5 ms·

Evidence of Ancient Solar Storms in Tree Rings Could Pinpoint Historical Events

51 points by curtis 8y ago

rl3 8y ago
>... they’ll be able to piece together more precise time stamps for history’s uncertainties: the construction of Egypt’s Great Pyramid of Giza, the collapse of the Mayan civilization, and maybe even the arrival of the Vikings in the Americas. That should require some really old trees, no? Wikipedia puts the The Great Pyramid of Giza for example at 2580–2560 BC. That's about 4600 years ago. https://en.m.wikipedia.org/wiki/List_of_oldest_trees https://en.m.wikipedia.org/wiki/List_of_oldest_trees According to that, there's only three known trees on the planet that were alive at the time. Of course, maybe I'm misunderstanding; perhaps it's the case that by accounting for the past few thousand years of solar events, carbon dating will become far more accurate even for periods in which no tree alive at the time is available today.
- curtis 8y ago
  You don't need a single tree across the entire timespan you want to look at. You can assemble a series of overlapping samples from a number of trees that lived at different times during the timespan of interest. From Wikipedia [1]: > A fully anchored and cross-matched chronology for oak and pine in central Europe extends back 12,460 years, and an oak chronology goes back 7,429 years in Ireland and 6,939 years in England. Comparison of radiocarbon and dendrochronological ages supports the consistency of these two independent dendrochronological sequences. Another fully anchored chronology that extends back 8500 years exists for the bristlecone pine in the Southwest US (White Mountains of California). [1] https://en.wikipedia.org/wiki/Dendrochronology#Growth_rings https://en.wikipedia.org/wiki/Dendrochronology#Growth_rings (the final paragraph of this section)
  - rl3 8y ago
    >You don't need a single tree across the entire timespan you want to look at. Yeah, I was thinking more in terms of scarcity being an issue for samples that existed during particularly ancient periods in question. However, it seems the samples need not be living nor complete, and we've quite the extensive archive of dead wood dating further back than I could have imagined.
  - lawlessone 8y ago
    does this mean they have samples of tree for every year between now and those nearly 12,460 years into the past?
- shagie 8y ago
  While the oldest living trees are there, its not living trees that are being dated. If you find a timber used in the construction of the pyramid, you can then match its tree rings up with another set of tree rings that overlap, and so on back to the present age. In theory. See https://www.crowcanyon.org/index.php/dendrochronology https://www.crowcanyon.org/index.php/dendrochronology The challenge is there are gaps and spots where it doesn't quite match up. A bad few years and it throws the tree rings off. However, if you can pinpoint some reference event that spans the globe, you can line the samples back up again. This is known as cross dating ( http://www.ltrr.arizona.edu/lorim/basic.html http://www.ltrr.arizona.edu/lorim/basic.html ) - it doesn't need to have a living tree. Radiocarbon dating will never be precise (being able to pin down a specific year) because of the probabilistic nature of decay and the errors on that are on the sample. Carbon dating only gives a one sigma. Something that is 3500 BP (before present) can have a +/- 60 year error on it. Give https://en.wikipedia.org/wiki/Calculation_of_radiocarbon_dates https://en.wikipedia.org/wiki/Calculation_of_radiocarbon_dat... a read.
  - rl3 8y ago
    That's incredibly interesting, thanks. >It doesn't need to have a living tree. Faulty assumption on my part. Obviously one can date dead wood just the same, I just assumed that non-living samples from ancient eras would be harder to come by or of lower quality having been deconstructed. While it seems that there's some truth to that, it couldn't be more wrong from a composite point of view.
  - tabs_masterrace 8y ago
    That's very cool, could be a interesting problem for using machine learning. Train it with all the pictures of tree rings with known age, and then see if it can reliably guess the age of something it hasn't seen.
    - willvarfar 8y ago
      Its much more efficiently solved with the naive 'represent the distance between each adjacent ring as a number' and slide the array of numbers representing the sample along the known line and for each possible offset, calculate the error. Then you're left with some shortlist of candidate dates and their probabilities. It reminds me of the algorithms for locating reads on the genome.

51 points by curtis 8y ago

rl3 8y ago

>... they’ll be able to piece together more precise time stamps for history’s uncertainties: the construction of Egypt’s Great Pyramid of Giza, the collapse of the Mayan civilization, and maybe even the arrival of the Vikings in the Americas. That should require some really old trees, no? Wikipedia puts the The Great Pyramid of Giza for example at 2580–2560 BC. That's about 4600 years ago. https://en.m.wikipedia.org/wiki/List_of_oldest_trees https://en.m.wikipedia.org/wiki/List_of_oldest_trees According to that, there's only three known trees on the planet that were alive at the time. Of course, maybe I'm misunderstanding; perhaps it's the case that by accounting for the past few thousand years of solar events, carbon dating will become far more accurate even for periods in which no tree alive at the time is available today.

curtis 8y ago
You don't need a single tree across the entire timespan you want to look at. You can assemble a series of overlapping samples from a number of trees that lived at different times during the timespan of interest. From Wikipedia [1]: > A fully anchored and cross-matched chronology for oak and pine in central Europe extends back 12,460 years, and an oak chronology goes back 7,429 years in Ireland and 6,939 years in England. Comparison of radiocarbon and dendrochronological ages supports the consistency of these two independent dendrochronological sequences. Another fully anchored chronology that extends back 8500 years exists for the bristlecone pine in the Southwest US (White Mountains of California). [1] https://en.wikipedia.org/wiki/Dendrochronology#Growth_rings https://en.wikipedia.org/wiki/Dendrochronology#Growth_rings (the final paragraph of this section)
- rl3 8y ago
  >You don't need a single tree across the entire timespan you want to look at. Yeah, I was thinking more in terms of scarcity being an issue for samples that existed during particularly ancient periods in question. However, it seems the samples need not be living nor complete, and we've quite the extensive archive of dead wood dating further back than I could have imagined.
- lawlessone 8y ago
  does this mean they have samples of tree for every year between now and those nearly 12,460 years into the past?
shagie 8y ago
While the oldest living trees are there, its not living trees that are being dated. If you find a timber used in the construction of the pyramid, you can then match its tree rings up with another set of tree rings that overlap, and so on back to the present age. In theory. See https://www.crowcanyon.org/index.php/dendrochronology https://www.crowcanyon.org/index.php/dendrochronology The challenge is there are gaps and spots where it doesn't quite match up. A bad few years and it throws the tree rings off. However, if you can pinpoint some reference event that spans the globe, you can line the samples back up again. This is known as cross dating ( http://www.ltrr.arizona.edu/lorim/basic.html http://www.ltrr.arizona.edu/lorim/basic.html ) - it doesn't need to have a living tree. Radiocarbon dating will never be precise (being able to pin down a specific year) because of the probabilistic nature of decay and the errors on that are on the sample. Carbon dating only gives a one sigma. Something that is 3500 BP (before present) can have a +/- 60 year error on it. Give https://en.wikipedia.org/wiki/Calculation_of_radiocarbon_dates https://en.wikipedia.org/wiki/Calculation_of_radiocarbon_dat... a read.
- rl3 8y ago
  That's incredibly interesting, thanks. >It doesn't need to have a living tree. Faulty assumption on my part. Obviously one can date dead wood just the same, I just assumed that non-living samples from ancient eras would be harder to come by or of lower quality having been deconstructed. While it seems that there's some truth to that, it couldn't be more wrong from a composite point of view.
- tabs_masterrace 8y ago
  That's very cool, could be a interesting problem for using machine learning. Train it with all the pictures of tree rings with known age, and then see if it can reliably guess the age of something it hasn't seen.
  - willvarfar 8y ago
    Its much more efficiently solved with the naive 'represent the distance between each adjacent ring as a number' and slide the array of numbers representing the sample along the known line and for each possible offset, calculate the error. Then you're left with some shortlist of candidate dates and their probabilities. It reminds me of the algorithms for locating reads on the genome.