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Earth Science

Antimatter In Lightning 169

Posted by Soulskill
from the doc-brown-can-now-power-his-warp-drive dept.
AMESN writes "The Fermi Gamma-ray Space Telescope, launched last year, detects gamma rays from light years away, but recently it detected gamma rays from lightning on Earth. And the energy of the gamma rays is specific to the decay of positrons, which are the antimatter flavor of electrons. Finding antimatter in lightning surprised researchers and suggests the electric field of the lightning somehow got reversed."
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Antimatter In Lightning

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  • by Anonymous Coward

    ... lightning is made of electro-matter, matter's bad-ass grandma!

  • The decay of positrons in the largescale discharge of electronic particles may very well lead to gamma ray emissions, however it is crucial to understand the energy output required to reverse the polarity of the discharge so that we can reproduce the phenomenon in a controlled laboratory.

    Or else the Romulans will destroy the Federation.

  • Crossover (Score:2, Interesting)

    by gmuslera (3436)
    Now the monster of frankenstein (powered by lightning) was in fact the first asimovian positronic robot (ok, the alpha one, without any law). With that much discussion about who could be the author to write Asimov's stories, maybe the original Mary Shelley could be the one worthy for that task.
  • Not that surprising (Score:5, Interesting)

    by tylersoze (789256) on Saturday November 07, 2009 @08:56AM (#30014044)

    Apparently they've detected gamma ray energies up to 20 MeV from thunderstorms, so given that amount of energy involved I wouldn't think it's that surprising that electron-positron pairs might be created in the process since an electron only has a mass of .511 MeV. The thunderstorms are basically operating like natural linear accelerators.

    • by astar (203020)

      hmm, no chance that it is something useful, like maybe a more efficient way to produce positrons?

      • by mikael (484)

        Yes, but you need someone to hold the kite steady while the thunderstorm passes overhead.

      • by SETIGuy (33768)
        There already is an efficient way to produce positrons. Bombard a target with any charged particle with kinetic energy greater than 1.022 MeV. Which appears to be what happens in a lightning bolt. This appears to be surprising only to journalists and slashdot readers.
  • reversal schmersal (Score:4, Insightful)

    by Anonymous Coward on Saturday November 07, 2009 @08:57AM (#30014052)

    Antimatter in lightning does not suggest that the electric field got reversed; that's nonsense. The electric field is a vector, and it can point in any direction.

    What it does suggest is either that the few positrons created or brought by cosmic rays are somehow concentrated by lightning, or that the strong electric fields in lightning are actually pulling a few positron-electron pairs out of the quantum electrodynamic vacuum. The first explanation is probably ruled out unless positron decay gamma rays are also seen all over in the atmosphere, just not as densely concentrated as in lightning.

    The second explanation is perfectly possible, if the electric fields in lightning are simply strong enough over large enough volumes of space. Any potential difference greater than 2 m c^2/e will in theory produce positrons and electrons from nothing; this is called 'the Schwinger Effect'. But the rate is ridiculously low unless the field is enormous, and it has not yet been observed. Relatively straightforward calculations would allow one to estimate what sort of electric fields lightning would need to involve, for the observations to be due to the Schwinger Effect.

    • Re: (Score:2, Funny)

      by Anonymous Coward

      quantum electrodynamic vacuum

      positron decay gamma rays

      You're good!

    • Re: (Score:2, Funny)

      by Hurricane78 (562437)

      reversal schmersal

      the Schwinger Effect

      Aaahh... a bit of German makes every scientific topic cool.
      We only lack a "färbottenärr Krruppstahl Gammastrrahlänn-Krriegsmaschinenapparraturrr" in there somewhere. Jawohl! ;)

      Wundabar! Jahaha!

      • Pfff... I thought Americans like German hard sounding words.

        Either you have never player Wolfenstein, or that was way over your head. ^^

    • Re: (Score:2, Interesting)

      by John Hasler (414242)

      Fusion reactions seem more likely.

    • by drinkypoo (153816)

      It's always been my understanding (well, since I was a pre-teen or so) that lightning is not a one-way process. My understanding is that the current flow does indeed reverse several times during a strike, that it's A/C and not D/C. Commentary?

      • by Chris Burke (6130)

        My understanding is that the current flow does indeed reverse several times during a strike, that it's A/C and not D/C. Commentary?

        Yes and not really, respectively. There are at least two transfers of charge, one in each direction, but they're by and large discreet events with current flowing one way. So, "alternating" in a sense, but each stroke is best understood as a DC event.

    • Last I checked, the Schwinger Effect involved several bisexuals and copious amounts of KY...
  • by Anonymous Coward

    Researchers have been looking for the tell-tale 0.511 MeV photons for decades in lightning storms. The idea is that a lightning channel could act like a natural particle accelerator. So electron-positron pairs could be created. But they have never been seen before from what I understand. But maybe these particles were created in much larger lightning bolts or perhaps the emissions are preferentially directed upwards into space ... dunno. Very interesting.

  • by mbone (558574) on Saturday November 07, 2009 @09:18AM (#30014132)

    It’s a surprise to have found the signature of positrons during a lightning storm, Briggs said.

    No, it's not.

    There is a long history of observations and theorizing about gamma ray flashes from lightning strikes and ball lightning, starting in the early 1970's :

    Is Ball Lightning caused by Antimatter Meteorites? [nature.com]
    D. E. T. F. ASHBY, C. WHITEHEAD, Nature 230, 180-182 (19 March 1971).

    This has also been observed in connection with "sprites [harvard.edu]".

    And from thunderclouds [arxiv.org] without lightning [arxiv.org].

    Oh, and it's also been observed from space before :

    RHESSI Observations of Terrestrial Gamma-Ray Flashes [harvard.edu]

    Now, not all of these reports include a positron annihilation signature at 511 KeV. But, 511 KeV emissions were explicitly reported from lightning in the 1970's [nature.com]. And, considering that lightning / thunderstorm related gamma rays are routinely observed with energies up to 10 MeV, there is plenty of energy to create positrons, and so I wouldn't be surprised if all of these reports included the positron annihilation line (or, at least the ones with sensitivity in that energy range).
     

    • by Anonymous Coward on Saturday November 07, 2009 @09:41AM (#30014220)

      Did you stumble into this forum by mistake? Come back when you have some baseless conjecture or a conspiracy theory.

    • Re: (Score:3, Informative)

      by mbone (558574)

      I am in Japan, and jet-lagged - I mean to say

      Now, not all of these abstracts report include a positron annihilation signature at 511 KeV.

      I have read these papers (and others) and IIRC 511 KeV reports are fairly common, but I don't have them in front of me to be sure.

    • Re: (Score:3, Interesting)

      by calidoscope (312571)

      And, considering that lightning / thunderstorm related gamma rays are routinely observed with energies up to 10 MeV, there is plenty of energy to create positrons, and so I wouldn't be surprised if all of these reports included the positron annihilation line (or, at least the ones with sensitivity in that energy range).

      Considering that pair production starts becoming significant at gamma energies above 5 MeV (threshold 1.022 MeV), I would be very surprised if there weren't some 0.511 MeV gammas from thunderstorms. It is also likely that the positrons could be formed by interaction between high energy electrons and matter.

      I would think that the gammas are produced in conjunction with sprites (cloud to ionosphere) rather than normal cloud to ground strokes.

    • Not 1971, but actually 1955 It was actually observed first in 1955 when the positrons in the lightning strike were channeled through the flux capacitor to take Marty McFly back to the future.
  • Is the radiation you observe when a positron is annihilated different from what you would see if, say, an electron collided with a proton?

    • by Lehk228 (705449)
      well to start with electrons and protons don't destroy each other. if they were somehow forced together and you threw in an anti-neutrino maybe you could force the reverse of a neutron decay and make them into a neutron, but first you would need to figure out how to force them all together and how to convince the quarks involved to shuffle identities.

      so if it's even possible within the laws of physics it's probably at least a thousand years before we can do anything like that, and i don't see any reason t
  • by Ancient_Hacker (751168) on Saturday November 07, 2009 @10:38AM (#30014436)

    Could it be the other way around, that cosmic rays trigger lightning? So the timing is just a coincidence?

    • No. These observations were made with a telescope. That means that they know what direction the gamma rays came from. Cosmic rays don't come up out of the Earth.

    • Could it be ... that cosmic rays trigger lightning?

      According to Wikipedia: [wikipedia.org] "Cosmic rays have been implicated in the triggering of electrical breakdown in lightning. It has been proposed that essentially all lightning is triggered through a relativistic process, "runaway breakdown" [wikipedia.org], seeded by cosmic ray secondaries. Subsequent development of the lightning discharge then occurs through "conventional breakdown" mechanisms."

  • And they can tell this is the decay of a positron and not an electron by what means? Shouldn't they have the same energy wavelength?

    • A positron "decays" by mutual annihilation with an electron. This results is the emission of two 511KeV photons.

  • ...call the contract lawyers.

  • by jasno (124830) on Saturday November 07, 2009 @12:19PM (#30015030) Journal

    Does anyone know what the cross section of a lightning bolt looks like? I've always wondered if forces akin to the skin-effect are trying to spread out the electrons while it's constrained in a tube of plasma. Is it round? Is it a sheet? What's the electron density like? What sorts of pressures would you expect in the center of a bolt?

    Just curious... but I'm unable to find a google hit and too dumb to simulate it.

    • > Does anyone know what the cross section of a lightning bolt looks like? I've
      > always wondered if forces akin to the skin-effect are trying to spread out
      > the electrons while it's constrained in a tube of plasma.

      Other way around. The magnetic field generated by the current pinches it.

    • The acoustics of thunder offer some insight into this. It definitely has area to its cross-section or thunder would be much quieter and bi-directional instead of omnidirectional. The pressure is comparatively quantifiable by measuring the SPL of the thunder from a distance, apply inverse square law, etc. Perhaps you can get to electron density from there.

      The shape of the cross-section of lightning could be measured reasonably accurately by recording a thunderstorm from multiple locations and determining

      • by jasno (124830)

        I expect the cross-section would be for the mostpart circular, since there is no conductive conduit apart from the air and rain. The electrons will want to be away from each other, but need to be close enough to energize the air to become a conductive conduit instead of a dielectric. Same reason atomic electron orbits are spherical.

        The acoustics of nuclear physics... *flexes nerd muscles*

        Agreed.. what I wonder though is do you end up with a tube of electrons surrounding a vacuum, or a more uniform distribution of electrons. What is the environment like that's created inside the plasma, and what happens to other high energy particles, say cosmic rays, that enter this region?

        • Re: (Score:3, Interesting)

          by TropicalCoder (898500)

          what I wonder though is do you end up with a tube of electrons surrounding a vacuum, or a more uniform distribution of electrons. What is the environment like that's created inside the plasma, and what happens to other high energy particles, say cosmic rays, that enter this region?

          I think we have a pretty good understanding of plasma. Just look at a florescent or neon lamp. A lightening bolt is a tube of mostly positively-charged nitrogen ions in a cloud of electrons. The super-heated gas glows brightly as

          • by jasno (124830)

            According to the wikipedia article on lightning, the average length of a strike is 30 microseconds. A 30 microsecond pulse of tens to hundreds of thousands of amps should definitely NOT be considered DC. You're correct that you're not dealing with a repetitive alternating current flow, but it is far, far removed from the quiescent state used when performing DC analysis. The change in current, and hence the magnetic field generated, is absolutely immense.

            Comparing the plasma created in a lightning strike

        • Definitely a tube surrounding a vacuum. Considering the relatively small amount of space and the volume of thunder produced, we're definitely talking about the instantaneous evacuation and 'revacuation' of the entire bolt of lightning. I don't even need an SPL meter for that.
  • why you need lightning to give life to inanimate flesh and time travel.
  • How are positrons in lightning any different that upper atmosphere lightning such as sprites [wikipedia.org]?
  • What were the odds of that? Seems as unlikely as getting hit by...well you know.
  • Lamest... summary... Ever! [/Comic Book Guy-mode]

Thufir's a Harkonnen now.

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