Earth May Have Been Hit By a Gamma-Ray Burst In 775 AD 157
The Bad Astronomer writes "Studies of carbon-14 in Japanese trees and beryllium-10 in Antarctic ice indicate the Earth was hit by a big radiation blast in 775 AD. Although very rare, occurring only once every million years or so, the most likely culprit is a gamma-ray burst, a cosmic explosion accompanying the birth of a black hole. While a big solar flare is still in the running, a GRB from merging neutron stars produces the ratio of carbon and beryllium observed, and also can explain why no bright explosion was seen at the time, and no supernova remnant is seen now."
Umm? How far away would it have been? (Score:1, Informative)
I thought a nearby GRB would wipe out all life, all the way down to viruses.
At least that's what Michia Kaku and his bullshit "science" documentaries on Discovery Channel have been telling me.
Re:Umm? How far away would it have been? (Score:5, Informative)
Depends on intensity I imagine. The article notes it had to be further then 3000 light years away or they'd have expected it to cause an extinction event - and also that there are "short" and "long" GRBs.
Re:Umm? How far away would it have been? (Score:5, Informative)
I thought a nearby GRB would wipe out all life, all the way down to viruses.
It would. But if it was farther away, it would just create a bunch of radioactive isotopes in the upper atmosphere while leaving life on the ground mostly unmolested.
If only someone had an estimate of how far away this one was, and had presented it in something that would describe this news item in detail. We could call it an "article".
For non-douches who also didn't RTFA, it's estimated at 3000 to 13000 ly away. For comparison, in Phil's book "Death from the Skies" he discusses what would happen as a result of a GRB from 100 ly away, and the result is Very Bad(tm).
His tree data is wrong (Score:5, Informative)
FTA: "In the last 3000 years, the maximum age of trees alive today, only one such event appears to have taken place."
The actual oldest trees are about 5,000 (http://en.wikipedia.org/wiki/List_of_oldest_trees)
Though that doesn't devalidate his main point (that this has only happened once in 3,000 years). I just wish he'd fact-check a bit more.
Re:How many times did this happen? (Score:5, Informative)
This is not a dupe, the first article pointed to tree rings, the second confirms the results using Antarctic ice.
Re:Umm? How far away would it have been? (Score:5, Informative)
For comparison, in Phil's book "Death from the Skies" he discusses what would happen as a result of a GRB from 100 ly away, and the result is Very Bad(tm).
Of course for all the preppers out there it should also be said that the closest confirmed GRB is 1.3 billion light-years from Earth, the observation period isn't very long but it's hardly a common occurrence. Which is also why I'm a little sceptic that we've had one right on our doorstep only a few thousand light years away.
Re:Effects on Humans and animals (Score:5, Informative)
According to this article [nature.com] from last year on the same event, the event caused an increase in the concentration of carbon-14 in the atmosphere of about 1.2%. That's apparently about 20 times the normal rate of variation, but the baseline level of carbon-14 is about a part per trillion, so we'd be talking about increasing the concentration of carbon-14 by about 10 parts per quadrillion. In contrast, the period of above-ground nuclear testing almost doubled the concentration at its peak in the early 1960s.
Given our indirect knowledge of the event in 775, it's unknown whether other radiological hazards would have been present in addition to the C14 spike, but there don't seem to be indications of mass dieoffs or famines.
Re:93 million miles (Score:4, Informative)
> I've heard the 775 C14 anomaly attributed to a very large solar storm period too, even those these guys dismiss the idea.
The article claims that it would have to be 10 times more intense than any solar storm ever recorded. The article admits that it's a possibility, but (for various reasons) unlikely.
Re:Umm? How far away would it have been? (Score:4, Informative)
There was another event that led to modification of the natural isotopes in North America:
http://ie.lbl.gov/paleo/paleo.html [lbl.gov]
http://abob.libs.uga.edu/bobk/nuclear.html [uga.edu]
Re:Umm? How far away would it have been? (Score:5, Informative)
also, couldnt a grb at worst wipe out life on just half the planet? Surely if you're on the "dark side of the earth" for this event, you would be safe.
Sure, if you can build the 40,000 km long, 30 km high wall around the terminator fast enough to prevent your part of atmosphere from getting spoiled with all the NO2 generated by the gamma burst interacting with the atmosphere.
Re:Umm? How far away would it have been? (Score:3, Informative)
Well, IIRC from the book, basically everything on the facing side of the earth would be dead and on fire. It would also entirely destroy the ozone layer in that hemisphere. Once the atmosphere had equalized, what would be left wouldn't be enough to protect the survivors from the sun, so they'd all die too, just more slowly and painfully.
Re:Umm? How far away would it have been? (Score:4, Informative)
From here [msn.com]:
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