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Earth Space Science

What Struck Earth in 775? 344

Posted by samzenpus
from the park-that-anywhere dept.
ananyo writes "Just over 1,200 years ago, the planet was hit by an extremely intense burst of high-energy radiation of unknown cause, scientists studying tree-ring data have found. The radiation burst, which seems to have hit between 774 and 775, was detected by looking at the amounts of the radioactive isotope carbon-14 in tree rings that formed during the 775 growing season in the Northern Hemisphere. The increase in 14C levels is so clear that the scientists conclude that the atmospheric level of 14C must have jumped by 1.2% over the course of no longer than a year, about 20 times more than the normal rate of variation (abstract). Yet, as the only known events that can produce a 14C spike are supernova explosions or giant solar flares, and neither event was observed at the time, astronomers have a cosmic mystery on their hands."
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What Struck Earth in 775?

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  • by MyLongNickName (822545) on Monday June 04, 2012 @08:53AM (#40207603) Journal

    I don't have a comment other than to say that I enjoy articles like this one. Please bring more like it and i will hit refresh 20 times to get yor page hit count up :)

  • by Anonymous Coward on Monday June 04, 2012 @08:55AM (#40207625)

    Would this mean carbon dating is inaccurate for items older than 1300 years?

    Time to redate the Shroud of Turin?

  • Volcano? (Score:2, Interesting)

    by Anonymous Coward on Monday June 04, 2012 @09:00AM (#40207683)

    A Volcano could have spit out the this stuff?

  • by vlm (69642) on Monday June 04, 2012 @09:09AM (#40207781)

    Yet, as the only known events that can produce a 14C spike are supernova explosions or ... and neither event was observed at the time

    ... was observed at the time in surviving northern written records.

    Are there any detailed written astronomical observations from the southern hemisphere from that long ago?

    Also it would be pretty funny if the two guys recording solar observations in 775 both had a rainstorm the day of the largest solar flare.

  • by Stirling Newberry (848268) on Monday June 04, 2012 @09:11AM (#40207807) Homepage Journal
    Since a near supernova enough to increase Carbon 14 levels would leave other effects, and the flares explanation is, similarly, weak.It is just as likely there was a temporary reduction in the earth's magnetic field that allowed more ambient cosmic rays to strike earth. While this amount of variation in the magnetic field is high, it isn't out of range of other events. It has the further advantage of not leaving a large number of highly visible effects, except for very strong auroras, which, given the date, might not have been recorded frequently or unequivocally enough.
  • by vlm (69642) on Monday June 04, 2012 @09:35AM (#40208017)

    It has the further advantage of not leaving a large number of highly visible effects

    What about geological magnetic field records?

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

    A lot of the initial geomagnetic reversal theory was figured out by basically plotting magnetic field strips across the sea floor using pretty crude equipment. Screwing around with the field that much would seem easy to detect now?

    I had a geologist roommate once... I know just enough about geology to be really dangerous (like programmer with screwdriver)

  • Re:Behind the Sun? (Score:5, Interesting)

    by forand (530402) on Monday June 04, 2012 @10:21AM (#40208491) Homepage

    If a GRB went off in the Galaxy then a few years of increased radioisotopes would be the least of the indicators. A mass extinction would be associated with such an event as most of the ionosphere would be striped from the Earth causing cosmic rays to reach the surface, this would have dramatic and lasting effects on life. I also neither implied nor stated that this was associated with a GRB.

    While supernova do not "stay lit in the sky for a very long time" you need to scale that with your time scale of the event. The Crab Nebula is the result of a supernova that went off in 1054 [wikipedia.org] (Earth time) and was visible to the human eye for a period of approximately 2 years after it went off. There is no associated increase in radioisotopes for that event, thus indicating that a larger (likely closer as well) event would have to be the cause of the increased radioisotopes observed in 775.

  • by sir-gold (949031) on Monday June 04, 2012 @10:24AM (#40208531)

    Carbon dating is already broken

    http://www.symmetrymagazine.org/breaking/2010/08/23/the-strange-case-of-solar-flares-and-radioactive-elements/ [symmetrymagazine.org]

    Solar flares (specifically neutrino radiation) affects decay rates of all radioactive materials. Carbon 14 dating assumes that the half-life is fairly constant, but the base level of neutrino radiation could have been much higher or lower for extended periods in the past, making carbon 14 gradually less accurate the farther you go back.

  • by spook brat (300775) on Monday June 04, 2012 @03:14PM (#40212151)

    Is it only demeaning if the beliefs are held by a major segment? There are still people who believe in or honor the Norse gods too, but I have yet to hear anyone get upset about the phrase "North Mythology".

    I'll give you your report about Norse mythology getting people upset, then. During my time in the Army I got to spend some time doing joint ops with the Norwegian military. I was given stern warnings by my buddies that the guys wearing hammer tattoos in the bar on base were not safe to taunt regarding their religion. Reason given: it's likely to get a violent response. I'm sure that when they're sober they would take some friendly ribbing just fine, but I felt no desire to see how a drunk Thor worshiper would react to being ridiculed at their base's bar for believing in a myth.

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