The Most Astounding Fact
Astrophysicist Dr. Neil DeGrasse Tyson was asked in an interview with TIME magazine, "What is the most astounding fact you can share with us about the Universe?" This is his answer.
Beautiful little video that is a joy to watch full screen
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Jahled Three shades of black, Tue 13 Mar 2012, 15:18,
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Any physicists who can help me here?
I understand how stars fuse H to make He,* and I can see how bigger stars might go on to fuse He into slightly heavier elements like Li, Be, B, C. But how do we get stuff as heavy as even Pb, let alone U?
I know that there were some whacking great stars in the early universe, but was any ever big enough to generate the whole periodic table? If not, from where did even the moderately heavy elements come?
Answers sufficiently simplified to be understood by someone lacking a science degree would be appreciated.
* OK, "understand" is the wrong word. But I can sort-of get my head around the basic idea, which is close enough.
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Enzyme is powered by sunlight, Tue 13 Mar 2012, 15:40,
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It was the magic man in the sky what done it, silly.
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Brandy_Bumwinkle, Tue 13 Mar 2012, 15:44,
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Never mind questions
Just believe
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TownsendsPublisher is all gravy baby, Tue 13 Mar 2012, 15:57,
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He'll probably claim he can't remember or something as equally ambiguous
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Jahled Three shades of black, Tue 13 Mar 2012, 15:59,
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Judging by the quality of the product...
"Mr God" was having a laugh, after an extended Friday afternoon liquid lunch. Hence my mission to excise the mistakes...
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pcmechanic There's no bottom to the depths of human stupidity, Tue 13 Mar 2012, 16:18,
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Something to do with supernovae
As you infer, "normal" fusion reactions in stellar cores, even super-massive ones, are not sufficiently energetic to produce the heavier elements alone. It requires the mind bogglingly huge energies present in a supernova to synthesise elements heavier than bismuth.
SCIENCE!
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P-MONKE We're all fucked, Tue 13 Mar 2012, 15:45,
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Ta!
So collapsing isn't enough? There has to be an explosion too?
Hmmm...
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Enzyme is powered by sunlight, Tue 13 Mar 2012, 15:48,
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Yeah: I know that.
But not all collapsing stars explode, do they? I heard somewhere that ours probably won't because it's not massive enough. It'll just go into retirement and eventually fade away, without ever producing a single atom of ruthenium.
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Enzyme is powered by sunlight, Tue 13 Mar 2012, 16:15,
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Yes, if it's big enough, apparently it does this collapse and then 'bounce' out - the atoms being at greater pressure fuels the hotter reaction (I think).
(, Tue 13 Mar 2012, 16:30, Reply)
Google 'The Science in Science Fiction'
and you'll find a link to amazon to an excellent book by Robert Bly. A fine read :)
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Jahled Three shades of black, Tue 13 Mar 2012, 15:54,
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Normal fusion that happens in stars can create all the elements up to lead. Once it gets to lead fusion is no longer sustainable under those conditions so the star 'stalls' and goes cold (if it is very small), nova (if it is medium sized) or supernova (if it is big).
It is in the nova and the supernova that the pressures and energies get high enough to fuse lead into heavier elements. That is where the rest of the table comes from.
The universe literally started with just sub-atomic particles. These came together to created electrons and protons, which joined to create neutrons and hydrogen.
Hydrogen gas then formed clouds via gravity and then liquids, and then, finally solids. These then collected more hydrogen and eventually, when a critical mass was reached it would create a star.
This star then worked away at creating stuff up to lead. Then BANG... we have heavier elements.
A very slow process... And an amazing one too.
(, Tue 13 Mar 2012, 16:59, Reply)
Iron peak
The nuclear binding energy of the elements (the energy holding the nucleus together, or the energy required to split the nucleus) increases from Hydrogen upwards through the lighter elements and peaks at Iron, where it then starts to decrease.
In other words, for elements up to iron, nuclear fusion releases energy and after iron nuclear fusion consumes energy. So the elements up to iron can be created in stars (stellar nucleosynthesis) whereas the elements heavier than iron need the much higher energy of a supernova to form (supernova nucleosynthesis).
This soup of elements knocks around the universe for a few billion years then coalesces into stuff like galaxies, planets, you, me, your iPhone, the cat, etc
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Raving Homasecsyouall the hours are good but the work sucks, Tue 13 Mar 2012, 17:08,
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...
But what are CATS made out of?
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Kung_Fu_Russ ran out of amusing signatures on, Tue 13 Mar 2012, 15:43,
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www.youtube.com/watch?v=8Sp-VFBbjpE
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BrokenCoccyx doesn't mind if you grope on, Tue 13 Mar 2012, 15:53,
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Watch "The Life of Stars" episode in the Carl Saga "Cosmos" series.
'splains it all.
(, Tue 13 Mar 2012, 15:57, Reply)