|WikiProject Physics||(Rated B-class, Mid-importance)|
|WikiProject Elements||(Rated B-class, Low-importance)|
- 1 Fission
- 2 Explosive Nucleosynthesis is a type of Stellar Nucleosynthesis
- 3 Changes in the structure at the end of the article
- 4 Big Bang Talk
- 5 Explosive Nucleosynthesis
- 6 Element abundance chart
- 7 Error in Big Bang Nucleosynthesis chart ?
- 8 Disbelief: Cf
- 9 Nuclear reactions
- 10 Retained Nuclear free energy
- 11 Stable isotope abundance
- 12 Natural Element Synthesis in the Universe
- 13 Heavy element synthesis in early universe
- 14 Curium
- Fission is used primarily in cosmic ray spallation, which can use either fusion or fission. New nuclei are just created (or synthesized as the name implies) from splitting a larger one. →ubεr nεmo→ lóquï 18:35, August 15, 2005 (UTC)
Explosive Nucleosynthesis is a type of Stellar Nucleosynthesis
Currently this page describes 4 types of nucleosynthesis, which I believe should be reduced to 3 types. Namely, explosive nucleosynthesis is a type of stellar nucleosynthesis. It is a very important type of nucleosynthesis, and I do not wish to delete any content from here, only move around things and reduce the number of categories. In the field of nuclear astrophysics, it is standard to do this. In fact, you will note that under the categorization of nuclear processes, we have many explosive stellar nucleosynthesis phenomena listed under stellar nucleosynthesis as they should be (like rp-, p-, s-, r-processes). Furthermore, big bang nucleosynthesis is technically explosive nucleosynthesis, just it is not stellar in origin, and I think making this change clears up possible confusion about that matter.
However, before I make this change, I wanted to get input as to how to best accomplish this task. Furthermore, the supernova nucleosynthesis page is actually larger than, and has more information than the r-process page, and I think this needs some correcting. DAID 05:41, 19 July 2007 (UTC)
- Long awaiting discussion on this point. I will plan to go ahead with this revision.DAID (talk) 06:49, 7 April 2010 (UTC)
Changes in the structure at the end of the article
Changes in the structure at the end of the article to improve the clarity and the coherence of the text. The order in the contents is now:
- Further readings
- See also
- Nuclear processes
Template:Nuclear Processes has been moved at the end of the article.
Cheers, Shinkolobwe 19:04, 30 October 2007 (UTC)
Big Bang Talk
... Ok, I'm sorry, but there are 0 proof references for this. These articles need to stop regarding to the Big Bang as something that actually occured in a fact, and start referring to these as unproven theories. The Big Bang cannot be studied, never was studied, and thus remains a distant theory. Colonel Marksman (talk) 04:42, 6 October 2008 (UTC)
- this jibe is an example of science illiteracy. re "proof": no theory in science is "proven"; all theories in science *prove useful*, and a theory is used only until a more *useful* theory (more accurate or more widely applicable to observable facts) comes along to replace it. (in other words, relativity did not "disprove" newtonian physics as newton used it.) re big bang: no other theory of the universe explains as many different observable facts, as observed with completely different methods and assumptions, with more accuracy and internal consistency, and predicts observations made after the theory was formulated, than the theory of the singularity. (in other words, it's tremendously useful.) Macevoy (talk) 16:49, 5 February 2010 (UTC)
We can measure primordial abundances. This can be used as a check to see if our theories of nuclear process can predict these ratios. While this is not direct evidence for the exact reaction paths, it is a useful constraint. It seems very hard to believe that some kind of early nucleosynthesis didn't occur because of the abundances we measure. It is extremely important to have an understanding of the primordial abundances because this is used in many theories of galactic evolution and formation. Not to mention population III stars, the first generation of stars which further enriched the interstellar medium out of which population II stars formed, on to population I stars (like our Sun).
Today, while the Big Bang its self has not been observed and won't ever be observed directly, there are many direct observations of the results of something like a "Big Bang". For example the cosmic microwave background. Sure we don't know for absolute certainty that a Big Bang occurred, but we do know that a Big Bang theory can explain what we do observe. This is exactly the same thing as nucleosynthesis in our Sun, we can actually go in and observe it happening in the Sun, temperatures and pressures would destroy anything we could send there to observe it. So how do we know that it is taking place? From the results of nucleosynthesis we observe, there is no other theory we could come up with that fit the rest of our physical knowledge and could explain the observed phenomenon, such as the age of the Sun, neutrino fluxes, etc.
Then the debate becomes, should wikipedia only contain absolute fact or also include leading theories on phenomenon. As an Astronomy PhD I find it extremely usefull that wikipedia not only contain proven facts, but also current leading theories(e.g. Black holes, which also can't be directly observed by definition)
- Both of the above remarks have some validity. Of course science doesn't deal with "absolute facts", but some theories are better established than others. The reader should be provided with some indication. The article also mentioned "dark matter" without mentioning the degree to which the existence of dark matter is hypothetical; compare the dark matter article in which the point is emphasized. I've added "theoretically" and "maybe" to the introduction. Nucleosynthesis (talk) 16:49, 26 November 2009 (UTC)
Element abundance chart
The Element abundance chart is not referenced and I will assume it's reasonable accuracy and note that it shows that the even Z numbered elements are generally approximately 10 times as abundant as the odd Z elements. This indication provides an argument for the existence of some kind of a balancing process related to that creating the nucleus. It also provides evidence of the existence of some kind of an unbalancing motion (like rotation) of the nucleus which causes this result.WFPM (talk) 00:24, 16 August 2009 (UTC)PS Excuse me! I found the reference later.WFPM (talk) 00:58, 16 August 2009 (UTC)
- Well, yes there's a ballancing which encourages protons and neutrons to go into orbitals in pairs. It's the same that produces pairing of electrons in orbitals in atoms (unpaired electrons producing free radicals). Electrons and nucleons are fermions with half-integer spin, and thus subject to the Pauli exclusion principle. Pairs of them can occupy the same space (same orbital) without a fight (though there may be some electromagnetic repulsion if they are charged). But three particles of the same type cannot do this, and the third one has to go into a higher energy level. For every particle with spin-1/2, two's company, three's a crowd. SBHarris 01:27, 16 August 2009 (UTC)
- If we can believe in the accuracy of the individual points, we could quantify the data and do a regression analysis of them and assign the variance to the relative factors. However the difference in the data re the even versus the odd Z elements makes me think that the even and odd Z data is such that they each compose samples of a separate population, and should be analyzed as such. Then we could get the least squares best fit lines for both categories and look at that and maybe determine more process information. Has that been done?WFPM (talk) 12:48, 16 August 2009 (UTC)
- With regard to the reported abundance values, It kind of explains why the makeup of organisms is influenced so much by their availability, and makes you wonder how an organism can get itself into the problem of having a deficiency of a necessary but rare element. So do you think that there might be the case that a deficiency, such as that of iodine might be the result of a change in the chemistry of the organism from the use of a lighter and more available element?WFPM (talk) 15:28, 16 August 2009 (UTC)
- I think organisms evolved to use what elements were useful and abundant in seawater, not the universe. Iodine is FAR and away more common in the ocean than the universe, or even the Earth's crust. So no real problem till organisms moved to land, then evolution had a problem (since it has a tough time going backwards). The same thing happened to animals on land needing sodium! Salt licks surfice there, but iodine is a real crimp for land animals in some places. And goitre for humans in non-coastal areas. SBHarris 03:26, 1 August 2010 (UTC)
The CNO process is described as that fission process capable of first causing the "triple Helium fusion" process capable of creating 6C12 and then higher Z atoms via proton accumulation additions. But it doesn't explain the existence of the reported incidence of an amount of 5B10. Could 5B10 have been created by the reaction of a deuterium atom with a double alpha particle in a manner similar to the triple alpha accumulation process? It is reported that the Proton-proton fusion process creates deuterons, which could then be closely associated with the helium atoms created by the Proton-proton accumulation process.WFPM (talk) 02:11, 11 October 2010 (UTC)
- I think it more likely that B-10 is formed from Be + T in the Big Bang, or Li-6 + alpha, and perhaps also from cosmic ray spallation from C-12 later. You might get some B-11 from B-10 plus free neutrons, again in the Big Bang. The problem with D + 2 alphas is that D is not stable enough to stand up to those conditions for long, being very susceptable to photolysis at those temperatures. It just breaks down back to p+n. D doesn't last long (a few minutes) in the interior of any star. Essentially all D we see is from the Big Bang, having survived that only because temperatures dropped so fast. SBHarris 06:32, 11 October 2010 (UTC)
I thought about that. But then it says that the !D2 goes on to be 1T3 and the 1T3 + 2He4 would get to be 5B11 and the chart doesn't say which B. And the fusion of 3 2He4 nuclei sounds even less probable than 2 2He4 + 1D2 or 1T3 because I can't imagine a 3 x 2He4 particle without imagining a split in one of them per my models. How about 4Be9? Isn't it made from 2 x 2He4 + 1n? Or 3Li6 + 1T3? Anyhow, I wind up with 6C12 being 2 2He4 + 2 1D2, and then with 4 more 1D2's being added to get 10Ne20, and then in the creation of a third 2He4 particle in the nucleus to make 12Mg. And thanks for the comment.WFPM (talk) 13:26, 11 October 2010 (UTC)
Anyway, the line on the chart kind of leads us to believe that the next element is physically related to and maybe formed from the previous element in the line. It's only after we read the article that we learn that the sequence of formation is proposedly caused by physical factors that permit carbon to be formed from helium, for example without having to pass through the lithium-beryllium-boron creation processes, and that these elements are created later by a "spallation" breakup process. So much for cursury reading!!!WFPM (talk) 20:52, 26 February 2012 (UTC)
Error in Big Bang Nucleosynthesis chart ?
How do He3 plus He4 create Li7 plus gamma? Charge isn't conserved.
- Good for you for noticing! You see the very same reaction on the right side, and the correct product is Be-7 and a gamma. If you make lithium it must be Li-6 and a proton or something. I'll see if I can drop a note to the chartmaker. SBHarris 03:22, 1 August 2010 (UTC)
Disbelief that Cf have ever been detected in supernovae, see Talk:Californium#Not_in_supernovae_.28I_presume.29. Rursus dixit. (mbork3!) 14:20, 30 November 2010 (UTC)
Under Minor Mechanisms, the discussion of Nuclear reactions suggests that alpha-induced nuclear reactions are the more likely process, compared to neutron induced. I am surprised by this claim, and no citations are given. I would think neutron-induced reactions would be much more common. Gierszep (talk) 01:30, 24 September 2011 (UTC)
Retained Nuclear free energy
If the atom is a real physical entity with an increasing volume real physical structure, then the exterior peripheral nucleons of a a rotating nucleus would have to have a larger amount of retained free energy than lesser volume atoms due to the kinetic energy involved in the rotation process. And of course the centrifugal force caused by the rotation would increase the instability factor of the surface located nucleons of the structure. And the decay mode most common in heavy isotopes is by electron (Beta-) emission, which would further reduce the strength of the attractive neutron forces. It therefor follows that the mode of decay resulting from the accumulation process would be for the emitted particle or particles to be those with the greatest amount of accumulated free energy.WFPM (talk) 06:20, 24 January 2012 (UTC)
Stable isotope abundance
- The abundance data in the chart is consistent with the fact that the even numbered elements have the higher value, and at least partially because they have a larger proportion of the stable isotopes than the odd numbered elements. This would indicate that the causative factors in stable isotope existence are 1: complicatedness of assembly, and 2: relative proportion of the stable isotope number possibilities. If the data re these causative factors is examined closely, it would appear that a formula could be worked out that would disclose and possibly improve the ambiguity of some of the items in the chart that do not conform to the logic of such a process of stable isotope creation.WFPM (talk) 16:54, 20 November 2012 (UTC)
A number of these nuclear stability trend lines have been determined and noted, and they are of a category of atomic numbers of the atomic number A, where the value A is related to to the increasing element numbers Z by the relationship where A is equal to 3 times the element number Z minus a "constant" even number. But with the "constant" even number being only an intermittent constant over a series of elements followed by by an increase of 2 for the next series of elements. As an example, the elements from 69 Thulium to 78 Platinum have a stability trend line formula of A = 3Z - 38. This indicates that the stability tendency for stable elements in this region is for each successive elements to acquire an additional proton plus 2 neutrons in order to remain in a condition of nuclear stability.WFPM (talk) 23:58, 17 October 2013 (UTC)
Natural Element Synthesis in the Universe
This may not be the best place to discuss this, but it may be sufficient. In addition, I'm no physicist, nor cosmologist that could directly contribute.
It would be interesting and informative to show the latest theories for each element's natural production in the universe on each element's wiki page. E.g., Supernova nucleosynthesis and Nucleosynthesis discuss some general element synthesis methods, but having the methods for each element would be more complete. Some element wiki pages discuss the method of nuclear synthesis, but showing the exact process(es) is rare.
Heavy element synthesis in early universe
Article currently says, "Because of the very short period in which nucleosynthesis occurred before it was stopped by expansion and cooling (about 20 minutes), no elements heavier than beryllium (or possibly boron) could be formed." This doesn't seem to accurately identify the critical factors, as elements like uranium are produced very quickly in supernovae and a helium flash only takes a few seconds. It appears that type Ia supernovae are also the result of runaway fusion reactions taking only a few seconds. A more accurate description for why more heavier elements weren't produced in the early universe would probably be either "protons (or other particles) disrupted the triple-alpha process", or that photons did. That is, if whatever process drove inflation in the early universe had been slower, the abundance of helium would have increased past 25% (by mass), and once it got high enough, heavier elements would have been quickly produced if photons weren't the main factor slowing synthesis. This is assuming that higher temperatures from fusion would not have somehow increased the rate of inflation.
Edit: Big_Bang_nucleosynthesis#Helium-4 says that helium was formed from neutrons combining with protons, not the proton–proton chain reaction. I'm not an expert here. "Deuterium is destroyed in the interiors of stars faster than it is produced," though this sentence from the deuterium article doesn't say whether it's destroyed only by fusion or if it's split into a proton and neutron, which possibly decays into a proton again. From the first link, "Once it was cool enough, the neutrons quickly bound with an equal number of protons"... this does make it seem like it was other particles, or photons, that disrupt deuterium nuclei at higher temperatures. Triple-alpha_process says that "The power released by the reaction is approximately proportional to the temperature to the 40th power, and the density squared. Contrast this to the PP chain which produces energy at a rate proportional to the fourth power of temperature and directly with density." This doesn't say that the PP chain has a peak in power output at a certain temperature, and thereafter decreases in power output as temperature rises. So it does seem like it's other particles, like the photons that now make up the cosmic microwave background, that disrupted synthesis in the early universe. But actually I'm not even sure if that makes sense since I don't really understand why things produce light at high temperatures, so I don't know if "photons" somehow had an existence in the early universe other than as a manifestation of high kinetic energy of particles.
Photodisintegration is the technical name. "photodisintegration's energy-absorbing effects temporarily reduce pressure and temperature within the star's core." So, some elements were formed in the early universe, but were then quickly destroyed. If the universe had started out as 90% helium, some would have quickly formed carbon while some of the rest would have quickly been destroyed, but then the carbon would also have been destroyed. 2601:600:8500:B2D9:437:47EB:9414:3B0E (talk) 22:47, 12 October 2015 (UTC)
Can`t this happen?
Decays into Cm242
- Anything can happen, but in practice this will not. Firstly you already have a nontrivial chance of fission when you bombard your 235U with neutrons, and then your intermediate step 237U has a ludicrously short half-life. Finally, raising the atomic number by multiple steps via alpha-particle or heavy-ion bombardment is a good way to reduce your yield to one atom at a time, so in practice the amounts of 242Cm you'll make by this method are going to be utterly insignificant and undetectable. Double sharp (talk) 15:35, 30 November 2016 (UTC)