for the entire system. Matter, therefore, is sometimes considered as anything that contributes to the energy–momentum of a system, that is, anything that is not purely gravity. This view is commonly held in fields that deal with general relativity such as cosmology . In this view, light and other massless particles and fields are all part of matter. In particle physics, fermions are particles that obey Fermi–Dirac statistics . Fermions can be elementary, like
12528-468: The genitive ). The verbal system has lost the infinitive , the synthetically -formed future, and perfect tenses and the optative mood . Many have been replaced by periphrastic ( analytical ) forms. Pronouns show distinctions in person (1st, 2nd, and 3rd), number (singular, dual , and plural in the ancient language; singular and plural alone in later stages), and gender (masculine, feminine, and neuter), and decline for case (from six cases in
12702-412: The lambda point of 2.1768 K (−270.9732 °C; −455.7518 °F), the isotope helium-4 exists in a normal colorless liquid state, called helium I . Like other cryogenic liquids, helium I boils when it is heated and contracts when its temperature is lowered. Below the lambda point, however, helium does not boil, and it expands as the temperature is lowered further. Helium I has
12876-631: The laws of nature . They coupled their ideas of soul, or lack thereof, into their theory of matter. The strongest developers and defenders of this theory were the Nyaya - Vaisheshika school, with the ideas of the Indian philosopher Kanada being the most followed. Buddhist philosophers also developed these ideas in late 1st-millennium CE, ideas that were similar to the Vaisheshika school, but ones that did not include any soul or conscience. Jain philosophers included
13050-552: The positron ) are the antiparticles of the quark and the lepton, are elementary fermions as well, and have essentially the same properties as quarks and leptons, including the applicability of the Pauli exclusion principle which can be said to prevent two particles from being in the same place at the same time (in the same state), i.e. makes each particle "take up space". This particular definition leads to matter being defined to include anything made of these antimatter particles as well as
13224-566: The soul ( jiva ), adding qualities such as taste, smell, touch, and color to each atom. They extended the ideas found in early literature of the Hindus and Buddhists by adding that atoms are either humid or dry, and this quality cements matter. They also proposed the possibility that atoms combine because of the attraction of opposites, and the soul attaches to these atoms, transforms with karma residue, and transmigrates with each rebirth . In ancient Greece , pre-Socratic philosophers speculated
13398-551: The strong interaction . Leptons also undergo radioactive decay, meaning that they are subject to the weak interaction . Leptons are massive particles, therefore are subject to gravity. In bulk , matter can exist in several different forms, or states of aggregation, known as phases , depending on ambient pressure , temperature and volume . A phase is a form of matter that has a relatively uniform chemical composition and physical properties (such as density , specific heat , refractive index , and so forth). These phases include
13572-417: The syntax of Greek have remained constant: verbs agree with their subject only, the use of the surviving cases is largely intact (nominative for subjects and predicates, accusative for objects of most verbs and many prepositions, genitive for possessors), articles precede nouns, adpositions are largely prepositional, relative clauses follow the noun they modify and relative pronouns are clause-initial. However,
13746-566: The 20th century on), especially from French and English, are typically not inflected; other modern borrowings are derived from Albanian , South Slavic ( Macedonian / Bulgarian ) and Eastern Romance languages ( Aromanian and Megleno-Romanian ). Greek words have been widely borrowed into other languages, including English. Example words include: mathematics , physics , astronomy , democracy , philosophy , athletics , theatre, rhetoric , baptism , evangelist , etc. Moreover, Greek words and word elements continue to be productive as
13920-408: The Earth by radioactive decay can collect in natural gas reserves in larger-than-expected quantities, in some cases having been released by volcanic activity. The first evidence of helium was observed on August 18, 1868, as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun . The line was detected by French astronomer Jules Janssen during
14094-460: The Earth, and for carbon-based or other life) have thus been created since the Big Bang in stars which were hot enough to fuse helium itself. All elements other than hydrogen and helium today account for only 2% of the mass of atomic matter in the universe. Helium-4, by contrast, comprises about 24% of the mass of the universe's ordinary matter—nearly all the ordinary matter that is not hydrogen. Helium
14268-538: The Greek alphabet since approximately the 9th century BC. It was created by modifying the Phoenician alphabet , with the innovation of adopting certain letters to represent the vowels. The variant of the alphabet in use today is essentially the late Ionic variant, introduced for writing classical Attic in 403 BC. In classical Greek, as in classical Latin, only upper-case letters existed. The lower-case Greek letters were developed much later by medieval scribes to permit
14442-540: The Greek language was the Cypriot syllabary (also a descendant of Linear A via the intermediate Cypro-Minoan syllabary ), which is closely related to Linear B but uses somewhat different syllabic conventions to represent phoneme sequences. The Cypriot syllabary is attested in Cyprus from the 11th century BC until its gradual abandonment in the late Classical period, in favor of the standard Greek alphabet. Greek has been written in
14616-446: The Greek word for the Sun, ἥλιος ( helios ). It is sometimes said that English chemist Edward Frankland was also involved in the naming, but this is unlikely as he doubted the existence of this new element. The ending "-ium" is unusual, as it normally applies only to metallic elements; probably Lockyer, being an astronomer, was unaware of the chemical conventions. In 1881, Italian physicist Luigi Palmieri detected helium on Earth for
14790-583: The Indo-European language family. It is native to Greece , Cyprus , Italy (in Calabria and Salento ), southern Albania , and other regions of the Balkans , Caucasus , the Black Sea coast, Asia Minor , and the Eastern Mediterranean . It has the longest documented history of any Indo-European language, spanning at least 3,400 years of written records. Its writing system is the Greek alphabet , which has been used for approximately 2,800 years; previously, Greek
14964-610: The United States set up the National Helium Reserve in 1925 at Amarillo, Texas , with the goal of supplying military airships in time of war and commercial airships in peacetime. Because of the Helium Act of 1925 , which banned the export of scarce helium on which the US then had a production monopoly, together with the prohibitive cost of the gas, German Zeppelins were forced to use hydrogen as lifting gas, which would gain infamy in
15138-522: The United States, by far the largest supplier of the gas today. Liquid helium is used in cryogenics (its largest single use, consuming about a quarter of production), and in the cooling of superconducting magnets , with its main commercial application in MRI scanners. Helium's other industrial uses—as a pressurizing and purge gas, as a protective atmosphere for arc welding , and in processes such as growing crystals to make silicon wafers —account for half of
15312-404: The acute during the late 20th century, and it has only been retained in typography . After the writing reform of 1982, most diacritics are no longer used. Since then, Greek has been written mostly in the simplified monotonic orthography (or monotonic system), which employs only the acute accent and the diaeresis. The traditional system, now called the polytonic orthography (or polytonic system),
15486-438: The alpha particles that emerge are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its nucleons are arranged into complete shells . It was also formed in enormous quantities during Big Bang nucleosynthesis . Helium-3 is present on Earth only in trace amounts. Most of it has been present since Earth's formation, though some falls to Earth trapped in cosmic dust . Trace amounts are also produced by
15660-410: The annihilation. In short, matter, as defined in physics, refers to baryons and leptons. The amount of matter is defined in terms of baryon and lepton number. Baryons and leptons can be created, but their creation is accompanied by antibaryons or antileptons; and they can be destroyed by annihilating them with antibaryons or antileptons. Since antibaryons/antileptons have negative baryon/lepton numbers,
15834-423: The antiparticle partners of one another. In October 2017, scientists reported further evidence that matter and antimatter , equally produced at the Big Bang , are identical, should completely annihilate each other and, as a result, the universe should not exist. This implies that there must be something, as yet unknown to scientists, that either stopped the complete mutual destruction of matter and antimatter in
16008-474: The arrival of Proto-Greeks, some documented in Mycenaean texts ; they include a large number of Greek toponyms . The form and meaning of many words have changed. Loanwords (words of foreign origin) have entered the language, mainly from Latin, Venetian , and Turkish . During the older periods of Greek, loanwords into Greek acquired Greek inflections, thus leaving only a foreign root word. Modern borrowings (from
16182-455: The atomic nuclei are composed) are destroyed—there are as many baryons after as before the reaction, so none of these matter particles are actually destroyed and none are even converted to non-matter particles (like photons of light or radiation). Instead, nuclear (and perhaps chromodynamic) binding energy is released, as these baryons become bound into mid-size nuclei having less energy (and, equivalently , less mass) per nucleon compared to
16356-650: The atoms definition. Alternatively, one can adopt the protons, neutrons, and electrons definition. A definition of "matter" more fine-scale than the atoms and molecules definition is: matter is made up of what atoms and molecules are made of , meaning anything made of positively charged protons , neutral neutrons , and negatively charged electrons . This definition goes beyond atoms and molecules, however, to include substances made from these building blocks that are not simply atoms or molecules, for example electron beams in an old cathode ray tube television, or white dwarf matter—typically, carbon and oxygen nuclei in
16530-765: The country. Prior to the Greco-Turkish War and the resulting population exchange in 1923 a very large population of Greek-speakers also existed in Turkey , though very few remain today. A small Greek-speaking community is also found in Bulgaria near the Greek-Bulgarian border. Greek is also spoken worldwide by the sizable Greek diaspora which has notable communities in the United States , Australia , Canada , South Africa , Chile , Brazil , Argentina , Russia , Ukraine ,
16704-441: The dative led to a rise of prepositional indirect objects (and the use of the genitive to directly mark these as well). Ancient Greek tended to be verb-final, but neutral word order in the modern language is VSO or SVO. Modern Greek inherits most of its vocabulary from Ancient Greek, which in turn is an Indo-European language, but also includes a number of borrowings from the languages of the populations that inhabited Greece before
16878-414: The difference between the rest mass of the products of the annihilation and the rest mass of the original particle–antiparticle pair, which is often quite large. Depending on which definition of "matter" is adopted, antimatter can be said to be a particular subclass of matter, or the opposite of matter. Antimatter is not found naturally on Earth, except very briefly and in vanishingly small quantities (as
17052-684: The disappearance of antimatter requires an asymmetry in physical laws called CP (charge–parity) symmetry violation , which can be obtained from the Standard Model, but at this time the apparent asymmetry of matter and antimatter in the visible universe is one of the great unsolved problems in physics . Possible processes by which it came about are explored in more detail under baryogenesis . Formally, antimatter particles can be defined by their negative baryon number or lepton number , while "normal" (non-antimatter) matter particles have positive baryon or lepton number. These two classes of particles are
17226-528: The earliest forms attested to four in the modern language). Nouns, articles, and adjectives show all the distinctions except for a person. Both attributive and predicative adjectives agree with the noun. The inflectional categories of the Greek verb have likewise remained largely the same over the course of the language's history but with significant changes in the number of distinctions within each category and their morphological expression. Greek verbs have synthetic inflectional forms for: Many aspects of
17400-399: The early forming universe, or that gave rise to an imbalance between the two forms. Two quantities that can define an amount of matter in the quark–lepton sense (and antimatter in an antiquark–antilepton sense), baryon number and lepton number , are conserved in the Standard Model. A baryon such as the proton or neutron has a baryon number of one, and a quark, because there are three in
17574-414: The early phase of the universe and still floating about. In cosmology , dark energy is the name given to the source of the repelling influence that is accelerating the rate of expansion of the universe . Its precise nature is currently a mystery, although its effects can reasonably be modeled by assigning matter-like properties such as energy density and pressure to the vacuum itself. Fully 70% of
17748-448: The early universe and the Big Bang theory require that this matter have energy and mass, but not be composed of ordinary baryons (protons and neutrons). The commonly accepted view is that most of the dark matter is non-baryonic in nature . As such, it is composed of particles as yet unobserved in the laboratory. Perhaps they are supersymmetric particles , which are not Standard Model particles but relics formed at very high energies in
17922-428: The electron—or composite, like the proton and neutron. In the Standard Model , there are two types of elementary fermions: quarks and leptons, which are discussed next. Quarks are massive particles of spin- 1 ⁄ 2 , implying that they are fermions . They carry an electric charge of − 1 ⁄ 3 e (down-type quarks) or + 2 ⁄ 3 e (up-type quarks). For comparison, an electron has
18096-446: The element's chemical inertness, and also the lack of interaction of helium atoms with each other, producing the lowest melting and boiling points of all the elements. In a similar way, the particular energetic stability of the helium-4 nucleus, produced by similar effects, accounts for the ease of helium-4 production in atomic reactions that involve either heavy-particle emission or fusion. Some stable helium-3 (two protons and one neutron)
18270-438: The elementary building blocks of matter, but also includes composites made from the constituents (atoms and molecules, for example). Such composites contain an interaction energy that holds the constituents together, and may constitute the bulk of the mass of the composite. As an example, to a great extent, the mass of an atom is simply the sum of the masses of its constituent protons, neutrons and electrons. However, digging deeper,
18444-504: The existence of a different phase of solid helium-4, designated the gamma-phase. It exists for a narrow range of pressure between 1.45 and 1.78 K. After an oil drilling operation in 1903 in Dexter, Kansas produced a gas geyser that would not burn, Kansas state geologist Erasmus Haworth collected samples of the escaping gas and took them back to the University of Kansas at Lawrence where, with
18618-412: The extent that one can speak of a new language emerging. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language. It is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, " Homeric Greek is probably closer to Demotic than 12-century Middle English
18792-429: The extraction process using low-temperature gas liquefaction was not developed in time to be significant during World War I, production continued. Helium was primarily used as a lifting gas in lighter-than-air craft. During World War II, the demand increased for helium for lifting gas and for shielded arc welding . The helium mass spectrometer was also vital in the atomic bomb Manhattan Project . The government of
18966-451: The few minutes after the Big Bang, before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible. This left the early universe with a very similar ratio of hydrogen/helium as is observed today (3 parts hydrogen to 1 part helium-4 by mass), with nearly all the neutrons in the universe trapped in helium-4. All heavier elements (including those necessary for rocky planets like
19140-518: The field of thermodynamics . In nanomaterials, the vastly increased ratio of surface area to volume results in matter that can exhibit properties entirely different from those of bulk material, and not well described by any bulk phase (see nanomaterials for more details). Phases are sometimes called states of matter , but this term can lead to confusion with thermodynamic states . For example, two gases maintained at different pressures are in different thermodynamic states (different pressures), but in
19314-447: The first generations. If this turns out to be the case, it would imply that quarks and leptons are composite particles , rather than elementary particles . This quark–lepton definition of matter also leads to what can be described as "conservation of (net) matter" laws—discussed later below. Alternatively, one could return to the mass–volume–space concept of matter, leading to the next definition, in which antimatter becomes included as
19488-435: The first time through its D 3 spectral line, when he analyzed a material that had been sublimated during a recent eruption of Mount Vesuvius . On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% rare-earth elements ) with mineral acids . Ramsay was looking for argon but, after separating nitrogen and oxygen from
19662-470: The four types of elementary fermions (the other two being antiquarks and antileptons, which can be considered antimatter as described later). Carithers and Grannis state: "Ordinary matter is composed entirely of first-generation particles, namely the [up] and [down] quarks, plus the electron and its neutrino." (Higher generations particles quickly decay into first-generation particles, and thus are not commonly encountered. ) This definition of ordinary matter
19836-408: The fractions of energy in the universe contributed by different sources. Ordinary matter is divided into luminous matter (the stars and luminous gases and 0.005% radiation) and nonluminous matter (intergalactic gas and about 0.1% neutrinos and 0.04% supermassive black holes). Ordinary matter is uncommon. Modeled after Ostriker and Steinhardt. For more information, see NASA . Ordinary matter, in
20010-431: The gas produced. A small but well-known use is as a lifting gas in balloons and airships . As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice . In scientific research, the behavior of the two fluid phases of helium-4 (helium I and helium II) is important to researchers studying quantum mechanics (in particular
20184-497: The gas, liberated by sulfuric acid , he noticed a bright yellow line that matched the D 3 line observed in the spectrum of the Sun. These samples were identified as helium by Lockyer and British physicist William Crookes . It was independently isolated from cleveite in the same year by chemists Per Teodor Cleve and Abraham Langlet in Uppsala , Sweden, who collected enough of the gas to accurately determine its atomic weight . Helium
20358-419: The heat. Helium II has no such valence band but nevertheless conducts heat well. The flow of heat is governed by equations that are similar to the wave equation used to characterize sound propagation in air. When heat is introduced, it moves at 20 meters per second at 1.8 K through helium II as waves in a phenomenon known as second sound . Helium II also exhibits a creeping effect. When
20532-565: The helium stays inside. If helium-3 is used, it can be readily observed by helium nuclear magnetic resonance spectroscopy . Many fullerenes containing helium-3 have been reported. Although the helium atoms are not attached by covalent or ionic bonds, these substances have distinct properties and a definite composition, like all stoichiometric chemical compounds. Under high pressures helium can form compounds with various other elements. Helium-nitrogen clathrate (He(N 2 ) 11 ) crystals have been grown at room temperature at pressures ca. 10 GPa in
20706-439: The help of chemists Hamilton Cady and David McFarland, he discovered that the gas consisted of, by volume, 72% nitrogen, 15% methane (a combustible percentage only with sufficient oxygen), 1% hydrogen , and 12% an unidentifiable gas. With further analysis, Cady and McFarland discovered that 1.84% of the gas sample was helium. This showed that despite its overall rarity on Earth, helium was concentrated in large quantities under
20880-449: The language show both conservative and innovative tendencies across the entire attestation of the language from the ancient to the modern period. The division into conventional periods is, as with all such periodizations, relatively arbitrary, especially because, in all periods, Ancient Greek has enjoyed high prestige, and the literate borrowed heavily from it. Across its history, the syllabic structure of Greek has varied little: Greek shows
21054-463: The late 15th century BC, was the first script used to write Greek. It is basically a syllabary , which was finally deciphered by Michael Ventris and John Chadwick in the 1950s (its precursor, Linear A , has not been deciphered and most likely encodes a non-Greek language). The language of the Linear B texts, Mycenaean Greek , is the earliest known form of Greek. Another similar system used to write
21228-436: The line was due to a new element, which he named after the Sun. The formal discovery of the element was made in 1895 by chemists Sir William Ramsay , Per Teodor Cleve , and Nils Abraham Langlet , who found helium emanating from the uranium ore cleveite , which is now not regarded as a separate mineral species, but as a variety of uraninite . In 1903, large reserves of helium were found in natural gas fields in parts of
21402-448: The many other countries of the Greek diaspora . Greek roots have been widely used for centuries and continue to be widely used to coin new words in other languages; Greek and Latin are the predominant sources of international scientific vocabulary . Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC, or possibly earlier. The earliest written evidence is
21576-414: The mass–energy density of the universe. Hadronic matter can refer to 'ordinary' baryonic matter, made from hadrons (baryons and mesons ), or quark matter (a generalisation of atomic nuclei), i.e. the 'low' temperature QCD matter . It includes degenerate matter and the result of high energy heavy nuclei collisions. In physics, degenerate matter refers to the ground state of a gas of fermions at
21750-545: The matter density in the universe appears to be in the form of dark energy. Twenty-six percent is dark matter. Only 4% is ordinary matter. So less than 1 part in 20 is made out of matter we have observed experimentally or described in the standard model of particle physics. Of the other 96%, apart from the properties just mentioned, we know absolutely nothing. Exotic matter is a concept of particle physics , which may include dark matter and dark energy but goes further to include any hypothetical material that violates one or more of
21924-512: The mid-1990s, a new plant in Arzew , Algeria, producing 17 million cubic metres (600 million cubic feet) began operation, with enough production to cover all of Europe's demand. Meanwhile, by 2000, the consumption of helium within the U.S. had risen to more than 15 million kg per year. In 2004–2006, additional plants in Ras Laffan , Qatar , and Skikda , Algeria were built. Algeria quickly became
22098-465: The morphological changes also have their counterparts in the syntax, and there are also significant differences between the syntax of the ancient and that of the modern form of the language . Ancient Greek made great use of participial constructions and of constructions involving the infinitive, and the modern variety lacks the infinitive entirely (employing a raft of new periphrastic constructions instead) and uses participles more restrictively. The loss of
22272-494: The neutral molecule He 2 , which has a large number of band systems , and HgHe, which is apparently held together only by polarization forces. Van der Waals compounds of helium can also be formed with cryogenic helium gas and atoms of some other substance, such as LiHe and He 2 . Theoretically, other true compounds may be possible, such as helium fluorohydride (HHeF), which would be analogous to HArF , discovered in 2000. Calculations show that two new compounds containing
22446-455: The next three elements after helium. This helium-4 binding energy also accounts for why it is a product of both nuclear fusion and radioactive decay . The most common isotope of helium in the universe is helium-4, the vast majority of which was formed during the Big Bang . Large amounts of new helium are created by nuclear fusion of hydrogen in stars . Helium was first detected as an unknown, yellow spectral line signature in sunlight during
22620-412: The number of fermions rather than the temperature, unlike normal states of matter. Degenerate matter is thought to occur during the evolution of heavy stars. The demonstration by Subrahmanyan Chandrasekhar that white dwarf stars have a maximum allowed mass because of the exclusion principle caused a revolution in the theory of star evolution. Degenerate matter includes the part of the universe that
22794-464: The order of 10 ppb , much higher than the approximately 5 ppt found in the Earth's atmosphere. A number of people, starting with Gerald Kulcinski in 1986, have proposed to explore the Moon, mine lunar regolith, and use the helium-3 for fusion . Liquid helium-4 can be cooled to about 1 K (−272.15 °C; −457.87 °F) using evaporative cooling in a 1-K pot . Similar cooling of helium-3, which has
22968-414: The ordinary quark and lepton, and thus also anything made of mesons , which are unstable particles made up of a quark and an antiquark. In the context of relativity , mass is not an additive quantity, in the sense that one cannot add the rest masses of particles in a system to get the total rest mass of the system. In relativity, usually a more general view is that it is not the sum of rest masses , but
23142-401: The original small (hydrogen) and large (plutonium etc.) nuclei. Even in electron–positron annihilation , there is no net matter being destroyed, because there was zero net matter (zero total lepton number and baryon number) to begin with before the annihilation—one lepton minus one antilepton equals zero net lepton number—and this net amount matter does not change as it simply remains zero after
23316-475: The other, so that the effective nuclear charge Z eff which each electron sees is about 1.69 units, not the 2 charges of a classic "bare" helium nucleus. The nucleus of the helium-4 atom is identical with an alpha particle . High-energy electron-scattering experiments show its charge to decrease exponentially from a maximum at a central point, exactly as does the charge density of helium's own electron cloud . This symmetry reflects similar underlying physics:
23490-447: The overall baryon/lepton numbers are not changed, so matter is conserved. However, baryons/leptons and antibaryons/antileptons all have positive mass, so the total amount of mass is not conserved. Further, outside of natural or artificial nuclear reactions, there is almost no antimatter generally available in the universe (see baryon asymmetry and leptogenesis ), so particle annihilation is rare in normal circumstances. Pie chart showing
23664-402: The pair of neutrons and the pair of protons in helium's nucleus obey the same quantum mechanical rules as do helium's pair of electrons (although the nuclear particles are subject to a different nuclear binding potential), so that all these fermions fully occupy 1s orbitals in pairs, none of them possessing orbital angular momentum, and each cancelling the other's intrinsic spin. This arrangement
23838-479: The particles to penetrate the thin glass wall of an evacuated tube , then creating a discharge in the tube, to study the spectrum of the new gas inside. In 1908, helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than 5 K (−268.15 °C; −450.67 °F). He tried to solidify it by further reducing the temperature but failed, because helium does not solidify at atmospheric pressure. Onnes' student Willem Hendrik Keesom
24012-408: The particulate theory of matter include the ancient Indian philosopher Kanada (c. 6th–century BCE or after), pre-Socratic Greek philosopher Leucippus (~490 BCE), and pre-Socratic Greek philosopher Democritus (~470–380 BCE). Matter should not be confused with mass, as the two are not the same in modern physics. Matter is a general term describing any 'physical substance'. By contrast, mass
24186-472: The perspective of quantum mechanics , helium is the second simplest atom to model, following the hydrogen atom . Helium is composed of two electrons in atomic orbitals surrounding a nucleus containing two protons and (usually) two neutrons. As in Newtonian mechanics, no system that consists of more than two particles can be solved with an exact analytical mathematical approach (see 3-body problem ) and helium
24360-418: The pressure, causing liquid to fountain out of the container. The thermal conductivity of helium II is greater than that of any other known substance, a million times that of helium I and several hundred times that of copper . This is because heat conduction occurs by an exceptional quantum mechanism. Most materials that conduct heat well have a valence band of free electrons which serve to transfer
24534-695: The program even though less than a cubic meter of the gas had previously been obtained. Some of this gas was used in the world's first helium-filled airship, the U.S. Navy's C-class blimp C-7, which flew its maiden voyage from Hampton Roads, Virginia , to Bolling Field in Washington, D.C., on December 1, 1921, nearly two years before the Navy's first rigid helium-filled airship, the Naval Aircraft Factory -built USS Shenandoah , flew in September 1923. Although
24708-467: The properties of known forms of matter. Some such materials might possess hypothetical properties like negative mass . In ancient India , the Buddhist , Hindu , and Jain philosophical traditions each posited that matter was made of atoms ( paramanu , pudgala ) that were "eternal, indestructible, without parts, and innumerable" and which associated or dissociated to form more complex matter according to
24882-497: The property of superfluidity ) and to those looking at the phenomena, such as superconductivity , produced in matter near absolute zero . On Earth, it is relatively rare—5.2 ppm by volume in the atmosphere . Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements ( thorium and uranium , although there are other examples), as the alpha particles emitted by such decays consist of helium-4 nuclei . This radiogenic helium
25056-399: The protons and neutrons are made up of quarks bound together by gluon fields (see dynamics of quantum chromodynamics ) and these gluon fields contribute significantly to the mass of hadrons. In other words, most of what composes the "mass" of ordinary matter is due to the binding energy of quarks within protons and neutrons. For example, the sum of the mass of the three quarks in a nucleon
25230-503: The quarks and leptons definition, constitutes about 4% of the energy of the observable universe . The remaining energy is theorized to be due to exotic forms, of which 23% is dark matter and 73% is dark energy . In astrophysics and cosmology , dark matter is matter of unknown composition that does not emit or reflect enough electromagnetic radiation to be observed directly, but whose presence can be inferred from gravitational effects on visible matter. Observational evidence of
25404-622: The regions of Apulia and Calabria in Italy. In the framework of the European Charter for Regional or Minority Languages , Greek is protected and promoted officially as a regional and minority language in Armenia, Hungary , Romania, and Ukraine. It is recognized as a minority language and protected in Turkey by the 1923 Treaty of Lausanne . The phonology , morphology , syntax , and vocabulary of
25578-554: The reserve to continue to sell the gas. Other large reserves were in the Hugoton in Kansas , United States, and nearby gas fields of Kansas and the panhandles of Texas and Oklahoma . New helium plants were scheduled to open in 2012 in Qatar , Russia, and the US state of Wyoming , but they were not expected to ease the shortage. In 2013, Qatar started up the world's largest helium unit, although
25752-419: The restoring force is the van der Waals force . These waves are known as third sound . Helium remains liquid down to absolute zero at atmospheric pressure, but it freezes at high pressure. Solid helium requires a temperature of 1–1.5 K (about −272 °C or −457 °F) at about 25 bar (2.5 MPa) of pressure. It is often hard to distinguish solid from liquid helium since the refractive index of
25926-408: The result of radioactive decay , lightning or cosmic rays ). This is because antimatter that came to exist on Earth outside the confines of a suitable physics laboratory would almost instantly meet the ordinary matter that Earth is made of, and be annihilated. Antiparticles and some stable antimatter (such as antihydrogen ) can be made in tiny amounts, but not in enough quantity to do more than test
26100-555: The same phase (both are gases). Antimatter is matter that is composed of the antiparticles of those that constitute ordinary matter. If a particle and its antiparticle come into contact with each other, the two annihilate ; that is, they may both be converted into other particles with equal energy in accordance with Albert Einstein 's equation E = mc . These new particles may be high-energy photons ( gamma rays ) or other particle–antiparticle pairs. The resulting particles are endowed with an amount of kinetic energy equal to
26274-574: The scale of elementary particles, a definition that follows this tradition can be stated as: "ordinary matter is everything that is composed of quarks and leptons ", or "ordinary matter is everything that is composed of any elementary fermions except antiquarks and antileptons". The connection between these formulations follows. Leptons (the most famous being the electron ), and quarks (of which baryons , such as protons and neutrons , are made) combine to form atoms , which in turn form molecules . Because atoms and molecules are said to be matter, it
26448-541: The second leading producer of helium. Through this time, both helium consumption and the costs of producing helium increased. From 2002 to 2007 helium prices doubled. As of 2012, the United States National Helium Reserve accounted for 30 percent of the world's helium. The reserve was expected to run out of helium in 2018. Despite that, a proposed bill in the United States Senate would allow
26622-421: The so-called wave–particle duality . A chemical substance is a unique form of matter with constant chemical composition and characteristic properties . Chemical substances may take the form of a single element or chemical compounds . If two or more chemical substances can be combined without reacting , they may form a chemical mixture . If a mixture is separated to isolate one chemical substance to
26796-609: The spectrum of the star ζ Puppis (these are now known to occur with Wolf–Rayet and other hot stars). Pickering attributed the observation (lines at 4551, 5411, and 10123 Å ) to a new form of hydrogen with half-integer transition levels. In 1912, Alfred Fowler managed to produce similar lines from a hydrogen-helium mixture, and supported Pickering's conclusion as to their origin. Bohr's model does not allow for half-integer transitions (nor does quantum mechanics) and Bohr concluded that Pickering and Fowler were wrong, and instead assigned these spectral lines to ionised helium, He. Fowler
26970-437: The stressed vowel; the so-called breathing marks ( rough and smooth breathing ), originally used to signal presence or absence of word-initial /h/; and the diaeresis , used to mark the full syllabic value of a vowel that would otherwise be read as part of a diphthong. These marks were introduced during the course of the Hellenistic period. Actual usage of the grave in handwriting saw a rapid decline in favor of uniform usage of
27144-445: The three familiar ones ( solids , liquids , and gases ), as well as more exotic states of matter (such as plasmas , superfluids , supersolids , Bose–Einstein condensates , ...). A fluid may be a liquid, gas or plasma. There are also paramagnetic and ferromagnetic phases of magnetic materials . As conditions change, matter may change from one phase into another. These phenomena are called phase transitions and are studied in
27318-447: The two phases are nearly the same. The solid has a sharp melting point and has a crystalline structure, but it is highly compressible ; applying pressure in a laboratory can decrease its volume by more than 30%. With a bulk modulus of about 27 MPa it is ~100 times more compressible than water. Solid helium has a density of 0.214 ± 0.006 g/cm at 1.15 K and 66 atm; the projected density at 0 K and 25 bar (2.5 MPa)
27492-467: The underlying nature of the visible world. Thales (c. 624 BCE–c. 546 BCE) regarded water as the fundamental material of the world. Anaximander (c. 610 BCE–c. 546 BCE) posited that the basic material was wholly characterless or limitless: the Infinite ( apeiron ). Anaximenes (flourished 585 BCE, d. 528 BCE) posited that the basic stuff was pneuma or air. Heraclitus (c. 535 BCE–c. 475 BCE) seems to say
27666-411: The universe within range of the best telescopes (that is, matter that may be visible because light could reach us from it) is made of baryonic matter. About 26.8% is dark matter, and about 68.3% is dark energy. The great majority of ordinary matter in the universe is unseen, since visible stars and gas inside galaxies and clusters account for less than 10 per cent of the ordinary matter contribution to
27840-568: Was a distinct dialect of Greek itself. Aside from the Macedonian question, current consensus regards Phrygian as the closest relative of Greek, since they share a number of phonological, morphological and lexical isoglosses , with some being exclusive between them. Scholars have proposed a Graeco-Phrygian subgroup out of which Greek and Phrygian originated. Among living languages, some Indo-Europeanists suggest that Greek may be most closely related to Armenian (see Graeco-Armenian ) or
28014-458: Was about 98.3% pure (2% nitrogen), which was adequate for airships. In 1945, a small amount of 99.9% helium was produced for welding use. By 1949, commercial quantities of Grade A 99.95% helium were available. For many years, the United States produced more than 90% of commercially usable helium in the world, while extraction plants in Canada, Poland, Russia, and other nations produced the remainder. In
28188-474: Was also isolated by American geochemist William Francis Hillebrand prior to Ramsay's discovery, when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed the lines to nitrogen . His letter of congratulations to Ramsay offers an interesting case of discovery, and near-discovery, in science. In 1907, Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei by allowing
28362-546: Was also used in Ancient Greek. Greek has occasionally been written in the Latin script , especially in areas under Venetian rule or by Greek Catholics . The term Frankolevantinika / Φραγκολεβαντίνικα applies when the Latin script is used to write Greek in the cultural ambit of Catholicism (because Frankos / Φράγκος is an older Greek term for West-European dating to when most of (Roman Catholic Christian) West Europe
28536-407: Was available to make elements 3, 4 and 5. It is barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon , carbon. However, due to the short lifetime of the intermediate beryllium-8, this process requires three helium nuclei striking each other nearly simultaneously (see triple-alpha process ). There was thus no time for significant carbon to be formed in
28710-541: Was by far the most widely spoken lingua franca in the Mediterranean world . It eventually became the official language of the Byzantine Empire and developed into Medieval Greek . In its modern form , Greek is the official language of Greece and Cyprus and one of the 24 official languages of the European Union . It is spoken by at least 13.5 million people today in Greece, Cyprus, Italy, Albania, Turkey , and
28884-470: Was eventually able to solidify 1 cm of helium in 1926 by applying additional external pressure. In 1913, Niels Bohr published his "trilogy" on atomic structure that included a reconsideration of the Pickering–Fowler series as central evidence in support of his model of the atom . This series is named for Edward Charles Pickering , who in 1896 published observations of previously unknown lines in
29058-600: Was further purified. By 1995, a billion cubic meters of the gas had been collected and the reserve was US$ 1.4 billion in debt, prompting the Congress of the United States in 1996 to discontinue the reserve. The resulting Helium Privatization Act of 1996 (Public Law 104–273) directed the United States Department of the Interior to empty the reserve, with sales starting by 2005. Helium produced between 1930 and 1945
29232-684: Was initially skeptical but was ultimately convinced that Bohr was correct, and by 1915 "spectroscopists had transferred [the Pickering–Fowler series] definitively [from hydrogen] to helium." Bohr's theoretical work on the Pickering series had demonstrated the need for "a re-examination of problems that seemed already to have been solved within classical theories" and provided important confirmation for his atomic theory. In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at temperatures near absolute zero ,
29406-405: Was observed. Existing theory explains this using the two-fluid model for helium II. In this model, liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a ground state , which are superfluid and flow with exactly zero viscosity, and a proportion of helium atoms in an excited state, which behave more like an ordinary fluid. In the fountain effect , a chamber
29580-522: Was possible, almost all first compound atomic nuclei to form were helium-4 nuclei. Owing to the relatively tight binding of helium-4 nuclei, its production consumed nearly all of the free neutrons in a few minutes, before they could beta-decay, and thus few neutrons were available to form heavier atoms such as lithium, beryllium, or boron. Helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis and binding energy ) and thus, once helium had been formed, no energetic drive
29754-480: Was recorded in writing systems such as Linear B and the Cypriot syllabary . The alphabet arose from the Phoenician script and was in turn the basis of the Latin , Cyrillic , Coptic , Gothic , and many other writing systems. The Greek language holds a very important place in the history of the Western world. Beginning with the epics of Homer , ancient Greek literature includes many works of lasting importance in
29928-566: Was under the control of the Frankish Empire ). Frankochiotika / Φραγκοχιώτικα (meaning 'Catholic Chiot') alludes to the significant presence of Catholic missionaries based on the island of Chios . Additionally, the term Greeklish is often used when the Greek language is written in a Latin script in online communications. The Latin script is nowadays used by the Greek-speaking communities of Southern Italy . The Yevanic dialect
30102-637: Was used for literary and official purposes in the newly formed Greek state. In 1976, Dimotiki was declared the official language of Greece, after having incorporated features of Katharevousa and thus giving birth to Standard Modern Greek , used today for all official purposes and in education . The historical unity and continuing identity between the various stages of the Greek language are often emphasized. Although Greek has undergone morphological and phonological changes comparable to those seen in other languages, never since classical antiquity has its cultural, literary, and orthographic tradition been interrupted to
30276-653: Was written by Romaniote and Constantinopolitan Karaite Jews using the Hebrew Alphabet . In a tradition, that in modern time, has come to be known as Greek Aljamiado , some Greek Muslims from Crete wrote their Cretan Greek in the Arabic alphabet . The same happened among Epirote Muslims in Ioannina . This also happened among Arabic-speaking Byzantine rite Christians in the Levant ( Lebanon , Palestine, and Syria ). This usage
#238761