the unseen world and other essays-第5章

按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！


ible　dispersion　of　radiant　energy　is　limited　by　its　extent。　Heat　and　light　cannot　travel　through　emptiness。　If　the　ether　is　bounded　by　surrounding　emptiness；　then　a　ray　of　heat；　on　arriving　at　this　limiting　emptiness；　would　be　reflected　back　as　surely　as　a　ball　is　sent　back　when　thrown　against　a　solid　wall。　If　this　be　the　case；　it　will　not　affect　our　conclusions　concerning　such　a　tiny　region　of　space　as　is　occupied　by　the　solar　system；　but　it　will　seriously　modify　Sir　William　Thomson's　suggestion　as　to　the　fate　of　the　universe　as　a　whole。　The　radiance　thrown　away　by　the　sun　is　indeed　lost　so　far　as　the　future　of　our　system　is　concerned；　but　not　a　single　unit　of　it　is　lost　from　the　universe。　Sooner　or　later；　reflected　back　in　all　directions；　it　must　do　work　in　one　quarter　or　another；　so　that　ultimate　stagnation　be　comes　impossible。　It　is　true　that　no　such　return　of　radiant　energy　has　been　detected　in　our　corner　of　the　world；　but　we　have　not　yet　so　far　disentangled　all　the　force…relations　of　the　universe　that　we　are　entitled　to　regard　such　a　return　as　impossible。　This　is　one　way　of　escape　from　the　consummation　of　things　depicted　by　our　authors。　Another　way　of　escape　is　equally　available；　if　we　suppose　that　while　the　ether　is　without　bounds　the　stellar　universe　also　extends　to　infinity。　For　in　this　case　the　reproduction　of　nebulous　masses　fit　for　generating　new　systems　of　worlds　must　go　on　through　space　that　is　endless；　and　consequently　the　process　can　never　come　to　an　end　and　can　never　have　had　a　beginning。　We　have；　therefore；　three　alternatives：　either　the　visible　universe　is　finite；　while　the　ether　is　infinite；　or　both　are　finite；　or　both　are　infinite。　Only　on　the　first　supposition；　I　think；　do　we　get　a　universe　which　began　in　time　and　must　end　in　time。　Between　such　stupendous　alternatives　we　have　no　grounds　for　choosing。　But　it　would　seem　that　the　third；　whether　strictly　true　or　not；　best　represents　the　state　of　the　case　relatively　to　our　feeble　capacity　of　comprehension。　Whether　absolutely　infinite　or　not；　the　dimensions　of　the　universe　must　be　taken　as　practically　infinite；　so　far　as　human　thought　is　concerned。　They　immeasurably　transcend　the　capabilities　of　any　gauge　we　can　bring　to　bear　on　them。　Accordingly　all　that　we　are　really　entitled　to　hold；　as　the　outcome　of　sound　speculation；　is　the　conception　of　innumerable　systems　of　worlds　concentrating　out　of　nebulous　masses；　and　then　rushing　together　and　dissolving　into　similar　masses；　as　bubbles　unite　and　break　upnow　here；　now　therein　their　play　on　the　surface　of　a　pool；　and　to　this　tremendous　series　of　events　we　can　assign　neither　a　beginning　nor　an　end。

＇3＇　Fortnightly　Review；　April；　1875。


We　must　now　make　some　more　explicit　mention　of　the　ether　which　carries　through　space　the　rays　of　heat　and　light。　In　closest　connection　with　the　visible　stellar　universe；　the　vicissitudes　of　which　we　have　briefly　traced；　the　all…pervading　ether　constitutes　a　sort　of　unseen　world　remarkable　enough　from　any　point　of　view；　but　to　which　the　theory　of　our　authors　ascribes　capacities　hitherto　unsuspected　by　science。　The　very　existence　of　an　ocean　of　ether　enveloping　the　molecules　of　material　bodies　has　been　doubted　or　denied　by　many　eminent　physicists；　though　of　course　none　have　called　in　question　the　necessity　for　some　interstellar　medium　for　the　transmission　of　thermal　and　luminous　vibrations。　This　scepticism　has　been；　I　think；　partially　justified　by　the　many　difficulties　encompassing　the　conception；　into　which；　however；　we　need　not　here　enter。　That　light　and　heat　cannot　be　conveyed　by　any　of　the　ordinary　sensible　forms　of　matter　is　unquestionable。　None　of　the　forms　of　sensible　matter　can　be　imagined　sufficiently　elastic　to　propagate　wave…motion　at　the　rate　of　one　hundred　and　eighty…eight　thousand　miles　per　second。　Yet　a　ray　of　light　is　a　series　of　waves；　and　implies　some　substance　in　which　the　waves　occur。　The　substance　required　is　one　which　seems　to　possess　strangely　contradictory　properties。　It　is　commonly　regarded　as　an　〃ether〃　or　infinitely　rare　substance；　but；　as　Professor　Jevons　observes；　we　might　as　well　regard　it　as　an　infinitely　solid　〃adamant。〃　〃Sir　John　Herschel　has　calculated　the　amount　of　force　which　may　be　supposed；　according　to　the　undulatory　theory　of　light；　to　be　exerted　at　each　point　in　space；　and　finds　it　to　be　1；148；000；000；000　times　the　elastic　force　of　ordinary　air　at　the　earth's　surface；　so　that　the　pressure　of　the　ether　upon　a　square　inch　of　surface　must　be　about　17；000；000；000；000；　or　seventeen　billions　of　pounds。〃＇4＇　Yet　at　the　same　time　the　resistance　offered　by　the　ether　to　the　planetary　motions　is　too　minute　to　be　appreciable。　〃All　our　ordinary　notions；〃　says　Professor　Jevons；　〃must　be　laid　aside　in　contemplating　such　an　hypothesis；　yet　＇it　is＇　no　more　than　the　observed　phenomena　of　light　and　heat　force　us　to　accept。　We　cannot　deny　even　the　strange　suggestion　of　Dr。　Young；　that　there　may　be　independent　worlds；　some　possibly　existing　in　different　parts　of　space；　but　others　perhaps　pervading　each　other；　unseen　and　unknown；　in　the　same　space。　For　if　we　are　bound　to　admit　the　conception　of　this　adamantine　firmament；　it　is　equally　easy　to　admit　a　plurality　of　such。〃

＇4＇　Jevons's　Principles　of　Science；　Vol。　II。　p。　145。　The　figures；　which　in　the　English　system　of　numeration　read　as　seventeen　billions；　would　in　the　American　system　read　as　seventeen　trillions。


The　ether；　therefore；　is　unlike　any　of　the　forms　of　matter　which　we　can　weigh　and　measure。　In　some　respects　it　resembles　a　fluid；　in　some　respects　a　solid。　It　is　both　hard　and　elastic　to　an　almost　inconceivable　degree。　It　fills　all　material　bodies　like　a　sea　in　which　the　atoms　of　the　material　bodies　are　as　islands；　and　it　occupies　the　whole　of　what　we　call　empty　space。　It　is　so　sensitive　that　a　disturbance　in　any　part　of　it　causes　a　〃tremour　which　is　felt　on　the　surface　of　countless　worlds。〃　Our　old　experiences　of　matter　give　us　no　account　of　any　substance　like　this；　yet　the　undulatory　theory　of　light　obliges　us　to　admit　such　a　substance；　and　that　theory　is　as　well　established　as　the　theory　of　gravitation。　Obviously　we　have　here　an　enlargement　of　our　experience　of　matter。　The　analysis　of　the　phenomena　of　light　and　radiant　heat　has　brought　us　into　mental　relations　with　matter　in　a　different　state　from　any　in　which　we　previously　knew　it。　For　the　supposition　that　the　ether　may　be　something　essentially　different　from　matter　is　contradicted　by　all　the　terms　we　have　used　in　describing　it。　Strange　and　contradictory　as　its　properties　may　seem；　are　they　any　more　strange　than　the　properties　of　a　gas　would　seem　if　we　were　for　the　first　time　to　discover　a　gas　after　heretofore　knowing　nothing　but　solids　and　liquids？　I　think　not；　and　the　conclusion　implied　by　our　authors　seems　to　me　eminently　probable；　that　in　the　so…called　ether　we　have　simply　a　state　of　matter　more　primitive　than　what　we　know　as　the　gaseous　state。　Indeed；　the　conceptions　of　matter　now　current；　and　inherited　from　barbarous　ages；　are　likely　enough　to　be　crude　in　the　extreme。　It　is　not　strange　that　the　study　of　such　subtle　agencies　as　heat　and　light　should　oblige　us　to　modify　them；　and　it　will　not　be　strange　if　the　study　of　electricity　should　entail　still　further　revision　of　our　ideas。

We　are　now　brought　to　one　of　the　profoundest　speculations　of　modern　times；　the　vortex…atom　theory　of　Helmholtz　and　Thomson；　in　which　the　evolution　of　ordinary　matter　from　ether　is　plainly　indicated。　The　reader　first　needs　to　know　what　vortex…motion　is；　and　this　has　been　so　beautifully　explained　by　Professor　Clifford；　that　I　quote　his　description　entire：　〃Imagine　a　ring　of　india…rubber；　made　by　joining　together　the　ends　of　a　cylindrical　piece　（like　a　lead…pencil　before　it　is　cut）；　to　be　put　upon　a　round　stick　which　it　will　just　fit　with　a　little　stretching。　Let　the　stick　be　now　pulled　through　the　ring　while　the　latter　is　kept　in　its　place　by　being　pulled　the　other　way　on　the　outside。　The　india…rubber　has　then　what　is　called　vortex…motion。　Before　the　ends　were　joined　together；　while　it　was　straight；　it　might　have　been　made　to　turn　around　without　changing　position；　by　rolling　it　between　the　hands。　Just　the　same　motion　of　rotation　it　has　on　the　stick；　only　that　the　ends　are　n