Hi Robin, Well I am including the mass-energy of the positron and the neutrino, which are emitted - added to the mass of the deuteron to suggest that all of these weigh considerably more than two protons. Therefore outside energy (momentum) would have to be employed, even though real energy is emitted and that looks like exotherm.
But even then, I admit that there is a math problem in that this particular electron neutrino from the diproton reaction apparently may not have the mass-energy which is seen and documented by experiments on earth -like SNO - where the mass-energy is in the several MeV range. Almost all solar neutrinos come from the diproton reaction but the Wiki entry suggests are much lower in energy than what is actually measured at SNO. Even with oscillation, I do not see how the energy could be lower on the sun where they are formed but higher when measured at SNO. In fact, it is only a guess as to what they are on the sun, despite what Wiki states as fact - since we obviously cannot measure them there. Bottom line: if they are 1 MeV neutrinos on the sun from two proton and beta decay, then the net diproton reaction is endothermic when we look at only the rest mass of the protons, and if they are 400 keV mass-energy, the reaction is balanced, and if they are 100 keV the reaction is exothermic. >>Actually The neutron has mass slightly larger than that of a proton: >>939.565378 MeV compared to 938.272046 MeV. Consequently, a deuteron has >>slightly more mass than a diproton. > >>That is one of the many reasons why the reaction on the Sun, the one that >>results in a deuteron is extraordinarily rare. It is basically endothermic. > >The mass of two protons is 2.014552933 amu. >The mass of a deuteron is 2.01355362 amu. > >RVS: Note that the deuteron is actually lighter than the two protons. IOW >this >reaction is exothermic. > >Not exactly true, Robin. Once again - the deuteron does NOT form directly >from two protons! Never. There is a required step which you are leaving out, >where outside energy is brought in. Both you and Terry are correct in that doing work by bringing the protons together should add mass to the system. However even without that, the reaction would be exothermic. (BTW, you get that energy back again when the reaction happens). There are two reasons the reaction is so slow. 1) It's a weak force reaction. 2) Tunneling. I have recently come to wonder whether or not tunneling can even happen in this case. That's because particles don't tunnel unless there is a net energy advantage in doing so, and there is none for two protons. So I am forced to consider the possibility that electron capture may be the sole means by which this reaction occurs in the Sun. I don't see how physicists could possibly measure the ratio of beta+ to electron capture reactions occurring in the core of the Sun anyway (see e.g. http://www.sns.ias.edu/~jnb/SNviewgraphs/NuclearFusion/nucfusion.html). (Any electron annihilation gammas created in the core would be thermalized long before they got to the surface.) Perhaps the ratio is determined from fusion experiments here on Earth, where annihilation gammas are more readily detected? Or perhaps it's just a calculated value? Or maybe this really is a WL reaction, where a proton is converted into a neutron momentarily while emitting a positron, and then the neutron fuses with a free proton in time to repay the loan before the thugs come knocking? > >The deuteron forms only from a diproton, which itself has formed from two >protons PLUS added mass from outside the reactants. If that mass has not >been added, which is the vast majority of the time, there is no reaction. > >IOW without added mass-energy which is brought in above the rest mass of the >reactants, the reaction is endothermic. > >With the added mass the reaction appears exothermic, but that is due to >added mass-energy from outside the reactants. Semantics allows either >depiction - exothermic or endothermic, depending on whether one is looking >at protons or diprotons. Since you were looking at protons, the reaction is >endothermic based on their rest mass. So according to you, 2.01355362 > 2.01455293 ????????? [snip] Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
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