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When the activity of the sun changes, it has direct effects on the earth. For example, when the sun is relatively inactive, the amount of a type of carbon called carbon-14 increases in the earth's atmosphere. Because carbon in the air is absorbed by trees, carbon-14 levels in tree rings actually reflect solar activity and unusual solar events in the past. The team took advantage of such a phenomenon by analyzing a specimen from a bristlecone pine tree, a species that can live for thousands of years, to look back deep into the history of the sun.
"We measured the 14C levels in the pine sample at three different laboratories in Japan, the US, and Switzerland, to ensure the reliability of our results," A. J. Timothy Jull of the University of Arizona says. "We found a change in 14C that was more abrupt than any found previously, except for cosmic ray events in AD 775 and AD 994, and our use of annual data rather than data for each decade allowed us to pinpoint exactly when this occurred."
[...] "Although this newly discovered event is more dramatic than others found to date, comparisons of the 14C data among them can help us to work out what happened to the sun at this time," Fusa Miyake of Nagoya University says. She adds, "We think that a change in the magnetic activity of the sun along with a series of strong solar bursts, or a very weak sun, may have caused the unusual tree ring data."
An abstract is available but the full article is paywalled; see: "Large 14C excursion in 5480 BC indicates an abnormal sun in the mid-Holocene" was published in PNAS at: www.pnas.org/cgi/doi/10.1073/pnas.1613144114
(Score: 2) by VLM on Wednesday February 08 2017, @01:40PM
I saw this in the queue and hit google yesterday, hard, trying to find 7000 year old supernova remnants. Unsuccessfully.
I was hoping to find some research papers dating prehistorical supernovas by looking at an astrophotograpy pix of the remains of a supernova from 1900, then comparing to an astrophotography pix from 2000 showing its 1/70th larger in 100 years implying it was a point source about 7000 years ago. Or when it was a point source it was an impressive radiation source. At least this seems a logical plan.
Another fun technique would be analysis of radiative cooling, so this gas cloud was "supernova hot" 7000 years ago and is now unfortunately probably pretty chill.
Maybe theres a way to mix in astrophysics where supernova remains contain some radioactive stuff and based on theoretical models the "stuff" we see in a stellar spectrum has been decaying for about 7000 years, assuming the astrophysics theories about stuff are correct.
Possibly 7000 years is too long and the remains are undetectable. Possibly no one has ever thought to try this, although astronomers are pretty creative and I'm sure someone has tried.
Its more fun to speculate that this is serious SETI and to get the attention of long lived semi-intelligent species you blow up a star (not your own presumably) in a highly controlled fashion. Maybe every 100K years some advanced civilization sends out a beacon like that. Its often enough that a civilization smart enough to figure out carbon dating would notice and rare enough that civilizations have to be pretty stable to actually catch a beacon transmission. Our next chance for SETI detection is in 97K years. By highly controlled fashion, at a low resolution a star went nuts and then blew up, but if you had gigahertz resolution optical sensors you'd notice the process of explosion was AM modulated and contained a couple terabits of digital data. Crude civilizations won't know anything but "there was a star in the sky in the daytime" and civs of our level only notice "Huh, that damned carbon dating Fed up again" but an advanced enough civilization, the kind that would turn the entire far side of the moon into an observatory, would tend to notice, perhaps exactly the kind of people you'd want to notice... And thats my free hard sci fi movie/book plot of the day....
Another fun sci fi plot is this is what happens when a star drive malfunctions on an exploration probe sent from 7001 Ly away, and "home" sent a second light speed exploration probe to our solar system 7000 years ago to WTF over the acident and anytime soon the aliens are going to appear in system and the aliens are gonna be all like "look at that goddam huge impact crater where our exploration ship hit Saturn's moon Mimas when warping out of system, I told you not to let a woman drive the space ship she was probably checking alienface book or holograph texting instead of looking out the window while she was supposed to be driving and ... hello, wtf is all this radio noise from planet 3?" Of course if something had enough energy to be a "star drive" and move ships at light speed, if it blew up, it would probably make such an enormous mess that we could detect it locally even if it happened on a system 100 Ly away. Of course a system 100 Ly away is just close enough to hear our early radio broadcasts if they happen to listen, so maybe it doesn't change the story much.
(Score: 2) by Sulla on Wednesday February 08 2017, @03:24PM
Such positive views of the universe. Could have just been that the star made itself noticed and got hit with a dark forest attack. One would need to be pretty far advanced to risk making oneself known, not sure I want to meet that race
\pessimest
Ceterum censeo Sinae esse delendam
(Score: 2) by VLM on Wednesday February 08 2017, @03:34PM
Here's another weird sci fi plot... The universe being really big, the odds of two advanced civilizations being diametrically opposite to the Earth or the solar system or for that matter our galaxy is roughly equal to "1" isn't it? Therefore the assumption that the only SETI transmission we can receive is omnidirectional broadcast is false, in that there is a 100% chance that friends are talking right past the earth right now, using some weird technology we probably haven't invented yet.
Aside from two friendly civilizations theory, there's a weaker assertion the odds are lower but near enough 100% there exists a homeworld and a colony diametrically opposed from the Earth, and the homeworld and colony are at least occasionally friendly and communicate with each other.
The odds of something weird existing approach 100% when the universe is large enough. Americans (and probably Russians) have been trained for decades via the cold war that civilization relations are small and simple and rare, but the universe is really big and under no obligation not to have rare things occur all the time. A third of a percent of us being born on the same birthday smells very unusual at first glance, but when applied to a 300+ million person country means a hell of a lot of people none the less share your rare and unusual birthday.