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New Theory Explains Periodic Mass Extinctions
i_like_spam writes "The theory that the dinosaurs were wiped out by an asteroid impact, the K-T extinction, is well known and supported by fossil and geological evidence. Asteroid impact theory does not apply to the other fluctuations in biodiversity, however, which follow an approximate 62 million-year cycle. As reported in Science, a new theory seems to explain periodic mass extinctions. The new theory found that oscillations in the Sun relative to the plane of the Milky Way correlate with changes in biodiversity on Earth. The researchers suggest that an increase in the exposure of Earth to extragalactic cosmic rays causes mass extinctions. The original paper describing the findings is available online."
The article suggests that this does not explain the K-T event, which is already adequately explained by the asteroid impact theory. This theory explains the cyclical decreases in biodiversity that seem to happen about once every 62 million years. The K-T event is not part of this cyclical pattern.
OK, I've only read the summary (I have a lecture to give half an hour from now to prepare for) but I can see some objections:
* My boss (David Penny, Massey University) argues that the mammals and birds were already outcompeting the dinosaurs at the end of the cretaceous, so the asteroid was at best a coup-de-grace for them.
* The "periodic extinctions" idea has been around for decades, including the possible link to oscillations through the galactic plane.
* Mass extinctions are sudden. The increase in extragalactic cosmic rays exposure would be slow, over millions of years.
* The extragalactic cosmic ray exposure changes should be highly regular. The extinctions are irregular.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
The Pioneer and Voyager probes weren't designed to specifically leave the solar system though, their primary mission was to probe the planets. If we made a probe dedicated to getting really far out of the solar system really fast (with no stops in between Earth and deep space, or indeed at all) then it would get there much faster.
The KT event, for example, had a much larger impact on biodiversity but happened off-cycle, and is pretty clearly the result of a specific meteor strike that we already know about.
Other events may have been volcanic or meteoric or the result of something we didn't know about.
All extinction events being triggered by only one type of external condition was never very likely.
Ben Hocking
Need a professional organizer?
The title of the summary is totally wrong. This has nothing to do with mass extinctions. Its looking at fossil Species and Family counts vs time correlated with Solar motion. The 62 MY cycle barely touches the Mass extinction events.
Better summary title - "Life's Diversity changes with Solar Galactic Orbit". Or something like that.
That's odd. The post-9/11 research into the effects of jet contrails suggested that they have two faint effects: mild warming and mild day/night temperature moderation. But the above quote seems to contradict that.
I am now even more suspicious of the conclusions of the contrail research, coming (as it did) in the middle of the global warming craze. Right now you can't even publish the simple observation that plants will grow usefully faster on a warmer Earth; no, you have to spin it as "OMG poison ivy will get worse!".
I'm ready to go nuclear/solar/wind, and drive an electric car, because I've always hated the power that petronomics gives to the backwards nations... but come on guys, can we at least give both sides a fair hearing?
FATMOUSE + YOU = FATMOUSE
You forgot to mention Christopher Columbus's theory that the earth is round... [...]when the rest of the so called "Intelligent" people of the world said it was flat.
LOL! You still believe that nursery school myth?
NO intelligent person in Columbus's time thought the world was flat -- as it clearly is not to anyone sufficiently observant. Columbus's problem is that he wanted to go to Asia via a western route, and everyone intelligent knew that with a circumference of about 25,000 miles, Eratosthenes having calculated it about 240 BC (as others had since). Hence they "knew" that with the sailing technology of the day, there was no way Columbus could make the voyage.
They were right, too. Had the Americas not been in his way, his expedition would have perished before he got as far as the longitude of Hawaii.
There is some evidence that Columbus may in fact have known that there was some land mass to the west considerably before Asia (the Vikings certainly did, and it is quite possible that fishermen who went as far as the Grand Banks were also aware). Whether from that he decided that Eratosthenes was wrong and the circumference was smaller (possibly influenced by Ptolemy's maps (from Geographica) which underestimated the circumference at about 18,000 miles), or whether he was just arguing that way to get backing for an expedition (with the secret purpose of discovering and exploiting just whatever land mass was there), we have no way of knowing.
That mistake alone discredits the rest of your post as to make it not even worth reading.
-- Alastair
BTW, even though Columbus "discovered" the Americas, it was Juan Sebastian Elcano who proved the world was round by sailing westward (modulo a few detours) until he returned to Spain. Yeah, everyone says it was Magellan, but Magellan died on the expedition in the Philippines, it was Elcano who assumed command at that point and finished the circumnavigation (along with a dozen or so shipmates).
-- Alastair