Warning: Creating default object from empty value in /home/egskil/public_html/blocks/navigation/block_navigation.php on line 198

Strict Standards: Declaration of question_calculated_qtype::get_actual_response() should be compatible with default_questiontype::get_actual_response($question, $state) in /home/egskil/public_html/question/type/calculated/questiontype.php on line 2162

Strict Standards: Declaration of question_calculated_qtype::print_question_grading_details() should be compatible with default_questiontype::print_question_grading_details(&$question, &$state, $cmoptions, $options) in /home/egskil/public_html/question/type/calculated/questiontype.php on line 2162

Strict Standards: Declaration of description_qtype::print_question() should be compatible with default_questiontype::print_question(&$question, &$state, $number, $cmoptions, $options, $context = NULL) in /home/egskil/public_html/question/type/description/questiontype.php on line 93

Strict Standards: Declaration of question_match_qtype::get_all_responses() should be compatible with default_questiontype::get_all_responses(&$question, &$state) in /home/egskil/public_html/question/type/match/questiontype.php on line 542

Strict Standards: Declaration of question_match_qtype::compare_responses() should be compatible with default_questiontype::compare_responses(&$question, $state, $teststate) in /home/egskil/public_html/question/type/match/questiontype.php on line 542

Strict Standards: Declaration of embedded_cloze_qtype::compare_responses() should be compatible with default_questiontype::compare_responses(&$question, $state, $teststate) in /home/egskil/public_html/question/type/multianswer/questiontype.php on line 728

Strict Standards: Declaration of question_multichoice_qtype::compare_responses() should be compatible with default_questiontype::compare_responses(&$question, $state, $teststate) in /home/egskil/public_html/question/type/multichoice/questiontype.php on line 549

Strict Standards: Declaration of question_shortanswer_qtype::compare_responses() should be compatible with default_questiontype::compare_responses(&$question, $state, $teststate) in /home/egskil/public_html/question/type/shortanswer/questiontype.php on line 412

Strict Standards: Declaration of question_shortanswer_qtype::test_response() should be compatible with default_questiontype::test_response(&$question, &$state, $answer) in /home/egskil/public_html/question/type/shortanswer/questiontype.php on line 412

Strict Standards: Declaration of question_numerical_qtype::has_wildcards_in_responses() should be compatible with question_shortanswer_qtype::has_wildcards_in_responses($question, $subqid) in /home/egskil/public_html/question/type/numerical/questiontype.php on line 39

Strict Standards: Declaration of question_numerical_qtype::compare_responses() should be compatible with question_shortanswer_qtype::compare_responses($question, $state, $teststate) in /home/egskil/public_html/question/type/numerical/questiontype.php on line 39

Strict Standards: Declaration of question_numerical_qtype::test_response() should be compatible with question_shortanswer_qtype::test_response(&$question, $state, $answer) in /home/egskil/public_html/question/type/numerical/questiontype.php on line 39

Strict Standards: Declaration of random_qtype::get_actual_response() should be compatible with default_questiontype::get_actual_response($question, $state) in /home/egskil/public_html/question/type/random/questiontype.php on line 384

Strict Standards: Declaration of random_qtype::print_question() should be compatible with default_questiontype::print_question(&$question, &$state, $number, $cmoptions, $options, $context = NULL) in /home/egskil/public_html/question/type/random/questiontype.php on line 384

Strict Standards: Declaration of question_truefalse_qtype::compare_responses() should be compatible with default_questiontype::compare_responses(&$question, $state, $teststate) in /home/egskil/public_html/question/type/truefalse/questiontype.php on line 311

Deprecated: Non-static method PEAR::setErrorHandling() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 63

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2339

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2340

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2341

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2342

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2343

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2344

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2345

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2346

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2347

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2348

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2349

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2350

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2351

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2352

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2353

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2354

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2355

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2356

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2357

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2358

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2359

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2360

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2361

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2362

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2363

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2364

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2365

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2366

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2367

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2368

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2369

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2370

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2371

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2372

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2373

Deprecated: Non-static method HTML_QuickForm::registerElementType() should not be called statically, assuming $this from incompatible context in /home/egskil/public_html/lib/formslib.php on line 2374

Strict Standards: Declaration of repository_instance_form::validation() should be compatible with moodleform::validation($data, $files) in /home/egskil/public_html/repository/lib.php on line 1763

Strict Standards: Declaration of repository_local::get_listing() should be compatible with repository::get_listing($path = '', $page = '') in /home/egskil/public_html/repository/local/lib.php on line 172

Strict Standards: Declaration of repository_recent::type_config_form() should be compatible with repository::type_config_form($mform, $classname = 'repository') in /home/egskil/public_html/repository/recent/lib.php on line 222

Strict Standards: Declaration of repository_upload::get_listing() should be compatible with repository::get_listing($path = '', $page = '') in /home/egskil/public_html/repository/upload/lib.php on line 197

Strict Standards: Declaration of repository_user::get_listing() should be compatible with repository::get_listing($path = '', $page = '') in /home/egskil/public_html/repository/user/lib.php on line 135

Warning: Creating default object from empty value in /home/egskil/public_html/blocks/settings/block_settings.php on line 132
Að greina aðalatriði í texta: Glóandi bómullarþráður lýsti í myrkrinu.

Glóandi bómullarþráður lýsti í myrkrinu.

Úr tímaritinu Sagan öll, 8. tölublað 2010.

Eftir Magnus Västerbro.

Í byrjun 19. aldar var mönnum orðið ljóst að með rafmagni mátti kveikja ljós. Vísindamenn kepptust við að finna upp aðferðir til að þekking þessi nýttist mönnum.

Árið 1802 átti merkilegur atburður sér stað í húsakynnum The Royal Institution í Lundúnum. Uppfinningamaðurinn og efnafræðingurinn Humphrey Davey gerði tilraun með kröftugustu rafhlöðum síns tíma. Hann sendi rafstraum eftir mjóum platínuvír, vírinn glóði og lýsti upp nánasta umhverfi sitt.

Davey hafði þarna hannað nokkuð frumstæða ljósaperu og nú tók við kapphlaup uppfinninga- og vísindamanna og stóð í um 75 ár. Sagnfræðingunum Robert Friedel og Paul Israel telst til að ekki færri en 22 uppfinningamenn hafi fundið upp nánast jafnmargar ljósaperur á 19. öld.

Aðferðin við að fá tein til að glóa spurðist um heim allan. Rafstraumi er hleypt á teininn, þráðinn. En til þess að hann brynni ekki upp til agna varð að koma honum fyrir í súrefnislausu glerhylki. Vandamálið var bara hvernig hægt yrði að framkvæma þetta. Hvernig tein eða þráð átti að nota? Hvernig var hægt að tæma allt súrefni úr glerhylkinu? Og hvernig yrði hægt að smíða ljósaperu sem tæki við rafstraumi frá uppsprettu – með öðrum orðum hvernig ætti að hanna kerfi til raflýsingar, þar sem fjöldi ljósapera sameinaðist um uppsprettuna en samt yrði hægt að kveikja og slökkva á hverri peru fyrir sig?

Vísindamenn veraldar brutu heilann um þetta og kepptust við að leysa gátuna mestan hluta 19. aldar.

Menn voru sammála um að sá sem fyrstur yrði til að leysa þessa ljósaperugátu yrði einn af helstu uppfinningamönnum mannkyns. Rafljós gætu umbylt samfélögum manna. Menn gætu þá athafnað sig á kvöldin og um nætur rétt eins og sól skini í heiði.

Einn af frumkvöðlum keppninnar var Englendingurinn Joseph Wilson Swan en árið 1860 fékk hann einkaleyfi á ljósaperu og í henni glóði kolaður pappír í næstum lofttæmdu rýminu. Þessa smíði Swans má vel telja fyrstu rafmagnsljósaperu heims en á henni voru nokkrir gallar. Í fyrsta lagi var ljósið dauft og í öðru lagi varð hún að vera alveg við uppsprettu rafmagnsins. Og þar sem peran var bara næstum lofttæmd en ekki alveg, slokknaði fljótt á henni.

Átján árum síðar hafði Swan gert nokkrar endurbætur á ljósaperu sinni. Í þetta sinn glóði kolaður bómullarþráður í heilar 13,5 klukkustundir. Handan Atlandshafsins sat auðugur og frægur Bandaríkjamaður, Thomas Edison, yfir leyndarmálum ljósaperunnar. Hann og aðstoðarmenn hans höfðu reynt að minnsta kosti 6.000 gerðir þráða úr öllum heimshornum þegar þeir komust að því að kolaður bómullarþráður lýsti best og lengst. Edison hafði einnig notfært sér nýja tegund lofttæmingartækis sem Þjóðverjinn Herman Sprengel hafði smíðað. Og ljósapera Edisons logaði lengur en Swans eða í rétt tæpar 15 klukkustundir.

Keppnin milli Swans og Edisons var allhörð um tíma. Swan kærði meira að segja Edison fyrir brot á einkaleyfi. Að lokum stóð þó Edison uppi sem „faðir ljósaperunnar“. Árið 1878 stofnaði hann Edison Electric Light Company. Tveimur árum seinna loguðu ljósaperur hans í 600 klukkustundir og uppfinningin sló í gegn.

Keppninni um ljósaperuna lauk með handsali. Að baki Edison stóðu fjársterkir menn og hann keypti einfaldlega réttinn að uppfinningu Swans. Hann keypti ýmislegt fleira, meðal annars betra glerhylki og átti það eftir að nýtast honum vel.

Sumir hafa ásakað Edison um að ræna uppfinningum annarra og gera að sínum. Hann átti í stöðugum einkaleyfismálaferlum víðs vegar um heiminn. Staðreyndin er þó sú að Edison bætti uppfinningar annarra.

Edison tókst þó fyrst og fremst að þróa kerfi rafala, rafkapla og rafmæla sem tengdust ljósaperunni svo að hún nýttist fullkomlega. Þrátt fyrir allt tók nokkurn tíma að fullkomna framleiðsluna. Fyrstu ljósaperurnar voru dýrar og bið var á rafvæðingu borga, bæja og sveita. Savoy-leikhúsið í Lundúnum varð fyrsta opinbera bygging í heimi sem lýst var með rafljósum, árið 1881. Sama ár voru fyrstu smáljósaperurnar framleiddar og settar í jólaseríur. Segja má að 20. öldin hafi verið öld ljósaperunnar og í stórborgum gátu menn starfað og stundað ýmislegt, jafnt á nótt sem degi.  En nú sér fyrir endann á sögu ljósaperunnar. Hún er að hverfa af markaði af umhverfisástæðum og sparnaðarpera að leysa hana af hólmi.

Síðast breytt: mivikudagur, 14 september 2011, 08:50 eh