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posted by Fnord666 on Thursday November 23 2017, @09:48AM   Printer-friendly
from the so-that's-what's-in-the-warp-nacelles dept.

Lightning can transmute nitrogen into carbon-14 and cause the emission of a positron, the antimatter counterpart of the electron:

Lightning can accelerate some electrons to almost the speed of light, and the electrons can then produce γ-rays. [Leonid] Babich proposed that when one of these γ-rays hits the nucleus of a nitrogen atom in the atmosphere, the collision can dislodge a neutron. After briefly bouncing around, most of the neutrons get absorbed by another nitrogen nucleus. This adds energy to the receiving nucleus and puts it in an excited state. As the receiving nucleus relaxes to its original state, it emits another γ-ray — contributing to the giveaway γ-ray glow.

Meanwhile, the nitrogen nucleus that has lost one neutron is extremely unstable. It decays radioactively over the next minute or so; in so doing, it emits a positron, which almost immediately annihilates with an electron, producing two 511-keV photons. This was the third signal, Enoto says. He suspects that his detectors were able to see it only because the briefly radioactive cloud was low, and moving towards the detectors. This combination of circumstances might help to explain why the photonuclear signature has been seen so rarely. Enoto says that his team has observed a few similar events, but that the one described in the paper is the only clear-cut event so far.

Babich also predicted that not all of the neutrons dislodged from nitrogen by a γ-ray are absorbed. Some of them instead will trigger the transmutation of another nitrogen nucleus into carbon-14, a radioactive isotope that has two more neutrons than ordinary carbon. This isotope can be absorbed by organisms; it then decays at a predictable rate long after the organism's death, which makes it a useful clock for archaeologists.

The main source of the carbon-14 in the atmosphere has generally been considered to be cosmic rays. In principle, lightning could also contribute to the supply. But it is not clear yet how much of the isotope is produced in this way, says Enoto, in part because it's possible that not all bolts initiate photonuclear reactions.

Photonuclear reactions triggered by lightning discharge (DOI: 10.1038/nature24630) (DX)


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  • (Score: 0) by Anonymous Coward on Thursday November 23 2017, @08:43PM (5 children)

    by Anonymous Coward on Thursday November 23 2017, @08:43PM (#600808)

    Yes, this is the problem I was originally mentioning. And I asked how much lightning would be required to cause a similar issue.

    I thought you were saying the tree ring/whatever calibration was supposed to get rid of this problem. Now I do not know what your point is, you seem to be agreeing with me.

  • (Score: 1) by khallow on Thursday November 23 2017, @09:11PM (4 children)

    by khallow (3766) Subscriber Badge on Thursday November 23 2017, @09:11PM (#600827) Journal

    I thought you were saying the tree ring/whatever calibration was supposed to get rid of this problem.

    Hmm, trees will absorb fairly predictable amounts of C14 and thus would be decent indicators of what past C14 concentrations were. So you can calibrate with good tree ring data. But you can't fix variation in C14 levels. No matter how perfect the knowledge of C14, there will still be some uncertainties with dating modern era organics with it.

    • (Score: 0) by Anonymous Coward on Friday November 24 2017, @05:38AM (3 children)

      by Anonymous Coward on Friday November 24 2017, @05:38AM (#600946)

      C-14 has a half-life of 5730 years. Then the doubling (eg due to nuclear testing) would introduce an uncertainty of that 5730 years. That is near the duration of all recorded human history... This is not insubstantial. All I was asking is whether the lightning effect could cause something similar.

      • (Score: 1) by khallow on Friday November 24 2017, @07:00AM (2 children)

        by khallow (3766) Subscriber Badge on Friday November 24 2017, @07:00AM (#600976) Journal

        Then the doubling (eg due to nuclear testing) would introduce an uncertainty of that 5730 years.

        It's not uncertainty. Things like trees and flesh absorb carbon in predictable ways.

        All I was asking is whether the lightning effect could cause something similar.

        Don't know. If climate change models are correct, more extreme storms should have higher levels of lightning and more lightning-based C14 generation. All I can say is that any enhanced production is being swamped by fossil fuel emissions which are very low in C14.

        • (Score: 0) by Anonymous Coward on Friday November 24 2017, @06:34PM (1 child)

          by Anonymous Coward on Friday November 24 2017, @06:34PM (#601098)

          All I can say is that any enhanced production is being swamped by fossil fuel emissions which are very low in C14.

          This was going on 1000 years ago? Honestly just the weird responses in this thread and what I've seen looking it up makes me think this whole carbon dating (maybe radioisotope dating in general?) strategy has some deep flaws. Its like people cant even understand simple questions about it.

          • (Score: 1) by khallow on Friday November 24 2017, @11:20PM

            by khallow (3766) Subscriber Badge on Friday November 24 2017, @11:20PM (#601177) Journal

            This was going on 1000 years ago?

            A previous poster, kanweg noted [soylentnews.org] that there has been variation in the past, but it wasn't enough to cause problems via tree ring data spanning the past 50,000 years.

            Honestly just the weird responses in this thread and what I've seen looking it up makes me think this whole carbon dating (maybe radioisotope dating in general?) strategy has some deep flaws. Its like people cant even understand simple questions about it.

            Don't see that myself. You (or other ACs) asked questions, you got pretty non-weird answers. Doesn't get more straightforward than that. Keep in mind you have a bunch of different people talking and not everyone reads the whole thread (I didn't) or remembers it even when they have read the whole thread. I came in after an AC comment about nuclear testing causing large variations in C14. So I was expecting a discussion about the very recent and large perturbations of C14, not the variations a thousand years ago which are much smaller.