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  • Physics!

    So, I'm currently in my 3rd year of college going for an eventual Ph.D. most likely focused in theoretical astro-particle physics. I've noticed there are at least a few people on here that are interested or are also studying physics. Figured it would be interesting to discuss current things going on in physics, or older things, or even theories or ideas you've come up by yourselves. I know I have a few. So, any takers?

  • #2
    OK -- here's a question I've been pondering.

    When a particle pair with spin is created in a weak force interaction -- say a spin up electron and a spin down electron -- then they are entangled.

    Here's the question: When one of these two electrons is annihilated in a positron+electron collision, does the paired electron also get destroyed to conserve spin? And if so, does the the other positron get destroyed? Does it have to be the entangled pair? Can it by any other opposite-spin particle that gets destroyed?

    Is it only possible for an up electron to combine with a down positron?

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    • #3
      Originally posted by TorrentMage View Post
      OK -- here's a question I've been pondering.

      When a particle pair with spin is created in a weak force interaction -- say a spin up electron and a spin down electron -- then they are entangled.

      Here's the question: When one of these two electrons is annihilated in a positron+electron collision, does the paired electron also get destroyed to conserve spin? And if so, does the the other positron get destroyed? Does it have to be the entangled pair? Can it by any other opposite-spin particle that gets destroyed?

      Is it only possible for an up electron to combine with a down positron?
      So, this is quantum physics and especially in this case of entanglement it's your interpretation that matters. In the end the actual observable physics is the same. What happens during the entanglement is up to you. Copenhagen would say that when the positron/electron annihilated the photons that were produced would have a specific spin which would collapse the wave function of the electron. Thus, giving it a specific spin. Then the entangled one would be left with the opposite spin. Many-worlds would say effectively the same thing, just with more mumbo-jumbo. Consistent Histories (which is my favorite, besides that quantum is just wrong) would say that each electron had a specific spin, we just weren't sure of it. And then the resulting events occur according to that. Does that answer your question?

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      • #4
        never been that interested in physics, but i am pretty damn excited to see what results the LHC produces

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        • #5
          I think i'm going back to college to study Theoretical Physics. And that just because of Quantum mechanics. We are at the breaking point of a big new paradigm shift and i wanna be a part of that revolution.
          And have we come any closer to the answer of what defines the observer?

          Comment


          • #6
            No... not really, DaegonPhyn.

            First, I should say I'm an engineering physicist. I never studied nuclear physics, so thus my question...

            Actually my question doesn't have anything to do with what happen to the particle pair during collapse, it has to do with conservation of universal spin during a weak force annihilation event.

            As I understand it, when a particle pair is created, if a spin up particle is created a spin down particle must be created at the same time.

            So I was wondering, if that's so, then what happens when a spin up electron interacts with a spin up positron.

            I have these possibilities in mind:

            1) This is not possible because spin up e+ interacting with spin up e- would leave a net spin imbalance of 2 spin down and only a spin down e+ can interact with a spin up e-.

            2) The up e+ and up e- annihilate each other, but the paired down e+ and down e- simultaneously vanish to conserve spin

            3) The up e+ and up e- annihilate each other, but two other random down particles of vanish to conserve spin

            4) Annihilation events do not conserve spin

            5) There is some other fact I am missing and something else happens.

            Comment


            • #7
              Originally posted by TorrentMage View Post
              No... not really, DaegonPhyn.

              First, I should say I'm an engineering physicist. I never studied nuclear physics, so thus my question...

              Actually my question doesn't have anything to do with what happen to the particle pair during collapse, it has to do with conservation of universal spin during a weak force annihilation event.

              As I understand it, when a particle pair is created, if a spin up particle is created a spin down particle must be created at the same time.

              So I was wondering, if that's so, then what happens when a spin up electron interacts with a spin up positron.

              I have these possibilities in mind:

              1) This is not possible because spin up e+ interacting with spin up e- would leave a net spin imbalance of 2 spin down and only a spin down e+ can interact with a spin up e-.

              2) The up e+ and up e- annihilate each other, but the paired down e+ and down e- simultaneously vanish to conserve spin

              3) The up e+ and up e- annihilate each other, but two other random down particles of vanish to conserve spin

              4) Annihilation events do not conserve spin

              5) There is some other fact I am missing and something else happens.
              So, I think you're missing that annihilation does conserve spin. The photons that are produced in the reaction conserve the spin. up e+ + up e- gets three photons(2 up, 1 down). down e+ + up e- gets two photons(1 down, 1 up). So 1-4 are all wrong. Does that answer your question?

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              • #8
                Yes, it does! Ah, you have set my mind to rest. One of these days I will check out a particle physics text and read up on the subject.

                Have you already studied quantum chromodynamics? I only got as far as quantum mechanics, and then branched off into solid state theory for a semester before leaving "pure physics" for other pastures.
                Last edited by TorrentMage; March 24, 2011, 12:15 AM.

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                • #9
                  That's good.

                  ....I wish. I'm actually still a Junior. Was taking a class on Nuclear and Particle Physics, but had to drop it because the teacher was terrible and expected us to know more advanced quantum physics than I know right now. But I've read up on the concepts of quantum and particle physics. I plan on going into Astro-Particle physics, so I'll probably eventually do quantum chromodynamics and such.

                  Comment


                  • #10
                    Re: Physics!

                    So, I guess you ve heard the controversial stories about the E-cat?
                    That will supposedly solve our energy problems.
                    They re planning to have an 1 MW plant in Greece by the end of autumn, which will likely settle the score.
                    However, I d be interested in an educated guess on what s actually going on in there.

                    So, here is the inventor's website Journal of Nuclear Physics
                    where he does answer question, albeit not always convincingly.

                    and the findings of the Swedish Skeptics society.Cold Fusion:

                    The basic idea is fairly simple. However the fact that Rossi won't reveal what the secret catalyst is, makes me suspicious, even if he claims he s keeping it a secret for patent reasons.

                    Comment


                    • #11
                      Re: Physics!

                      Originally posted by Tsosmi View Post
                      So, I guess you ve heard the controversial stories about the E-cat?
                      That will supposedly solve our energy problems.
                      They re planning to have an 1 MW plant in Greece by the end of autumn, which will likely settle the score.
                      However, I d be interested in an educated guess on what s actually going on in there.

                      So, here is the inventor's website Journal of Nuclear Physics
                      where he does answer question, albeit not always convincingly.

                      and the findings of the Swedish Skeptics society.Cold Fusion:

                      The basic idea is fairly simple. However the fact that Rossi won't reveal what the secret catalyst is, makes me suspicious, even if he claims he s keeping it a secret for patent reasons.
                      I don't know too much about nuclear physics, but right from the start this makes no sense whatsoever. A fusion reaction is when two atoms combine and produces energy. A fission reaction is when an atom splits into two or more atoms and produces energy. Both reactions need an input of energy, but the resulting energy output is higher. The reason a fusion reaction puts out energy is because the binding energy of elements from hydrogen to iron decreases. So when you fuse two elements below iron you get extra energy from the lower binding energy. That energy is the output. In fission the reverse occurs. Elements after iron increase in binding energy, so splitting an atom gets extra energy from the lower binding energy. Also, the energy required to fuse elements before iron is lower than the energy required to split them. And the reverse is true for elements after iron.

                      In this case nickel is being "fused" with a proton (which is just hydrogen) and becomes copper. The reason the copper doesn't fission instead of fusing may simply be because nickel and copper are very near iron so the binding energy difference between fission/fusion for them is tiny. So perhaps my initial response isn't completely valid. It's possible that this is not a hoax and it's actually valid. But it's useless except for purely scientific purposes. The energy being put in must be (unless the current nuclear physics theories are completely wrong) higher than what's coming out. So for energy production purposes it's not at all useful.

                      Here's a graph of the binding energy as a function of element (or number of neutrons + protons). When I say binding energy I actually mean binding energy per nucleon (neutron/proton), which I didn't mention before.



                      If I wasn't clear about something or you need something else explained, please don't hesitate to ask. I probably wasn't very clear with my explanation and would be happy to clear it up.

                      Comment


                      • #12
                        Re: Physics!

                        Well, first off, thanks for responding and sorry for being an ass and taking like a month to post here again:) Been busy tho:< All i did on T-I since then was hand out my bonus SCC invite

                        I know the basics about fission and fusion, at least enough to understand this is neither, at least not in the way we know fusion works. But this was too complicated for me, and intriguing, as it will be a very important scientific breakthrough if that thing does produce the amounts of energy they claim it does.

                        With my very limited knowledge, I recall that in the process of fusion, the rules for the binding energy released when you fuse smaller nuclei to eventually form iron, apply only for nuclei of similar sizes. That s not the case here, as , while copper and nickel are indeed near Iron, they re only "fused" with 1 proton, a hydrogen atom as you said. And I really don't know what happens in that case.

                        I m also wondering what happens with the positive charges on both nuclei. From past fusion expirements, I ve read that it takes insanely hot temperature for the Coulomb barrier to be overcome, and that's clearly not the case there. Perhaps that s the role of the invetor's secret catalysers. And this is where I m stuck! Because I can't think of any suitable catalysts, and neither can any scientist currently occupying himself with the project.

                        And yet, apparently it works...
                        There was an experiment in Bologna on February 10, where , with no other power other than 80 Watts for the instruments, the power output was between 15-20KWatts.
                        Here 's the link, in case you re interested!
                        Cold Fusion: 18 hour test excludes combustion - NyTeknik
                        Anyway, I m still very suspicious, and I don't think I ll be able to grasp how that thing works, but I believe finding a new energy source is of uttermost importance right now, hence why I m interested in figuring the "catalyzer" out.
                        Well, apparently, they ve already agreed to build 1 MW powerplants , so we ll know soon enough whether it works or not.

                        Comment


                        • #13
                          Re: Physics!

                          I'm fairly certain that the rules for binding energy release apply even if the nuclei sizes aren't about the same, simply because I can't see a reason why that wouldn't be. The energy release has nothing to do with what elements are fusing/fissioning. Just the amount of protons/neutrons in the atom. I could be wrong, but that would definitely be new knowledge for me.

                          Hydrogen atoms (protons) also give off energy when they fuse. Basically this happens because the gluons that hold together the three quarks of the proton lose some of their energy when they join together with more protons/neutrons. It's just easier to hold together a structure with more protons/neutrons present, until the electromagnetic force between the protons becomes high enough to counter the weak force caused by the gluons. I mean, there are fusion reactions going on in stars that are just a helium fusing with iron to make nickel. I don't see why hydrogen can't do the same.

                          A couple things in that article are a bit fishy. First off, the scientist says that only 0.4 grams of hydrogen was removed during the whole process. That makes no sense because hydrogen gas leaks out of anything very easily. The only really good way to store hydrogen is to put it in a pressurized container, so that it becomes a liquid. But the pressures involved in that are over 100 atmospheres. Over those 18 hours that he had the thing running, I very much doubt only 0.4 grams leaked out.

                          Also, have you looked at the website for the company developing those powerplants? There is absolutely nothing on it. Just a very simple front page. I feel that any company willing to work on such a large project would have the money to develop a better website, especially since they probably want funding. Very, very fishy.

                          I would love to see some alternative power sources as well. But I'm very skeptical when anyone starts mentioning an alternative power source that they just happened to discover by accident. They're stepping on an area of physics that is fairly well understood, and claiming that they've found something that is new and can't be explained is very fishy to me.

                          Comment


                          • #14
                            Re: Physics!

                            First off, you re probably right about the binding energies. It makes sense, and I can't find any credible resources that claim otherwise, prolly a brainfart on my part, my knowledge on physics is pretty rusty.
                            Now, back 2 the Catalyser thingy. You do make a good point about the Hydrogen. However, if memory serves, according to the Swedish physicists, he did have the hydrogen in a separate container, perhaps for that very reason?Oh, and no argument on the website, its just a frontpage indeed.
                            Welcome [In case any1 else ever bothers!]. It does link to the patent though (or the patent application?)
                            Don't get me wrong, I m quite sceptical too. Which is exactly why I posted it here in the first place. But, while I 'm usually rather pessimistic, in this case, I want to believe so bad!
                            The story kind of reminds me of the Fleischmann & Pons 1989 experiment on "cold fusion", where they used Palladium instead of nickel. They even concluded its some kind of nuclear reaction the same way. "too much energy for a chemical reaction, therefore it has to be nuclear"

                            Anyway, I ll try to show you, as apparently no1 else cares:) what I think I ve figured out so far,after some extra research of my own, feel free to correct me :)
                            The only Ni isotope feasible for a fusion reaction is Ni58.
                            So the reaction has to be
                            58Ni + 1H -> 59Cu

                            Which is endothermic, right?
                            But Cu59 has a T 1/2 of approx 81.5 seconds, which is incredibly short.
                            It decades emmitting positrons, thus producing more energy than it takes to make the original fusion happen.Hence:
                            59Cu -> 59Ni + B+ + y
                            The sequence of events I just described is consistent with the construction; a fuel cell is a suitable medium for utilizing the production of positrons as an electricity source.
                            The end result should be energy in the region of 600 kWh/g, which is pretty insane in itself, since for Rossi to achieve the advertised number (100kWh/g) means he only manages to collect ~ 15% of the total energy available.

                            However, the mystery of how he gets the Hydrogen and Nickel nuclei close enough to fuse remains. Also, where did the gamma radiation go?

                            My point being, I m not ready to call BS yet, not until we re informed about the exact process. Imo, then and only then can one draw definitive conclusions.
                            Last edited by Tsosmi; May 9, 2011, 06:22 PM. Reason: bollocks

                            Comment


                            • #15
                              Re: Physics!

                              I think they just put up the patent application link a day ago, because of the fraud attempt they mention.

                              The Fleischmann and Pons experiment isn't 100% doubted, especially since scientists here and there have reproduced it (sort of). They issue is that they claimed to be able to do it consistently, which no one else could do. There is something that was fairly recently done that claims to be reproducible and is just a better version of the original Fleischmann/Pons experiment. But I read that a few years ago now and haven't heard anything since.

                              I found the small paper that I think you got those calculations from (Giuliano Bettini). I don't know too much about nuclear physics, but from a quick look through I don't see anything wrong. The gamma radiation that gets produced is from the positron that is emitted annihilating with an electron. Then that gamma radiation is the energy that is measured. That's where it goes, either into the detector that is set up or to heat up the material.

                              As for how/why the Hydrogen and Nickel fuse, I'm at a loss. In the Fleischmann and Pons experiment, if it is valid, palladium is able to have hydrogen packed very densely into it's structure, because of the way palladium atoms assemble themselves. At a certain point that packing is able to reach some critical density (critical mass isn't really the proper word) and then fusion begins. The experiment I mentioned was able to more efficiently pack hydrogen into the palladium and so were able to have more reproducible results.

                              I'm leaving an open mind on this one, too, because any kind of new physics and new energy source is an awesome thing. But without any kind of proper scientific reason behind why this is happening, and the lack of any kind of actual data, makes me somewhat skeptical. Pretty much the same as you.

                              Personally, I think what we should focus on right now is controlling hot fusion and siphoning energy off of that. It's fairly well understood and the National Ignition Facility experiment is almost ready to do actual controlled fusion. There are also plenty of other similar projects being built now or working on getting funding.

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