# Tag Info

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Heavy elements couldn't form right after the Big Bang because there aren't any stable nuclei with 5 or 8 nucleons. Source: Wikipedia (user Pamputt) In the Big Bang nucleosynthesis, the main product was $^4He$, because it is the most stable light isotope: 20 minutes after the Big Bang, helium-4 represented about 25% of the mass of the Universe, and the ...

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In the case of a supernova explosion it is possible to create heavy elements through fusion. Supernovae have a tremendous amount of energy in a very small volume but not as much energy per volume as there was in our early universe. So, what is the major difference? Why didn't the Big Bang create heavy elements? I just want to point out, too much ...

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Jupiter's mass is too small to produce nuclear fusion. Jupiter would need to be about 75 times as massive to fuse hydrogen and become a star http://en.wikipedia.org/wiki/Jupiter This wikipedia page explains the detailed requirements of nuclear fusion: http://en.wikipedia.org/wiki/Nuclear_fusion

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The Sun fuses protons, and this is a very slow process because there is no bound state of two protons. Hydrogen bombs fuse deuterium and tritium, and this is much, much faster because there is a bound state of these nucleides. You might like to have a look at: How much faster is the fusion we make on earth compared to the fusion that happens in the sun? ...

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This question is answered in detail by the so-called "Big Bang Nucleosynthesis", the theory about the creation of the nuclei in the early Universe. Almost out of nothing, it allows one to determine that 75% of the nuclear mass was coming in hydrogen, 25% in helium, and some small traces of lithium appeared, too. Even though Gamow used to think that all ...

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There is a minor change to yyahn's answer. The isotopes Deuterium, and Lithium7 which are present in small amounts -left over from the big bang, can fuse at lower mass than pure hydrogen burning. The estimate is at around 65 mass Jupiter Lithium fuses with hydrogen to form two helium nuclei. Brown dwarfs as light as 13 mass Jupiter can ignite Deuterium ...

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To answer the question simply, $E=mc^2$. Energy is a manifestation of mass, and mass is a manifestation of energy. In a fusion or fission process, the total "energy" of the system remains constant, it just changes shape. By "energy" I mean the totality of the already present energy, and the bound energy of the mass that takes part in the reaction.

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This'll be a very rough order of magnitude estimate, but as you'll see it's good enough. Suppose that two hydrogen atoms bump into each other. In order to fuse, the nuclei have to tunnel to within about a nuclear distance of $10^{-15}$ m of each other. The tunneling probability is something like $e^{-(2mE)^{1/2}L/\hbar}$, where $E$ is the energy gap, $m$ ...

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The analogy is facile. Helium fuses at a temperature ($10^8\ \text{K}$) roughly ten times higher than hydrogen ($10^7\ \text{K}$), so a better analogy would be alcohol and thermite. That higher temperature is achieved only by massive gravitational contraction after hydrogen fusion [EDIT: in the core] is exhausted. EDIT: To expand, different mass stars ...

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There are quite a few novel energy technologies coming through. I guess that without quantification, "breakthrough" is a subjective term. Below, I've tried to list all the energy technologies that I know of, that are not yet at commercialisation, but could be within 50 years, and that could offer at least tens of gigawatts of power. They are, in descending ...

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You actually make reference to something which is of crucial importance to the answer to this question: "With a tokamak, I imagine that if you double the linear dimensions, the plasma volume (and hence the power production) will increase eightfold, whereas area that you have to protect against fast neutrons will only quadruple. So once you master the ...

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The WKB approximation states that in one dimension, the tunneling probability $P$ can be approximated as $\ln P=-\frac{2\sqrt{2m}}{\hbar}\int_a^b \sqrt{V-E} dx$ , where the limits of integration $a$ and $b$ are the classical turning points, $m$ is the reduced mass, the electrical potential $V$ is a function of $x$, and $E$ is the total energy. Setting ...

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Lithium and other light elements (e.g. beryllium) can be formed indirectly from supernovae via cosmic ray spallation, a process where protons and neutrons are ejected when a cosmic ray collides with another atom. The nucleons can then form new elements. Nakamura & Shigeyama (2004) were able to calculate yields for 6Li, 7Li, and isotopes of Beryllium and ...

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As dmckee says in his comment - Population III stars have no metals (a tiny bit of lithium and beryllium), but they are not "pure hydrogen stars", they still have the big bang fraction of Helium. Taking the second part of your question first. These "stars" will last for ever. Their final fate is to become a completely degenerate ball of helium, supported by ...

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If they didn't release energy, they wouldn't happen. The alternative, nuclear reactions that require energy, clearly need said amount of energy, which has to come from somewhere, e.g. kinetic energy involved in the collision of two nuclei (even ones that release energy usually have a "barrier" and some amount of initial kinetic energy is needed to overcome ...

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Elements heavier than iron are produced mainly by neutron-capture inside stars, although there are other more minor contributors (cosmic ray spallation, radioactive decay). Neutron capture can occur rapidly (the r-process) and occurs mostly inside supernova explosions (though other mechanisms such as merging neutron stars have been mooted). The free ...

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The Sun obviously produces far more energy per second than is required to fuse an iron nucleus with some other nucleus. The problem is concentrating all that energy on the iron nucleus. It's not enough to known that it takes the energy from $n$ hydrogen fusions to fuse one iron nucleus, it's getting the energetic products from those $n$ hydrogen fusion ...

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Gravity is not needed in any way (it only helps to increase the pressure inside the stars but the pressure may be "mimicked" in other ways) and the energy needed for these transmutations isn't extremely high. It's just the nuclear energy conditions. See https://en.wikipedia.org/wiki/Synthesis_of_precious_metals Consequently, one may produce gold in ...

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The problem with attempting to fuse two protons is that there is no bound state $^2$He, for the rather obvious reason that there are no neutrons present to hold the two protons together. The fusion of two protons requires one of them to undergo beta plus decay while the two protons are close, and the probability of this is vanishingly small. It happens in ...

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This is a very difficult question to answer. There are (at least) two reasons. First, we have detailed, numerically exact wave functions for stable, light nuclei only up to, just recently, $A=12$ (like $^{12}C$). The Argonne-Los Alamos-Urbana collaboration uses quantum Monte Carlo (QMC) techniques to evaluate the ground and excited states of bound nucleons ...

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From what I have read in "American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer" Teller was the first one to express this concern before the Trinity test. Also quoting from: http://www.sciencemusings.com/2005/10/what-didnt-happen.html Physicist Edward Teller considered another possibility. The huge temperature of a fission explosion -- ...

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The reaction rate doesn't increase that quickly with temperature, but pressure does. If you perturb a solar model, making a zone near the core marginally hotter, the increased pressure will rapidly (at roughly the soundspeed divided by a characteristic length) cause it to expand. That lowers the pressure and temperature enough to substantially quench the ...

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As far as a catastrophic plasma disruption is concerned, it might be a problem for the first wall, and hence the ability to use the reactor. But despite the high energy per nucleon, the desity of the plasma is extremely low, the total energy is dominated by the energy in the magnetic fields, and thats not tremendous. Of course you do have the radioactivity ...

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These are valid questions. I am a graduate student in the program so it won't surprise you that I will advocate for it, nonetheless, if you'd like to double check my claims, you're welcome to. Let's go in order: We are hoping that the next major breakthrough does come from ITER: the first burning plasma. But it is BECAUSE of the fact that a machine like ...

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The next serious advance that is not an speculative/fringe idea is most likely to be fusion power. Harnessing the power of nuclear fusion has long been a goal for energy production since the first hydrogen bomb was created in the 1950s. Creating controlled fusion, rather than the chaotic variety has proven a rather challenging task here on Earth however. ...

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No, Jupiter is simply not massive enough to sustain nuclear fusion (and effectively become a star). Off the top of my head, I remember the statistic that it needs to be roughly 10 times bigger in order to generate the necessary gravitational forces at the core to initiate fusion and become a star.

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I will give you an analogy. Molotov bombs are made by filling a plastic bottle with gasoline, attaching a wick ingeniously, lighting it and throwing it on a target, usually a car or a policeman controlling a demonstration. Now there are a number of BTUs of energy in this bottle of gasoline. I can ask paraphrasing you Could we put these Molotov s to ...

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The Sun's energy, of course, comes from fusion. I think there's a small and totally insignificant amount of fission going on as well. The majority of the Sun's mass is hydrogen, and the vast majority of what isn't hydrogen is helium (with the ratio changing over billions of years as hydrogen is fused into helium). But since the Sun formed from the same ...

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For some recent information on the running battle between cold fusion researchers and myself over my proposed conventional (non-nuclear) explanation of the Fleishmann-Pons(-Hawkins) effect, you might want to look here: https://docs.google.com/open?id=0B3d7yWtb1doPc3otVGFUNDZKUDQ (referenced in this: ...

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