outer space outer space space void exists bodies including earth completely consists hard vacuum containing low density particles predominantly hydrogen electromagnetic radiation magnetic fields dust cosmic rays temperature set background radiation number density hydrogen cubic metre temperature millions space accounts ordinary matter outer space local concentrations condensed stars observations provide evidence mass unknown form called dark matter matter electromagnetic forces data indicates majority mass energy universe poorly understood vacuum energy space label dark energy space takes volume universe star systems consist entirely space firm boundary outer space begins line altitude sea level conventionally start outer space space treaties records keeping framework international space law established passed united_nations treaty claims national sovereignty permits states freely explore outer space despite drafting resolutions peaceful uses outer space anti satellite weapons tested earth orbit humans began physical exploration space 20th century advent high altitude balloon flights followed manned rocket launches earth orbit achieved soviet_union spacecraft reached known planets solar system high cost getting space manned limited low earth orbit moon outer space represents challenging environment human exploration dual hazards vacuum radiation negative effect human physiology causes muscle bone loss addition health environmental issues economic cost putting objects including humans space high apollo program cost approximately discovery bce greek philosopher aristotle suggested nature vacuum principle known horror concept built 5th century bce argument greek philosopher denied possible existence void space based idea vacuum exist west widely held centuries space late 17th century french philosopher argued entirety space filled ancient china schools thought concerning nature heavens bear resemblance modern understanding 2nd century convinced space infinite extending mechanism supported sun stars surviving books school said heavens void substance likewise sun moon company stars float space moving standing italian scientist knew air mass subject gravity demonstrated established force resisted formation vacuum remain pupil create apparatus produce vacuum experiment resulted mercury created scientific sensation europe french mathematician reasoned column mercury supported air column ought shorter higher altitude air pressure lower brother law repeated experiment mountain central france found column shorter inches decrease pressure demonstrated carrying half balloon mountain watching gradually expand contract descent german scientist constructed vacuum pump device principle horror correctly noted atmosphere earth surrounds planet like shell density gradually declining altitude concluded vacuum earth moon 15th century german theologian speculated universe lacked center believed universe infinite held finite lacked bounds contained ideas led infinite dimension space italian philosopher 16th century extended concept infinite universe filled substance called cause resistance motions heavenly bodies english philosopher arrived similar conclusion arguing stars visible surrounded thin void concept originated ancient greek philosophers including aristotle conceived medium heavenly bodies moved concept universe filled remained vogue scientists early 20th century form viewed medium light experiment tried detect earth motion medium looking changes speed light depending direction planet motion result indicated wrong concept idea abandoned replaced theory special holds speed light vacuum fixed constant independent observer motion frame reference professional support concept infinite universe englishman scale universe remained unknown successful measurement distance nearby star german showed star compared modern value corresponds distance light years distance determined american measuring galaxy new technique discovered established galaxy extension lay outside way earliest known estimate temperature outer space swiss physicist estimated radiation background stars concluded space heated temperature british physicist similar calculation derive temperature german physicist total measured energy cosmic rays estimate temperature modern concept outer space based big bang proposed belgian physicist theory holds universe originated compact form undergone continuous expansion background energy released initial expansion steadily decreased density leading prediction american temperature temperature space term outer space english poet lady poem maiden moscow expression outer space astronomical term later popularized writings shorter term space actually older mean region earth sky paradise lost formation state according big bang theory universe originated extremely hot dense state billion years ago began expanding rapidly years later universe cooled sufficiently allow combine form hydrogen called happened matter energy allowing travel freely space matter remained following initial expansion undergone collapse create stars astronomical objects leaving deep vacuum forms called outer space light finite velocity theory size directly universe leaves open question universe finite infinite present day shape universe determined measurements cosmic microwave background satellites like microwave probe observations indicate universe flat meaning parallel paths point remain parallel travel space limit universe local gravity flat universe combined measured mass density universe accelerating expansion universe indicates space non zero vacuum energy called dark energy estimates average energy density universe equivalent cubic meter including dark energy dark matter matter ordinary matter composed account total energy density density cubic meters density universe clearly uniform ranges relatively high density including high density structures planets stars black holes conditions vast lower density terms visible matter unlike matter dark matter dark energy concentrated dark energy account majority mass energy universe dark energy influence orders magnitude smaller influence gravity matter dark matter way environment outer space closest known perfect vacuum effectively friction allowing stars planets freely ideal deep vacuum space devoid matter contains hydrogen cubic meter comparison air breathe contains molecules cubic meter sparse density matter outer space means electromagnetic radiation travel great distances scattered mean free path space billion light years spite extinction absorption scattering dust gas important factor astronomy stars planets retain attraction clearly boundary density atmospheric gas gradually decreases distance object indistinguishable surrounding environment earth atmospheric pressure drops kilometres miles altitude compared definition standard pressure altitude gas pressure rapidly insignificant compared radiation pressure sun dynamic pressure solar wind range large pressure temperature composition varies greatly space weather temperature vacuum measured terms activity gas earth radiation fills vacuum different temperature temperature gas meaning gas radiation universe filled created known cosmic microwave background radiation likely large number called cosmic background current black body temperature background radiation gas temperatures outer space temperature higher example sun temperatures range million outside protective atmosphere magnetic field obstacles passage space energetic particles known cosmic rays particles energies ranging extreme ultra high energy cosmic rays peak cosmic rays occurs energies approximately heavier high energy range cosmic rays damage electronic components pose health threat space travelers according like space burned metallic odor suits equipment similar scent arc torch despite harsh environment life forms found withstand extreme space conditions extended periods species carried facility survived exposure days seeds exposed space years strain survived days exposed low earth orbit simulated environment hypothesis suggests rocks ejected outer space life planets successfully transport life forms world scenario occurred early history solar system potentially bearing rocks exchanged venus earth mars effect human bodies sudden exposure low pressure rapid cause lungs large pressure differential inside outside chest victim fully open flow air slow prevent rapid blood occur soft tissues shock cause increase oxygen consumption leads consequence rapid oxygen dissolved blood lungs try partial pressure gradient blood arrives brain humans animals lose consciousness seconds die minutes blood body pressure drops kpa condition called steam body twice normal size slow circulation tissues elastic prevent slowed pressure blood vessels blood remains liquid swelling reduced flight suit caps fitted elastic designed 1960s shuttle prevents pressures low kpa space suits needed provide oxygen breathing prevent water loss essential prevent space suits use kpa pure oxygen earth surface pressure high prevent nitrogen dissolved blood cause sickness gas managed humans evolved life earth gravity exposure shown effects health human body initially experience space motion sickness cause overall duration space sickness varies typically lasts days body new environment longer term exposure results muscle deterioration skeleton effects exercise effects include fluid slowing system decreased production red blood cells balance disorders weakening immune system lesser symptoms include loss body mass nasal congestion sleep disturbance face long duration space travel radiation pose acute health hazard exposure radiation sources high energy cosmic rays result fatigue damage immune system changes white blood cell count longer symptoms include increased risk cancer plus damage eyes nervous system lungs tract round trip mars mission lasting years nearly entire body traversed high energy cause damage cells fortunately particles significantly provided aluminium walls spacecraft diminished water containers barriers impact cosmic rays produces additional radiation affect crew research needed assess radiation hazards determine suitable boundary clear boundary earth atmosphere space density atmosphere gradually decreases altitude increases standard boundary designations established line altitude working definition boundary altitude calculated vehicle travel faster velocity order derive sufficient aerodynamic lift atmosphere support united_states people travel altitude miles nasa feet entry altitude termed roughly marks boundary atmospheric drag noticeable beginning process switching steering maneuvering air surfaces scientists reported detailed measurements instrument measures direction speed allowed establish boundary earth boundary represents gradual transition tens kilometers relatively gentle winds earth atmosphere violent flows charged particles space reach speeds mph altitude atmospheric pressure matches pressure water temperature human body called armstrong line named american physician located altitude armstrong line throat lungs away specifically exposed tears lungs away altitude human body requires pressure suit capsule survive legal status outer space treaty provides basic framework international space law covers legal use outer space nation states includes definition outer space moon bodies treaty states outer space free nation states explore subject claims national sovereignty prohibits deployment nuclear weapons outer space treaty passed signed ussr united_states_of_america united_kingdom january treaty ratified states signed additional states beginning outer space subject multiple resolutions concerning international operation peaceful uses outer space preventing arms race space additional space law treaties negotiated drafted remains legal prohibition deploying conventional weapons space anti satellite weapons successfully tested ussr china moon treaty turned jurisdiction heavenly bodies including bodies international community treaty ratified nation currently practices manned states ecuador colombia brazil kenya indonesia met colombia declaration meeting countries known declaration claim control segment path corresponding country claims internationally accepted earth orbit spacecraft enters orbit horizontal velocity acceleration gravity equal acceleration horizontal component velocity low earth orbit velocity mph contrast fastest manned airplane speed achieved excluding speeds achieved spacecraft mph achieve orbit spacecraft travel faster sub energy required reach earth velocity altitude times energy needed merely climb corresponding altitude spacecraft subject drag earth atmosphere cause altitude decrease rate decay depends satellite cross area mass variations air density upper atmosphere decay rapid measured days satellite descends start burn atmosphere escape velocity required pull free earth field altogether space mph earth gravity reaches far past van allen radiation belt keeps moon orbit average distance region space gravity planet tends dominate motion objects presence bodies planet known hill sphere earth sphere radius regions space partial vacuum different regions defined winds dominate extend point winds way extends earth atmosphere outer reaches earth magnetic field gives way solar wind space space extends solar wind gives way winds medium space continues edges galaxy fades void region outer space near earth includes upper region atmosphere van allen radiation belt lies outer boundary forms interface planet solar wind inner boundary physical properties behavior near earth space affected behavior sun space weather field study sun impact solar system planets volume defined direction sun pressure solar wind giving typical distance earth center planet tail extend outward earth moon passes tail roughly days month time surface shielded solar wind populated electrically charged particles low motions controlled earth magnetic field form medium storm like disturbances powered solar wind drive electrical currents earth upper atmosphere storms regions radiation belts strongly disturbed storms increase energetic permanently damage satellite electronics disrupting telecommunications gps technologies hazard low earth orbit create seen near magnetic poles meets definition outer space atmospheric density kilometers line sufficient produce significant drag satellites region contains material left previous manned launches potential hazard spacecraft debris enters earth atmosphere periodically space region outside earth atmosphere extending moon orbit including points referred lunar space space space space sun planets solar system region dominated medium extends influence environment starts dominate magnetic field particle sun space defined solar wind continuous stream charged particles sun creates atmosphere kilometers space wind particle density moving velocity mph distance strength varies depending activity level solar wind discovery planets means stars possess media volume space nearly total vacuum mean free path astronomical unit distance earth space completely sparsely filled cosmic rays include atomic particles gas dust small dozen types organic molecules discovered date microwave cloud dust visible night faint band called light space contains magnetic field generated sun generated planets saturn mercury earth magnetic fields shaped influence solar wind shape long tail extending outward planet magnetic fields trap particles solar wind sources creating belts magnetic particles van allen radiation belt planets magnetic fields mars gradually eroded solar wind space space physical space galaxy influence star contents space called medium approximately mass medium consists lone hydrogen remainder consists enriched trace amounts heavier formed stellar ejected medium stellar winds evolved stars begin shed outer formation explosion generate expanding shock wave consisting ejected materials density matter medium vary considerably average particles cold molecular clouds hold number molecules exist space tiny dust particles tally molecules discovered radio astronomy steadily increasing rate new species year large regions higher density matter known molecular clouds allow chemical reactions occur including formation organic species chemistry driven collisions energetic cosmic rays penetrate cold dense clouds hydrogen resulting example split relatively abundant carbon produce carbon turn lead organic chemical reactions local medium region space sun interest proximity interaction solar system volume nearly region space known local bubble characterized lack dense cold clouds forms cavity galaxy dense molecular clouds lying borders actual distance border cavity varies volume contains stars local gas surround stars volume sphere varying depending local density medium local bubble contains dozens warm clouds temperatures stars moving sufficiently high peculiar generate bow medium decades assumed sun bow shock data nasa voyager showed sun bow shock exist instead authors argue bow wave defines transition solar wind flow medium bow shock boundary termination shock called solar system space space physical space huge spaces galaxy clusters called surrounding stretching organized structure material called medium density times average density universe consists hydrogen consisting equal numbers gas falls medium heats temperatures high collisions energy cause bound escape hydrogen temperatures called warm hot medium hot terrestrial standards called warm computer observations indicate half atomic matter universe exist warm hot state gas falls structures galaxy clusters intersections cosmic heat reaching temperatures called medium exploration applications majority human history space explored remote observation initially eye prior advent reliable rocket technology closest humans come reaching outer space use balloon flights explorer manned balloon flight reached altitude greatly exceeded launch german rocket climbed altitude satellite launched russian rocket achieving earth orbit altitude kilometres followed human sent orbit humans escape earth orbit board apollo achieved lunar orbit reached maximum distance earth spacecraft reach escape velocity soviet performed fly moon probe revealed presence solar wind performed fly planet venus contact lost reaching venus successful mission fly venus spacecraft perform fly mars reached planet time spacecraft successfully examined solar system planets minor planets remain fundamental tool exploration outer space observation earth august voyager man object leave solar system enter space absence air makes outer space surface moon ideal locations astronomy electromagnetic spectrum evidenced spectacular pictures sent space allowing light billion years ago time big bang observed location space ideal dust near infrared radiation mask faint sources planets moving infrared past dust increase effectiveness instrument likewise site like crater far moon shield radio radio frequency interference earth based observations spacecraft earth orbit essential technology modern civilization allow direct monitoring weather conditions relay long range communications including telephone calls television signals provide means precise navigation allow remote sensing earth role serves wide variety purposes including tracking soil moisture agriculture prediction water outflow seasonal snow packs detection diseases plants trees surveillance military activities deep vacuum space attractive environment certain industrial processes require surfaces like mining space manufacturing requires significant investment little prospect immediate return important factor total expense high cost placing mass earth orbit inflation adjusted dollars according estimate proposed concepts addressing issue include non rocket momentum exchange space elevators
Outer space