Cats is a sung-through musical composed by Andrew Lloyd Webber, based on Old Possum's Book of Practical Cats by T. S. Eliot; the musical tells the story of a tribe of cats called the Jellicles and the night they make what is known as the "Jellicle choice" and decide which cat will ascend to the Heaviside Layer and come back to a new life. Directed by Trevor Nunn and choreographed by Gillian Lynne, Cats first opened in the West End in 1981 and with the same creative team on Broadway in 1982, it won numerous awards, including Best Musical at both the Laurence Olivier Awards and the Tony Awards. By 1994, the musical had grossed over $2 billion worldwide; the London production ran for 21 years and the Broadway production ran for 18 years, both setting new records. Actresses Elaine Paige and Betty Buckley became associated with the musical; the most well-known song from Cats, "Memory", has been recorded by more than 150 recording artists. Cats was the longest-running Broadway show in history from 1997 until 2006 when it was surpassed by The Phantom of the Opera.
As of 2018, it is the fourth-longest-running Broadway show and the sixth-longest-running West End show. Cats has been performed around the world many times and has been translated into more than 20 languages; the Japanese production by the Shiki Theatre Company has performed over 10,000 shows since it first opened in 1983. The musical was adapted into a direct-to-video film in 1998, with a 2019 film adaptation by Tom Hooper set to follow. After the overture, the cats explain the Jellicle tribe and its purpose; the cats notice that they are being watched by a human audience, proceed to explain how the different cats of the tribe are named. This is followed by a ballet dance performed by Victoria the White Cat to signal the beginning of the Jellicle Ball. At this moment, the show's main narrator, explains that tonight the Jellicle patriarch Old Deuteronomy will make an appearance and choose one of the cats to be reborn into a new life on the Heaviside Layer; the first contender Munkustrap introduces is Jennyanydots, a large tabby cat who lazes around all day, but come nighttime, she becomes active, teaching mice and cockroaches various activities to curb their destructive habits.
Just as Jennyanydots finishes her song, the music changes hence Munkustrap's annoying younger brother, Rum Tum Tugger, makes his extravagant entrance in front of the tribe. He is fickle and unappeasable, "for he will do as he do do, there's no doing anything about it"; as Rum Tum Tugger's song fades, a shabby old grey cat stumbles out wanting to be reconciled. All the cats explain her unfortunate state. Grizabella leaves and the music changes to a cheerful upbeat number as Bustopher Jones, a fat cat in "a coat of fastidious black", is brought to the stage. Bustopher Jones is among the elite of the cats, visits prestigious gentlemen's clubs. A loud crash startles the tribe and the cats run offstage in fright. Hushed giggling sounds signal the entrance of Mungojerrie and Rumpleteazer, a pair of near-identical cats, they are petty burglars mischievous, they enjoy causing trouble around their human neighbourhood. After they finish, they are confronted by the rest of the cats; the Jellicle patriarch, Old Deuteronomy, arrives before the tribe.
He is a large old cat that "has lived many lives" and "buried nine wives". He is the cat; the Jellicles put on a play for Old Deuteronomy, telling a story about two dog tribes clashing in the street and subsequently being scared away by the Great Rumpus Cat. After a moral from Old Deuteronomy about the destiny of Jellicle cats and Pollicle dogs, a second loud crash from Macavity, sends the alarmed cats scurrying. After a quick patrol for Macavity, Old Deuteronomy deems it a false alarm and summons the cats back as the main celebration begins, in which the cats sing and display their "Terpsichorean powers". During the Ball, Grizabella reappears and tries to dance along, but her age and decrepit condition prevent her from doing so. Once again, she is shunned by the other cats. After the Jellicle Ball, Old Deuteronomy contemplates "what happiness is". However, the cats do not understand him, so he has Jemima, the youngest of all Jellicles, sing it in simpler terms. Gus — short for Asparagus — shuffles forward as the next cat to be introduced.
He was once a famous actor but is now old and "suffers from palsy which makes his paws shake." He is accompanied by his caretaker, who tells of his exploits. Gus remembers how he once played the infamous pirate captain, Growltiger a.k.a. the Terror of the Thames. Gus tells the story about the pirate captain's romance with Lady Griddlebone, how Growltiger was overtaken by the Siamese and forced to walk the plank to his death. Back in the present, after Gus exits, Skimbleshanks is seen sleeping in the corner, he is the cat, unofficially in charge of the night train to Glasgow. Sk
Everybody Is Going to Heaven
Everybody Is Going to Heaven is the second studio album by American rock band Citizen. The album charted within the top 20 on various Billboard charts; the group announced they were in the process of recording their next album on January 5, 2015. Discussing the writing process, guitarist Nick Hamm said the group was "doing whatever we feel like" and that the songs were "twice as big as Youth. It's Citizen, but it's turned up to 11". Everybody Is Going to Heaven has been described as alternative rock, emo and shoegazing. On April 26, 2015, Everybody Is Going to Heaven was announced for release in June, revealing its cover art. In addition, a short snippet of a song was available on the group's website. On May 5, "Cement" was made available for streaming via Noisey. On June 3, a music video was released for "Stain"; the video, directed by Max Moore, premiered via Vice. Everybody Is Going to Heaven was made available for streaming on June 9 via Spin, before being released on June 23 through Run for Cover Records.
On October 21, a music video was released for "Yellow Love". Directed by Moore, it features two people stabbing themselves with knives. According to Noisey, proceeding this is a "a strange reaction that plays out for the rest of the duration. One could expound that it's a visual representation of the song's lyrics seen real". In October and November, the group supported Circa Survive on their headlining US tour. In January 2016, the group went on a tour of the UK with Turnover. "Numb Yourself" was released as a radio single on February 19. In March and April, the group went on a US tour alongside Sorority Noise and Milk Teeth. On May 8, an outtake, titled "Nail in Your Hand", was released for free download from the group's website. In August, the group appeared at Reading Festival in the UK. In November, the group went on a tour of Australia. "Cement" – 3:42 "Dive into My Sun" – 4:20 "Numb Yourself" – 3:25 "Heaviside" – 3:49 "My Favorite Color" – 3:43 "Weave Me" – 4:35 "Stain" – 3:41 "Ten" – 3:26 "Yellow Love" – 3:41 "Ring of Chain" – 5:35Japanese bonus track "Nail in Your Hand" – 3:11 Everybody Is Going to Heaven at YouTube
Medium wave is the part of the medium frequency radio band used for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz, using channels spaced every 9 kHz, in North America an extended MW broadcast band ranges from 525 kHz to 1705 kHz, using 10 kHz spaced channels. The term is a historic one, dating from the early 20th century, when the radio spectrum was divided on the basis of the wavelength of the waves into long wave, medium wave, short wave radio bands. Wavelengths in this band are long enough that radio waves are not blocked by buildings and hills and can propagate beyond the horizon following the curvature of the Earth. Practical groundwave reception extends to 200–300 miles, with greater distances over terrain with higher ground conductivity, greatest distances over salt water. Most broadcast stations use groundwave to cover their listening area. Medium waves can reflect off charged particle layers in the ionosphere and return to Earth at much greater distances.
At night in winter months and at times of low solar activity, the lower ionospheric D layer disappears. When this happens, MW radio waves can be received many hundreds or thousands of miles away as the signal will be reflected by the higher F layer; this can allow long-distance broadcasting, but can interfere with distant local stations. Due to the limited number of available channels in the MW broadcast band, the same frequencies are re-allocated to different broadcasting stations several hundred miles apart. On nights of good skywave propagation, the skywave signals of a distant station may interfere with the signals of local stations on the same frequency. In North America, the North American Regional Broadcasting Agreement sets aside certain channels for nighttime use over extended service areas via skywave by a few specially licensed AM broadcasting stations; these channels are called clear channels, they are required to broadcast at higher powers of 10 to 50 kW. Broadcasting in the United States was restricted to two wavelengths: "entertainment" was broadcast at 360 meters, with stations required to switch to 485 meters when broadcasting weather forecasts, crop price reports and other government reports.
This arrangement had numerous practical difficulties. Early transmitters were technically crude and impossible to set on their intended frequency and if two stations in the same part of the country broadcast the resultant interference meant that neither could be heard clearly; the Commerce Department intervened in such cases but left it up to stations to enter into voluntary timesharing agreements amongst themselves. The addition of a third "entertainment" wavelength, 400 meters, did little to solve this overcrowding. In 1923, the Commerce Department realized that as more and more stations were applying for commercial licenses, it was not practical to have every station broadcast on the same three wavelengths. On 15 May 1923, Commerce Secretary Herbert Hoover announced a new bandplan which set aside 81 frequencies, in 10 kHz steps, from 550 kHz to 1350 kHz; each station would be assigned one frequency, no longer having to broadcast weather and government reports on a different frequency than entertainment.
Class A and B stations were segregated into sub-bands. Today in most of the Americas, mediumwave broadcast stations are separated by 10 kHz and have two sidebands of up to ±5 kHz in theory. In the rest of the world, the separation is 9 kHz, with sidebands of ±4.5 kHz. Both provide adequate audio quality for voice, but are insufficient for high-fidelity broadcasting, common on the VHF FM bands. In the US and Canada the maximum transmitter power is restricted to 50 kilowatts, while in Europe there are medium wave stations with transmitter power up to 2 megawatts daytime. Most United States AM radio stations are required by the Federal Communications Commission to shut down, reduce power, or employ a directional antenna array at night in order to avoid interference with each other due to night-time only long-distance skywave propagation; those stations which shut down at night are known as "daytimers". Similar regulations are in force for Canadian stations, administered by Industry Canada. In Europe, each country is allocated a number of frequencies.
In most cases there are two power limits: a lower one for omnidirectional and a higher one for directional radiation with minima in certain directions. The power limit can be depending on daytime and it is possible, that a station may not work at nighttime, because it would produce too much interference. Other countries may only operate low-powered transmitters on the same frequency, again subject to agreement. For example, Russia operates a high-powered transmitter, located in its Kaliningrad exclave and used for external broadcasting, on 1386 kHz; the same frequency is used by low-powered local radio stations in the United Kingdom, which has 250 medium-wave transmitters of 1 kW and over. International mediumwave broadcasting in Europe has decreased markedly with
T. S. Eliot
Thomas Stearns Eliot, "one of the twentieth century's major poets" was an essayist, publisher and literary and social critic. Born in St. Louis, Missouri, in the United States, to a prominent Boston Brahmin family, he moved to England in 1914 at the age of 25, settling and marrying there, he became a British subject in 1927 at the age of 39. Eliot attracted widespread attention for his poem "The Love Song of J. Alfred Prufrock", seen as a masterpiece of the Modernist movement, it was followed by some of the best-known poems in the English language, including The Waste Land, "The Hollow Men", "Ash Wednesday", Four Quartets. He was known for his seven plays Murder in the Cathedral and The Cocktail Party, he was awarded the Nobel Prize in Literature in 1948, "for his outstanding, pioneer contribution to present-day poetry". The Eliots were a Boston Brahmin family with roots in New England. Thomas Eliot's paternal grandfather, William Greenleaf Eliot, had moved to St. Louis, Missouri, to establish a Unitarian Christian church there.
His father, Henry Ware Eliot, was a successful businessman and treasurer of the Hydraulic-Press Brick Company in St Louis. His mother, Charlotte Champe Stearns, wrote poetry and was a social worker, a new profession in the early 20th century. Eliot was the last of six surviving children. Eliot was born at a property owned by his grandfather, William Greenleaf Eliot, his four sisters were between 19 years older. Known to family and friends as Tom, he was the namesake of Thomas Stearns. Eliot's childhood infatuation with literature can be ascribed to several factors. First, he had to overcome physical limitations as a child. Struggling from a congenital double inguinal hernia, he could not participate in many physical activities and thus was prevented from socializing with his peers; as he was isolated, his love for literature developed. Once he learned to read, the young boy became obsessed with books and was absorbed in tales depicting savages, the Wild West, or Mark Twain's thrill-seeking Tom Sawyer.
In his memoir of Eliot, his friend Robert Sencourt comments that the young Eliot "would curl up in the window-seat behind an enormous book, setting the drug of dreams against the pain of living." Secondly, Eliot credited his hometown with fuelling his literary vision: "It is self-evident that St. Louis affected me more than any other environment has done. I feel that there is something in having passed one's childhood beside the big river, incommunicable to those people who have not. I consider myself fortunate to have been born here, rather than in Boston, or New York, or London."From 1898 to 1905, Eliot attended Smith Academy, where his studies included Latin, Ancient Greek and German. He began to write poetry when he was fourteen under the influence of Edward Fitzgerald's Rubaiyat of Omar Khayyam, a translation of the poetry of Omar Khayyam, he said the results were gloomy and despairing and he destroyed them. His first published poem, "A Fable For Feasters", was written as a school exercise and was published in the Smith Academy Record in February 1905.
Published there in April 1905 was his oldest surviving poem in manuscript, an untitled lyric revised and reprinted as "Song" in The Harvard Advocate, Harvard University's student magazine. He published three short stories in 1905, "Birds of Prey", "A Tale of a Whale" and "The Man Who Was King"; the last mentioned story reflects his exploration of the Igorot Village while visiting the 1904 World's Fair of St. Louis; such a link with primitive people antedates his anthropological studies at Harvard. Eliot lived in St. Louis, Missouri for the first sixteen years of his life at the house on Locust St. where he was born. After going away to school in 1905, he only returned to St. Louis for visits. Despite moving away from the city, Eliot wrote to a friend that the "Missouri and the Mississippi have made a deeper impression on me than any other part of the world."Following graduation, Eliot attended Milton Academy in Massachusetts for a preparatory year, where he met Scofield Thayer who published The Waste Land.
He studied philosophy at Harvard College from 1906 to 1909, earning his bachelor's degree after three years, instead of the usual four. While a student, Eliot was graduated with a pass degree, he recovered and persisted, attaining a B. A. in an elective program best described as comparative literature in three years, an M. A. in English literature in the fourth. Frank Kermode writes that the most important moment of Eliot's undergraduate career was in 1908 when he discovered Arthur Symons's The Symbolist Movement in Literature; this introduced him to Jules Laforgue, Arthur Rimbaud, Paul Verlaine. Without Verlaine, Eliot wrote, he might never have heard of Tristan Corbière and his book Les amours jaunes, a work that affected the course of Eliot's life; the Harvard Advocate published some of his poems and he became lifelong friends with Conrad Aiken, the American writer and critic. After working as a philosophy assistant at Harvard from 1909 to 1910, Eliot moved to Paris where, from 1910 to 1911, he studied philosophy at the Sorbonne.
He read poetry with Henri Alban-Fournier. From 1911 to 1914, he was back at Harvard studying Indian Sanskrit. Eliot was awarded a scholarship to Merton College, Oxford, in 1914, he first visited Marb
Nature is a British multidisciplinary scientific journal, first published on 4 November 1869. It is one of the most recognizable scientific journals in the world, was ranked the world's most cited scientific journal by the Science Edition of the 2010 Journal Citation Reports and is ascribed an impact factor of 40.137, making it one of the world's top academic journals. It is one of the few remaining academic journals that publishes original research across a wide range of scientific fields. Research scientists are the primary audience for the journal, but summaries and accompanying articles are intended to make many of the most important papers understandable to scientists in other fields and the educated public. Towards the front of each issue are editorials and feature articles on issues of general interest to scientists, including current affairs, science funding, scientific ethics and research breakthroughs. There are sections on books and short science fiction stories; the remainder of the journal consists of research papers, which are dense and technical.
Because of strict limits on the length of papers the printed text is a summary of the work in question with many details relegated to accompanying supplementary material on the journal's website. There are many fields of research in which important new advances and original research are published as either articles or letters in Nature; the papers that have been published in this journal are internationally acclaimed for maintaining high research standards. Fewer than 8% of submitted papers are accepted for publication. In 2007 Nature received the Prince of Asturias Award for Humanity; the enormous progress in science and mathematics during the 19th century was recorded in journals written in German or French, as well as in English. Britain underwent enormous technological and industrial changes and advances in the latter half of the 19th century. In English the most respected scientific journals of this time were the refereed journals of the Royal Society, which had published many of the great works from Isaac Newton, Michael Faraday through to early works from Charles Darwin.
In addition, during this period, the number of popular science periodicals doubled from the 1850s to the 1860s. According to the editors of these popular science magazines, the publications were designed to serve as "organs of science", in essence, a means of connecting the public to the scientific world. Nature, first created in 1869, was not the first magazine of its kind in Britain. One journal to precede Nature was Recreative Science: A Record and Remembrancer of Intellectual Observation, created in 1859, began as a natural history magazine and progressed to include more physical observational science and technical subjects and less natural history; the journal's name changed from its original title to Intellectual Observer: A Review of Natural History, Microscopic Research, Recreative Science and later to the Student and Intellectual Observer of Science and Art. While Recreative Science had attempted to include more physical sciences such as astronomy and archaeology, the Intellectual Observer broadened itself further to include literature and art as well.
Similar to Recreative Science was the scientific journal Popular Science Review, created in 1862, which covered different fields of science by creating subsections titled "Scientific Summary" or "Quarterly Retrospect", with book reviews and commentary on the latest scientific works and publications. Two other journals produced in England prior to the development of Nature were the Quarterly Journal of Science and Scientific Opinion, established in 1864 and 1868, respectively; the journal most related to Nature in its editorship and format was The Reader, created in 1864. These similar journals all failed; the Popular Science Review survived longest, lasting 20 years and ending its publication in 1881. The Quarterly Journal, after undergoing a number of editorial changes, ceased publication in 1885; the Reader terminated in 1867, Scientific Opinion lasted a mere 2 years, until June 1870. Not long after the conclusion of The Reader, a former editor, Norman Lockyer, decided to create a new scientific journal titled Nature, taking its name from a line by William Wordsworth: "To the solid ground of nature trusts the Mind that builds for aye".
First owned and published by Alexander Macmillan, Nature was similar to its predecessors in its attempt to "provide cultivated readers with an accessible forum for reading about advances in scientific knowledge." Janet Browne has proposed that "far more than any other science journal of the period, Nature was conceived and raised to serve polemic purpose." Many of the early editions of Nature consisted of articles written by members of a group that called itself the X Club, a group of scientists known for having liberal and somewhat controversial scientific beliefs relative to the time period. Initiated by Thomas Henry Huxley, the group consisted of such important scientists as Joseph Dalton Hooker, Herbert Spencer, John Tyndall, along with another five scientists and mathematicians, it was in part its scientific liberality that made Nature a longer-lasti
In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere. Since it is not limited by the curvature of the Earth, skywave propagation can be used to communicate beyond the horizon, at intercontinental distances, it is used in the shortwave frequency bands. As a result of skywave propagation, a signal from a distant AM broadcasting station, a shortwave station, or – during sporadic E propagation conditions a distant VHF FM or TV station – can sometimes be received as as local stations. Most long-distance shortwave radio communication – between 3 and 30 MHz – is a result of skywave propagation. Since the early 1920s amateur radio operators, limited to lower transmitter power than broadcast stations, have taken advantage of skywave for long distance communication. Skywave propagation is distinct from: groundwave propagation, where radio waves travel near Earth's surface without being reflected or refracted by the atmosphere – the dominant propagation mode at lower frequencies, line-of-sight propagation, in which radio waves travel in a straight line, the dominant mode at higher frequencies.
The ionosphere is a region of the upper atmosphere, from about 80 km to 1000 km in altitude, where neutral air is ionized by solar photons and cosmic rays. When high frequency signals enter the ionosphere obliquely, they are back-scattered from the ionized layer as scatter waves. If the midlayer ionization is strong enough compared to the signal frequency, a scatter wave can exit the bottom of the layer earthwards as if reflected from a mirror. Earth's surface diffusely reflects the incoming wave back towards the ionosphere. Like a rock "skipping" across water, the signal may "bounce" or "skip" between the earth and ionosphere two or more times. Since, at shallow incidence, losses remain quite small, signals of only a few watts can sometimes be received many thousands of miles away as a result; this is. If the ionization is not great enough, the scatter wave is deflected downwards, subsequently upwards such that it exits the top of the layer displaced. Sky wave propagation occurs in the waveguide formed by the ground and ionosphere, each serving as reflectors.
With a single "hop," path distances up to 3500 km may be reached. Transatlantic connections are obtained with two or three hops; the layer of ionospheric plasma with equal ionization is not fixed, but undulates like the surface of the ocean. Varying reflection efficiency from this changing surface can cause the reflected signal strength to change, causing "fading" in shortwave broadcasts. VHF signals with frequencies above about 30 MHz penetrate the ionosphere and are not returned to the Earth's surface. E-skip is a notable exception, where VHF signals including FM broadcast and VHF TV signals are reflected to the Earth during late spring and early summer. E-skip affects UHF frequencies, except for rare occurrences below 500 MHz. Frequencies below 10 MHz, including broadcasts in the mediumwave and shortwave bands, propagate most efficiently by skywave at night. Frequencies above 10 MHz propagate most efficiently during the day. Frequencies lower than 3 kHz have a wave length longer than the distance between the Earth and the ionosphere.
The maximum usable frequency for skywave propagation is influenced by sunspot number. Skywave propagation is degraded – sometimes – during geomagnetic storms. Skywave propagation on the sunlit side of the Earth can be disrupted during sudden ionospheric disturbances; because the lower-altitude layers of the ionosphere disappear at night, the refractive layer of the ionosphere is much higher above the surface of the Earth at night. This leads to an increase in the "skip" or "hop" distance of the skywave at night. Amateur radio operators are credited with the discovery of skywave propagation on the shortwave bands. Early long-distance services used surface wave propagation at low frequencies, which are attenuated along the path. Longer distances and higher frequencies using this method meant more signal attenuation. This, the difficulties of generating and detecting higher frequencies, made discovery of shortwave propagation difficult for commercial services. Radio amateurs conducted the first successful transatlantic tests in December 1921, operating in the 200 meter mediumwave band —the shortest wavelength available to amateurs.
In 1922 hundreds of North American amateurs were heard in Europe at 200 meters and at least 30 North American amateurs heard amateur signals from Europe. The first two-way communications between North American and Hawaiian amateurs began in 1922 at 200 meters. Although operation on wavelengths shorter than 200 meters was technically illegal, amateurs began to experiment with those wavelengths using newly available vacuum tubes shortly after World War I. Extreme interference at the upper edge of the 150-200 meter band—the official wavelengths allocated to amateurs by the Second National Radio Conference in 1923—forced amateurs to shift to shorter and shorter wavelengths.
Gas is one of the four fundamental states of matter. A pure gas may be made up of individual atoms, elemental molecules made from one type of atom, or compound molecules made from a variety of atoms. A gas mixture would contain a variety of pure gases much like the air. What distinguishes a gas from liquids and solids is the vast separation of the individual gas particles; this separation makes a colorless gas invisible to the human observer. The interaction of gas particles in the presence of electric and gravitational fields are considered negligible, as indicated by the constant velocity vectors in the image; the gaseous state of matter is found between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention. High-density atomic gases super cooled to low temperatures are classified by their statistical behavior as either a Bose gas or a Fermi gas.
For a comprehensive listing of these exotic states of matter see list of states of matter. The only chemical elements that are stable diatomic homonuclear molecules at STP are hydrogen, nitrogen and two halogens: fluorine and chlorine; when grouped together with the monatomic noble gases – helium, argon, krypton and radon – these gases are called "elemental gases". The word gas was first used by the early 17th-century Flemish chemist Jan Baptist van Helmont, he identified the first known gas other than air. Van Helmont's word appears to have been a phonetic transcription of the Ancient Greek word χάος Chaos – the g in Dutch being pronounced like ch in "loch" – in which case Van Helmont was following the established alchemical usage first attested in the works of Paracelsus. According to Paracelsus's terminology, chaos meant something like "ultra-rarefied water". An alternative story is that Van Helmont's word is corrupted from gahst, signifying a ghost or spirit; this was because certain gases suggested a supernatural origin, such as from their ability to cause death, extinguish flames, to occur in "mines, bottom of wells and other lonely places".
In contrast, French-American historian Jacques Barzun speculated that Van Helmont had borrowed the word from the German Gäscht, meaning the froth resulting from fermentation. Because most gases are difficult to observe directly, they are described through the use of four physical properties or macroscopic characteristics: pressure, number of particles and temperature; these four characteristics were observed by scientists such as Robert Boyle, Jacques Charles, John Dalton, Joseph Gay-Lussac and Amedeo Avogadro for a variety of gases in various settings. Their detailed studies led to a mathematical relationship among these properties expressed by the ideal gas law. Gas particles are separated from one another, have weaker intermolecular bonds than liquids or solids; these intermolecular forces result from electrostatic interactions between gas particles. Like-charged areas of different gas particles repel, while oppositely charged regions of different gas particles attract one another. Gaseous compounds with polar covalent bonds contain permanent charge imbalances and so experience strong intermolecular forces, although the molecule while the compound's net charge remains neutral.
Transient, randomly induced charges exist across non-polar covalent bonds of molecules and electrostatic interactions caused by them are referred to as Van der Waals forces. The interaction of these intermolecular forces varies within a substance which determines many of the physical properties unique to each gas. A comparison of boiling points for compounds formed by ionic and covalent bonds leads us to this conclusion; the drifting smoke particles in the image provides some insight into low-pressure gas behavior. Compared to the other states of matter, gases have low viscosity. Pressure and temperature influence the particles within a certain volume; this variation in particle separation and speed is referred to as compressibility. This particle separation and size influences optical properties of gases as can be found in the following list of refractive indices. Gas particles spread apart or diffuse in order to homogeneously distribute themselves throughout any container; when observing a gas, it is typical to specify a frame of length scale.
A larger length scale corresponds to a global point of view of the gas. This region must be sufficient in size to contain a large sampling of gas particles; the resulting statistical analysis of this sample size produces the "average" behavior of all the gas particles within the region. In contrast, a smaller length scale corresponds to a particle point of view. Macroscopically, the gas characteristics measured are either in terms of the gas particles themselves or their surroundings. For example, Robert Boyle studied pneumatic chemistry for a small portion of his career. One of his experiments related the macroscopic properties of volume of a gas, his experiment used a J-tube manometer which looks like a test tube in the shape of the letter J. Boyle trapped an inert gas in the closed end of the test tube with a column of mercury, thereby ma