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Crazy questions

  1. Jun 20, 2009 #1
    If our sun will took around 15 billion years to convert hydrogen (Atomic#1) in helium (Atomic#2) how much time it took, since big bang, to generate heavy atoms like all we have on earth as iron, uranium, plutonium and etc ?
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  3. Jun 20, 2009 #2


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    There are many different processes leading to the formation of heavy elements. The two most important are (1) fusion processes from helium to iron and (2) supernovae explosions for all the heavier elements.

    The first stars forming after the big bang were generally much larger than the sun. As a result they burned out much faster and process (1) followed immediately. Finally after they reached the iron stage there was nothing to prevent a complete gravitational collapse leading to a supernova explosion for stars with enough mass (somewhat larger than the sun's) with process (2) creation.
  4. Jun 21, 2009 #3


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    Yeah, as mathman said: it comes from heavier stars than our Sun. Stars much more massive than our Sun last only a tens to hundreds of millions of years, depending upon their mass.
  5. Jun 21, 2009 #4


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    And, our sun is only about 4 1/2 billion years old. 15 billion years is closer to the age of the universe itself.
  6. Jun 21, 2009 #5
    What I ment reffering to the 15 billion years was the time expected to sun consume all hydrogen, for sure it´s not sun´s age.
    Referring to answer about larger stars time to agregate atoms up to iron being faster than time for our sun to consume it own, dear fellows, how can this assumption be assumed and verified ? Or it´s only an assumption.
  7. Jun 21, 2009 #6


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    Oh, it's a pretty solid result.

    Basically, as a star gets more massive, it gets hotter. That means it puts out more energy per unit time. And, as it turns out, the increase in energy output per unit time is faster than the increase in mass, so that the more massive a star is, the shorter it lives.

    Here's a little website that describes this in more detail:

    The basic idea is that for a relatively low-mass star like our Sun, it is more or less straightforward to calculate how long it will last, based upon the energy release of hydrogen fusing into helium and based upon the Sun's temperature (this tells us how much hydrogen it has to burn to keep shining at the level it's shining). Then you have to know how the nuclear fusion processes in the centers of stars vary with temperature and pressure (which we know based upon terrestrial tests of nuclear fusion processes). Then it's straightforward to compute the relationship between how massive a star is (at least for low-mass stars) and how long it lives.

    Things get more complicated, of course, for stars that are able to fuse heavier elements, so the lifetimes get more and more uncertain as the stars get more massive. But it is quite clear that the more massive a star is, the shorter it lives.
  8. Jun 21, 2009 #7
    Thanks Chalnoth for clarifying me on that, but ( always one) being coherent with my rebel mind, all this today explanations can only be rational under standard knowledge and perception of today scientific minds, so what if (another question):
    Gravity is the main force to generate atoms aggregation like you described and knowing that matter don´t have known symmetry (two different stable poles) at least on our side of universe, why matter can´t be understood as a gravity conductor, immerse in a gravitational vectorial field, somewhere and somehow generated ?
    Thesis analogy: If you can establish a let us say magnetic north and south pole planes (infinite and distant enough) and you have two pieces (let us say spherical) one much bigger than the other and closer enough among them (regarding to pole planes distance) of a ferromagnetic material, and you start analyze magnetic forces, you will find it equations and behavior, including force´s lines, like matter immerse in a supposed gravitational field, including orbits, stability and so on…
    I know that seems absurd by let us make a mind exercise.
    This idea could justify, as well as yours (current), atoms aggregation ?
  9. Jun 21, 2009 #8


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    I'm sorry, but this is just too vague. The problem is that physics is, at its heart, mathematical. To have a hope of describing anything new, you have to describe it in those terms. Anything else just doesn't have the specificity to really judge whether or not it is accurate.
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