All the material objects around you are composed of submicroscopic units we call molecules. And molecules in turn are composed of individual atoms. Molecules frequently break apart and then form new molecules. On the other hand, virtually all the atoms you come in to contact with through the course of your life, the ones in the ground beneath you, the air you breath, the food you eat, those that make up every living thing, including you, have existed for billions of years and were created in places very unlike our planet. How those atoms came about is what I want to share with you. It all started 14 billion years ago with an event we call The Big Bang, which resulted in a universe consisting of gas alone. There were no stars and no planets. The gas was made up only of atoms belonging to the simplest elements. It was about 75 percent hydrogen and almost all the rest was helium. No elements like carbon, oxygen or nitrogen existed. No iron, silver or gold. In some places, the density of this gas was slightly higher than in others. Due to gravity, those places attracted even more gas, which further strengthened the pull of gravity, which then drew more gas in, and so on. Eventually, large dense gas balls formed, shrinking under their own gravity and consequently heating up on the inside. At some point, the core of such a ball gets hot enough that nuclear fusion occurs. Hydrogen atoms smash together to form helium, accompanied by a great release of energy, strong enough to counteract the shrinking force of the gravity. When the energy pushing out from the fusion reactions matches the gravity pulling all the gas inwards, an equilibrium occurs. From this a star is born. Over its lifetime, the fusion reactions in the core of a massive star will produce not only helium, but also carbon, oxygen, nitrogen and all the other elements in the periodic table up to iron. But eventually, the core's fuel runs out, leaving it to collapse completely. That causes an unbelievably powerful explosion we call a supernova. Now there are two things to note about how supernovas create elements. First, this explosion releases so much energy that fusion goes wild forming elements with atoms even heavier than iron like silver, gold and uranium. Second, all the elements that had been accumulating in the core of the star, like carbon, oxygen, nitrogen, iron, as well as all of those formed in the supernova explosion, are ejected in to interstellar space where they mix with the gas that's already there. History then repeats itself. Gas clouds, now containing many elements besides the original hydrogen and helium, have higher density areas that attract more matter, and so on. As before, new stars result. Our sun was born this way about 5 billion years ago. That means that the gas it arose from had itself been enriched with many elements from supernova explosions since the universe began. So that's how the sun wound up with all the elements. It's still mostly hydrogen at 71 percent, with most of the rest being helium at 27 percent. But bear in mind that while the first stars were made up of hydrogen and helium alone, the remaining elements in the periodic table make up two percent of the sun. And what about Earth? Planets form as an incidental process to star formation out of the same gas cloud as the star itself. Small planets like ours don't have enough gravity to hold on to much hydrogen or helium gas since both of those are very light. So, even though carbon, nitrogen, oxygen and so on made up only two percent of the gas cloud from which Earth was formed, these heavier elements form the bulk of our planet and everything on it. Think about this: with the exception of hydrogen and some helium, the ground you walk on, the air you breath, you, everything is made of atoms that were created inside stars. When scientists first worked this out over the first half of the 20th Century, the famous astronomer Harlow Shapley commented, "We are brothers of the boulders, cousins of the clouds."
Evnisliga tilfarið rundan um teg er gjørt úr ersmáum eindum, vit nevna mýl. Mýl eru gjørd úr einstøkum atomum. Mýl fara ofta sundur og mynda síðan nýggj mýl. Hinvegin eru flestu mýlini, tú kemur í samband við onkuntíð í lívinum, í jørðini undir tær, í luftini, tú andar, matinum tú etur; tey, sum mynda alt livandi - harímillum teg, hava verið til í milliardir ár og vórðu til uttan fyri jørðina. Hvussu mýlini fyrst komu til, er tað, eg fari at siga tykkum frá. Tað byrjaði 14 milliardir á síðan við tí, vit nevna "The Big Bang," sum førdi til ein alheim, sum bert var gjørdur úr gassi. Har vóru ongar stjørnur ella gongustjørnur. Gassið var gjørt úr atomum av einfaldastu evnunum. Tað var 75 prosent brint og mest sum restin var helium. Eingi evni sum kolevni, súrevni ella køvievni vóru til. Einki jarn, silvur ella gull. Onkrastaðni var evnisnøgdin í gassi størri enn aðrastaðni. Atdráttarmegin dró meira gass hagar, sum styrkti um atdráttarmegina sjálva, sum fekk meira gass til og so framvegis. At enda vórðu tættar gasskúlur, sum hoknaðu undan egnu atdráttarmegini og hitnaðust innan. Kjarnur hitnaðu so mikið, at tað elvdi til sambræðing. Brintmýl runnu saman og myndaðu helium og loysti nógva orku, so nógva, at hon mótvirkaði minkandi megina í tyngdarkraftini. Tá ið orkan frá sambræðingum møtist við tyngdarkraftini, sum dregur øll gass inn, verður javnvágur. Úr hesum føðist stjørnan. Í síni ævi fara sambræðingar í kjarnuni á eini stjørnu ikki bert at framleiða helium, men eisini kolevni, súrevni, køvievni og øll hini evnini á periodisku skipanini fram til jarn. Men at enda er orkan í kjarnuni útbrend, so hon syndrast fullkomiliga. Hetta elvir til eina ótrúliga spreinging, vit nevna supernova. Tvey mál eru galdandi, um hvussu supernovur skapa evni. Tað fyrsta: Spreingingin loysir so nógva orku, at sambræðingin verður baldrut og formar evni við atomum, tyngri enn jarn, so sum silvur, gull og uran. Tað næsta: Evnini, sum rúgvaðust upp í stjørnukjarnini, so sum kol, ilt, køvievni, jarn, umframt øll tey, sum vórðu av supernovu- spreingingini, verða skotin út í stjørnurúmdina, har tey blanda seg við gassini, sum longu eru har. Søgan endurtekur seg. Gassskýggj, ið nú hava fleiri onnur evni enn upprunaligu brint og helium, hava størri evnisnógdarøki, sum draga at sær meira tilfar o.s.fr. Sum áður verða aðrar stjørnur. Sólin hjá okkum varð soleiðis til fyri uml. 5 mia. árum síðan. Tað merkir, at gassið, hon spratt úr, sjálvt var ríkað við fleiri evnum frá supernovuspreingingum, síðan universið byrjaði. Soleiðis endaði sólin við øllum evnunum. Hon er enn mest úr brinti, 71 prosent, har mesta restin er helium, 27 prosent. Legg til merkis, at meðan tær fyrstu stjørnurnar vóru av brinti og heliumi eina, umboðar restin av periodisku skipanini tvey prosent av sólini. Og hvat við jørðini? Gongustjørnur eru tilvildarlig úrslit av stjørnumyndan úr sama gassskýggi, sum stjørnan sjálv. Smáar gongustjørnu hava ikki kraft at bera nakað serligt brint- ella heliumsgass, tí tey bæði eru sera løtt. So hóast kolevni, køvievni, ilt o.s.fr. bert umboðaðu 2 prosent av gassskýggjunum, sum jørðin varð burturúr, eru tyngri evnini í meiriluta í okkara gongustjørnu og alt á henni. Hugsa um hetta: fyri uttan brint og nakað av heliumi er jørðin undir tær, luftin, tú andar, tú; alt er gjørt úr atomum, sum vórðu til úr stjørnum. Tá ið vísindafólk fyrst skiltu hetta í fyrru hálvu í 20. øld, viðmerkti kendi stjørnufrøðingurin Harlow Shapley "Vit eru brøður av grýti, systkin av ský"