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Underground Experiment Confirms Fusion Powers the Sun 141

Posted by Soulskill
from the if-you-lost-a-bet,-go-pay-up dept.
sciencehabit writes: Scientists have long believed that the power of the sun comes largely from the fusion of protons into helium, but now they can finally prove it (abstract). An international team of researchers using a detector buried deep below the mountains of central Italy has detected neutrinos—ghostly particles that interact only very reluctantly with matter—streaming from the heart of the sun. Other solar neutrinos have been detected before, but these particular ones come from the key proton-proton fusion reaction that is the first part of a chain of reactions that provides 99% of the sun's power.
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Underground Experiment Confirms Fusion Powers the Sun

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  • Well, interesting read anyhow...
    • by wallsg (58203) on Wednesday August 27, 2014 @06:05PM (#47769885)

      Obvious is different from proven.

      • it caught me by surprise as well. but thinking about it more it's mind blowing to think that there are a lot of things we take as fact when they may just be assertions. like fusion powering the sun, for example. I call this the Wikipedia phallacy.
        • by wallsg (58203)

          I think (hope) you mean "fallacy"...

          • by Anonymous Coward on Wednesday August 27, 2014 @06:44PM (#47770201)

            it caught me by surprise as well. but thinking about it more it's mind blowing to think that there are a lot of things we take as fact when they may just be assertions. like fusion powering the sun, for example. I call this the Wikipedia phallacy.

            I think (hope) you mean "fallacy"...

            No, he has it right. By analogy with "democracy", "oligarchy", "anarchy", and so forth, naturally Wikipedia is a "phallacy" since it's quite well established that many of the editors there who run the place are pricks.

          • A less polite person might suggest that the parent comment meant to use "phallacy" as a synonym for "dickheadedness" which may not technically be a word but let's face it, we've all had days when we wished that it was one.

        • Couldn't they have gotten there pretty easily by balancing the forces? You have a mostly hydrogen ball of gas (we can tell from the spectrum of light we get).Gravity would collapse it, something needs to be pushing back at nearly the same force. Hydrogen fusion is a possible solution, do the math and yeah the fusion rate expected given the gravitational forces matches the current balance of forces re: heat expansion, solar wind and gravity. Shy of proposing some magical force that happens not using the matt

          • That's a theory with no physical evidence. This is physical evidence of fusion.
            • No I'd say that is a theory explaining the physical evidence: sun doesn't collapse on itself, is hot, heavier elements exist. Detecting the neutrinos is yet another piece of physical evidence supporting an already existing theory.

              • ok but there are many reasons the sun may not collapse on itself. the neutrino thing locks in one of the many explanations.
        • by doccus (2020662)
          What surprised me is that they can differentiate between types of neutrinos! Astounding...
      • by Anonymous Coward

        They can't "prove" it. There could be other theories that predict the same result. For example something else could be powering the proton-proton fusion that is creating these neutrinos.

      • by Bondolon (1000444)
        Yeah, but we didn't need to detect proton-proton neutrinos to know that fusion powers the sun, because we have myriad other indicators (spectrum, energy output, solar wind) that agree with the current theory. The fact that we have now seen proton-proton neutrinos is cool as hell, but this will never be "proven" significantly more than it currently is, unless science changes drastically to allow for deductive facts. Science allows for an inductive form of "proof" (something being so probable it will likely n
        • by dnavid (2842431) on Wednesday August 27, 2014 @11:28PM (#47771761)

          Yeah, but we didn't need to detect proton-proton neutrinos to know that fusion powers the sun, because we have myriad other indicators (spectrum, energy output, solar wind) that agree with the current theory. The fact that we have now seen proton-proton neutrinos is cool as hell, but this will never be "proven" significantly more than it currently is, unless science changes drastically to allow for deductive facts. Science allows for an inductive form of "proof" (something being so probable it will likely never be demonstrated wrong) that's less rigorous than the logical kind, and fusion in the Sun has long been under that label. For analogy, we didn't have to wait until Sputnik had orbited Earth to know that Earth was round (since that was known to academics 2000 years earlier), but it certainly made people feel more confident in that fact when it happened.

          Science allows for deductive facts to carry scientific weight. I have no idea why you would think it does not.

          Science uses both deduction and induction, because while induction is not as absolutely rigorous as deduction, its not possible to deduce the entire cosmos from first principles. One of the axioms of Science is that the universe is not completely random and operates on the basis of rules that govern its behavior, and those rules can be discovered through observation. Universal gravitation is an induction, because there's no way to deduce that gravity operates in the same way everywhere. The presumption is that its highly unlikely that gravity operates the same way in every place we directly measure it, and also operates in a consistent way in every place we can indirectly measure it, but somehow operates differently in every place we just happened to not directly or indirectly observe it.

          All logical deduction must start with fixed axioms, and depending on what physical scientific laws you consider strong enough to be axiomatic, you can deduce a lot which is considered scientifically rigorous. For example, when we observe photons striking a detector, we *deduce* they were emitted from somewhere along the path the photon struck the detector. You could argue that's just an induction; that we're only guessing because that's how we've observed photons to behave in the past, but at some point that's sophistry, because it rejects the notion that Scientific reasoning can contain any axioms. Without some reasonable starting point - like being able to trust observations at all - you can't do Science at all.

          Also, I doubt there exists any significant number of people who were suddenly more confident the Earth is an oblate spheroid after the launch of Sputnik than before. Nor am I sure how the launch of Sputnik demonstrates the Earth is approximately spherical better than all other demonstrations of that fact prior to Sputnik. Sputnik did not itself observe the Earth, and observers of Sputnik did not get significantly more information from Sputnik in a scientific sense that other observations of Earth's curvature prior to that point.

          • by Bondolon (1000444)
            Of course deductions carry scientific weight, but they don't serve as meaningful evidence and instead as the basis of a hypothesis. The very nature of an axiom in science is that of a logically-unproven premise that, itself, can't be used to scientifically "prove" a concept. Therefore, it's necessary that induction be used to justify a deduction, but any logician will assert/concede/stand-completely-baffled-at-any-counter-assertion that inductive evidence could ever be used to logically prove a deduction. T
            • by Bondolon (1000444)

              any logician will assert/concede/stand-completely-baffled-at-any-counter-assertion that inductive evidence could ever be used to logically prove a deduction

              Also, I clearly meant but completely mistyped that logicians assert, etc. that inductions can "never" be used as logical proof of deductions.

            • by cwsumner (1303261)

              ... I'm certainly not pretending that people were suddenly convinced because of Sputnik that the Earth was round. ...

              I was there, then. For an appalling number of people, it actually did change their minds. Of course, some still believe the world is flat... 8-P

            • by dnavid (2842431)

              Of course deductions carry scientific weight, but they don't serve as meaningful evidence and instead as the basis of a hypothesis.

              Genuinely logical deductions carry equal or greater weight as experiments. Logical deduction is part of the process of scientific analysis. Logical deduction is in fact the glue that connects otherwise disconnected scientific theories. Without logical deduction, scientific theories would be disconnected semantic dust.

              Without the rules of math and logic, you can't do scientific analysis. Experiments are the data, logic and math are the engine. Its logic that tells us if the Earth is spherical its not cu

      • by bobbied (2522392)

        Obvious != proven

        Proven != Obvious

        You are correct, they are totally different.

      • by lgw (121541) on Wednesday August 27, 2014 @08:23PM (#47770843) Journal

        Another surprising fact about fusion in the Sun is that the fusion power generated is about 1.5 watts per ton of core. Even in conditions in the core of the sun, fusion is hard, and the particular reaction process just confirmed was at the end of a long chain of reasoning explaining what we do see. So I think this actually give evidence that a bunch of stuff in Wikipedia about processes in the Sun is also true. (If a different fusion process was found, then we'd likely be wrong about how much power is generated, and thus about the rate and manner that that power eventually makes it to the surface and gets radiated).

        • by mark_osmd (812581) on Wednesday August 27, 2014 @08:54PM (#47771029)
          Another surprising fact, the Sun's core is so dense (150 g/cc) that a metric ton of core only needs the volume of a cube 19cm per side to occupy.
          • by CheeseyDJ (800272)
            Here's another good one - if you could heat a pinhead here on Earth to the same temperature as the Sun's core (about 15 million Kelvin), it would incinerate everything within a 100km (60 mile) radius.
            • by lgw (121541)

              But the only reason the Sun's core is that hot is that it's a nearly perfect insulator. Give a small heater enough time in a perfectly insulated room and it will eventually get quite hot. Matter gets quite odd when light pressure is the dominant force.

        • Uh, nope. Given that the core weighs about a third of Sun's total mass, the ~3.8e26 or so watts generated in the ~7e26 tons of core mean that about half a watt is produced per each ton.
    • Neutrino detectors have been around for some time, including a large one at the South Pole. Others are located at Tsukuba, Japan and Lead, SD. What has prevented those detectors from finding solar neutrinos?

    • Can't actually "prove" it, this just makes it much more likely.

      Phone back when they actually go to the sun and check inside.

  • I'm with the other two posters who also thought this was considered fact.
    • And scientists test facts when they can. Michelson-Morley has been replicated several times with greater levels of precision, still finding no aether drift. This is a new way to test that proton-proton fusion is going on in the Sun, and so somebody took it. (Imagine what would happen if we found that those neutrinos weren't there. Fun times for physicists and astronomers!)

      Of course, everybody wants to be the one who finds something that is not what we predicted, but the odds of that aren't good. You

  • I hope no-one finds the off switch.

    • by bobbied (2522392)

      No need of one... Eventually the Sun will run short of fuel... Then you will see some SERIOUS global warming as the Earth will be within the burning part of the Sun...

      • by Anonymous Coward

        Don't worry, life on Earth will be extinct well before that, and the human race way earlier. Oh, we may have some time yet, a lot on our scale, but eventually we'll be gone. Think of it! The conquests of millennia, the art, the philosophy, the knowledge of generations, all those wars, struggles, endeavours... All for nothing. Lost forever. Left to decay and erosion, and all traces of it lost into the ocean of magma that will be this once living planet. No more Blue Marble. No more anything!

  • by AikonMGB (1013995) on Wednesday August 27, 2014 @06:08PM (#47769905) Homepage

    Nothing has been proven. Scientists have long had a theory about how the Sun powers itself. That theory can be used to make predictions, such as the type of neutrinos that we should expect to see emanating from the Sun. An experiment was devised to test such a prediction, the hypothesis being that this type of neutrinos is being produced and thus will be detected. Having performed the experiment, we see that the results match what we expected, validating the hypothesis. This is important and significant, and it provides further evidence suggesting the widely accepted theory is accurate, but it does not -- nor can it -- constitute a proof.

    The other interesting result would be if the expected neutrino type was not detected by this experiment, invalidating the hypothesis. This would raise further questions such as: is there some other mechanism powering the Sun? Is there something deficient in our understanding of neutrinos that prevented us from detecting them despite them being there? Was there an error in the test setup (i.e. is it repeatable by other parties)?

    • by AikonMGB (1013995)
      s/this type of neutrinos/this type of neutrino/
    • And there is the matter of neutrino oscillation [wikipedia.org], which could in itself nullify these results.
      • by dnavid (2842431)

        And there is the matter of neutrino oscillation [wikipedia.org], which could in itself nullify these results.

        Unlikely, because research has both confirmed the process of neutrino oscillation and allowed observers to account for the oscillation in neutrino measurements. Also, neutrino oscillation can only reduce the number of neutrinos you observe (relative to the amount you think you should), so neutrino oscillation cannot in any way erase a signal, it can only make a signal harder to detect. The problem with the neutrinos observed in the article in question is that they are the p-p neutrinos which have relative

        • But, again, neutrino oscillation can't nullify these results, because oscillation only makes neutrinos harder to detect (by changing their "flavor"). It doesn't create neutrino signals where none originally existed (at least not in this sense).

          Sure it can: By "oscillating" other flavors of neutrino into the type they're looking for, when they weren't there in the first place (or not in sufficient number).

          They'll need to look at the ratio of the various types and back-calculate to eliminate other possible s

          • by dnavid (2842431)

            But, again, neutrino oscillation can't nullify these results, because oscillation only makes neutrinos harder to detect (by changing their "flavor"). It doesn't create neutrino signals where none originally existed (at least not in this sense).

            Sure it can: By "oscillating" other flavors of neutrino into the type they're looking for, when they weren't there in the first place (or not in sufficient number).

            They'll need to look at the ratio of the various types and back-calculate to eliminate other possible signals, or combinations of them, to see if there is a way for other (possibly unexpected) reactions to produce a signal that looks like the ones expected and/or observed.

            Yes and no. Yes, its possible for neutrino oscillation to take a different flavor neutrino than expected and oscillate its type to become one you were expecting. But neutrino oscillation doesn't alter energy. As a practical matter, I don't believe there exists a particle interaction that generates large amounts of muon or tau neutrinos at coincidentally the same energy as the proton-proton generated electron neutrino.

    • by radtea (464814)

      Nothing has been proven.

      Correct.

      Science is the discipline of publicly testing ideas by systematic observation, controlled experiment and Bayesian inference. As such, proof is simply not relevant to what it does, which is produce knowledge. Knowledge--unlike faith--is inherently uncertain.

      It'll take a few hundred years for the popular science press to catch up to this. What is being presented here is evidence that the idea p-p fusion powers the sun is correct, so the posterior pluasibility of that idea goes up, although not to 1 (w

      • by gtall (79522)

        "Science is the discipline of publicly testing ideas by systematic observation, controlled experiment and Bayesian inference. As such, proof is simply not relevant to what it does"

        No it isn't. Physics is built using mathematics, indeed, it is the language of physics. Mathematical proof is central to much of physics otherwise there would be few predictions. Physics as we know it would be impossible without mathematics.

        Science in general uses the language of and reasoning of mathematics, even biology. Even pa

        • by mbone (558574)

          It is in my experience rare to meet a physicist who cares much about mathematical rigor, or who uses proofs in their work. Occasionally it is important (e.g., in some "no-go" theorems), but I feel certain that most physicists would object to saying that "Mathematical proof is central to much of physics." It is in fact notorious that much of existing physics was done and completed before anything like mathematical rigor (and, thus, proof) was brought to the subject at hand, nor did the achievement of rigor a

    • by khallow (566160) on Wednesday August 27, 2014 @07:07PM (#47770357)
      Or we could just realize that "proof" in empirical science means something different than it does in pure mathematics.
      • by AthanasiusKircher (1333179) on Wednesday August 27, 2014 @07:30PM (#47770507)

        Or we could just realize that "proof" in empirical science means something different than it does in pure mathematics.

        THIS. By GP's standard, >99% of the uses of the word "proof" in the English language are invalid. Almost all uses of the word "proof" in thousands of legal statutes around the world are bogus and meaningless.

        And, empirically, from looking at actual scientific methods as practiced, it's clear that scientists clearly do NOT treat all scientific theories as equally "falsifiable." Some are treated as "proven," if not in a strict mathematical-philosophical sense. It would take a LOT more to overturn a basic established law of physics than some off-the-cuff guess ("hypothesis") in a new experiment. So what exactly is it that we are doing when we verify and reverify and reverify a basic well-established tenet of basic science over centuries if not, in essence, proving "proof" of it (in any reasonable sense of the English word outside of the strange world of pure math and logic puzzles).

      • by Skarjak (3492305)
        This comment is severely underrated. The GP is a pedantic explanation of the scientific process. The use of the word "proven" is quite adequate here considering how rock solid our evidence for the sun's fusion processes are.
        • http://mathsci2.appstate.edu/~... [appstate.edu] invites you all to seek enlightenment through its teachingsâZ.

          Things can be proven. - You just have to accept that all provable things exist within a minute fantasy world which affirms itself. The study of these fantasy worlds is called axiomatic set theory.

          GÃdel further proved that proof itself becomes a fantasy when your fantasy becomes elaborate enough. He labeled this rather odd artifact 'Incompleteness'.

          Consequently many teeth were gnashed among the faithless

      • by Pfhorrest (545131)

        Etymologically, to prove means to test. Hence phrases like "proving grounds" and, more tellingly, "the exception that proves the rule" -- an apparent exception, an anomaly, which puts the rule to the test.

        So a well-tested theory is "proven" in an etymologically sound way, just a way that doesn't mean "demonstrated to be true with absolute certainty".

    • by dnavid (2842431)

      Nothing has been proven. Scientists have long had a theory about how the Sun powers itself. That theory can be used to make predictions, such as the type of neutrinos that we should expect to see emanating from the Sun. An experiment was devised to test such a prediction, the hypothesis being that this type of neutrinos is being produced and thus will be detected. Having performed the experiment, we see that the results match what we expected, validating the hypothesis. This is important and significant, and it provides further evidence suggesting the widely accepted theory is accurate, but it does not -- nor can it -- constitute a proof.

      Science is not about proof in the mathematical sense. Science is about amassing confirmation. To say something doesn't prove a theory in Science is like saying something doesn't prove a poem. Scientific proof is about sufficient confirmation of a theory as to make it the most useful and reasonable explanation for a set of observations.

      In the case of solar fusion, the basic *idea* that the Sun is powered by fusion processes is sufficiently well demonstrated that its essentially a scientific fact: its "pro

    • The other interesting result would be if the expected neutrino type was not detected by this experiment, invalidating the hypothesis. This would raise further questions such as: is there some other mechanism powering the Sun? Is there something deficient in our understanding of neutrinos that prevented us from detecting them despite them being there?

      That almost happened, in the early days of neutrino dectection - before things like old mines full of purified water and 3-D arrays of photodetectors running fo

      • by pomakis (323200)
        The Arthur C. Clarke sci-fi novel "The Songs Of Distant Earth" (1986) used the Case Of The Missing Neutrinos as the opening premise of the story. I quote: "The experiment worked; solar neutrinos were detected. But - there were far too few of them. [...] By the end of the twentieth century, the astrophysicists had been forced to accept a disturbing conclusion - though as yet no one realized its full implications. There was nothing wrong with the theory, or with the equipment. The trouble lay inside the Su
        • A pitty, thugh. By the time this was discovered I had done an outline for a five-volume fiction cycle, working through at least four genres, based on the sun going "putt" from time to time. B-b

          The Arthur C. Clarke sci-fi novel "The Songs Of Distant Earth" (1986) used the Case Of The Missing Neutrinos as the opening premise [followed by "the sun is about to nova" and humanity having] a few hundred years to develop interstellar-travel technology before the Sun went nova. 'Twas a good story.

          Indeed it was.

          In m

  • at first I thought the underground experiment was conducted by anonymous on 4chan or something. but no, it's in fact an underground bunker lair for detecting invisible particles from the sun. that's astounding. now that the experiment is done can I lease the facility for my evil lair? why? no reason.
  • by StefanJ (88986) on Wednesday August 27, 2014 @06:12PM (#47769949) Homepage Journal

    . . . the last professor in the once-prestigious Solar Combustion Sciences department clutches his chest, winces, and slumps face-down on his desk.

  • using a detector buried deep below the mountains of central Italy

    The linked article is in Italiano; unfortunately, my grasp of the language is limited to "ciao" and "vaffanculo."

  • by mbone (558574) on Wednesday August 27, 2014 @06:26PM (#47770059)

    It has been known since the 1960's that the Sun produces energy from fusion, but the actual neutrino's observed then (and until now) were high energy electron neutrinos that actually came from relatively unimportant fusion chains (from the standpoint of energy production), not the proton-proton chain though to produce most of the Sun's energy. Since there was a "neutrino problem" (the Sun appeared to produce only 1/3 of the neutrinos predicted by theory), some people did think that for whatever reason the main energy source - the proton–proton chain reaction - was for some reason mostly shut down, presumably as part of some long period oscillation in the Sun's deep interior (although Arthur C Clarke wrote a novel, "The Songs of Distant Earth," in which it was a permanent shutdown of the Sun's fusion, and a prelude to our Sun going supernova). At that time, the inability to directly see the pp chain seemed like a big deal, but since the discovery of neutrino oscillations (which nicely explain the factor of 1/3), and also with solar interior modeling from helioseismology, there has been a pretty solid consensus that the pp chain was running the Sun, even if there was no direct observation of it.

    Now it has been proved. In 1990 that would have been a big deal, but now it is more a matter of just being satisfyingly complete in our observations of the Sun.

    • by ScentCone (795499)

      but the actual neutrino's observed then (and until now) were high energy electron neutrinos

      I don't know why these observations are being thought of as a big deal. Why go to all the trouble of building some big underground Italian detector when we can see, right here, that passing neutrinos hit the /. servers and cause apostrophes to appear randomly (but due to a quirk of quantum behavior, almost always right in front of the letter 's').

    • by slew (2918)

      Buuuttttt think about the Electric Universe Theorists? ;^)

    • by Anonymous Coward

      the pp chain was running the Sun, even if there was no direct observation of it.

      *gigglesnort*

    • Good god man, Hans Bethe worked out the fusion processes in the Sun in the late 1930s.

      http://en.wikipedia.org/wiki/B... [wikipedia.org]

      • by mbone (558574)

        Good god man, Hans Bethe worked out the fusion processes in the Sun in the late 1930s.

        http://en.wikipedia.org/wiki/B... [wikipedia.org]

        Yes, but there was no direct observational evidence of it until the Homestake neutrino experiment in the 1960's. Theory is nice, but in physics the experiment's the thing. (And, when the Homestake experiment came up 66% short, there was no shortage of people claiming that Bethe was wrong in one way or another.)

        • by rubycodez (864176)

          Yes there was some direct observational evidence, the predicted nuclei being present in the sun for both the hydrogen to helium and O-C-N. You are speaking of refinement of the model and gathering of more evidence. I was just miffed by someone saying "known since the 1960s", that's in my lifetime and I know for fact my grandfather was a kid when fusion known, in 1920 Eddington had the gist of what happens in the Sun: hydrogen to helium with 0.7% of energy converted to energy.

    • satisfyingly complete in our observations of the Sun.

      Yeah right.
      Could you please explain why the corona's temperature is higher than a million Kelvin, then?
      http://en.wikipedia.org/wiki/C... [wikipedia.org]

  • 'chain of reactions that provides 99% of the sun's power'

    What is the other 1% that powers the sun?
  • by Anonymous Coward on Wednesday August 27, 2014 @06:40PM (#47770181)
    But how the hell did they manage to coax the Sun underground, in order to conduct this experiment?

    One of these days, I'm going to RTFA.

  • by Tablizer (95088) on Wednesday August 27, 2014 @07:03PM (#47770333) Homepage Journal

    Making huge discoveries about the universe without leaving mom's basement? Nerdgasm!

  • by luckymutt (996573)
    This may be a daft question, but if "the key proton-proton fusion reaction that is the first part of a chain of reactions that provides 99% of the sun's power." then what is the other 1% of the sun's power if not the chain of reactions?

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