181-414: Outer space (or simply space ) is the expanse that exists beyond Earth's atmosphere and between celestial bodies . It contains ultra-low levels of particle densities , constituting a near-perfect vacuum of predominantly hydrogen and helium plasma , permeated by electromagnetic radiation , cosmic rays , neutrinos , magnetic fields and dust . The baseline temperature of outer space, as set by
362-520: A scrivener . He lived in and worked from a house in Cheapside at Bread Street, where the Mermaid Tavern was located. The elder Milton was noted for his skill as a composer of music, and this talent left his son with a lifelong appreciation for music and friendships with musicians such as Henry Lawes . The prosperity of Milton's father allowed his eldest son to obtain a private tutor, Thomas Young ,
543-423: A spacecraft must travel faster than a sub-orbital spaceflight along an arcing trajectory . The energy required to reach Earth orbital velocity at an altitude of 600 km (370 mi) is about 36 MJ /kg, which is six times the energy needed merely to climb to the corresponding altitude. The escape velocity required to pull free of Earth's gravitational field altogether and move into interplanetary space
724-515: A warrant was issued for his arrest and his writings were burnt. He re-emerged after a general pardon was issued, but was nevertheless arrested and briefly imprisoned before influential friends intervened, such as Marvell, now an MP. Milton married for a third and final time on 24 February 1663, marrying Elizabeth (Betty) Minshull, aged 24, a native of Wistaston , Cheshire. He spent the remaining decade of his life living quietly in London, only retiring to
905-521: A Dutch law philosopher, playwright, and poet. Milton left France soon after this meeting. He travelled south from Nice to Genoa , and then to Livorno and Pisa . He reached Florence in July 1638. While there, Milton enjoyed many of the sites and structures of the city. His candour of manner and erudite neo-Latin poetry earned him friends in Florentine intellectual circles, and he met the astronomer Galileo who
1086-449: A Reformed faith and a Humanist spirit, led to enigmatic outcomes. Milton's apparently contradictory stance on the vital problems of his age, arose from religious contestations, to the questions of the divine rights of kings. In both the cases, he seems in control, taking stock of the situation arising from the polarization of the English society on religious and political lines. He fought with
1267-607: A Scottish Presbyterian with an MA from the University of St Andrews . Young's influence also served as the poet's introduction to religious radicalism. After Young's tutorship, Milton attended St Paul's School in London, where he began the study of Latin and Greek; the classical languages left an imprint on both his poetry and prose in English (he also wrote in Latin and Italian). Milton's first datable compositions are two psalms written at age 15 at Long Bennington . One contemporary source
1448-435: A boundary marked in most places by a temperature inversion (i.e. a layer of relatively warm air above a colder one), and in others by a zone that is isothermal with height. Although variations do occur, the temperature usually declines with increasing altitude in the troposphere because the troposphere is mostly heated through energy transfer from the surface. Thus, the lowest part of the troposphere (i.e. Earth's surface)
1629-529: A career as pamphleteer and publicist under Charles I 's increasingly autocratic rule and Britain's breakdown into constitutional confusion and ultimately civil war. While once considered dangerously radical and heretical, Milton contributed to a seismic shift in accepted public opinions during his life that ultimately elevated him to public office in England. The Restoration of 1660 and his loss of vision later deprived Milton much of his public platform, but he used
1810-409: A collection of his letters and the Latin prolusions from his Cambridge days. An unfinished religious manifesto, De doctrina christiana , probably written by Milton, lays out many of his heterodox theological views, and was not discovered and published until 1823. Milton's key beliefs were idiosyncratic, not those of an identifiable group or faction, and often they go well beyond the orthodoxy of
1991-582: A cottage during the Great Plague of London — Milton's Cottage in Chalfont St. Giles , his only extant home. During this period, Milton published several minor prose works, such as the grammar textbook Art of Logic and a History of Britain . His only explicitly political tracts were the 1672 Of True Religion , arguing for toleration (except for Catholics), and a translation of a Polish tract advocating an elective monarchy. Both these works were referred to in
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#17330859992772172-469: A density of one proton per four cubic meters. The density of the universe is clearly not uniform; it ranges from relatively high density in galaxies—including very high density in structures within galaxies, such as planets, stars, and black holes —to conditions in vast voids that have much lower density, at least in terms of visible matter. Unlike matter and dark matter, dark energy seems not to be concentrated in galaxies: although dark energy may account for
2353-571: A dinner given by the English College, Rome , despite his dislike for the Society of Jesus , meeting English Catholics who were also guests—theologian Henry Holden and the poet Patrick Cary . He also attended musical events, including oratorios, operas, and melodramas. Milton left for Naples toward the end of November, where he stayed only for a month because of the Spanish control. During that time, he
2534-505: A factor of 1/ e (0.368) every 7.64 km (25,100 ft), (this is called the scale height ) -- for altitudes out to around 70 km (43 mi; 230,000 ft). However, the atmosphere is more accurately modeled with a customized equation for each layer that takes gradients of temperature, molecular composition, solar radiation and gravity into account. At heights over 100 km, an atmosphere may no longer be well mixed. Then each chemical species has its own scale height. In summary,
2715-517: A hazard to astronauts, even in low Earth orbit. They create aurorae seen at high latitudes in an oval surrounding the geomagnetic poles . xGeo space is a concept used by the US to refer to space of high Earth orbits , ranging from beyond geosynchronous orbit (GEO) at approximately 35,786 km (22,236 mi), out to the L2 Earth-Moon Lagrange point at 448,900 km (278,934 mi). This
2896-511: A layer in which temperatures rise with increasing altitude. This rise in temperature is caused by the absorption of ultraviolet radiation (UV) from the Sun by the ozone layer, which restricts turbulence and mixing. Although the temperature may be −60 °C (−76 °F; 210 K) at the tropopause, the top of the stratosphere is much warmer, and may be near 0 °C. The stratospheric temperature profile creates very stable atmospheric conditions, so
3077-506: A majority of the mass-energy in the universe, dark energy's influence is 5 orders of magnitude smaller than the influence of gravity from matter and dark matter within the Milky Way. Outer space is the closest known approximation to a perfect vacuum . It has effectively no friction , allowing stars, planets , and moons to move freely along their ideal orbits , following the initial formation stage. The deep vacuum of intergalactic space
3258-646: A manservant, Milton embarked upon a tour of France and Italy for 15 months that lasted until July or August 1639. His travels supplemented his study with new and direct experience of artistic and religious traditions, especially Roman Catholicism. He met famous theorists and intellectuals of the time and was able to display his poetic skills. For specific details of what happened within Milton's " grand tour ", there appears to be just one primary source : Milton's own Defensio Secunda . There are other records, including some letters and some references in his other prose tracts, but
3439-574: A mass of about 5.15 × 10 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner with increasing altitude, with no definite boundary between the atmosphere and outer space . The Kármán line , at 100 km (62 mi) or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi). Several layers can be distinguished in
3620-485: A million miles away, were found to be reflected light from ice crystals in the atmosphere. When light passes through Earth's atmosphere, photons interact with it through scattering . If the light does not interact with the atmosphere, it is called direct radiation and is what you see if you were to look directly at the Sun. Indirect radiation is light that has been scattered in the atmosphere. For example, on an overcast day when you cannot see your shadow, there
3801-733: A protective buffer between the Earth's surface and outer space , shields the surface from most meteoroids and ultraviolet solar radiation , keeps it warm and reduces diurnal temperature variation (temperature extremes between day and night ) through heat retention ( greenhouse effect ), redistributes heat and moisture among different regions via air currents , and provides the chemical and climate conditions allowing life to exist and evolve on Earth. By mole fraction (i.e., by quantity of molecules ), dry air contains 78.08% nitrogen , 20.95% oxygen , 0.93% argon , 0.04% carbon dioxide , and small amounts of other trace gases . Air also contains
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#17330859992773982-444: A round-trip Mars mission lasting three years, a large fraction of the cells in an astronaut's body would be traversed and potentially damaged by high energy nuclei. The energy of such particles is significantly diminished by the shielding provided by the walls of a spacecraft and can be further diminished by water containers and other barriers. The impact of the cosmic rays upon the shielding produces additional radiation that can affect
4163-410: A rural idyll; Hammersmith was then a "suburban village" falling into the orbit of London, and even Horton was becoming deforested and suffered from the plague. He read both ancient and modern works of theology, philosophy, history, politics, literature, and science in preparation for a prospective poetical career. Milton's intellectual development can be charted via entries in his commonplace book (like
4344-755: A scrapbook), now in the British Library . As a result of such intensive study, Milton is considered to be among the most learned of all English poets. In addition to his years of private study, Milton had command of Latin, Greek, Hebrew, French, Spanish, and Italian from his school and undergraduate days; he also added Old English to his linguistic repertoire in the 1650s while researching his History of Britain , and probably acquired proficiency in Dutch soon after. Milton continued to write poetry during this period of study; his Arcades and Comus were both commissioned for masques composed for noble patrons, connections of
4525-528: A secretary, and Edward was Milton's first biographer. Milton's poetry was slow to see the light of day, at least under his name. His first published poem was "On Shakespeare" (1630), anonymously included in the Second Folio edition of William Shakespeare 's plays in 1632. An annotated copy of the First Folio has been suggested to contain marginal notes by Milton. Milton collected his work in 1645 Poems in
4706-479: A simulated Martian environment. The lithopanspermia hypothesis suggests that rocks ejected into outer space from life-harboring planets may successfully transport life forms to another habitable world. A conjecture is that just such a scenario occurred early in the history of the Solar System, with potentially microorganism -bearing rocks being exchanged between Venus, Earth, and Mars. The lack of pressure in space
4887-638: A spacecraft; similarly, " space-based " means based in outer space or on a planet or moon. The size of the whole universe is unknown, and it might be infinite in extent. According to the Big Bang theory, the very early universe was an extremely hot and dense state about 13.8 billion years ago which rapidly expanded . About 380,000 years later the universe had cooled sufficiently to allow protons and electrons to combine and form hydrogen—the so-called recombination epoch . When this happened, matter and energy became decoupled, allowing photons to travel freely through
5068-534: A strained relationship with them. On 12 November 1656, Milton was married to Katherine Woodcock at St Margaret's, Westminster . She died on 3 February 1658, less than four months after giving birth to her daughter Katherine, who also died. Milton married for a third time on 24 February 1663 to Elizabeth Mynshull or Minshull (1638–1728), the niece of Thomas Mynshull, a wealthy apothecary and philanthropist in Manchester . The marriage took place at St Mary Aldermary in
5249-445: A variable amount of water vapor , on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature and atmospheric pressure vary with altitude . Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and respiration of terrestrial animals is found only within 12 kilometres (7.5 mi) from the ground. Earth's early atmosphere consisted of accreted gases from
5430-481: Is Brief Lives of John Aubrey , an uneven compilation including first-hand reports. In the work, Aubrey quotes Christopher, Milton's younger brother: "When he was young, he studied very hard and sat up very late, commonly till twelve or one o'clock at night". Aubrey adds, "His complexion exceeding faire—he was so faire that they called him the Lady of Christ's College." In 1625, Milton gained entry to Christ's College at
5611-544: Is 14 °C (57 °F; 287 K) or 15 °C (59 °F; 288 K), depending on the reference. The average atmospheric pressure at sea level is defined by the International Standard Atmosphere as 101325 pascals (760.00 Torr ; 14.6959 psi ; 760.00 mmHg ). This is sometimes referred to as a unit of standard atmospheres (atm) . Total atmospheric mass is 5.1480×10 kg (1.135×10 lb), about 2.5% less than would be inferred from
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5792-514: Is Spent ," titled by a later editor, John Newton , "On His Blindness," is presumed to date from this period. Cromwell's death in 1658 caused the English Republic to collapse into feuding military and political factions. Milton, however, stubbornly clung to the beliefs that had originally inspired him to write for the Commonwealth. In 1659, he published A Treatise of Civil Power , attacking
5973-421: Is a continuous stream of charged particles emanating from the Sun which creates a very tenuous atmosphere (the heliosphere ) for billions of kilometers into space. This wind has a particle density of 5–10 protons /cm and is moving at a velocity of 350–400 km/s (780,000–890,000 mph). Interplanetary space extends out to the heliopause where the influence of the galactic environment starts to dominate over
6154-408: Is about 1.2 kg/m (1.2 g/L, 0.0012 g/cm ). Density is not measured directly but is calculated from measurements of temperature, pressure and humidity using the equation of state for air (a form of the ideal gas law ). Atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula . More sophisticated models are used to predict
6335-442: Is about 11,200 m/s (40,300 km/h; 25,100 mph). Orbiting spacecraft with a perigee below about 2,000 km (1,200 mi) are subject to drag from the Earth's atmosphere, which decreases the orbital altitude. The rate of orbital decay depends on the satellite's cross-sectional area and mass, as well as variations in the air density of the upper atmosphere. At altitudes above 800 km (500 mi), orbital lifetime
6516-414: Is about 28.946 or 28.96 g/mol. This is decreased when the air is humid. The relative concentration of gases remains constant until about 10,000 m (33,000 ft). In general, air pressure and density decrease with altitude in the atmosphere. However, temperature has a more complicated profile with altitude and may remain relatively constant or even increase with altitude in some regions (see
6697-500: Is about five times the Moon's orbital distance , but which distance is also far less than the distance between Earth and any adjacent planet. Interplanetary space within the Solar System is the space between the eight planets, the space between the planets and the Sun, as well as that space beyond the orbit of the outermost planet Neptune where the solar wind remains active. The solar wind
6878-685: Is also possible that, like Isaac Newton four decades later, Milton was sent home from Cambridge because of the plague , which afflicted Cambridge in 1625. At Cambridge, Milton was on good terms with Edward King ; he later dedicated " Lycidas " to him. Milton also befriended theologian Roger Williams , tutoring Williams in Hebrew in exchange for lessons in Dutch . Despite developing a reputation for poetic skill and general erudition, Milton suffered from alienation among his peers during his time at Cambridge. Having once watched his fellow students attempting comedy upon
7059-465: Is among history's most influential and impassioned defences of freedom of speech and freedom of the press . His desire for freedom extended beyond his philosophy and was reflected in his style, which included his introduction of new words (coined from Latin and Ancient Greek ) to the English language . He was the first modern writer to employ unrhymed verse outside of the theatre or translations. Milton
7240-442: Is because clouds (H 2 O) are strong absorbers and emitters of infrared radiation. This is also why it becomes colder at night at higher elevations. The greenhouse effect is directly related to this absorption and emission effect. Some gases in the atmosphere absorb and emit infrared radiation, but do not interact with sunlight in the visible spectrum. Common examples of these are CO 2 and H 2 O. The refractive index of air
7421-1429: Is called paleoclimatology . The three major constituents of Earth's atmosphere are nitrogen , oxygen , and argon . Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppm by mole fraction in the coldest portions of the atmosphere to as much as 5% by mole fraction in hot, humid air masses, and concentrations of other atmospheric gases are typically quoted in terms of dry air (without water vapor). The remaining gases are often referred to as trace gases, among which are other greenhouse gases , principally carbon dioxide, methane, nitrous oxide, and ozone. Besides argon, other noble gases , neon , helium , krypton , and xenon are also present. Filtered air includes trace amounts of many other chemical compounds . Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition, pollen and spores , sea spray , and volcanic ash . Various industrial pollutants also may be present as gases or aerosols, such as chlorine (elemental or in compounds), fluorine compounds and elemental mercury vapor. Sulfur compounds such as hydrogen sulfide and sulfur dioxide (SO 2 ) may be derived from natural sources or from industrial air pollution. Mole fraction
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7602-447: Is close to, but just greater than, 1. Systematic variations in the refractive index can lead to the bending of light rays over long optical paths. One example is that, under some circumstances, observers on board ships can see other vessels just over the horizon because light is refracted in the same direction as the curvature of Earth's surface. The refractive index of air depends on temperature, giving rise to refraction effects when
7783-511: Is co-populated by groups of co-orbital Near-Earth Objects (NEOs), such as horseshoe librators and Earth trojans , with some NEOs at times becoming temporary satellites and quasi-moons to Earth. Deep space is defined by the United States government as all of outer space which lies further from Earth than a typical low-Earth-orbit, thus assigning the Moon to deep-space. Other definitions vary
7964-445: Is described as the "greatest English author" by his biographer William Hayley , and he remains generally regarded "as one of the preeminent writers in the English language ", though critical reception has oscillated in the centuries since his death, often on account of his republicanism . Samuel Johnson praised Paradise Lost as "a poem which ... with respect to design may claim the first place, and with respect to performance,
8145-489: Is divided into overlapping regions of space. Near-Earth space is the region of space extending from low Earth orbits out to geostationary orbits . This region includes the major orbits for artificial satellites and is the site of most of humanity's space activity. The region has seen high levels of space debris, sometimes dubbed space pollution , threatening any space activity in this region. Some of this debris re-enters Earth's atmosphere periodically. Although it meets
8326-437: Is free for all nation states to explore and is not subject to claims of national sovereignty, calling outer space the "province of all mankind". This status as a common heritage of mankind has been used, though not without opposition, to enforce the right to access and shared use of outer space for all nations equally, particularly non-spacefaring nations. It prohibits the deployment of nuclear weapons in outer space. The treaty
8507-484: Is located beyond the orbit of the Moon and therefore includes cislunar space. Translunar space is the region of lunar transfer orbits , between the Moon and Earth. Cislunar space is a region outside of Earth that includes lunar orbits , the Moon's orbital space around Earth and the Lagrange points . The region where a body's gravitational potential remains dominant against gravitational potentials from other bodies,
8688-477: Is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase. The atoms and molecules are so far apart that they can travel hundreds of kilometres without colliding with one another. Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space . These free-moving particles follow ballistic trajectories and may migrate in and out of
8869-473: Is measured in centuries. Below about 300 km (190 mi), decay becomes more rapid with lifetimes measured in days. Once a satellite descends to 180 km (110 mi), it has only hours before it vaporizes in the atmosphere. Space in proximity to the Earth is physically similar to the remainder of interplanetary space, but is home to a multitude of Earth–orbiting satellites and has been subject to extensive studies. For identification purposes, this volume
9050-419: Is measured in terms of the kinetic activity of the gas, as it is on Earth. The radiation of outer space has a different temperature than the kinetic temperature of the gas, meaning that the gas and radiation are not in thermodynamic equilibrium . All of the observable universe is filled with photons that were created during the Big Bang, which is known as the cosmic microwave background radiation (CMB). (There
9231-440: Is named after Theodore von Kármán , who argued for an altitude where a vehicle would have to travel faster than orbital velocity to derive sufficient aerodynamic lift from the atmosphere to support itself, which he calculated to be at an altitude of about 83.8 km (52.1 mi). This distinguishes altitudes below as the region of aerodynamics and airspace , and above as the space of astronautics and free space . There
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#17330859992779412-445: Is no direct radiation reaching you, it has all been scattered. As another example, due to a phenomenon called Rayleigh scattering , shorter (blue) wavelengths scatter more easily than longer (red) wavelengths. This is why the sky looks blue; you are seeing scattered blue light. This is also why sunsets are red. Because the Sun is close to the horizon, the Sun's rays pass through more atmosphere than normal before reaching your eye. Much of
9593-464: Is no internationally recognized legal altitude limit on national airspace, although the Kármán line is the most frequently used for this purpose. Objections have been made to setting this limit too high, as it could inhibit space activities due to concerns about airspace violations. It has been argued for setting no specified singular altitude in international law, instead applying different limits depending on
9774-443: Is not devoid of matter , as it contains a few hydrogen atoms per cubic meter. By comparison, the air humans breathe contains about 10 molecules per cubic meter. The low density of matter in outer space means that electromagnetic radiation can travel great distances without being scattered: the mean free path of a photon in intergalactic space is about 10 km, or 10 billion light years. In spite of this, extinction , which
9955-547: Is quite likely a correspondingly large number of neutrinos called the cosmic neutrino background .) The current black body temperature of the background radiation is about 2.7 K (−455 °F). The gas temperatures in outer space can vary widely. For example, the temperature in the Boomerang Nebula is 1 K (−458 °F), while the solar corona reaches temperatures over 1,200,000–2,600,000 K (2,200,000–4,700,000 °F). Magnetic fields have been detected in
10136-627: Is slowed by the pressure containment of blood vessels, so some blood remains liquid. Swelling and ebullism can be reduced by containment in a pressure suit . The Crew Altitude Protection Suit (CAPS), a fitted elastic garment designed in the 1960s for astronauts, prevents ebullism at pressures as low as 2 kilopascals (0.3 psi). Supplemental oxygen is needed at 8 km (5 mi) to provide enough oxygen for breathing and to prevent water loss, while above 20 km (12 mi) pressure suits are essential to prevent ebullism. Most space suits use around 30–39 kilopascals (4–6 psi) of pure oxygen, about
10317-513: Is so tenuous that some scientists consider it to be part of interplanetary space rather than part of the atmosphere). It extends from the thermopause (also known as the "exobase") at the top of the thermosphere to a poorly defined boundary with the solar wind and interplanetary medium . The altitude of the exobase varies from about 500 kilometres (310 mi; 1,600,000 ft) to about 1,000 kilometres (620 mi) in times of higher incoming solar radiation. The upper limit varies depending on
10498-481: Is sometimes referred to as volume fraction ; these are identical for an ideal gas only. ppm: parts per million by molecular count The concentration of CO 2 has been increasing in recent decades , as has that of CH 4 . Water vapor is about 0.25% by mass over full atmosphere Water vapor varies significantly locally The average molecular weight of dry air, which can be used to calculate densities or to convert between mole fraction and mass fraction,
10679-535: Is the absorption and scattering of photons by dust and gas, is an important factor in galactic and intergalactic astronomy . Stars, planets, and moons retain their atmospheres by gravitational attraction. Atmospheres have no clearly delineated upper boundary: the density of atmospheric gas gradually decreases with distance from the object until it becomes indistinguishable from outer space. The Earth's atmospheric pressure drops to about 0.032 Pa at 100 kilometres (62 miles) of altitude, compared to 100,000 Pa for
10860-445: Is the body's sphere of influence or gravity well, mostly described with the Hill sphere model. In the case of Earth this includes all space from the Earth to a distance of roughly 1% of the mean distance from Earth to the Sun, or 1.5 million km (0.93 million mi). Beyond Earth's Hill sphere extends along Earth's orbital path its orbital and co-orbital space. This space
11041-456: Is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12 km (7.5 mi; 39,000 ft), although this altitude varies from about 9 km (5.6 mi; 30,000 ft) at the geographic poles to 17 km (11 mi; 56,000 ft) at the Equator , with some variation due to weather. The troposphere is bounded above by the tropopause ,
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#173308599927711222-503: Is the most immediate dangerous characteristic of space to humans. Pressure decreases above Earth, reaching a level at an altitude of around 19.14 km (11.89 mi) that matches the vapor pressure of water at the temperature of the human body . This pressure level is called the Armstrong line , named after American physician Harry G. Armstrong . At or above the Armstrong line, fluids in
11403-412: Is too low to conduct a significant amount of energy to or from the skin. This layer is completely cloudless and free of water vapor. However, non-hydrometeorological phenomena such as the aurora borealis and aurora australis are occasionally seen in the thermosphere. The International Space Station orbits in this layer, between 350 and 420 km (220 and 260 mi). It is this layer where many of
11584-475: Is typically the warmest section of the troposphere. This promotes vertical mixing (hence, the origin of its name in the Greek word τρόπος, tropos , meaning "turn"). The troposphere contains roughly 80% of the mass of Earth's atmosphere. The troposphere is denser than all its overlying layers because a larger atmospheric weight sits on top of the troposphere and causes it to be most severely compressed. Fifty percent of
11765-403: Is widely regarded as one of the greatest poets in English literature, though his oeuvre has drawn criticism from notable figures, including T. S. Eliot and Joseph Addison . According to some scholars, Milton was second in influence to none but William Shakespeare . In one of his books, Samuel Johnson praised him for having the power of "displaying the vast, illuminating the splendid, enforcing
11946-554: The Andromeda Galaxy was first measured. Humans began the physical exploration of space later in the same century with the advent of high-altitude balloon flights . This was followed by crewed rocket flights and, then, crewed Earth orbit, first achieved by Yuri Gagarin of the Soviet Union in 1961. The economic cost of putting objects, including humans, into space is very high, limiting human spaceflight to low Earth orbit and
12127-504: The Bishops' Wars presaged further armed conflict, Milton began to write prose tracts against episcopacy , in the service of the Puritan and Parliamentary cause. Milton's first foray into polemics was Of Reformation touching Church Discipline in England (1641), followed by Of Prelatical Episcopacy , the two defences of Smectymnuus (a group of Presbyterian divines named from their initials;
12308-464: The Bogotá Declaration , they claimed control of the segment of the geosynchronous orbital path corresponding to each country. These claims are not internationally accepted. An increasing issue of international space law and regulation has been the dangers of the growing number of space debris . A spacecraft enters orbit when its centripetal acceleration due to gravity is less than or equal to
12489-517: The De Doctrina , where he denies the dual natures of man and argues for a theory of Creation ex Deo . Milton was a "passionately individual Christian Humanist poet." He appears on the pages of seventeenth century English Puritanism, an age characterized as "the world turned upside down." He was a Puritan and yet was unwilling to surrender conscience to party positions on public policy. Thus, Milton's political thought, driven by competing convictions,
12670-641: The Exclusion debate, the attempt to exclude the heir presumptive from the throne of England— James, Duke of York —because he was Roman Catholic. That debate preoccupied politics in the 1670s and 1680s and precipitated the formation of the Whig party and the Glorious Revolution . Milton died on 8 November 1674, just a month before his 66th birthday. He was buried in the church of St Giles-without-Cripplegate , Fore Street , London. However, sources differ as to whether
12851-577: The F-layer of the ionosphere where they encounter enough atmospheric drag to require reboosts every few months, otherwise, orbital decay will occur resulting in a return to Earth. Depending on solar activity, satellites can experience noticeable atmospheric drag at altitudes as high as 700–800 km. The division of the atmosphere into layers mostly by reference to temperature is discussed above. Temperature decreases with altitude starting at sea level, but variations in this trend begin above 11 km, where
13032-550: The International Union of Pure and Applied Chemistry (IUPAC) definition of standard pressure . Above this altitude, isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from the Sun and the dynamic pressure of the solar wind . The thermosphere in this range has large gradients of pressure, temperature and composition, and varies greatly due to space weather . The temperature of outer space
13213-443: The Moon . On the other hand, uncrewed spacecraft have reached all of the known planets in the Solar System . Outer space represents a challenging environment for human exploration because of the hazards of vacuum and radiation . Microgravity has a negative effect on human physiology that causes both muscle atrophy and bone loss . The use of the short version space , as meaning 'the region beyond Earth's sky', predates
13394-473: The University of Cambridge , where he graduated with a BA in 1629, ranking fourth of 24 honours graduates that year in the University of Cambridge. Preparing, at that time, to become an Anglican priest, he stayed on at Cambridge where he received his MA on 3 July 1632. Milton may have been rusticated (suspended) in his first year at Cambridge for quarrelling with his tutor, Bishop William Chappell . He
13575-506: The background radiation from the Big Bang , is 2.7 kelvins (−270 °C; −455 °F). The plasma between galaxies is thought to account for about half of the baryonic (ordinary) matter in the universe, having a number density of less than one hydrogen atom per cubic metre and a kinetic temperature of millions of kelvins . Local concentrations of matter have condensed into stars and galaxies . Intergalactic space takes up most of
13756-469: The centrifugal acceleration due to the horizontal component of its velocity. For a low Earth orbit , this velocity is about 7,800 m/s (28,100 km/h; 17,400 mph); by contrast, the fastest piloted airplane speed ever achieved (excluding speeds achieved by deorbiting spacecraft) was 2,200 m/s (7,900 km/h; 4,900 mph) in 1967 by the North American X-15 . To achieve an orbit,
13937-499: The cosmic microwave background using satellites like the Wilkinson Microwave Anisotropy Probe . These observations indicate that the spatial geometry of the observable universe is " flat ", meaning that photons on parallel paths at one point remain parallel as they travel through space to the limit of the observable universe, except for local gravity. The flat universe, combined with the measured mass density of
14118-588: The infrared to around 1100 nm. There are also infrared and radio windows that transmit some infrared and radio waves at longer wavelengths. For example, the radio window runs from about one centimetre to about eleven-metre waves. Emission is the opposite of absorption, it is when an object emits radiation. Objects tend to emit amounts and wavelengths of radiation depending on their " black body " emission curves, therefore hotter objects tend to emit more radiation, with shorter wavelengths. Colder objects emit less radiation, with longer wavelengths. For example,
14299-433: The magnetosphere or the solar wind. Every second, the Earth loses about 3 kg of hydrogen, 50 g of helium, and much smaller amounts of other constituents. The exosphere is too far above Earth for meteorological phenomena to be possible. However, Earth's auroras —the aurora borealis (northern lights) and aurora australis (southern lights)—sometimes occur in the lower part of the exosphere, where they overlap into
14480-402: The mesopause that marks the top of this middle layer of the atmosphere. It is the coldest place on Earth and has an average temperature around −85 °C (−120 °F ; 190 K ). Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can condense into polar-mesospheric noctilucent clouds of ice particles. These are the highest clouds in
14661-464: The parliamentary cause , and he also begins to synthesize the ideal of neo-Roman liberty with that of Christian liberty. Milton also courted another woman during this time; we know nothing of her except that her name was Davis and she turned him down. However, it was enough to induce Mary Powell into returning to him which she did unexpectedly by begging him to take her back. They had two daughters in quick succession following their reconciliation. With
14842-451: The solar nebula , but the atmosphere changed significantly over time, affected by many factors such as volcanism , impact events , weathering and the evolution of life (particularly the photoautotrophs ). Recently, human activity has also contributed to atmospheric changes , such as climate change (mainly through deforestation and fossil fuel -related global warming ), ozone depletion and acid deposition . The atmosphere has
15023-428: The temperature section). Because the general pattern of the temperature/altitude profile, or lapse rate , is constant and measurable by means of instrumented balloon soundings , the temperature behavior provides a useful metric to distinguish atmospheric layers. This atmospheric stratification divides the Earth's atmosphere into five main layers: The exosphere is the outermost layer of Earth's atmosphere (though it
15204-511: The tropopause . This layer extends from the top of the troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to the stratopause at an altitude of about 50 to 55 km (31 to 34 mi; 164,000 to 180,000 ft). The atmospheric pressure at the top of the stratosphere is roughly 1/1000 the pressure at sea level . It contains the ozone layer , which is the part of Earth's atmosphere that contains relatively high concentrations of that gas. The stratosphere defines
15385-424: The zodiacal light . Interplanetary space contains the magnetic field generated by the Sun. There are magnetospheres generated by planets such as Jupiter, Saturn, Mercury and the Earth that have their own magnetic fields. These are shaped by the influence of the solar wind into the approximation of a teardrop shape, with the long tail extending outward behind the planet. These magnetic fields can trap particles from
15566-556: The " Good Old Cause ". On 27 April 1667, Milton sold the publication rights for Paradise Lost to publisher Samuel Simmons for £5 (equivalent to approximately £770 in 2015 purchasing power), with a further £5 to be paid if and when each print run sold out of between 1,300 and 1,500 copies. The first run was a quarto edition priced at three shillings per copy (about £23 in 2015 purchasing power equivalent), published in August 1667, and it sold out in eighteen months. Milton followed up
15747-504: The "TY" belonged to Milton's old tutor Thomas Young), and The Reason of Church-Government Urged against Prelaty . He vigorously attacked the High-church party of the Church of England and their leader William Laud , Archbishop of Canterbury , with frequent passages of real eloquence lighting up the rough controversial style of the period, and deploying a wide knowledge of church history. He
15928-419: The 17-year-old Mary Powell. The marriage got off to a poor start as Mary did not adapt to Milton's austere lifestyle or get along with his nephews. Milton found her intellectually unsatisfying and disliked the royalist views she had absorbed from her family. It is also speculated that she refused to consummate the marriage. Mary soon returned home to her parents and did not come back until 1645, partly because of
16109-656: The Cardinal. Around March, Milton travelled once again to Florence, staying there for two months, attending further meetings of the academies, and spending time with friends. After leaving Florence, he travelled through Lucca, Bologna, and Ferrara before coming to Venice . In Venice, Milton was exposed to a model of Republicanism, later important in his political writings, but he soon found another model when he travelled to Geneva. From Switzerland, Milton travelled to Paris and then to Calais before finally arriving back in England in either July or August 1639. On returning to England where
16290-729: The City of London. Despite a 31-year age gap, the marriage seemed happy, according to John Aubrey , and lasted more than 12 years until Milton's death. (A plaque on the wall of Mynshull's House in Manchester describes Elizabeth as Milton's "3rd and Best wife".) Samuel Johnson, however, claims that Mynshull was "a domestic companion and attendant" and Milton's nephew Edward Phillips relates that Mynshull "oppressed his children in his lifetime, and cheated them at his death". His nephews, Edward and John Phillips (sons of Milton's sister Anne), were educated by Milton and became writers themselves. John acted as
16471-418: The Earth's magnetosphere and the solar wind. The inner boundary is the ionosphere . The variable space-weather conditions of geospace are affected by the behavior of the Sun and the solar wind; the subject of geospace is interlinked with heliophysics —the study of the Sun and its impact on the planets of the Solar System. The day-side magnetopause is compressed by solar-wind pressure—the subsolar distance from
16652-520: The Egerton family, and performed in 1632 and 1634 respectively. Comus argues for the virtuousness of temperance and chastity . He contributed his pastoral elegy Lycidas to a memorial collection for one of his fellow-students at Cambridge. Drafts of these poems are preserved in Milton's poetry notebook, known as the Trinity Manuscript, because it is now kept at Trinity College , Cambridge. It
16833-649: The Entry Interface), when atmospheric drag becomes noticeable, thus beginning the process of switching from steering with thrusters to maneuvering with aerodynamic control surfaces. The Kármán line , established by the Fédération Aéronautique Internationale , and used internationally by the United Nations , is set at an altitude of 100 km (62 mi) as a working definition for the boundary between aeronautics and astronautics. This line
17014-509: The Kármán line, significant atmospheric effects such as auroras still occur. Meteors begin to glow in this region, though the larger ones may not burn up until they penetrate more deeply. The various layers of Earth's ionosphere , important to HF radio propagation, begin below 100 km and extend beyond 500 km. By comparison, the International Space Station and Space Shuttle typically orbit at 350–400 km, within
17195-469: The Morning of Christ's Nativity", "Epitaph on the admirable Dramaticke Poet, W. Shakespeare" (his first poem to appear in print), L'Allegro , and Il Penseroso . It appears in all his writings that he had the usual concomitant of great abilities, a lofty and steady confidence in himself, perhaps not without some contempt of others; for scarcely any man ever wrote so much, and praised so few. Of his praise he
17376-640: The Parliamentary victory in the Civil War, Milton used his pen in defence of the republican principles represented by the Commonwealth. The Tenure of Kings and Magistrates (1649) defended the right of the people to hold their rulers to account, and implicitly sanctioned the regicide ; Milton's political reputation got him appointed Secretary for Foreign Tongues by the Council of State in March 1649. His main job description
17557-755: The Puritans against the Cavaliers i.e. the King's party, and helped win the day. But the very same constitutional and republican polity, when tried to curtail freedom of speech, Milton, given his humanistic zeal, wrote Areopagitica . . . [ sic ] Areopagitica was written in response to the Licensing Order, in November 1644. Milton's political thought may be best categorized according to respective periods in his life and times. The years 1641–42 were dedicated to church politics and
17738-459: The Sun is approximately 6,000 K (5,730 °C ; 10,340 °F ), its radiation peaks near 500 nm, and is visible to the human eye. Earth is approximately 290 K (17 °C; 62 °F), so its radiation peaks near 10,000 nm, and is much too long to be visible to humans. Because of its temperature, the atmosphere emits infrared radiation. For example, on clear nights Earth's surface cools down faster than on cloudy nights. This
17919-450: The Sun. It is the space between the stars or stellar systems within a nebula or galaxy. Interstellar space contains an interstellar medium of sparse matter and radiation. The boundary between an astrosphere and interstellar space is known as an astropause . For the Sun, the astrosphere and astropause are called the heliosphere and heliopause. Approximately 70% of the mass of the interstellar medium consists of lone hydrogen atoms; most of
18100-468: The United States designated people who travel above an altitude of 50 mi (80 km) as astronauts. Astronaut wings are now only awarded to spacecraft crew members that "demonstrated activities during flight that were essential to public safety, or contributed to human space flight safety." In 2009, measurements of the direction and speed of ions in the atmosphere were made from a sounding rocket . The altitude of 118 km (73.3 mi) above Earth
18281-420: The aptly-named thermosphere above 90 km. Because in an ideal gas of constant composition the speed of sound depends only on temperature and not on pressure or density, the speed of sound in the atmosphere with altitude takes on the form of the complicated temperature profile (see illustration to the right), and does not mirror altitudinal changes in density or pressure. The density of air at sea level
18462-421: The atmosphere also cools by emitting radiation, as discussed below. The combined absorption spectra of the gases in the atmosphere leave "windows" of low opacity , allowing the transmission of only certain bands of light. The optical window runs from around 300 nm ( ultraviolet -C) up into the range humans can see, the visible spectrum (commonly called light), at roughly 400–700 nm and continues to
18643-399: The atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or similarly before sunrise. They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known as transient luminous events (TLEs) occasionally form in the mesosphere above tropospheric thunderclouds . The mesosphere is also
18824-489: The atmosphere based on characteristics such as temperature and composition, namely the troposphere , stratosphere , mesosphere , thermosphere (formally the ionosphere ) and exosphere . The study of Earth's atmosphere and its processes is called atmospheric science (aerology), and includes multiple subfields, such as climatology and atmospheric physics . Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann . The study of historic atmosphere
19005-637: The average sea level pressure and Earth's area of 51007.2 megahectares, this portion being displaced by Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather . If the entire mass of the atmosphere had a uniform density equal to sea level density (about 1.2 kg per m ) from sea level upwards, it would terminate abruptly at an altitude of 8.50 km (27,900 ft). Air pressure actually decreases exponentially with altitude, dropping by half every 5.6 km (18,000 ft) or by
19186-584: The awful, darkening the gloomy and aggravating the dreadful." John Milton was born in Bread Street , London, on 9 December 1608, the son of composer John Milton and his wife Sarah Jeffrey. The senior John Milton (1562–1647) moved to London around 1583 after being disinherited by his devout Catholic father Richard "the Ranger" Milton for embracing Protestantism . In London, the senior John Milton married Sarah Jeffrey (1572–1637) and found lasting financial success as
19367-496: The blood empties into the lungs to try to equalize the partial pressure gradient. Once the deoxygenated blood arrives at the brain, humans lose consciousness after a few seconds and die of hypoxia within minutes. Blood and other body fluids boil when the pressure drops below 6.3 kilopascals (1 psi), and this condition is called ebullism . The steam may bloat the body to twice its normal size and slow circulation, but tissues are elastic and porous enough to prevent rupture. Ebullism
19548-414: The blue light has been scattered out, leaving the red light in a sunset. Different molecules absorb different wavelengths of radiation. For example, O 2 and O 3 absorb almost all radiation with wavelengths shorter than 300 nanometres . Water (H 2 O) absorbs at many wavelengths above 700 nm. When a molecule absorbs a photon, it increases the energy of the molecule. This heats the atmosphere, but
19729-516: The body adjusts to the new environment. Longer-term exposure to weightlessness results in muscle atrophy and deterioration of the skeleton, or spaceflight osteopenia . These effects can be minimized through a regimen of exercise. Other effects include fluid redistribution, slowing of the cardiovascular system , decreased production of red blood cells , balance disorders, and a weakening of the immune system . Lesser symptoms include loss of body mass, nasal congestion, sleep disturbance, and puffiness of
19910-416: The bulk of the information about the tour comes from a work that, according to Barbara Lewalski , "was not intended as autobiography but as rhetoric, designed to emphasise his sterling reputation with the learned of Europe." He first went to Calais and then on to Paris, riding horseback, with a letter from diplomat Henry Wotton to ambassador John Scudamore . Through Scudamore, Milton met Hugo Grotius ,
20091-499: The case, in particular based on the craft and its purpose. Spacecraft have flown over foreign countries as low as 30 km (19 mi), as in the example of the Space Shuttle. The Outer Space Treaty provides the basic framework for international space law. It covers the legal use of outer space by nation states, and includes in its definition of outer space , the Moon, and other celestial bodies. The treaty states that outer space
20272-577: The cause of death was consumption or gout . According to an early biographer, his funeral was attended by "his learned and great Friends in London, not without a friendly concourse of the Vulgar." A monument was added in 1793, sculpted by John Bacon the Elder . Milton and his first wife Mary Powell (1625–1652) had four children: Mary Powell died on 5 May 1652 from complications following Deborah's birth. Milton's daughters survived to adulthood, but he always had
20453-411: The center of the Earth is typically 10 Earth radii. On the night side, the solar wind stretches the magnetosphere to form a magnetotail that sometimes extends out to more than 100–200 Earth radii. For roughly four days of each month, the lunar surface is shielded from the solar wind as the Moon passes through the magnetotail. Geospace is populated by electrically charged particles at very low densities,
20634-453: The college stage, he later observed, "they thought themselves gallant men, and I thought them fools". Milton also was disdainful of the university curriculum, which consisted of stilted formal debates conducted in Latin on abstruse topics. His own corpus is not devoid of humour, notably his sixth prolusion and his epitaphs on the death of Thomas Hobson . While at Cambridge, he wrote some of his well-known shorter English poems, including "On
20815-612: The concept of a state-dominated church (the position known as Erastianism ), as well as Considerations touching the likeliest means to remove hirelings , denouncing corrupt practises in church governance. As the Republic disintegrated, Milton wrote several proposals to retain a non-monarchical government against the wishes of parliament, soldiers, and the people. Upon the Restoration in May 1660, Milton, fearing for his life, went into hiding, while
20996-473: The continent and spent time at Geneva with Diodati's uncle after he returned to Rome. In Defensio Secunda , Milton proclaimed that he was warned against a return to Rome because of his frankness about religion, but he stayed in the city for two months and was able to experience Carnival and meet Lukas Holste , a Vatican librarian who guided Milton through its collection. He was introduced to Cardinal Francesco Barberini who invited Milton to an opera hosted by
21177-444: The continually expanding space. Matter that remained following the initial expansion has since undergone gravitational collapse to create stars, galaxies and other astronomical objects, leaving behind a deep vacuum that forms what is now called outer space. As light has a finite velocity, this theory constrains the size of the directly observable universe. The present day shape of the universe has been determined from measurements of
21358-573: The crew. Further research is needed to assess the radiation hazards and determine suitable countermeasures. The transition between Earth's atmosphere and outer space lacks a well-defined physical boundary, with the air pressure steadily decreasing with altitude until it mixes with the solar wind. Various definitions for a practical boundary have been proposed, ranging from 30 km (19 mi) out to 1,600,000 km (990,000 mi). High-altitude aircraft , such as high-altitude balloons have reached altitudes above Earth of up to 50 km. Up until 2021,
21539-448: The definition of outer space, the atmospheric density inside low-Earth orbital space, the first few hundred kilometers above the Kármán line, is still sufficient to produce significant drag on satellites. Geospace is a region of space that includes Earth's upper atmosphere and magnetosphere . The Van Allen radiation belts lie within the geospace. The outer boundary of geospace is the magnetopause , which forms an interface between
21720-415: The definition. Various authorities consider it to end at about 10,000 kilometres (6,200 mi) or about 190,000 kilometres (120,000 mi)—about halfway to the moon, where the influence of Earth's gravity is about the same as radiation pressure from sunlight. The geocorona visible in the far ultraviolet (caused by neutral hydrogen) extends to at least 100,000 kilometres (62,000 mi). This layer
21901-452: The drafting of UN resolutions for the peaceful uses of outer space, anti-satellite weapons have been tested in Earth orbit . The concept that the space between the Earth and the Moon must be a vacuum was first proposed in the 17th century after scientists discovered that air pressure decreased with altitude. The immense scale of outer space was grasped in the 20th century when the distance to
22082-540: The exiled Charles II and his party published the defence of monarchy Defensio Regia pro Carolo Primo , written by leading humanist Claudius Salmasius . By January of the following year, Milton was ordered to write a defence of the English people by the Council of State . Milton worked more slowly than usual, given the European audience and the English Republic's desire to establish diplomatic and cultural legitimacy, as he drew on
22263-419: The face. During long-duration space travel, radiation can pose an acute health hazard . Exposure to high-energy, ionizing cosmic rays can result in fatigue, nausea, vomiting, as well as damage to the immune system and changes to the white blood cell count. Over longer durations, symptoms include an increased risk of cancer, plus damage to the eyes, nervous system , lungs and the gastrointestinal tract . On
22444-575: The friend of many gentlemen eminent in rank and learning, whose private academies I frequented—a Florentine institution which deserves great praise not only for promoting humane studies but also for encouraging friendly intercourse. He left Florence in September to continue to Rome. With the connections from Florence, Milton was able to have easy access to Rome's intellectual society. His poetic abilities impressed those like Giovanni Salzilli, who praised Milton within an epigram. In late October, Milton attended
22625-434: The gas molecules are so far apart that its temperature in the usual sense is not very meaningful. The air is so rarefied that an individual molecule (of oxygen , for example) travels an average of 1 kilometre (0.62 mi; 3300 ft) between collisions with other molecules. Although the thermosphere has a high proportion of molecules with high energy, it would not feel hot to a human in direct contact, because its density
22806-477: The harsh environment, several life forms have been found that can withstand extreme space conditions for extended periods. Species of lichen carried on the ESA BIOPAN facility survived exposure for ten days in 2007. Seeds of Arabidopsis thaliana and Nicotiana tabacum germinated after being exposed to space for 1.5 years. A strain of Bacillus subtilis has survived 559 days when exposed to low Earth orbit or
22987-590: The high energy range, the flux of electrons is only about 1% of that of protons. Cosmic rays can damage electronic components and pose a health threat to space travelers. Smells produced returning from low Earth orbit extravehicular activity have a burned/metallic odor, similar to the scent of arc welding fumes, resulting from oxygen in low Earth orbit around the ISS, which clings to suits and equipment. Other regions of space could have very different smells, like that of different alcohols in molecular clouds . Despite
23168-607: The international co-operation in the peaceful uses of outer space and preventing an arms race in space. Four additional space law treaties have been negotiated and drafted by the UN's Committee on the Peaceful Uses of Outer Space . Still, there remains no legal prohibition against deploying conventional weapons in space, and anti-satellite weapons have been successfully tested by the USA, USSR, China, and in 2019, India. The 1979 Moon Treaty turned
23349-663: The interstellar medium, including the heavy elements previously formed within the star's core. The density of matter in the interstellar medium can vary considerably: the average is around 10 particles per m, but cold molecular clouds can hold 10–10 per m. Atmosphere of Earth The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth 's planetary surface (both lands and oceans ), known collectively as air , with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes ), all retained by Earth's gravity . The atmosphere serves as
23530-587: The jurisdiction of all heavenly bodies (including the orbits around such bodies) over to the international community. The treaty has not been ratified by any nation that currently practices human spaceflight. In 1976, eight equatorial states (Ecuador, Colombia, Brazil, The Republic of the Congo, Zaire, Uganda, Kenya, and Indonesia) met in Bogotá, Colombia: with their "Declaration of the First Meeting of Equatorial Countries", or
23711-439: The large pressure differential between inside and outside the chest. Even if the subject's airway is fully open, the flow of air through the windpipe may be too slow to prevent the rupture. Rapid decompression can rupture eardrums and sinuses, bruising and blood seep can occur in soft tissues, and shock can cause an increase in oxygen consumption that leads to hypoxia . As a consequence of rapid decompression, oxygen dissolved in
23892-403: The layer where most meteors burn up upon atmospheric entrance. It is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft. The mesosphere is mainly accessed by sounding rockets and rocket-powered aircraft . The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by
24073-568: The learning marshalled by his years of study to compose a riposte. On 24 February 1652, Milton published his Latin defence of the English people Defensio pro Populo Anglicano , also known as the First Defence . Milton's pure Latin prose and evident learning exemplified in the First Defence quickly made him a European reputation, and the work ran to numerous editions. He addressed his Sonnet 16 to 'The Lord Generall Cromwell in May 1652' beginning "Cromwell, our chief of men ...", although it
24254-401: The magnetic field and particle flux from the Sun. The distance and strength of the heliopause varies depending on the activity level of the solar wind. The heliopause in turn deflects away low-energy galactic cosmic rays, with this modulation effect peaking during solar maximum. The volume of interplanetary space is a nearly total vacuum, with a mean free path of about one astronomical unit at
24435-482: The mass of Earth's atmosphere is distributed approximately as follows: By comparison, the summit of Mount Everest is at 8,848 m (29,029 ft); commercial airliners typically cruise between 10 and 13 km (33,000 and 43,000 ft) where the lower density and temperature of the air improve fuel economy; weather balloons reach 30.4 km (100,000 ft) and above; and the highest X-15 flight in 1963 reached 108.0 km (354,300 ft). Even above
24616-503: The midst of the excitement attending the possibility of establishing a new English government. The anonymous edition of Comus was published in 1637, and the publication of Lycidas in 1638 in Justa Edouardo King Naufrago was signed J. M. Otherwise. The 1645 collection was the only poetry of his to see print until Paradise Lost appeared in 1667. Milton's magnum opus , the blank-verse epic poem Paradise Lost ,
24797-513: The most distant high-z sources, indicating the presence of magnetic fields. Outside a protective atmosphere and magnetic field, there are few obstacles to the passage through space of energetic subatomic particles known as cosmic rays. These particles have energies ranging from about 10 eV up to an extreme 10 eV of ultra-high-energy cosmic rays . The peak flux of cosmic rays occurs at energies of about 10 eV, with approximately 87% protons, 12% helium nuclei and 1% heavier nuclei. In
24978-524: The motions of which are controlled by the Earth's magnetic field . These plasmas form a medium from which storm-like disturbances powered by the solar wind can drive electrical currents into the Earth's upper atmosphere. Geomagnetic storms can disturb two regions of geospace, the radiation belts and the ionosphere. These storms increase fluxes of energetic electrons that can permanently damage satellite electronics, interfering with shortwave radio communication and GPS location and timing. Magnetic storms can be
25159-588: The notion that a single material substance which is "animate, self-active, and free" composes everything in the universe: from stones and trees and bodies to minds, souls, angels, and God. Fallon claims that Milton devised this position to avoid the mind-body dualism of Plato and Descartes as well as the mechanistic determinism of Hobbes . According to Fallon, Milton's monism is most notably reflected in Paradise Lost when he has angels eat (5.433–439) and apparently engage in sexual intercourse (8.622–629) and
25340-504: The orbital decay of satellites. The average mass of the atmosphere is about 5 quadrillion (5 × 10 ) tonnes or 1/1,200,000 the mass of Earth. According to the American National Center for Atmospheric Research , "The total mean mass of the atmosphere is 5.1480 × 10 kg with an annual range due to water vapor of 1.2 or 1.5 × 10 kg, depending on whether surface pressure or water vapor data are used; somewhat smaller than
25521-401: The orbital distance of the Earth. This space is not completely empty, and is sparsely filled with cosmic rays, which include ionized atomic nuclei and various subatomic particles. There is gas, plasma and dust, small meteors , and several dozen types of organic molecules discovered to date by microwave spectroscopy . A cloud of interplanetary dust is visible at night as a faint band called
25702-461: The outbreak of the Civil War . In the meantime, her desertion prompted Milton to publish a series of pamphlets over the next three years arguing for the legality and morality of divorce beyond grounds of adultery. ( Anna Beer , author of a 2008 biography of Milton, points to a lack of evidence and the dangers of cynicism in urging that it was not necessarily the case that the private life so animated
25883-578: The period to develop many of his major works. Milton's views developed from extensive reading, travel, and experience that began with his days as a student at Cambridge in the 1620s and continued through the English Civil War , which started in 1642 and continued until 1651. By the time of his death in 1674, Milton was impoverished and on the margins of English intellectual life but famous throughout Europe and unrepentant for political choices that placed him at odds with governing authorities. John Milton
26064-478: The previous estimate. The mean mass of water vapor is estimated as 1.27 × 10 kg and the dry air mass as 5.1352 ±0.0003 × 10 kg." Solar radiation (or sunlight) is the energy Earth receives from the Sun . Earth also emits radiation back into space, but at longer wavelengths that humans cannot see. Part of the incoming and emitted radiation is absorbed or reflected by the atmosphere. In May 2017, glints of light, seen as twinkling from an orbiting satellite
26245-574: The principles of the Revolution. Alexander Morus , to whom Milton wrongly attributed the Clamor (in fact by Peter du Moulin ), published an attack on Milton, in response to which Milton published the autobiographical Defensio pro se in 1655. Milton held the appointment of Secretary for Foreign Tongues to the Commonwealth Council of State until 1660, although after he had become totally blind, most of
26426-554: The public polemicising.) In 1643, Milton had a brush with the authorities over these writings, in parallel with Hezekiah Woodward , who had more trouble. It was the hostile response accorded the divorce tracts that spurred Milton to write Areopagitica; A speech of Mr. John Milton for the Liberty of Unlicenc'd Printing, to the Parlament of England , his celebrated attack on pre-printing censorship. In Areopagitica , Milton aligns himself with
26607-467: The publication Paradise Lost with its sequel Paradise Regained , which was published alongside the tragedy Samson Agonistes in 1671. Both of these works also reflect Milton's post-Restoration political situation. Just before his death in 1674, Milton supervised a second edition of Paradise Lost , accompanied by an explanation of "why the poem rhymes not", and prefatory verses by Andrew Marvell . In 1673, Milton republished his 1645 Poems , as well as
26788-438: The remainder consists of helium atoms. This is enriched with trace amounts of heavier atoms formed through stellar nucleosynthesis . These atoms are ejected into the interstellar medium by stellar winds or when evolved stars begin to shed their outer envelopes such as during the formation of a planetary nebula . The cataclysmic explosion of a supernova propagates shock waves of stellar ejecta outward, distributing it throughout
26969-639: The same as the partial pressure of oxygen at the Earth's surface. This pressure is high enough to prevent ebullism, but evaporation of nitrogen dissolved in the blood could still cause decompression sickness and gas embolisms if not managed. Humans evolved for life in Earth gravity , and exposure to weightlessness has been shown to have deleterious effects on human health. Initially, more than 50% of astronauts experience space motion sickness . This can cause nausea and vomiting, vertigo , headaches, lethargy , and overall malaise. The duration of space sickness varies, but it typically lasts for 1–3 days, after which
27150-422: The satellites orbiting the Earth are present. The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere. It extends from the stratopause at an altitude of about 50 km (31 mi; 160,000 ft) to the mesopause at 80–85 km (50–53 mi; 260,000–280,000 ft) above sea level. Temperatures drop with increasing altitude to
27331-565: The second, among the productions of the human mind", though he (a Tory ) described Milton's politics as those of an "acrimonious and surly republican". Milton was revered by poets such as William Blake , William Wordsworth , and Thomas Hardy . Phases of Milton's life parallel the major historical and political divisions in Stuart England at the time. In his early years, Milton studied at Christ's College, Cambridge , and then travelled, wrote poetry mostly for private circulation, and launched
27512-467: The solar wind and other sources, creating belts of charged particles such as the Van Allen radiation belts. Planets without magnetic fields, such as Mars, have their atmospheres gradually eroded by the solar wind. Interstellar space is the physical space outside of the bubbles of plasma known as astrospheres , formed by stellar winds originating from individual stars, or formed by solar wind emanating from
27693-625: The space around just about every class of celestial object. Star formation in spiral galaxies can generate small-scale dynamos , creating turbulent magnetic field strengths of around 5–10 μ G . The Davis–Greenstein effect causes elongated dust grains to align themselves with a galaxy's magnetic field, resulting in weak optical polarization . This has been used to show ordered magnetic fields that exist in several nearby galaxies. Magneto-hydrodynamic processes in active elliptical galaxies produce their characteristic jets and radio lobes . Non-thermal radio sources have been detected even among
27874-503: The start of outer space in space treaties and for aerospace records keeping. Certain portions of the upper stratosphere and the mesosphere are sometimes referred to as "near space". The framework for international space law was established by the Outer Space Treaty , which entered into force on 10 October 1967. This treaty precludes any claims of national sovereignty and permits all states to freely explore outer space . Despite
28055-405: The starting point of deep-space from, "That which lies beyond the orbit of the moon," to "That which lies beyond the farthest reaches of the Solar System itself." The International Telecommunication Union responsible for radio communication , including with satellites, defines deep-space as, "distances from the Earth equal to, or greater than, 2 million km (1.2 million mi)," which
28236-447: The stratosphere lacks the weather-producing air turbulence that is so prevalent in the troposphere. Consequently, the stratosphere is almost completely free of clouds and other forms of weather. However, polar stratospheric or nacreous clouds are occasionally seen in the lower part of this layer of the atmosphere where the air is coldest. The stratosphere is the highest layer that can be accessed by jet-powered aircraft . The troposphere
28417-412: The temperature gradient is large. An example of such effects is the mirage . John Milton John Milton (9 December 1608 – 8 November 1674) was an English poet, polemicist, and civil servant . His 1667 epic poem Paradise Lost , written in blank verse and including twelve books, was written in a time of immense religious flux and political upheaval. It addressed the fall of man , including
28598-444: The temperature stabilizes over a large vertical distance through the rest of the troposphere. In the stratosphere , starting above about 20 km, the temperature increases with height, due to heating within the ozone layer caused by the capture of significant ultraviolet radiation from the Sun by the dioxygen and ozone gas in this region. Still another region of increasing temperature with altitude occurs at very high altitudes, in
28779-593: The temptation of Adam and Eve by the fallen angel Satan and God 's expulsion of them from the Garden of Eden . Paradise Lost elevated Milton's reputation as one of history's greatest poets. He also served as a civil servant for the Commonwealth of England under its Council of State and later under Oliver Cromwell . Milton achieved fame and recognition during his lifetime; his celebrated Areopagitica (1644), written in condemnation of pre-publication censorship ,
28960-442: The thermopause varies considerably due to changes in solar activity. Because the thermopause lies at the lower boundary of the exosphere, it is also referred to as the exobase . The lower part of the thermosphere, from 80 to 550 kilometres (50 to 342 mi) above Earth's surface, contains the ionosphere . The temperature of the thermosphere gradually increases with height and can rise as high as 1500 °C (2700 °F), though
29141-429: The thermosphere. The exosphere contains many of the artificial satellites that orbit Earth. The thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause (which separates it from the mesosphere) at an altitude of about 80 km (50 mi; 260,000 ft) up to the thermopause at an altitude range of 500–1000 km (310–620 mi; 1,600,000–3,300,000 ft). The height of
29322-406: The throat and lungs boil away. More specifically, exposed bodily liquids such as saliva, tears, and liquids in the lungs boil away. Hence, at this altitude, human survival requires a pressure suit, or a pressurized capsule. Out in space, sudden exposure of an unprotected human to very low pressure , such as during a rapid decompression, can cause pulmonary barotrauma —a rupture of the lungs, due to
29503-527: The time. Their tone, however, stemmed from the Puritan emphasis on the centrality and inviolability of conscience. He was his own man, but he was anticipated by Henry Robinson in Areopagitica . While Milton's beliefs are generally considered to be consistent with Protestant Christianity, Stephen Fallon argues that by the late 1650s, Milton may have at least toyed with the idea of monism or animist materialism,
29684-419: The total mass of the atmosphere is located in the lower 5.6 km (3.5 mi; 18,000 ft) of the troposphere. Nearly all atmospheric water vapor or moisture is found in the troposphere, so it is the layer where most of Earth's weather takes place. It has basically all the weather-associated cloud genus types generated by active wind circulation, although very tall cumulonimbus thunder clouds can penetrate
29865-430: The tropopause from below and rise into the lower part of the stratosphere. Most conventional aviation activity takes place in the troposphere, and it is the only layer accessible by propeller-driven aircraft . Within the five principal layers above, which are largely determined by temperature, several secondary layers may be distinguished by other properties: The average temperature of the atmosphere at Earth's surface
30046-426: The universe and the accelerating expansion of the universe , indicates that space has a non-zero vacuum energy , which is called dark energy . Estimates put the average energy density of the present day universe at the equivalent of 5.9 protons per cubic meter, including dark energy, dark matter, and baryonic matter (ordinary matter composed of atoms). The atoms account for only 4.6% of the total energy density, or
30227-424: The use of full term "outer space", with the earliest recorded use of this meaning in an epic poem by John Milton called Paradise Lost , published in 1667. The term outward space existed in a poem from 1842 by the English poet Lady Emmeline Stuart-Wortley called "The Maiden of Moscow", but in astronomy the term outer space found its application for the first time in 1845 by Alexander von Humboldt . The term
30408-421: The volume of the universe , but even galaxies and star systems consist almost entirely of empty space. Most of the remaining mass-energy in the observable universe is made up of an unknown form, dubbed dark matter and dark energy . Outer space does not begin at a definite altitude above Earth's surface. The Kármán line , an altitude of 100 km (62 mi) above sea level , is conventionally used as
30589-476: The work was done by his deputies, Georg Rudolph Wecklein , then Philip Meadows , and from 1657 by the poet Andrew Marvell . By 1652, Milton had become totally blind; the cause of his blindness is debated but bilateral retinal detachment or glaucoma are most likely. His blindness forced him to dictate his verse and prose to amanuenses who copied them out for him; one of these was Andrew Marvell. One of his best-known sonnets, " When I Consider How My Light
30770-457: Was Charles Mason who made the extraordinary discovery, in the library of Trinity College, of a packet of thirty loose and tattered folio leaves, almost covered with the handwriting of Milton . It is thought that Mason recognised the nature of this material around 1735 and the loose-leaf sheets were bound for the first time in 1736; the Trinity Manuscript has been described as “the chief treasure of Trinity Library” . In May 1638, accompanied by
30951-515: Was certainly at home in London in the Lent Term 1626; there he wrote Elegia Prima , his first Latin elegy , to Charles Diodati, a friend from St Paul's. Based on remarks of John Aubrey , Chappell "whipt" Milton. This story is now disputed, though certainly Milton disliked Chappell. Historian Christopher Hill notes that Milton was apparently rusticated, and that the differences between Chappell and Milton may have been either religious or personal. It
31132-539: Was composed by the blind and impoverished Milton from 1658 to 1664 (first edition), with small but significant revisions published in 1674 (second edition). As a blind poet, Milton dictated his verse to a series of aides in his employ. It has been argued that the poem reflects his personal despair at the failure of the Revolution yet affirms an ultimate optimism in human potential. Some literary critics have argued that Milton encoded many references to his unyielding support for
31313-455: Was eventually popularized through the writings of H. G. Wells after 1901. Theodore von Kármán used the term of free space to name the space of altitudes above Earth where spacecrafts reach conditions sufficiently free from atmospheric drag, differentiating it from airspace , identifying a legal space above territories free from the sovereign jurisdiction of countries. " Spaceborne " denotes existing in outer space, especially if carried by
31494-559: Was introduced to Giovanni Battista Manso , patron to both Torquato Tasso and to Giambattista Marino . Originally, Milton wanted to leave Naples in order to travel to Sicily and then on to Greece, but he returned to England during the summer of 1639 because of what he claimed in Defensio Secunda were "sad tidings of civil war in England." Matters became more complicated when Milton received word that his childhood friend Diodati had died. Milton in fact stayed another seven months on
31675-570: Was not published until 1654. In 1654, Milton completed the second defence of the English nation Defensio secunda in response to an anonymous Royalist tract "Regii Sanguinis Clamor ad Coelum Adversus Parricidas Anglicanos" [The Cry of the Royal Blood to Heaven Against the English Parricides], a work that made many personal attacks on Milton. The second defence praised Oliver Cromwell , now Lord Protector, while exhorting him to remain true to
31856-645: Was passed by the United Nations General Assembly in 1963 and signed in 1967 by the Union of Soviet Socialist Republics (USSR), the United States of America (USA), and the United Kingdom (UK). As of 2017, 105 state parties have either ratified or acceded to the treaty. An additional 25 states signed the treaty, without ratifying it. Since 1958, outer space has been the subject of multiple United Nations resolutions. Of these, more than 50 have been concerning
32037-445: Was supported by his father's investments, but Milton became a private schoolmaster at this time, educating his nephews and other children of the well-to-do. This experience and discussions with educational reformer Samuel Hartlib led him to write his short tract Of Education in 1644, urging a reform of the national universities. In June 1642, Milton paid a visit to the manor house at Forest Hill, Oxfordshire , and, aged 34, married
32218-500: Was the midpoint for charged particles transitioning from the gentle winds of the Earth's atmosphere to the more extreme flows of outer space. The latter can reach velocities well over 268 m/s (880 ft/s). Spacecraft have entered into a highly elliptical orbit with a perigee as low as 80 to 90 km (50 to 56 mi), surviving for multiple orbits. At an altitude of 120 km (75 mi), descending spacecraft such as NASA 's Space Shuttle begin atmospheric entry (termed
32399-545: Was to compose the English Republic's foreign correspondence in Latin and other languages, but he also was called upon to produce propaganda for the regime and to serve as a censor. In October 1649, he published Eikonoklastes , an explicit defence of the regicide, in response to the Eikon Basilike , a phenomenal best-seller popularly attributed to Charles I that portrayed the King as an innocent Christian martyr . A month later
32580-627: Was under house arrest at Arcetri , as well as others. Milton probably visited the Florentine Academy and the Accademia della Crusca along with smaller academies in the area, including the Apatisti and the Svogliati . In [Florence], which I have always admired above all others because of the elegance, not just of its tongue, but also of its wit, I lingered for about two months. There I at once became
32761-414: Was very frugal; as he set its value high, and considered his mention of a name as a security against the waste of time, and a certain preservative from oblivion. After receiving his MA, Milton moved to Hammersmith , his father's new home since the previous year. He also lived at Horton , Berkshire, from 1635 and undertook six years of self-directed private study. Hill argues that this was not retreat into
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