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Space Science

Galactic Origin For 62M-Year Extinction Cycle? 221

Posted by kdawson from the turn-us-over-we're-done-on-this-side dept.
Hugh Pickens writes "Cosmologist Adrian Mellott has an article in Seed Magazine discussing his search for the mechanism behind the mass extinctions in earth's history that seem to occur with a period of about 62 million years. Scientists have identified nearly 20 mass extinctions throughout the fossil record, including the end-Permian event about 250 million years ago that killed off about 95 percent of life on Earth. Mellott notes that as our solar system orbits the Milky Way's center, it oscillates through the galactic plane with a period of around 65 million years. 'The space between galaxies is not empty. It's actually full of rarefied hot gas,' says Mellott. 'As our galaxy falls into the Local Supercluster, it should disturb this gas and create a shock wave, like the bow shock of a jet plane,' generating cascades of high-energy subatomic particles and radiation called 'cosmic rays.' These effects could cause enhanced cloud formation and depletion of the ozone layer, killing off many small organisms at the base of the food chain and potentially leading to a population crash. So where is the earth now in the 62-million year extinction cycle? '[W]e are on the downside of biodiversity, a few million years from hitting bottom,' writes Mellott."
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Galactic Origin For 62M-Year Extinction Cycle? More

Galactic Origin For 62M-Year Extinction Cycle?

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  • I read about it in books which must have been published 30 years ago, though I think the theory than was than the gravitational field of passing stars was changing the orbit of comets in the Oort cloud and causing comet impacts.

    • Re:Not a new idea (Score:5, Informative)

      by Cyberax ( 705495 ) on Tuesday June 30, 2009 @05:19AM (#28525967)

      It's unlikely. Another star (the size of our Sun) needs to pass about 2 light-years near the Sun to significantly disturb the Oort cloud. And Sun-like starts are not that common.

      However, Sun's gravitational field is so weak in the Oort cloud that even _Galactic tides_ can eject objects from it. Few years ago I helped my friend to write a computer simulation of this for his thesis.

      • Re: (Score:3, Informative)

        by Anonymous Coward

        Unlikely? With, *currently*,
        - Alpha Centauri [wikipedia.org] A+B massing 1.100 + 0.907 solar masses 4.365 ly away, and
        - Sirius [wikipedia.org] A+B massing 2.02 + 0.978 solar masses 8.6 ly away,
        I don't see what's so unlikely about having stars the size of our Sun passing within 2 light-years of the Sun once every 62 My.

      • "Sun-like stars (sic) are not that common."

        Isn't the Sun a run-of-the-mill main sequence star? I thought it typified "common"?

        • Re: (Score:2)

          by Cyberax ( 705495 )

          Sun is more massive than an average star.

          In fact, our Sun is more massive than 90% of stars (I might misremember this number, but it should be pretty close).

    • Re:Not a new idea (Score:4, Interesting)

      by Jaysyn ( 203771 ) on Tuesday June 30, 2009 @06:53AM (#28526425) Homepage Journal

      Niven & Pournelle's "Lucifer's Hammer" started out with a nice description of this happening.

    • Re: (Score:3, Interesting)

      by ErkDemon ( 1202789 )
      see also:

    • Re: (Score:2, Informative)

      by mdwh2 ( 535323 )

      though I think the theory than was than the gravitational field of passing stars was changing the orbit of comets in the Oort cloud and causing comet impacts.

      So in other words, it is a new idea, as the one you read about was a different idea.

    • Re: (Score:3, Insightful)

      by Daniel Dvorkin ( 106857 ) *

      I read about it in books which must have been published 30 years ago, though I think the theory than was than the gravitational field of passing stars was changing the orbit of comets in the Oort cloud and causing comet impacts.

      Which was, as it happens, a completely different idea from the one discussed in TFA.

      Do you have any idea how different the scales involved are -- the movements of a few local stars in the scenario you're discussing, vs. the movements of galaxies and clusters of galaxies in this case?

  • Not news (Score:3, Informative)

    by BigBadBus ( 653823 ) on Tuesday June 30, 2009 @04:29AM (#28525761) Homepage
    BBC documentary series Horizon, c.late 1980s

    • Remember how many people on the planet think that just *believing* something is ok ("I believe in a god", "I blieve there is no global warming" etc etc) - it will take 5 million years to get everybody to accept this and start working on a solution!

  • Clouds? (Score:5, Informative)

    by TapeCutter ( 624760 ) * on Tuesday June 30, 2009 @04:30AM (#28525765) Journal
    Mabye cosmic rays effect the ozone layer, I don't really know. However claiming that CR's increase cloud cover is stretching the science well beyond what is known [slashdot.org].

    • Re:Clouds? (Score:5, Interesting)

      by e2ka ( 708498 ) on Tuesday June 30, 2009 @07:08AM (#28526507) Homepage

      This [web.cern.ch] should help our understanding.

    • Re:Clouds? (Score:5, Informative)

      by Burnhard ( 1031106 ) on Tuesday June 30, 2009 @07:25AM (#28526621)

      Mabye cosmic rays effect the ozone layer, I don't really know.

      A recent paper shows that this may indeed by the case [uwaterloo.ca]

      However claiming that CR's increase cloud cover is stretching the science well beyond what is known.

      Given that Svensmark's team has been granted an experiment slot at CERN [web.cern.ch], at least many of those in the Physics community believe it's a plausible hypothesis. There is research out there demonstrating some causal link between cloud cover and Cosmic Rays. [harvard.edu] Science is all about reaching beyond what is known. It would be pretty a pointless exercise otherwise.

      • Thanks for the informative update. I was unaware anyone had found evidence of an 11yr cycle, that has been a major crticisim of the idea. Not sure why you didn't post this when we last "debated" the idea. ;)

        • Re:Clouds? (Score:4, Informative)

          by Burnhard ( 1031106 ) on Tuesday June 30, 2009 @08:00AM (#28526925)

          Not sure why you didn't post this when we last "debated" the idea. ;)

          All such theories should be described as tentative, in the absence of solid physical evidence (i.e. not just correlation). The CERN experiment will at least show what and how cloud condensation nuclei can be generated by Cosmic Rays. This may, or may not, be the start of a paradigm shift in Climate Science. We will wait and see.

          • Yep all science is tenative and it's models are constantly improving. As you probaly know the IPCC rate clouds as having a low level of scientific understanding, regardless of the outcome getting a better handle on the CR idea will assist in modeling cloud formation [earthsimulator.org.uk]

          • Re: (Score:3)

            by Kismet ( 13199 )

            How about calling them hypotheses?

            Let's reserve "theory" for something that actually has solid evidence.

            • Re:Clouds? (Score:5, Insightful)

              by jc42 ( 318812 ) on Tuesday June 30, 2009 @10:39AM (#28529159) Homepage Journal

              How about calling them hypotheses?
              Let's reserve "theory" for something that actually has solid evidence.

              That would go over well in a scientific forum. OTOH, in the mass media and the general population, "theory" is used the same way that scientists use "hypothesis", for a guess that's consistent with known data but hasn't been tested.

              So the question is: Is slashdot a scientific or a general-reader forum? The best answer is "both". There are lots of techie geeks here; there are lots of non-techie readers with an interest in tech stuff. So we get what you'd expect: Different people use the terminology differently, and most of them can't be bothered to make their definitions clear.

              I get as annoyed as others here at the frequent blatant disregard for the proper scientific terminology. But I remind myself that this isn't really a scientific forum; it's a general-reader forum with an emphasis on techological issues. So getting our terminological act together here is probably hopeless. A large fraction of the readers don't understand such issues. And a small fraction are actively opposed to correct terminology. All this is quite normal for a mixed-level forum such as this. And we need such forums to get better information out to the public than the mass media can provide.

              Still, it probably doesn't hurt to occasionally point out the technical definition of a term, for the benefit of non-tech readers who are amenable to such details. In this case, we could just point out that in scientific circles, "theory" refers to a hypothesis that has been fairly thoroughly tested, has passed the tests, and is generally accepted as the best explanation we have at present. Something that explains all known data but hasn't been tested much isn't a "theory"; it's a "hypothesis".

              We have good theories of cloud formation in low-level weather phenomena. For clouds at higher altitudes (>10 or 20 km), we mostly have hypotheses. People have done a lot of mathematical modelling, which is interesting but doesn't qualify as scientific testing, so the results aren't proper (scientific) theories yet. But to the mass media, they are theories, since the media is using a different dictionary.

    • Ironic considering cosmic rays were discovered by the use of Wilson cloud chambers [wikipedia.org].

  • Its also possible... (Score:4, Funny)

    by bmgoau ( 801508 ) on Tuesday June 30, 2009 @04:41AM (#28525817) Homepage

    Its also possible that my opening of a coke can will unsettle the quantum state of the water molecules vaporized in the air consequentially causing a pony to spontaneously appear. But as much as i wish it to be true, it aint going to happen (at least not for a really long time).

    The whole point of the 65 million year cycle was not only the extinctions, but also the discover of elements in the ground only found as a result of asteroid impacts. Tha'ts why researches spend to much time trying to find a large mass that could disturb the Kuiper belt.

  • Brain full? (Score:4, Insightful)

    by clickclickdrone ( 964164 ) on Tuesday June 30, 2009 @05:08AM (#28525921)
    As others have noticed, this is hardly new. I'm starting to think we just have too much knowledge these days. I've lost count of the number of 'discoveries' that are already known, both in IT and the wider areas of science and beyond. It's effectively impossible for people to fully grasp the entire sum of knowledge in their field with the result we're starting to spend time 'reinventing the wheel' to a depressing level.

    • I'm starting to think we just have too much knowledge these days.

      Certainly too much data, perhaps too much knowledge, definitely too little insight.

      Isn't it the same problem popping up in the IP arena? You know, patents and such.

    • Re:Brain full? (Score:5, Funny)

      by feepness ( 543479 ) on Tuesday June 30, 2009 @06:10AM (#28526177)

      I'm starting to think we just have too much knowledge these days. I've lost count of the number of 'discoveries' that are already known, both in IT and the wider areas of science and beyond.

      Sorry, somebody already thought of that.

      Probably the Simpson's.

    • Re: (Score:3, Insightful)

      by Kjella ( 173770 )

      People have always been reinventing the wheel, that is when we haven't had dark ages and lost the wheel in the first place. It just shows the importance of putting knowledge in a context. By all means I'm not saying wikipedia is perfect in content, but the basic idea of hyperlinking up documents to related concepts makes it 1000% user-friendlier than the dead tree encyclopedias I grew up with.

      We do have a few books like that too, trying to give a bird's eye view of a topic. I remember using one of those in

    • Re: (Score:2, Interesting)

      by kjllmn ( 1337665 )

      So the next thing would be an area of knowledge which deals with precisely this. Not philosophically, but more in terms of optimizing knowledge acquisition and management - or something like that. Or, speaking of reinventing the wheel, perhaps there already is?

    • I've never read anything about gases and radiation causing the extinction cycles, I'd be curious to know where everyone has seen this before. What I have heard is that the same undulating motion of our solar system through the "denser" galactic plane brings us into contact with more asteroids.

    • Re: (Score:2)

      by delt0r ( 999393 )
      this is /.

      What where you expecting? Field expert reviewed news stories?

  • Comment removed (Score:4, Funny)

    by account_deleted ( 4530225 ) on Tuesday June 30, 2009 @05:11AM (#28525929)
    Comment removed based on user account deletion

  • From a Galactic Origin (Score:5, Funny)

    by Toutatis ( 652446 ) on Tuesday June 30, 2009 @05:44AM (#28526059)
    All this has happened before and will happen again.

  • Examine It For Yourself (Score:5, Insightful)

    by TerribleNews ( 1195393 ) on Tuesday June 30, 2009 @05:52AM (#28526089)

    Take a look at wikipedia's graph of extinctions [wikipedia.org] from the article about the history of life [wikipedia.org]. I haven't done any actual signal analysis on this data.

    I would buy that there is a bit more energy in the per 62 million years signal, but I wouldn't call it clockwork-like regularity. If they came up with a p-value of 0.01, I'd say that there must be something happening, but I would expect a little more consistency out of a big cosmic event like the one they're describing.

    • Re: (Score:3, Insightful)

      by Late Adopter ( 1492849 )
      I don't know that I'd expect that much consistency. The actual effects are indirect, cosmic ray flux leads to climate change leads to decreased biodiversity leads to ecological collapse. I would expect large amounts of variation in the timing in any one of those steps, just due to their chaotic nature.

      So, statistically speaking, the case loosens up quite a bit. I would need to see more evidence of the mechanisms to be persuaded one way or the other.

  • The reapers are coming! (Score:4, Funny)

    by Redlite ( 1588373 ) on Tuesday June 30, 2009 @06:21AM (#28526249)
    Shut down the mass relays!

  • can't wait to see it in action the next michael bay movie

  • '[W]e are on the downside of biodiversity, a few million years from hitting bottom,'

    Ha! With good ol' human ingenuity, I'm sure we can hit bottom a lot faster than that!

  • Adrian Melott (Score:2, Informative)

    by Anonymous Coward

    Not to be anal, but his name is spelled Adrian Melott , with one L. This spelling will help if you google his name.

    I attend the University of Kansas (where he teaches), and know this guy is associated with some pretty far out ideas.

  • Sure, but where's the silver surfer come to warn of Galactus? Maybe Jack Chick was right all along [yourmomsbasement.com]

  • Guess that means no Duke Nukem Forever this time around. Hopefully they'll time-capsule the source, at least.

  • So when the stars are right, the living creatures of Earth all die. Sounds like it's nearly time for Cthulhu to rise again!

  • Interesting idea. But what about the Iridium anomaly [wikipedia.org] then?

  • This hypothesis is old and was used as part of the story "Calculating God" written by Robert J. Sawyer in 2000. It's an excellent book which I can heartily recommend. You might also be familiar with his work through the "Hominids" alternate earth trilogy.

  • Ohai-Thanks for the mindnumbing oversimplification (Score:3, Insightful)

    by Phizzle ( 1109923 ) on Tuesday June 30, 2009 @10:28AM (#28528995) Homepage
    Usupported by actual data. If you look at the Phanerozoic biodiversity data, it doesnt validate the 62 million years extinction cycle theory. You cant just take a small subset, selectively ignore data points that don't fit into your theory and preach the end of the world. Admittedly that does seem to sell books.

  • What?! I'm outraged!

    Humans are responsible for all bad things! Humans are not part of nature! That's what the media tells me. How dare something else be responsible! How dare our actions not be as important as we think they are!

  • Not fault of galactic arms (Score:3, Informative)

    by Nyrath the nearly wi ( 517243 ) on Tuesday June 30, 2009 @11:04AM (#28529623) Homepage

    Spiral Arms Did Not Cause Climate Change on Earth

    A new map of the Milky Way galaxy proves that the sun's motion through the spiral arms could not have caused a well-known climate-change cycle.

    http://www.technologyreview.com/blog/arxiv/23763/ [technologyreview.com]

  • 20 Million Years Late... (Score:4, Informative)

    by DynaSoar ( 714234 ) on Tuesday June 30, 2009 @12:40PM (#28531675) Journal

    ... and a dollar short.

    This is twice in a week that someone has made assertions about mass extinctions, and both times their (different) numbers don't match the commonly accepted numbers http://en.wikipedia.org/wiki/Milky_way [wikipedia.org] . (No, the Big W is not necessarily authoritative, but the sources referenced are.)

    The solar system orbits the galactic center in 220 Myr. It oscillates through the galactic plane 2.7 times per orbit. That's a period of 81.5 Myr, and each crossing at half-period being 40.75 Myr. I doubt anyone would consider that an acceptable error margin.

    Furthermore, the matter density in the galactic plane oscillates with a period 1/2 that of the galactic rotation, expanding out from the center in waves (density wave 25 Myr; spiral structure 50 Myr). Passing through the plane would have little effect unless these two coincide.

  • Only One Question Matters (Score:3, Insightful)

    by Nom du Keyboard ( 633989 ) on Tuesday June 30, 2009 @01:58PM (#28532985)
    Only one question matters: when is the next one due?

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