The biggest mystery in astrophysics is the mismatch between reactions fusion reation rate on earth and those seen in space. This mismatch is caused by electron screening and what’s more, this screening is much more intense than screening theory predicts.
With regards to electron cloud screening of the nucleus, recognize that the way elements fusion in space cannot be predicted by any current nuclear theory but must be measured through observation. Cheers: Axil ** On Mon, Jul 23, 2012 at 6:09 PM, <[email protected]> wrote: > In reply to David Roberson's message of Mon, 23 Jul 2012 00:51:37 -0400 > (EDT): > Hi, > [snip] > > > >Relative is the operational word here Robin. I misunderstood your > description of the 2 billion years half life of He2. > > He2 doesn't have a half-life of billions of years. The pp reaction does, > but > that's a reaction between two separate protons, not He2 (i.e. the protons > are > separate for most of their lives, only combining to form He2 for very brief > instants during their life-time). > He2, only exists for a tiny instant, I would guess < 1E-20 seconds. > This fact combined with the "long" half-life of beta decays in general, is > why > the half-life of the pp reaction is so large. (Note that a long half-life > implies only a small chance of a reaction occurring). > IOW the chance of the pp reaction occurring is the product of two small > chances, > so it's very small, which in turn makes the half-life of the combined > reaction > very long. > [snip] > > >Your suggestion about the percentage of H that reacts per second begs a > question. Would it not be possible for the core temperature to adjust > downward to accommodate the rate that exists? I have always wondered why > stars did not in fact explode immediately upon first ignition unless some > form of negative feedback controls the rate of energy production. One > would think that the region that first ignited would generate a large > amount of energy that would raise the temperature in the immediate area. A > higher temperature would suggest that more fusion would occur leading to > ever higher temperature until boom. > > > >Dave > > You may be right about the negative feedback. As a region heats up it > should > expand reducing the density, which in turn should drop the fusion rate. > However a fast reaction would overcome this, witness the H-bomb. > Regards, > > Robin van Spaandonk > > http://rvanspaa.freehostia.com/project.html > >
