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Die meeste diagramme wat ek van sonlig sien, lyk soos volg:
.
Hulle toon aan dat die sonstraling as 'dun lyne' wat die aarde tref, vir basiese meetkundige ontledings beskou kan word. Verder, teen 'n ewening, tref die strale die horison van elke punt op die aarde (behalwe die pole) direk vanuit die ooste. Die deursnee van die aarde maak dus glad nie saak nie, dit is die hoek waarteen die strale slaan.
Ek is nuuskierig - hoe ver sal hierdie konseptuele raam my neem? Wat is 'n beter manier om te konseptualiseer hoe die sonlig die aarde tref?
Daar is nie 'n beter manier om dit te konseptualiseer nie, want dit is hoe dit gebeur. Die son is baie groot en baie ver weg, en die strale wat ons bereik, is effektief parallel. Dit is alreeds die beste manier om te konseptualiseer hoe lig die aarde tref - as daar 'n beter een sou wees, sou u waarskynlik daarvan in plaas van op hierdie manier gehoor het.
Dit is 'n benadering van die eerste orde en werk goed vir eenvoudige modelle van bestraling van die atmosfeer of die aardoppervlak.
Maar deur 'n eenvoudige eksperiment met 'n gatkamera of 'n enkele lens, kan dit blyk dat hierdie model nie in beeldsituasies werk nie. Die son is 'n "uitgebreide voorwerp", wat beteken dat dit nie 'n puntbron is nie, dus die beeld wat u kry, is nie wat u van 'n puntbron sou verwag nie. Erger nog, selfs al was die son 'n puntbron, verskil die afstand tot die meetkundige fokuspunt effens van die afstand as al die sonstrale heeltemal parallel was. Sien die Lensmaker's Formula, $ frac {1} {f} = frac {1} {p} + frac {1} {q} $ waar p en q onderskeidelik die afstande van die lens tot die bron en die beeld is. (Ek sal dit waarsku vir 'n redelike lens, sê die brandpuntafstand) $ f = 10 m $, die verskil tussen brandpunt vir parallelle strale en strale vanaf 'n puntbron $ 150 ruimte miljoen ruimte km $ weg is belaglik klein)
Net so, as u die umbra en penumbra wil modelleer tydens 'n sons- of maansverduistering, moet u die fisiese omvang van die son in ag neem.
Gebruik sonlig of verloor dit
'N Nuwe & ldquosolar huisvesting- & rdquo-wet kan sonstrale wat op dakke en parkeerterreine val in stede benut en die doelstellings van energiedemokrasie bevorder.
Onderwerpe:
Deel:
Sonpanele op 'n dak in Queens, NY (Foto deur Steven Pisano via Flickr).
'N Nuwe & ldquosolar huisvestingswet & rdquo kan sonstrale wat op dakke en parkeerterreine in stede val, benut en die doelstellings van energiedemokrasie bevorder.
Wat as ons gryp na die sonlig wat ongebruik op dakke, parkeerterreine en ander stedelike oppervlaktes val? Daaruit kan ons elektrisiteit opwek en sodoende die belangrike oorgang weg van fossielbrandstowwe bevorder. Hierdie voorstel mag vir sommige radikaal klink. Maar in werklikheid brei sonopstal bloot verslete Amerikaanse tradisies van landelike, landbou-nedersetting uit.
Fotone duik daagliks van die ruimte af op pakhuisdakke regoor die land. Hierdie fotone, indien vasgelê, kan bydra tot fotosintese en elektrisiteit opwek.
Na die aankoop van die Louisiana-aankoop in 1803, het die Verenigde State die beste manier oorweeg om voordele te ontwikkel en te versprei oor 'n uitgestrekte gebied wat strek van New Orleans tot die Great Plains. Inheemse Amerikaners sou onbeskaamd onteien word, natuurlik, en hoe presies? Die land se antwoord op die vraag berus op die balansering van privaat eiendom en openbare besittings, 'n poging wat in die eerste opstalwet van 1862 uitgekristalliseer het.
Die Homestead Act het 'n wortel aangebied terwyl hy met 'n stok gedreig het. In 1862 het die federale regering gedeeltes van 'n openbare grond en 'n ander land, gesteelde inheemse Amerikaanse lande, en 'n feitlike setlaars en 'n nuwe land, gratis toegestaan. Terwyl die burgeroorlog aan die gang was, het & ldquosettlers & rdquo diegene uitgesluit wat die wapens teen die Amerikaanse regering gehad het. & Rdquo (Nota aan Trump-ondersteuners: laat u klubs tuis.) Die term & ldquosettlers & rdquo was ook bedoel om groot ondernemings uit te sluit: die wet beperk baie tot 160 hektaar, genoeg vir 'n gesin wat die halfdroë Weste bewerk, maar nie genoeg vir 'n landbaron nie. Dit was die wortel. Die stokkie het ter sprake gekom toe boere nie kon boer nie en bloot grond aangehou het as bespiegeling vir latere verkoop. Die wet het 'n proeftydperk van vyf jaar opgelê waartydens enige grond wat langer as ses maande onbeset was of in die steek gelaat is, aan die regering sou terugkeer. & Rdquo Met ander woorde, die stok was 'n terugneming. Immers, waarom die moeite doen om 'n akker van inheemse mense te steel en dit vermoedelik te vermors op blote jag en versameling, of as u dit beter, produktiewer kan gebruik? In teorie het hierdie wildernis 'n tuin verander. Die Wet op die opstal het Amerikaanse setlaars genoop om die huis te bou, te plant, gewasse te plant, vee te verhoog en produksie in die algemeen te verskerp.
In hierdie atmosfeer van geleentheid en bedreiging het die bekendste grensvrou in die Amerikaanse literatuur, Laura Ingalls Wilder, grootgeword. Haar vader, Charles Ingalls, het 'n opstal in Minnesota bekom, maar moes dit gou verbeur weens die nie-gebruik. Gelukkig het die wet hom 'n tweede kans gegee. & ldquoAs oom Sam bereid is om vir ons 'n plaas te gee & hellip, & rdquo het hy aan sy vrou en dogters verduidelik, & ldquoI sê laat & rsquos dit neem. & rdquo In 1880 vestig hulle hulle suksesvol in die Dakota-gebied. In hierdie geval het die wet sy doel bereik en gesteelde grond aan setlaars gegee om te ontwikkel. Daaropvolgende wetgewing sou die Ingalls ook die regte en ldquoof vang & rdquo op water en minerale gegee het, mits hulle die hulpbronne produktief gebruik. Maar die Ingalls het net die land gebruik, en hulle ervaring was nie universeel nie. Baie Westerse grond het in die hande van spekulante geval voordat dit uiteindelik in die hande van spoorweg- en mynboukorporasies oorgegaan het.
In 1862 het die Wet op die huishouding privaat eiendom en openbare goed gebalanseer. Vandag behou dit progressiewe potensiaal.
Die Wet op die huishouding behou steeds 'n progressiewe potensiaal. Die Volledige Idiot & rsquos Guide to Urban Homesteading stel maniere voor om die wet te gebruik om vakante persele wettig te bekom en te bewerk. As 'n ander voorbeeld bepleit die aktivisadvokaat Dana May Christensen 'n nuwe Wet op Homestead ten bate van kleurgemeenskappe in Detroit. Onder skoffel en troffel, voer sy aan, kan die stad & rsquos baie vakante persele gelyktydig minder werk en ondervoeding verminder. Hierdie reg op tuin is die hedendaagse wortel wat tuisgemaak moet word en behoort te speel in die stryd om stedelike sosiale geregtigheid regoor die Verenigde State.
Maar hierdie wortel weerspieël slegs een aspek van die Act & rsquos-potensiaal van vandag. Vir die opstel van sonkrag is die stokkie meer relevant. Die stokkie is van toepassing op hulpbronne wat in die besit is. Die dreigement beweer dat hierdie hulpbronne, wat onproduktief gebruik word, die regering moet & amp; omskryf, en eintlik beskryf word as & ldquopublic domain & rdquo in die Act & rsquos-titel.
Die meeste sonlig val op stede sonder & ldquocapture. & Rdquo Byvoorbeeld, fotone daal daagliks van die ruimte af op pakhuisdakke regoor die land. As hierdie fotone vasgevang word, kan dit bydra tot fotosintese, elektrisiteit opwek of, op die minste, 'n dakverligting verlig. Maar hulle word selde gevang en in gebruik geneem.
As eienaars van dakke en parkeerterreine nie sonlig effektief gebruik nie, verbeur hulle hul regte op hierdie bron.
'N Gewone dak absorbeer sommige fotone inerte en bons ander af. Die teer, gordelroos of leisteen wat dakke bedek, laat die sonlig effektief heeltemal weg. Parkeerterreine is nog minder ontvanklik vir sonskyn: hulle lei fotone van enige positiewe funksie af en kanaliseer dit per ongeluk na die negatiewe stedelike hitte-eiland-effek. As eienaars van dakke en parkeerterreine nie sonlig effektief gebruik nie, verbeur hulle hul regte op hierdie hulpbron en mdashas Ingalls het sy grondregte in Minnesota gedoen.
Sonreserwes behoort aan die regering terug te keer. & Rdquo Die uitdrukking van 1862 kan 'n nuutgevonde, openbare sonarea onderskryf. Aangesien sonlig onbenut bly val, moet ons die president Lincoln & rsquos Homestead Act moderniseer en verstedelik. Terwyl ons dit ondersoek, laat ons dit ook & ldquosolarize & rdquo. Opruiming deur sonkrag kan die Green New Deal begin en energiedemokrasie meebring.
Vandag kan ons sonlig as 'n planeetgrootte Louisiana-aankoop beskou. In hierdie geval is sonlig egter 'n oneindige bron, eerder as omring deur grense en water. Ons ster stuur voortdurend 162,000 terawatts energie na die Aarde en rsquos-atmosfeer, waarvan 39,000 terawatts die ruimte terugbons. Dit beteken dat 'n netto hulpbron van 123 000 terwatts beskikbaar is en die tarief ongeveer 10 000 keer groter is as al die energie wat mense doelbewus verbruik om elektrisiteit op te wek, geboue te verhit, vuuroondjies te vervoer en alles te vervoer. Hierdie fotongrens strek wyd, maar in teenstelling met die Louisiana-aankoop in 1803, erken die wet baie daarvan as reeds besit.
In die privaatheid of as 'n algemene gemeenskap is stedelike inwoners en veral swart en bruin mense wat uitgesluit is van energie-eise en -besluite, gereed om die onbenutte sonbron toe te pas.
Die kwekers en tuiniers in die landelike en voorstedelike gebiede van die Verenigde State beweer elke dag sonstrale op hul grond in private besit, maar stede en dorpe gebruik hierdie hulpbron selde. Alledaagse stedelike sentrums vermors sonlig deur die terawatt as dit na die dorre stofkom van parkeerterreine en dakke stort, geïgnoreer. Intussen is daar groot bevolkings en swart mense van swart en bruin mense wat uitgesluit is van energie-eise en besluite en bly langs en onder die oppervlaktes. Stedelike inwoners kan die grens van hierdie metropolitaanse fotongrens wees. Privaat of as 'n onderdak is hulle gereed om die onbestede sonbron toe te pas.
Miskien is sonlig nog nie meer gebruik nie, want dit is moeilik om as hulpbron of as enige ander te waardeer ding enigsins. Dit lê nie stil voor die landmeter & rsquos kompas en die setlaar & rsquos ploeg nie. Dit jaag verby, word skaars as golf en deeltjie deur die gereedskap van fisika en sterrekunde aangekeer. In die 1920's het die term & ldquophoton & rdquo 'n minimale vorm aan die lig gegee, met die naam van 'n konsep wat Einstein in 1905 vir die eerste keer beskryf het. Fototorpedo's en die wandelende, fotoniese robot het gevolg, danksy die skeppers van Star Trek en sy vervolgverhale. & ldquo Ek is 'n geheimsinnige ding, masseloos maar kragtig, & rdquo skryf Kim Stanley Robinson, vanuit die perspektief van 'n foton, in sy klimaatfiksieroman Die Ministerie vir die Toekoms. Inderdaad kragtig, want fotone skud elektrone in die silikonplate van 'n fotovoltaïese paneel. Ten spyte van al hierdie fotoniese dubbelsinnigheid produseer fotone iets wat ons kan meet, en baie goed: watt, kilowatt, megawatt, gigawatt, en uiteindelik terawatt.
Natuurlik gee watt nie sonligmassa nie, maar korreleer dit sonlig met die oppervlak. Op 'n helder Julie-dag in New Jersey sal byvoorbeeld 5 of 6 kilowatt-uur fotone in elke vierkante meter van my dakpanele breek. Met ongeveer 20 persent doeltreffendheid sal die vierkante meter ongeveer 1 kilowatt-uur per dag lewer. Promoteurs van sonenergie verwys na hierdie soort syfers as sonreserwes en gebruik dieselfde taal as die mynbou- en petroleumbedryf. Sonreserwes word gemeet in megawatt-uur en mdashrather as ton of vate soos olie of steenkool & mdash maar dit is reserwes, van tyd eerder as volume, almal dieselfde.
Scenario's vir die energietransisie en -dash insluitend die Green New Deal en mdash het meestal winkelsentrums, parkeerterreine en die stedelike Verenigde State heeltemal misgekyk.
Volgens Brian Ross van die Great Plains Institute bevat die meeste stede oppervlakreserwes van sonlig wat voldoende is om tussen 25 en sku & ndash en skaam 70 persent van hul jaarlikse elektrisiteitsverbruik te dek. Die wye verskeidenheid jaarlikse gigawatt-ure beteken potensiële jaarlikse produksie. Beskou dit as die opbrengs in verfynde yster of petrol en mdashor, meer gepas, as 'n graanoes. In die Great Plains, bo-op Minnesota-koringland, is daar 96 hektaar dakke en parkeerterreine en mdashthe Mall of America. Dit is een deel in 145,000 van die oppervlakte wat benodig word om die jaarlikse elektrisiteitsverbruik van Amerika en Rsquos te voorsien. Ons het byna 145 000 winkelsentrums in die Verenigde State, tesame met meer as 19 000 stede, dorpe en dorpe. Dit kan die naam van Minnesota & rsquos Metropolitan Council & rsquos solar dataset & mdash & ldquosurface [s] met mening aangehaal word. & Rdquo
Tot dusver het scenario's vir die oorgang na energie meestal winkelsentrums, parkeerplekke en die stedelike Verenigde State heeltemal misgekyk. Die meeste voorstanders van die Green New Deal wil panele op die dakke van enkelhuise, voorstedelike huise of op die grond in die buitewyke monteer. Princeton University & rsquos & ldquoNet Zero America & rdquo & shy & mdashdie mees gedetailleerde plan nog vir die opstel van sonkrag- en windplase en mdashex sluit enige gebied met 'n bevolkingsdigtheid van meer as 100 mense per vierkante kilometer in en dring aan op 'n 500 meter paneelvrye buffersone en 'n turbine-vrye buffersone van 1 kilometer. Hierdie oppervlakdigtheidsmaatreëls en paneelvrye buffergebiede is ongegrond en hoewel vinnig draaiende lemme 'n fisiese risiko inhou, is dit nie PV-panele nie. Tog het bure van sonplase gekla en betoog. In die staat New York, skryf Jim Shultz, en die rebelle van die energie van hernubare energie en die rdquo betoog die vervanging van hooivelde met grondpanele.
Daar was egter nog nie 'n stedelike opstand teen die sonkrag op die dak nie. New Yorkers en Los Angelinos eis nie 'n buffersone nie. Inteendeel, stedelike huiseienaars en huurders hou van toegang tot soninfrastruktuur. Hulle weet dat silikonplate elektriese rekeninge sal verlaag en die elektrone sal laat vloei. Boonop, in 'n krisis soos die onlangse winterstorm wat steenkool, gas en die elektriese netwerk in Texas en die sonkrag in die sonkrag ontwrig het, kan lewens red.
Stedelike huiseienaars en huurders is besig om toegang te verkry tot soninfrastruktuur. Nou kan reëlings wat 'sonkrag' en 'sonkrag' genoem word, groepe huiseienaars toelaat om hulpbronne en dakruimte saam te voeg.
Dit is hoe energiedemokrasie kan lyk. Die voorloper en mdasha het meer as twintig jaar gelede van nutsdienste en mdash begin af, toe die federale regering en sommige state huiseienaars gesubsidieer het om panele op hul dakke te plaas. Ek het twee en twintig daarvan geïnstalleer. Hierdie eerste vlaag van sonkrag het meestal welgestelde Amerikaners bevoordeel: diegene wat losstaande huise met groot, dwarsvrye dakke besit. 'N Gelukkige paar het hul elektrisiteitsrekeninge tot bykans nul gesny en krediete vir hernubare sonkrag aan die netwerk verkoop. Toe, ongeveer tien jaar gelede, het inwoners van woonstelgeboue en ander inwoners met lae en matige inkomste 'n deel van die pastei geëis. Nou kan reëlings wat 'sonkrag' en 'sonkrag' genoem word, groepe huiseienaars toelaat om hulpbronne en dakruimte saam te voeg. In sommige gevalle kan huurders sonkragaanbiedings koop wat elders geleë is. Om sake nog beter te maak, kan stedelike panele funksioneer as 'n mikro-rooster op eilande. Dit beteken dat as die rooster moontlik daal as gevolg van 'n orkaan wat deur koolstofstowwe aangedryf word, of 'n brand, en die mdashurban PV die energie benodig vir miljoene kwesbare mense.
Wat is die aansporings om al daardie lewensreddende silikon na die buitewyke en verder te verban? In ooreenstemming met die manier waarop die meeste besluite bepaal word, is installasie op afstand doeltreffender en voordeliger vir beleggers en base in die bedryf. Beleggers sou eerder 22 000 panele op die grond neerlê as om 1 000 dakke op verskillende plekke te klim. Elke dak benodig meer opgeleide werknemers en moontlik elektriese werkers met vakbonde wat billike lone van installateurs eis, 'n opkomende oligopol bestaan uit Sunrun, Sunnova en 'n paar ander ondernemings. Vir hierdie maatskappye begin die sonbeleggingsgrens presies waar die grens begin: 500 meter verby die laaste pakhuis, parkeerterrein, vakbond en plaaslike gemeenskap.
Om die idee van openbare beheer oor stedelike sonlig in die praktyk uit te leef, moet sonregte van grondregte afgesny word, net soos wat waterregte nou werk. Fotone reën uit die ruimte, dus kan 'n mens dit feitlik onafhanklik van die grond oes. Oor 'n parkeerterrein onderskep PV-afdakke byvoorbeeld sonlig in die lug voordat dit die teer tref. Dakgemonteerde panele neem andersins dakgebonde fotone vas. Diegene wat plaveisel en gordelroos besit, sonder om sonbronne produktief te benut, het hierdie geleentheid & mdashand vir meer as vyf jaar verwaarloos. Hulle het hul eis verbeur soos die afwesige Charles Ingalls in Minnesota gedoen het. In hierdie geval hoef hierdie grondgebruikers egter nie elders heen te trek nie. Hulle vermors watt eerder as hektaar. As hulle nie van die sonbron gebruik maak nie, moet verteenwoordigers van die publieke domein slegs 'n paneel tussen die oppervlaktes wat hulle besit en die lug laat gly. Dit is 'n verrassende eenvoudige maneuver. Prokureurs en wetgewing tref 'n fyn onderskeid tussen grond, minerale en water. Hierdie bronne het almal verskillende doeleindes, en verskillende partye kan dit binne dieselfde landelike akker besit. Net so kan een persoon in die stad 'n woonstel op die grondvlak besit, 'n ander, die woonstel bo en 'n derde, die grond onder albei. Sonlig is die leë dakwoonstel.
Om hierdie idee te laat praktiseer, moet sonkragregte van grondregte geskei word, net soos wat waterregte nou werk. Maar fotone kan reeds onafhanklik van die grond vasgelê word.
As u & rsquore nog nie oortuig is nie, laat & rsquos 'n paar grade van die vertikale kant draai. Die meeste van ons sal beswaar maak as 'n nuwe wolkekrabber ons omgewing oorskadu, want ons voel dat die inwoners van 'n woonstel geregtig is op sonlig en ten minste op strale wat lankal skuins of horisontaal oor aangrensende lae dakke geval het. Dit is natuurlik harde gevegte en die ontwikkelaar wen dikwels. In New York is ondersteuners van die Brooklyn Botaniese Tuin byvoorbeeld besig met 'n & ldquoFight vir sonlig, & rdquo, aangesien kaktusse in glas, lighonger, binnekort kan val onder die skaduwee van 'n toring wat beplan word om 150 laterale voet weg te bou. In die Verenigde Koninkryk sal die vetplante waarskynlik in die hof geld. Die UK & rsquos Law and Property Act van 1925 erken die reg van & ldquoancient lights, & rdquo 'n reg wat in die gemenereg reeds in 1663 bestaan. Oud, hier, beteken nie baie oud nie: enige venster twintig jaar of langer in posisie en enige persoon of huisplant daaragter en het die reg om 'n gewaarborgde stroom fotone te geniet. Wee die huiseienaar wat met 'n venster opstaan. Sy verloor haar regte op strale. Op dieselfde manier mag hoogtes skaduwee gooi op gewone, vensterlose mure. Dit is die reël om vas te lê in die praktyk: die eerste venster wat voor sonlig gelê word, kry die fotone. Beskou nou PV-panele op dieselfde manier as vensters wat plat of amper so lê. In enige hoek moet dieselfde reël geld: gebruik sonlig of verloor dit.
In huistaal sal ongebruikte sonlig vir die publieke domein omdraai en hoe sal dit in die praktyk lyk? Om ongebruikte sonlig deur die publiek te benut, bring munisipale werkers lere na die geboue, klim op die dakke, klap panele op vrye ruimtes en bedraad dit na die rooster. (Amazon, as u dit lees, wil u dalk voorlopig sonkrag op al u pakhuise installeer vir u eie elektrisiteit, terwyl u nog die kans het.) As die stad lekker wil speel, sal dit dak-eienaars & mdashsay gee , Walmart of Donald Trump en mdasha kans om PV te installeer vir hul eie voordeel en bespaar op elektriese rekeninge. 'N Staatsagentskap sal goed geplaas wees om die bedreiging te maak en, indien nodig, die & ldquoreverted & rdquo-fotone in elektrone te omskep. Laat & rsquos in New York bly, waar aktiviste 'n nut wil skep met die naam Public Power NYC. Inwoners van die stad sou hul elektrisiteit demokraties besit en beheer. Nadat die beleggers ontslae geraak het en winsgewend was wat die meeste nutsdienste belemmer, kon die liggaam die prys van elektrisiteit verlaag en die beskikbaarheid daarvan vir inwoners met 'n lae inkomste waarborg. Public Power NYC kan ook fotoniese oppervlaktes oor die vyf distrikte gryp en hergebruik. In een van hierdie reëlings sou verkose owerhede die PV-panele en ander infrastruktuur besit, wat voldoen aan 'n sentrale eis van energiedemokrasie.
Maar daar is ook ander modelle. Na die heraanwending van sonkragregte van foton-verkwisters, kon oom Sam en plaaslike regerings die wortelkant van die Homestead Act laat herleef. Openbare liggame kan huurkontrakte op die dak aan derde partye toeken. As aansoekers vir hierdie voordele kan Sunrun en dies meer hul voetspore vergroot. Die implementering van 'n limiet van 160 hektaar sal egter sulke groot spelers uitsluit en ruimte skep vir sonkragopwekkers in die omgewing. Miskien kan & mdashas in 'n ander plan energiedemokrasie & mdashcommunity-hokkies panele koop en op dakplate installeer. Die hok sou die koste van die huur van oppervlakte bespaar en die besparings aan inwoners deurgee in die vorm van goedkoper elektrisiteit, terwyl 'n betroubare mikronetwerk aangebied word wanneer die hoofnetwerk afneem. Veral in swart gemeenskappe en kleurgemeenskappe kan die opstel van sonkrag die regsgeleerde Shalanda Baker noem en die transformasiegeregtigheid binne die energiestelsel noem. & Rdquo
Die vorme van huisvesting in die son wissel dan van blote openbare plig tot volle openbare besit. Hoe dit ook al sy, ons kom lewend uit en het 'n mate van burgerlike gesag oor energie.
In die gees van daardie & ldquoenergy revolusie, & rdquo, kan die Homestead Act ook nie-gewelddadige burgerlike ongehoorsaamheid regverdig. Die wet het reeds. Aan die einde van die wortel het die huiswerk 'n praktyk gewettig wat skaars verskil van hurk. Die nedersetter het sy huis gebou en sy gewasse in die openbare domein of op Indiese grond geplant sonder om 'n sent huur aan iemand te betaal. Vir 'n opgedateerde weergawe hiervan, word die Volledige Idiot & rsquos Guide to Urban Homesteading beskryf & ldquoguerilla tuinmaak & rdquo as & ldquogrowing op grond wat nie & rsquot behoort aan jou, sonder om toestemming van die eiendom eienaar. & rdquo Sommige & ldquoguerrilla projekte [is] openlike, & rdquo entoesias die gids, & ldquowith prominente openbare ruimtes skielik omskep in tuine. & rdquo Miskien kan iemand saad begrawe in 'n mediaan vir voedseldemokrasie, wat glad nie 'n slegte idee is nie. Maar elektriese en sonkrag-plakkers vereis meer tegnologie en beplanning en mdashas wat deur solarpunk wetenskapfiksie uiteengesit word. In & ldquoMidsummer Night & rsquos Heist & rdquo deur Commando Jugendstil en Tales van die EV Studio, dra aktiviste Milan & rsquos Piazza della Scala met fotovoltaïese en ldquostelae. & Rdquo Dawn versterk hulle en vul die plein met opgeneemde musiek.
Om langafstand-sonkrag in Wilder-styl te ontwerp, moet 'n mens nog baie bespiegel. Beskou die besoedelde, energie-uitgehongerde toekoms van Paolo Bacigalupi & rsquos klimaatsfiksie: fossielbrandstowwe is weg, elektrisiteit is skaars en desperate aasdiere verhandel die meer tasbare ekwivalente kalorieë of wind-up en ldquokink-fonteine. & Rdquo In hierdie konteks 'n onbewaakte dak of parkering baie bied geleentheid. Om 05:00 klim jy teen die mure of oor die heining. U stel u draagbare sonpanele en battery op. U laai die battery op sonstrale en huur dit teen sonsondergang aan 'n & ldquoswank & rdquo wat yskassiewatt vir die nag benodig. Met dagbreek haal u die battery op en begin weer. Namate litium en silikon goedkoper en goedkoper word as elektrisiteit duurder word, kan boerdery die hellandskap van 2100 oorheers. Of in 2021 kan bekwame, letterlik fotogeniese aksies en vandag met 'n toerusting en energie-demokrasie begin. (In werklikheid sou Texans hierdie tegniek kon gebruik tydens hul verskriklike verduistering, toe die son aanhou skyn en elektriese tariewe tot 75 keer normaal opgeskiet het.) Ons het die keuse om nou of later op te tree. As ons nou nie sonkrag aanwend vir utopie nie, kan ons kleinkinders sonkrag onder dystopie sit.
In 1862 en daarna het die boerdery die boerdery produktief gemaak vir baie mense wat andersins geen toegang tot grond gehad het nie. Hierdie koloniale voertuig het die beperkings op die mark en privaat eiendom oorkom. Dit was 'n groter voordeel vir wit Amerikaners en mdash, alhoewel nie, as 'n mens inheemse Amerikaners oorweeg die groter goed. Green & Deal wil & rsquos vandag dieselfde doen, om infrastruktuur en grondgebruik te herontwerp vir 'n groter voordeel. Privaat eiendom en markkragte kan help, maar net geleidelik. Die vinnige oorgang van koolwaterstowwe na hernubare energie vereis sentrale beplanning en administratiewe uitwerking. Vir baie Amerikaners is so 'n sosialisme 'n ooreenkoms. Hulle bewaar eerder ons huidige politieke ekonomie as die voorwaardes vir 'n menslike en nie-menslike lewe. Daardie posisie klink absurd. Desondanks is 'n regs-linkse stryd & mdash & ldquocapitalism teenoor die klimaat, & rdquo soos Naomi Klein 'n onlangse boek en mdashis ondertitels wat reeds aan die gang is.
Baie Amerikaners bewaar eerder ons huidige politieke ekonomie as die voorwaardes vir die menslike en nie-menslike lewe. Maar daar is derde opsies en onverwagte kombinasies wat hulle andersins kan oortuig.
Maar daar is derde opsies en onverwagte kombinasies. Met 'n bietjie verbeelding kan voorstanders van hernieubare huishoudelike praktyke en ander setlaarspraktyke vir 'n heel ander bevolking hersien en gebruik word vir stedelike huurders met verskillende agtergronde. Laat my die bemagtigende logika herhaal: 1) sonlig is 'n materiële hulpbron 2) eienaars van groot oppervlaktes sonder plantegroei, PV-panele, of, ten minste, dekstoele vermors die bron 3) in die belang van openbare beswil, die regering of enige klimaat. -gesinde groepe moet van sulke hulpbronne gebruik maak en dit gebruik om die energietransisie te bevorder en lewens te red. Hierdie drie beginsels kan beleid van verskillende sterkte rig. Aan die minder kragtige einde kan munisipaliteite die installering van panele op alle geskikte, onskaduwde nuwe geboue aanmoedig, laat druk en uiteindelik aandring. Op 'n meer direkte manier kan munisipaliteite 'n belangrike domein aanroep om onderdakke te benut. Selfs die bedreiging van 'n vooraanstaande domein kan pakhuise en groot bokse laat vorm. Amazon installeer panele stadig, hier en daar. Met 'n bietjie druk van die regering, kan die firma wat byna alles op 'n dag aflewer, ook elektronies teen ligte spoed vanaf bo- en ldquofulfilment-sentrums & rdquo op vyf kontinente versend. Dit sou 'n baie kapitaalvriendelike manier wees om klimaatsapokalips te vermy. Aan die ander kant van die skaal, kan beroepe en plakkersbewegings lei tot bekostigbare sonkragopwekking wat saam besit word en mdashand ook help om klimaatsapokalips te vermy.
Die vorme van huisvesting in die son wissel dan van blote openbare plig tot volle openbare besit. Hoe dit ook al sy, ons kom lewend uit en het 'n mate van burgerlike gesag oor energie. Die klimaatsnood eis optrede. Die Green New Deal kan en moet hierdie vorm van aksie aanvaar. Sonlig val tans êrens onopgeëis. Soos Pa vir Laura Ingalls Wilder gesê het, & ldquolet & rsquos vat dit. & Rdquo
Help om die volgende generasie swart joernaliste, redakteurs en uitgewers te finansier.
Boston-oorsig& rsquos Swart stemme in die openbare sfeergenootskap is ontwerp om die ernstige gebrek aan diversiteit in die media aan te spreek deur aspirant-swartmedia-professionele mense opleiding, mentorskap, netwerkgeleenthede en werksessies vir loopbaanontwikkeling te bied. Die program word befonds met die ruim steun van Derek Schrier, voorsitter van Boston-oorsig& rsquos raad van adviseurs, die Ford Foundation, en die Carnegie Corporation van New York, maar ons het nog 50 000 dollar oor om die genootskap vir die volgende twee jaar ten volle te finansier. Om die doel te bereik, as jy maak 'n belastingaftrekbare donasie tot 31 Augustus aan ons genootskapfonds, dit sal ooreenstem met 1: 1, tot $ 25.000& mdashso tree asseblief nou op om u impak te verdubbel. Klik hier om meer te wete te kom oor die program en ons 2021-2022-genote.
Inkomende sonlig
Alle materie in die heelal met 'n temperatuur bo absolute nul (die temperatuur waarteen alle atoom- of molekulêre beweging stop) straal energie uit oor 'n reeks golflengtes in die elektromagnetiese spektrum. Hoe warmer iets is, hoe korter is die piekgolflengte van uitgestraalde energie. Die warmste voorwerpe in die heelal straal meestal gammastrale en x-strale uit. Koeler voorwerpe straal meestal langer golflengte uit, insluitend sigbare lig, termiese infrarooi, radio en mikrogolwe.
Die Sun & rsquos-oppervlaktemperatuur is 5500 ° C en die piekstraling is sigbaar in golflengtes van die lig. Aarde & rsquos effektiewe temperatuur & mdashdie temperatuur wat dit sien as u dit vanuit die ruimte bekyk & mdashis -20 & deg C, en dit straal energie uit wat bereik word in termiese infrarooi golflengtes. (Illustrasie verwerk van Robert Rohde.)
Gloeilampe straal 40 tot 100 watt uit. The Sun lewer 1.360 watt per vierkante meter. 'N Ruimtevaarder wat die son in die gesig staar, het 'n oppervlakte van ongeveer 0,85 vierkante meter, dus hy of sy ontvang energie gelykstaande aan 19 60-wat gloeilampe. (Foto & kopie 2005 Paul Watson.)
Die oppervlak van die son het 'n temperatuur van ongeveer 5800 Kelvin (ongeveer 5.500 grade Celsius, of ongeveer 10.000 grade Fahrenheit). By die temperatuur is die meeste energie wat die son uitstraal sigbare en naby-infrarooi lig. Op die gemiddelde afstand van die aarde (ongeveer 150 miljoen kilometer) van die son, is die gemiddelde intensiteit van sonenergie wat die top van die atmosfeer bereik wat direk na die son kyk, ongeveer 1.360 watt per vierkante meter, volgens die metings van die mees onlangse NASA-satelliet missies. Hierdie hoeveelheid krag staan bekend as die totale sonbestraling. (Voordat wetenskaplikes ontdek het dat dit gedurende die sonvlek-siklus met 'n klein hoeveelheid wissel, word totale sonbestraling soms & die sonkonstante genoem. & # 8221)
'N Watt is die meting van krag, of die hoeveelheid energie wat iets oor tyd opwek of gebruik. Hoeveel krag is 1 360 watt? 'N Gloeilamp gebruik 40 tot 100 watt. 'N Mikrogolfoond gebruik ongeveer 1000 watt. As u net een uur lank al die sonenergie wat oor 'n enkele vierkante meter aan die bokant van die atmosfeer aankom en direk in die gesig staar na die son en # 8212 'n gebied wat nie wyer is as 'n volwassene se uitgestrekte armwydte nie, kan u vang en hergebruik; genoeg om 'n yskas die hele dag te laat werk.
Die totale sonbestraling is die maksimum moontlike krag wat die son kan lewer aan 'n planeet op die aarde se gemiddelde afstand vanaf die son. Die basiese meetkunde beperk die werklike sonenergie wat die aarde onderskep het. Slegs die helfte van die aarde word ooit tegelykertyd deur die son verlig, wat die totale sonbestraling halveer.
Energie van sonlig versprei nie eweredig oor die aarde nie. Een halfrond is altyd donker en ontvang glad nie sonstraling nie. Aan die dagligkant kry slegs die punt direk onder die son volle sonstraling. From the equator to the poles, the Sun’ rays meet Earth at smaller and smaller angles, and the light gets spread over larger and larger surface areas (red lines). (NASA illustration by Robert Simmon.)
In addition, the total solar irradiance is the maximum power the Sun can deliver to a surface that is perpendicular to the path of incoming light. Because the Earth is a sphere, only areas near the equator at midday come close to being perpendicular to the path of incoming light. Everywhere else, the light comes in at an angle. The progressive decrease in the angle of solar illumination with increasing latitude reduces the average solar irradiance by an additional one-half.
The solar radiation received at Earth&rsquos surface varies by time and latitude. This graph illustrates the relationship between latitude, time, and solar energy during the equinoxes. The illustrations show how the time of day (A-E) affects the angle of incoming sunlight (revealed by the length of the shadow) and the light’s intensity. On the equinoxes, the Sun rises at 6:00 a.m. everywhere. The strength of sunlight increases from sunrise until noon, when the Sun is directly overhead along the equator (casting no shadow). After noon, the strength of sunlight decreases until the Sun sets at 6:00 p.m. The tropics (from 0 to 23.5° latitude) receive about 90% of the energy compared to the equator, the mid-latitudes (45°) roughly 70%, and the Arctic and Antarctic Circles about 40%. (NASA illustration by Robert Simmon.)
Averaged over the entire planet, the amount of sunlight arriving at the top of Earth’s atmosphere is only one-fourth of the total solar irradiance, or approximately 340 watts per square meter.
When the flow of incoming solar energy is balanced by an equal flow of heat to space, Earth is in radiative equilibrium, and global temperature is relatively stable. Anything that increases or decreases the amount of incoming or outgoing energy disturbs Earth’s radiative equilibrium global temperatures must rise or fall in response.
Reflecting sunlight could cool the Earth's ecosystem
Published in the Proceedings of National Academy of Sciences, researchers in the Climate Intervention Biology Working Group -- including Jessica Hellmann from the University of Minnesota Institute on the Environment -- explored the effect of solar climate interventions on ecology.
Composed of climate scientists and ecologists from leading research universities internationally, the team found that more research is needed to understand the ecological impacts of solar radiation modification (SRM) technologies that reflect small amounts of sunlight back into space. The team focused on a specific proposed SRM strategy -- referred to as stratospheric aerosol intervention (SAI)) -- to create a sulfate aerosol cloud in the stratosphere to reduce a portion of incoming sunlight and radiation. In theory, this cloud could be controlled in size and location.
SAI is like placing tiny reflective particles in the atmosphere to bounce a portion of the solar radiation back to space, so that some of the radiation does not reach -- and warm -- Earth.
The team emphasizes that greenhouse gas emissions reduction and conservation of biodiversity and ecosystem functions must be the priority.
"We are just starting to consider the risks and benefits of geoengineering, and it's critical that we include ecosystems in cost-benefit studies," said Hellmann, director at the U of M Institute on the Environment. "We should only pursue geoengineering if its benefits strongly outweigh its downsides. Because our efforts to stem climate change are modest and slow, the case for considering geoengineering is growing, and this paper represents the ecologists chiming in to the geoengineering conversation."
The complexity of cascading relationships between ecosystems and climate under SAI -- in combination with the timing, amount, length and termination of SAI scenarios -- means that SAI is not a simple thermostat that turns down the heat a couple of degrees. Other potential effects of SAI include shifts in rainfall and increases in surface UV rays. While SAI might cool an overheated Earth, it would not be able to counter all of the effects of rising atmospheric CO2, such as halting ocean acidification.
"When we approach complex questions like these, there is a broad scale, theoretical understanding of the inherent patterns of biodiversity across the surface of Earth, but this understanding is often informed by finer-scale experiments that test the biological and physical mechanisms underlying those patterns," said Phoebe Zarnetske, study co-lead and an associate professor in Michigan State University's Department of Integrative Biology and the Ecology, Evolution, and Behavior program.
"I hope the paper can convince ecologists that research about nature's responses to solar geoengineering is not just important, but also interesting -- touching on core ecological questions about topics as varied as photosynthesis and animal migration," said U of M alum Shan Kothari, who contributed to the study during his time at the College of Biological Sciences before going to the University of Montreal.
Kothari said that an example of how other scientists can consider the study's findings is to contemplate the unique conditions resulting from solar geoengineering scenarios that may aid or impede the ability for ecosystems to store carbon. He added that such research could help the international community consider solar geoengineering with a stronger awareness of the potential risks and benefits involved.
Study Your Yard's Sunlight
Get started by recording how much sunlight your yard receives over time. Assess light patterns every hour or two throughout the course of a day, noting where shadows fall and for how long. Keep in mind that in spring, bare-branched trees may give the illusion of sunny spots beneath, but once they leaf out, they often create heavy shade during summer and into fall. Buildings and walls also cast shadows consider those structures as you plot the sun&aposs path over your patch of earth.
Use marking flags or stakes to indicate light and shadow in your yard. Or you can create a light map on paper. Start with a few sheets of tracing paper, sketching a copy of your yard&aposs outline on each page. About two hours after sunrise, observe where light and shade fall and mark them on the tracing paper, noting the time. Repeat the process through the day, each time using a different sheet of paper. Stop recording about an hour before dusk. Use a pencil to mark shady sections of the yard on each page. Label sun and shade pockets to indicate whether they reflect morning or afternoon conditions. Layer the pages together, and you&aposll get an accurate picture of how much light your yard receives. Create a composite drawing to use as a one-page light map.
A Second Look at Sunlight
A year ago scientists everywhere were scrambling to get their minds around SARS-CoV-2, a novel coronavirus that caused the pandemic from which we are only now beginning to emerge. The world clung to every new development, every bit of science that could provide clues to managing life in the presence of this mysterious killer.
Many science-backed COVID-19 management concepts remain unchanged to this day: handwashing with soap and warm water disrupts the virus’ lipid membrane. Social distancing can attenuate the virus’s spread, ideally keeping it out of a host until it degrades. Other notions, such as droplet contact being the primary mode of transmission, were modified when emerging evidence showed that under certain conditions, the virus could remain suspended in air for extended periods of time.
In a letter in the Journal of Infectious Diseases, a team of researchers from UC Santa Barbara, Oregon State University, University of Manchester and ETH Zurich examines another of SARS-CoV-2’s well known characteristics — its vulnerability to sunlight. Their conclusion? It might take more than UV-B rays to explain sunlight inactivation of SARS-CoV-2.
The idea that an additional mechanism might be in play came when the team compared data from a July 2020 study that reported rapid sunlight inactivation of SARS-CoV-2 in a lab setting, with a theory of coronavirus inactivation by solar radiation that was published just a month earlier.
“The theory assumes that inactivation works by having UV-B hit the RNA of the virus, damaging it,” said UC Santa Barbara mechanical engineering professor and lead author Paolo Luzzatto-Fegiz. Judging from the discrepancies between the experimental results and the predictions of the theoretical model, however, the research team felt that RNA inactivation by UV-B “might not be the whole story.”
According to the letter, the experiments demonstrated virus inactivation times of about 10-20 minutes — much faster than predicted by the theory.
“The theory predicts that inactivation should happen an order of magnitude slower,” Luzzatto-Fegiz said. In the experiments, viruses in simulated saliva and exposed to UV-B lamps were inactivated more than eight times faster than would have been predicted by the theory, while those cultured in a complete growth medium before exposure to UV-B were inactivated more than three times faster than expected. To make the math of the theory fit the data, according to the letter, SARS-CoV-2 would have to exceed the highest UV-B sensitivity of any currently known virus.
Or, Luzzato-Fegiz and colleagues reasoned, there could be another mechanism at play aside from RNA inactivation by UV-B rays. For instance, UV-A, another, less energetic component of sunlight might be playing a more active role than previously thought.
“People think of UV-A as not having much of an effect, but it might be interacting with some of the molecules in the medium,” he said. Those reactive intermediate molecules in turn could be interacting with the virus, hastening inactivation. It’s a concept familiar to those who work in wastewater treatment and other environmental science fields.
“So, scientists don’t yet know what’s going on,” Luzzatto-Fegiz said “Our analysis points to the need for additional experiments to separately test the effects of specific light wavelengths and medium composition.”
Results of such experiments might provide clues into new ways of managing the virus with widely available and accessible UV-A and UV-B radiation. While UV-C radiation is proved effective against SARS-CoV-2, this wavelength does not reach the earth’s surface and must be manufactured. Although UV-C is presently used in air filtration and in other settings, its short wavelengths and high energy also makes UV-C the most damaging form of UV radiation, limiting its practical application and raising other safety concerns.
Co-author and UCSB mechanical engineering professor Yangying Zhu added that UV-A turning out to be capable of inactivating the virus could be very advantageous: there are now widely available inexpensive LED bulbs that are many times stronger than natural sunlight, which could accelerate inactivation times. UV-A could potentially be used far more broadly to augment air filtration systems at relatively low risk for human health, especially in high-risk settings such as hospitals and public transportation, but the specifics of each setting warrant consideration, said co-author Fernando Temprano-Coleto.
Research in this paper was conducted also by François J. Peaudecerf at ETH Zurich and Julien Landel at University of Manchester.
How should I think about sunlight for the purposes of analyzing the angles it makes w/ earth? - Sterrekunde
Satellite images are like maps: they are full of useful and interesting information, provided you have a key. They can show us how much a city has changed, how well our crops are growing, where a fire is burning, or when a storm is coming. To unlock the rich information in a satellite image, you need to:
- Look for a scale
- Look for patterns, shapes, and textures
- Define the colors (including shadows)
- Find north
- Consider your prior knowledge
These tips come from the Earth Observatory&rsquos writers and visualizers, who use them to interpret images daily. They will help you get oriented enough to pull valuable information out of satellite images.
Look for a Scale
One of the first things people want to do when they look at a satellite image is identify the places that are familiar to them: their home, school, or place of business a favorite park or tourist attraction or a natural feature like a lake, river, or mountain ridge. Some images from military or commercial satellites are detailed enough to show many of these things. Such satellites zoom in on small areas to collect fine details down to the scale of individual houses or cars. In the process, they usually sacrifice the big picture.
Images from the commercial WorldView-2 satellite (top) can show street by street details of the September 2013 flood in Boulder, Colorado, while the scientific Landsat 8 satellite (lower) can be zoomed in to give a city size scale. (Worldview-2 image based on data ©2013 DigitalGlobe. Landsat image by Jesse Allen and Robert Simmon, using data from the USGS Earth Explorer.)
NASA satellites take the opposite approach. Earth science researchers typically want a wide-angle lens to see whole ecosystems or atmospheric fronts. As a result, NASA images are less detailed but cover a wider area, ranging from the landscape scale (185 kilometers across) to an entire hemisphere. The level of detail depends on the satellite&rsquos spatial resolution. Like digital photographs, satellite images are made up of little dots called pixels. The width of each pixel is the satellite&rsquos spatial resolution.
Commercial satellites have a spatial resolution down to 50 centimeters per pixel. The most detailed NASA images show 10 meters in each pixel. Geostationary weather satellites, which observe a whole hemisphere at a time, are much less detailed, seeing one to four kilometers in a pixel.
Raw Landsat scenes (top) provide a landscape view, while MODIS (lower) provides a wider view. The images are from September 17 (Landsat) and September 14 (MODIS), 2013. (Landsat image by Jesse Allen and Robert Simmon, using data from the USGS Earth Explorer. MODIS image by Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC.)
Depending on the image resolution, a city may fill an entire satellite image with grids of streets or it may be a mere dot on a landscape. Before you begin to interpret an image, it helps to know what the scale is. Does the image cover 1 kilometer or 100? What level of detail is shown? Images published on the Earth Observatory include a scale.
You can learn different things at each scale. For example, when tracking a flood, a detailed, high-resolution view will show which homes and businesses are surrounded by water. The wider landscape view shows which parts of the county or metropolitan area are flooded and perhaps where the water is coming from. A broader view would show the entire region&mdashthe flooded river system or the mountain ranges and valleys that control the flow. A hemispheric view would show the movement of weather systems connected to the floods.
GOES satellites offer a nearly full view of the Earth&rsquos disk. This image shows North and South America on September 14, 2013. (Image by the NASA/NOAA GOES Project Science Office.)
Look for patterns, shapes, and textures
If you have ever spent an afternoon identifying animals and other shapes in the clouds, you&rsquoll know that humans are very good at finding patterns. This skill is useful in interpreting satellite imagery because distinctive patterns can be matched to external maps to identify key features.
Bodies of water&mdashrivers, lakes, and oceans&mdashare often the simplest features to identify because they tend to have unique shapes and they show up on maps.
Other obvious patterns come from the way people use the land. Farms usually have geometric shapes&mdashcircles or rectangles&mdashthat stand out against the more random patterns seen in nature. When people cut down a forest, the clearing is often square or has a series of herring-bone lines that form along roads. A straight line anywhere in an image is almost certainly human-made, and may be a road, a canal, or some kind of boundary made visible by land use.
Straight lines and geometric shapes in this image of Reese, Michigan, are a result of human land use. Roads cut diagonally across the squares that define farm fields. (NASA Earth Observatory image by Jesse Allen and Robert Simmon, using ALI data from the NASA EO-1 team.)
Geology shapes the landscape in ways that are often easier to see in a satellite image. Volcanoes and craters are circular, and mountain ranges tend to run in long, sometimes wavy lines. Geologic features create visible textures. Canyons are squiggly lines framed by shadows. Mountains look like wrinkles or bumps.
These features can also affect clouds by influencing the flow of air in the atmosphere. Mountains force air up, where it cools and forms clouds. Islands create turbulence that results in swirling vortices or wakes in the clouds. When you see a line of clouds or vortices, they provide a clue about the topography of the land below.
Central Chile and Argentina offer a wide range of geographic features, including snow-covered mountains, canyons, and volcanoes. (NASA image courtesy Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC.)
Occasionally, shadows can make it hard to tell the difference between mountains and canyons. This optical illusion is called relief inversion. It happens because most of us expect an image to be lit from the top left corner. When the sunlight comes from another angle (especially from the lower edge), the shadows fall in ways we don&rsquot expect and our brains turn valleys into mountains to compensate. The problem is usually resolved by rotating the image so the light appears to come from the top of the image.
Define Colors
The colors in an image will depend on what kind of light the satellite instrument measured. True-color images use visible light&mdashred, green and blue wavelengths&mdashso the colors are similar to what a person would see from space. False-color images incorporate infrared light and may take on unexpected colors. In a true color image, common features appear as follows:
Water
Water absorbs light, so it is usually black or dark blue. Sediment reflects light and colors the water. When suspended sand or mud is dense, the water looks brown. As the sediment disperses, the water&rsquos color changes to green and then blue. Shallow waters with sandy bottoms can lead to a similar effect.
Sunlight reflecting off the surface of the water makes the water look gray, silver, or white. This phenomenon, known as sunglint, can highlight wave features or oil slicks, but it also masks the presence of sediment or phytoplankton.
Sunglint makes it possible to see current patterns on the ocean&rsquos surface around the Canary Islands. (NASA image courtesy Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC.)
Frozen water&mdashsnow and ice&mdashis white, gray, and sometimes slightly blue. Dirt or glacial debris can give snow and ice a tan color.
Plants
Plants come in different shades of green, and those differences show up in the true-color view from space. Grasslands tend to be pale green, while forests are very dark green. Land used for agriculture is often much brighter in tone than natural vegetation.
In some locations (high and mid latitudes), plant color depends on the season. Spring vegetation tends to be paler than dense summer vegetation. Fall vegetation can be red, orange, yellow, and tan leafless and withered winter vegetation is brown. For these reasons, it is helpful to know when the image was collected.
The forests covering the Great Smoky Mountains of the Southeastern United States change colors from brown to green to orange to brown as the seasons progress. (NASA images courtesy Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC.)
In the oceans, floating plants&mdashphytoplankton&mdashcan color the water in a wide variety of blues and greens. Submerged vegetation like kelp forests can provided a shadowy black or brown hue to coastal water.
Bare ground
Bare or very lightly vegetated ground is usually some shade of brown or tan. The color depends on the mineral content of the soil. In some deserts such as the Australian Outback and the southwestern United States, exposed earth is red or pink because it contains iron oxides like hematite (Greek for blood-like). When the ground is white or very pale tan, especially in dried lakebeds, it is because of salt-, silicon-, or calcium-based minerals. Volcanic debris is brown, gray, or black. Newly burned land is also dark brown or black, but the burn scar fades to brown before disappearing over time.
Cities
Densely built areas are typically silver or gray from the concentration of concrete and other building materials. Some cities have a more brown or red tone depending on the materials used for rooftops.
The contrast between Warsaw&rsquos modern and historic neighborhoods is easily visible by satellite. The new Stadion Narodowy is brilliant white. &Sacuteródmie&sacutecie (Inner City) was rebuilt after World War II and most areas appear beige or gray. But some neighborhoods rebuilt with older-style buildings, such as the red tile and green copper roofs of Stare Miasto (Old Town). (Image courtesy NASA/USGS Landsat.)
Atmosfeer
Clouds are white and gray, and they tend to have texture just as they do when viewed from the ground. They also cast dark shadows on the ground that mirror the shape of the cloud. Some high, thin clouds are detectable only by the shadow they cast.
Smoke is often smoother than clouds and ranges in color from brown to gray. Smoke from oil fires is black. Haze is usually featureless and pale gray or a dingy white. Dense haze is opaque, but you can see through thinner haze. The color of smoke or haze usually reflects the amount of moisture and chemical pollutants, but it&rsquos not always possible to tell the difference between haze and fog in a visual interpretation of a satellite image. White haze may be natural fog, but it may also be pollution.
Clouds, fog, haze and snow are sometimes difficult to distinguish in satellite imagery, as in this MODIS image of the Himalaya from November 1, 2013. (Image adapted from MODIS Worldview.)
Dust ranges in color, depending on its source. It is most often slightly tan, but like soil, can be white, red, dark brown, and even black due to different mineral content.
Volcanic plumes also vary in appearance, depending on the type of eruption. Plumes of steam and gas are white. Ash plumes are brown. Resuspended volcanic ash is also brown.
Colors in Context
Looking at a satellite image, you see everything between the satellite and the ground (clouds, dust, haze, land) in a single, flat plane. This means that a white patch might be a cloud, but it could also be snow or a salt flat or sunglint. The combination of context, shape, and texture will help you tell the difference.
For example, shadows cast by clouds or mountains can be easy to mistake for other dark surface features like water, forest, or burned land. Looking at other images of the same area taken at another time can help eliminate confusion. Most of the time, context will help you see the source of the shadow&mdasha cloud or mountain&mdashby comparing the shape of the shadow to other features in the image.
Find North
When you get lost, the simplest way to figure out where you are is to find a familiar landmark and orient yourself with respect to it. The same technique applies to satellite images. If you know where north is, you can figure out if that mountain range is running north to south or east to west, or if a city is on the east side of the river or the west. These details can help you match the features to a map. On the Earth Observatory, most images are oriented so that north is up. All images include a north arrow.
Consider your Prior Knowledge
Perhaps the most powerful tool for interpreting a satellite image is knowledge of the place. If you know that a wildfire burned through a forest last year, it&rsquos easy to figure out that the dark brown patch of forest is probably a burn scar, not a volcanic flow or shadow.
Land burned by Yosemite&rsquos Rim Fire is gray brown in comparison to the unburned brown and green landscape around it. See this linked map that helps differentiate between burned land and non-burned land. (NASA Earth Observatory images by Robert Simmon, using Landsat 8 data from the USGS Earth Explorer.)
Having local knowledge also allows you to connect satellite mapping to what&rsquos happening in everyday life, from social studies, economics, and history (for example, population growth, transport, food production) to geology (volcanic activity, tectonics) to biology and ecology (plant growth and ecosystems) to politics and culture (land and water use) to chemistry (atmospheric pollution) and to health (pollution, habitat for disease carriers).
For example, land ownership and land use policy is contrasted in the pair of images below. In Poland, small parcels of privately owned land surround the Niepolomice Forest. The government has managed the forest as a unit since the thirteenth century. While the canopy isn't a solid, unbroken green, the forest is largely intact. The lower image shows a checkerboard combination of private and public land near Washington&rsquos Okanogan-Wenatchee National Forest. The U.S. Forest Service manages the forest under a mixed use policy that preserves some forest, while opening other sections to logging. Lighter green areas indicate that logging has occurred on federal, state, or private land. Parcels of private land are much larger in this part of the western United States than in Poland.
Land use and conservation policies define the forest area in both Poland (top) and the U.S. state of Washington (lower). (NASA Earth Observatory images by Robert Simmon, using Landsat 8 data from the USGS Earth Explorer.)
If you lack knowledge of the area shown, a reference map or atlas can be extremely valuable. A map gives names to the features you can see in the image, and that gives you the ability to look for additional information. Several online mapping services even provide a satellite view with features labeled. Historic maps, such as those found at the Library of Congress or in the David Rumsey Map Collection, can help you identify changes and may even help you understand why those changes occurred.
Whether you are looking at Earth for science, history, or something else, also consider the Earth Observatory as a key resource. The site hosts a rich, deep archive of more than 12,000 interpreted satellite images covering a wide range of topics and locations. The archive includes images of natural events as well as more diverse featured images. If the Earth Observatory does not have an image of an area or topic that interests you, please let us know. We&rsquore always looking for new ways to explore our world from space.
How do plants protect themselves against too much sunlight?
That a switching protein plays a role in protecting a plant from too much sunlight was already known, but how exactly was not yet understood. The research group of Anjali Pandit has now discovered that this protein changes shape when there is too much sunlight. The results have been published in Nature Communications.
Plants need light, but in full sunlight so-called photodamage can occur: acidification takes place in the chloroplasts of the plant. The hypothesis is that the switch protein PsbS reacts to this acidification and sends a signal to the light antenna of the plant. This antenna then switches itself off and ensures that the bright sunlight shining on the plant is converted into heat, so that the plant is no longer damaged.
Chemist Anjali Pandit, her former Ph.D. candidate Maithili Krishnan of the Leiden Institute of Chemistry and researchers of VU Amsterdam have now discovered how the switching effect of the PsbS protein works: they discovered that the protein changes its shape when there is a surplus of sunlight. To this end, they made targeted mutations on the protein. Subsequently, using advanced NMR and infrared laser techniques, they managed to show where essential structural changes take place in the protein.
The protection mechanism in which the PsbS protein plays a crucial role is important for plants, but it also limits how efficiently a plant can convert sunlight into energy. Pandit: "That is why it is important that we learn more about the mechanisms behind photosynthesis. By tinkering with photosynthesis, for example by fine-tuning this protection mechanism against damage, we can improve crops. Think of a higher food production and a better tolerance against drought." Earlier research shows that tobacco plants with increased PsbS production yield 15 percent more biomass.
The next step is to find out how PsbS transmits a warning signal in the plant and how this leads to the adjustment of the photosynthesis reaction. For this, a team of researchers, of which Pandit is part of, will join forces with the help of a NWO ENW-GROOT grant from 2020. "With this kind of fundamental research, we hope to contribute to global food security in a changing climate."
Solar Cells: Costs, Challenges, and Design
Over the past 20 years, the costs associated with solar cells, the structures capable of converting light energy into electricity, have been steadily decreasing. The National Renewable Energy Laboratory, a US government lab that studies solar cell technology, estimates contributors to the increasing affordability of solar. They estimate that hard costs, the costs of the physical solar cell hardware, and soft costs, which include labor or costs to obtain required government permits, are about equal (Figure 1). Soft costs have decreased because there are more potential consumers and more installation experts for new solar cells, so companies can produce solar cells in bulk and install them easily. Hard costs are less than half of what they were in the year 2000, mostly due to decreasing material costs and an increased ability of cells to capture light. Engineering more cost-effective and efficient solar cells has required careful consideration of the physics involved in solar capture in addition to innovative design.
Figure 1: Costs associated with solar power. Solar cells become less expensive when the cost of the labor and materials use to build them go down, or when they become better at turning incoming light into electricity.
Because solar cells are used to convert light into electricity, they need to be composed of some material that’s good at capturing energy from light. This material can be sandwiched between two metal plates which carry the electricity captured from light energy to where it is needed, like the lights of a home or machines of a factory (Figure 2). Choosing the right material to capture light involves measuring the difference between two energy levels called the valence band and the conduction band. The lower-energy valence band is filled with many small negatively charged particles called electrons, but the higher-energy conduction band is mostly empty. When electrons are hit with particles of light, called photons, they can absorb enough energy to jump from the low-energy conduction band into the high-energy valence band. Once in the valence band, the extra energy in the electron can be harvested as electricity. It’s as if the electrons are sitting at the bottom of a hill (the conduction band) and being hit by a photon that gives them the energy to leap to the top (the valance band).
The amount of energy needed for electrons to jump into the valence band depends on the type of material. Essentially, the size of the metaphorical hill varies based on the properties of a given material. The size of this energy gap matters because it impacts how efficiently solar cells convert light into electricity. Specifically, if photons hit the electrons with less energy than the electron needs to jump from the valence band to the conduction band, none of the light’s energy is captured. Alternatively, If the light has more energy than is needed to overcome that gap, then the electron captures the precise energy it needs and wastes the remainder. Both of these scenarios lead to inefficiencies in solar harvesting, making the choice of solar cell material an important one.
Historically, silicon has been the most popular material for solar cells (Figure 2). One reason for this popularity lies in the size of the gap between silicon’s conduction and valence bands, as the energy of most light particles is very close to the energy needed by silicon’s electrons to jump the energy gap. Theoretically, about 32% of light energy could be converted into electric energy with a silicon solar cell. This may not seem like a lot, but it is significantly more efficient than most other materials. Additionally, silicon is also inexpensive. It is one of the most abundant elements on earth, and the cost of refining it has decreased dramatically since 1980. The solar cell and electronics industries have driven the decrease in purification cost as they have learned better bulk purification techniques to drive the demand of solar cells and consumer electronics.
Figure 2: Light energy capture in solar cells. When light hits a solar cell, it causes it causes electrons to jump into a conduction band, allowing the light energy to be harvested. Here yellow electrons (labeled e) move through the silicon atoms (labeled Si) in the solar cell when hit by a photon.
In addition to decreasing material costs, clever engineering tricks are pushing the efficiency of silicon solar cells closer to their theoretical maximum. In order for photons to be converted into energy, they must first collide with an electron. One trick to increase the likelihood of a photon/electron collision involves patterning the silicon in solar cells in microscopic pyramid shapes. When light is absorbed into a pyramid, it travels further, increasing the probability that the light will collide with the electrons in the silicon before escaping the cell.
In a similar tactic, chemists and material scientists have designed anti-reflective coatings to put on the front of solar cells to prevent useful light from being reflected back into space without ever hitting an electron in the solar cell. Likewise, putting a reflector on the back of the solar cell also allows more light to be harvested. The light that reaches the solar cell and makes it all the way through to the back without hitting an electron gets bounced to the front of the cell, giving the cell another chance of collecting the light.
Currently, the cost of silicon-based solar cells continues to decrease, and, despite predictions to the contrary, the cost of silicon itself continues to decrease. Silicon solar cells are likely to remain popular for the next few years. Alternatives to silicon solar cells have been developed but aren’t far enough along to be commercially viable.
Archangel Zadkiel
Archangel Zadkiel is known for helping students remember facts and figures for tests healing painful memories remembering your Divine spiritual origin and missions and choosing forgiveness.
In Jewish rabbinic writings, Zadkiel is described as the archangel who inspires forgiveness and compassion in people. In the Kabbalah, Zadkiel (as Tzadkiel) presides over the fourth, or Chesed, Sephirah on the Tree of Life. The Chesed sphere relates to practicing unconditional kindness and love as a manifestation of God upon Earth.
Zadkiel is one of the seven archangels in the Gnostic tradition, as well as in the Pseudo-Dionysius writings. Under his alternative name Zachariel, he was identified as one of the seven archangels by Pope Saint Gregory. Zadkiel has long been regarded as the “angel of memory,” who can support students and those who need to remember facts and figures.
When To Call On Archangel Zadkiel
Archangel Zadkiel’s dual focus upon forgiveness and memory can help you heal emotional pain from your past. The archangel can work with you on releasing old anger or feelings of victimhood so that you can remember and live your Divine life purpose. As you ask Zadkiel for emotional healing, he’ll shift your focus away from painful memories and toward the recollection of the beautiful moments of your life.
Archangel Zadkiel is a great healer of the mind, who gently leads you by the hand to take responsibility for your own happiness. He is also the keeper of the Violet Flame and is called on to transmute negative energys.
Color: Deep Violet
Gemstone: Amethyst
The Angelic Realm – About Angels, Communicating with Angels and the Nine Choirs of Angels
Angel Evening Dates and Locations – We run regular Angel Evenings in Essex, Bournemouth and Berkshire. These are informal events where we have guided meditation and Angelic Reiki taster sessions on request. It’s a great chance to come along and meet us and learn a little more about what we do.
Our Angelic Reiki Courses – View information on our Angelic Reiki workshops from beginner to practitioner level. Courses run regularly across the UK and occasionally in Europe and the USA.
