Antimatter In Lightning 169
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."
Been looking a long time (Score:2, Informative)
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.
Re:what exactly did they detect? (Score:2, Informative)
...it could also mean the direct conversion of electrons to energy by some other unexplained means.
then for that energy we would need 2 electrons, not one.
Either way, it would be a hell of a discovery, potentially leading to matter-to-energy conversion power generation. To hell with fusion power, this is better!
well isn't fusion a way of matter-to-energy conversion power generator?
This was first observed in 1971 (Score:5, Informative)
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).
Re:This was first observed in 1971 (Score:3, Informative)
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:This was first observed in 1971 (Score:3, Informative)
Why not indeed ?
This sounds reasonable to me :
The lightning associated gamma rays can be inferred as due to bremsstrahlung associated with electrons released moments after the return stroke and the likely radiation associated with radioactive decay products in the interactions of protons generated in the lightning with the atmospheric constituents
(from Jayanthi et al., 2006 [harvard.edu]).
Although the previous reports of lightning induced fusion from Slashdot [slashdot.org] are intriguing.
Re:what exactly did they detect? (Score:3, Informative)
Yes, but it's not as clean as direct annihilation would be. It generates neutrons which make the materials used for containment radioactive.
Depends on the starting elements. Among others, He3+He3->He4+2p+E. No free neutrons generated, only protons and energy.
Re:Electron-Proton Collisions? (Score:5, Informative)
No, you don't get annihilation from electrons and protons.
You do get radiation, if things are energetic enough. If the electron becomes bound to the proton, you get emissions at one of the Hydrogen lines.
If, for example, the electron went all the way to the Hydrogen ground state, you would have emissions at the limit of the Lyman Series [wikipedia.org], up in the hard UV at 91 nanometers.
If things are more energetic, you will get electrons and protons combining to form free neutrons. These will decay [gsu.edu] (this decay is called beta decay) and release gamma rays at 782 KeV, but since the half life of free neutrons is 10.3 minutes, this will be really spread out in time and hard to see. Free neutrons have been directly detected from lightning strikes, so some of this is presumably going on.
Re:what exactly did they detect? (Score:3, Informative)
No, of all our technology to produce power it still involves boiling water.
Except for internal combustion, photovoltaic solar, molten-sodium solar, hydroelectric, wind, or using an alternator instead of a break to provide resistance to excersie equipment.
Yeah, so, aside from all of those, everything uses boiling water.
Re:Electron-Proton Collisions? (Score:5, Informative)
Electron-proton collisions will not lead to a 511 KeV line. That's due to electron-positron collisions.
Re:what exactly did they detect? (Score:5, Informative)
From the first paragraph of the article:
During its first 14 months of operation, the flying observatory has detected 17 gamma-ray flashes associated with terrestrial storms -- and some of those flashes have contained a surprising signature of antimatter.
In other words, they have detected 17 gamma-ray flashes due to lightning, and some of them have the signature of antimatter (i.e. the electron-positron annihilation).
I'm not sure how that's not exactly what you're saying they didn't say. Just because they didn't say 511 KeV? If 511 KeV is the signature of electron-positron antimatter collitions, and they've found the signature of antimatter collisions in some (not all) of the storms, wouldn't that suggest they are seeing 511 KeV bursts?
Here's more:
During two recent lightning storms, Fermi recorded gamma-ray emissions of a particular energy that could have been produced only by the decay of energetic positrons, the antimatter equivalent of electrons.
It seems pretty specific about what they are seeing, it is simply stated in a high-level language that the common interested-but-not-knowledgeable reader can understand.
This is essentially an online science news magazine, not a journal for published papers seeking peer review. They are only going to give you the gist of the information at a high-level, and from there if you have better knowledge of the subject you should have an automatic deeper insight into what they might be seeing.
It's not like it's some amature job either, the space telescope was built to find this sort of thing, so finding these signatures is not like some wack job pop-sci company pushing nonsense in a press conference to attract investors before folding in a few years.
Re:positrons vs electrons (Score:1, Informative)
Um, because electrons don't decay, douchington?
Re:what exactly did they detect? (Score:5, Informative)
Boiling water isn't a direct electrical source either, it's all about energy conversion. The easiest way to convert heat into electricity is to first convert it to kinetic energy. The easiest, cheapest, and safest way to convert heat energy to kinetic energy is to boil water and creat a pressure differential to drive a piston or turbine or what have you. It's very effective, and there isn't any compound likely to do the job better than H2O that isn't also prohibitively expensive.
Heat is the easiest form of raw energy to produce, and if boiling water is the easiest, cheapest, and safest way to convert heat energy into kinetic energy (which is then trivial to convert to electrical energy at very high conversion rates).
Heat engines are also still the most efficient form of energy conversion available to us. A typical modern steam turbine generator will convert close to 50% of the heat energy to electricity, and in some applications can convert as much as 90%. Combustion engines are typically in the 30% range, but getting higher, though they have a theoretical hard limit at 37%. Photvoltaic is coming along, but frankly it's still young and the readily available PV cells compare poorly to combustion and turbine engines. The theoretical limit for a single cell is about 40% efficiency (with light concentrators), but new techniques are working around that limit (they use multiple materials in the cell, effectively combining several cells in one) and the current record is around 43%.
The big problem PV has vs combustion or turbine engines is energy density - the fuel sources the later two methods use are significantly more energy dense than plain sunlight. Sunlight throws a lot of energy everywhere, but only a little in any particular spot. Concentrating it effectively has always been a problem.