5 ms·
Sun's galactic journey linked to mass extinctions (2013)
- DrScump 10y agoFull paper, with some illustrations (free): http://saj.matf.bg.ac.rs/187/pdf/043-052.pdf http://saj.matf.bg.ac.rs/187/pdf/043-052.pdf
- yelnatz 10y agoWelp, we're about to enter one of the arms. It's been nice knowing you guys.
- internaut 10y agohttps://news.ycombinator.com/item?id=11905555 https://news.ycombinator.com/item?id=11905555
- JumpCrisscross 10y ago> Summed over the entirety of its orbital path over the last 500 Myr, based on the new weighted symmetrical model, we find that the Sun has spent ∼60% of its time in the spiral arms This is a statistical observation. In any case, do you have a source for your assertion? http://saj.matf.bg.ac.rs/187/pdf/043-052.pdf http://saj.matf.bg.ac.rs/187/pdf/043-052.pdf
- yelnatz 10y agoMy prediction is based on their newly weighted symmetrical model given at figure 2. All previous extinction events are when the sun is in the galaxy arms, and we are currently entering one of them.
- JumpCrisscross 10y agoPardon me. Could you point me to a source showing we are entering one of them?
- yelnatz 10y agohttp://i.imgur.com/u69Qd6Y.png http://i.imgur.com/u69Qd6Y.png Yellow dot is where we are right now, as you can see we are entering one of the black lines. 6 blue dots represent the known mass extinctions, they all lie on black lines. 5 orange dots represent proposed new mass extinction events proposed in the paper.
- basicplus2 10y agonot sure this is new... if I remember correctly our galaxies arms rotate along their length and cross each other every (approx) 140 million years which disturbs our kuiper belt which dislodges numerous items which rain down destruction on earth approx 70 million years later, so Jupiter mops up most but not all.
- mirimir 10y agoThe authors seem to assume that there's a spiral arm pattern that rotates coherently. What's the evidence for that?
- benjoffe 10y agoIt's believed that the spiral arms are quasi-static and that the stars move in and out of these regions of higher density. See: https://en.wikipedia.org/wiki/Density_wave_theory https://en.wikipedia.org/wiki/Density_wave_theory
- mirimir 10y agoYes, that's what I vaguely recalled. But we don't have enough observations to test that hypothesis. I wonder, through, whether alternate-path gravitational lensing could provide enough snapshots of some other galaxy to be useful.
- marcosscriven 10y agoI really don't understand how the solar system can orbit the galaxy faster than the spiral arms and be in accordance with Kepler's 2nd law?
- fivesigma 10y agoSpiral arms aren't static objects, they are a denser region of the galaxy as stars pass through them. There's also a small speed variance between different systems, so on average it all evens out. Then there's dark matter which adds an additional factor to the orbital speed.
- egjerlow 10y agoIt is better to view the spiral arms as 'transient' in the same way you would view a momentary queue in traffic - although the jam itself moves slowly or not at all, the individual cars that make it up move through the jam and eventually exit on the other side.
- marcosscriven 10y agoInteresting: "Measurements in the late 1960s showed that the orbital velocity of stars in spiral galaxies with respect to their distance from the galactic center is indeed higher than expected from Newtonian dynamics but still cannot explain the stability of the spiral structure." https://en.wikipedia.org/wiki/Spiral_galaxy#Origin_of_the_spiral_structure https://en.wikipedia.org/wiki/Spiral_galaxy#Origin_of_the_sp...
- stephengillie 10y agoWasn't the higher than expected orbital velocity among the first evidence of dark matter?
- rusanu 10y agoRubin-Ford effect https://en.wikipedia.org/wiki/Vera_Rubin#Galaxy_rotation_problem_and_Dark_matter https://en.wikipedia.org/wiki/Vera_Rubin#Galaxy_rotation_pro...
- vivekd 10y agoI remember Stephyen Jay Gould wrote an essay caleed the "cosmic dance of Shiva" where he talked about how the fossil record suggests that mass extinction events at regular intervals of 20 something million years. He wrote that since it would be difficult to find a terrestrial explanation for an extinction event at regular intervals, so it made sense to look at factors from outer space. This could be the sort of missling link in Gould's theory. I can't find a non-paywalled version of Goud's article but here is another one talking about mass extinctions at regular intervals http://www.theatlantic.com/science/archive/2015/11/the-next-mass-extinction/413884/ http://www.theatlantic.com/science/archive/2015/11/the-next-...
- DrScump 10y agoHere's a great interview by John Batchelor (free podcast): https://audioboom.com/boos/4073570-mass-extinction-and-the-structure-of-the-milky-way-jonti-horner-m-d-filipovic-e-j-crawford-n-f-h-tothill https://audioboom.com/boos/4073570-mass-extinction-and-the-s...