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"South side of Milky Way may protect us from cosmic rays and mass extinctions"
As the Earth’s solar system travels around the center of the Milky Way galaxy, it also wobbles up and down from the galaxy’s disc. U.S. scientists found that these swings take about 62 million years to complete—thus, may expose the Earth to higher doses of dangerous cosmic ray that may also cause mass extinctions. "
Mass extinction comes every 62 million years, UC physicists discover[/url]
With surprising and mysterious regularity, life on Earth has flourished and vanished in cycles of mass extinction every 62 million years,
dinosaurs and millions of other life forms went extinct about 65 million years ago.
Seven out of 10 biologists believe the world is now in the midst of the fastest mass extinction of living things in the 4.5 billion-year history of the planet, according to a poll conducted by the American Museum of Natural History and the Louis Harris survey research firm.
That makes it faster even than the crash which occurred when the dinosaurs died some 65 million years ago.
Remember the dinosaurs? Kings of the hill for 150 million years, then phttt, gone, poster animals of mass extinction. There have actually been five mass extinctions in the Earth's past — and we're well on our way to number six, says Peter Raven, an expert in plant conservation.
The world's species face an unprecedented crisis. The rate at which they are being lost is alarming, even when compared with the extinction episode of 70 million years ago when the dinosaurs disappeared. No-one knows exactly what the current extinction rate is, but recent calculations by leading scientists put it at between 1,000 and 10,000 times greater than it would naturally be.
Is everything seeming to slowly come together? Why is there a 65 million year extinction cycle? Why is this being kept so quiet? Is this a sign of 2012, and hard times ahead? What are the thoughts on all this?
ok...above I would argue that if there is a mass extinction every 62 to 70 million years, (some believe the earth is only about 7,000 years old +/-)
then, how could dinasaurs thrive for 150 million years?
they would have been extinct 2 or 3 times.
Also, given the approximations of this "theory", we could be extinct between tommorrow and anothe 8 or so million years.
I guess it could happen in 2012. If it's even 100 years later, I'm buying an old Rush album.
With a 3-million year uncertainty in the calculations, that 64 million year cycle matches well enough with the 62 million year cycle of extinctions. The match resonates with Richard Muller, who says of the KU team: “They succeeded where I failed in coming up with a possible explanation for the effect that we observed.” And if they’re right, we have time to prepare for the next major event, since the Solar System has just passed the mid-plane of the galaxy. The next peak occurs in ten to twelve million years, assuming the KU theorists are onto something.
The extinction event that cries out for explanation here is the most recent, the Cretaceous/Tertiary dinosaur extinction that dates back some 65 million years. It’s exceptional in this context because it occurred within two million years of the Solar System’s mid-plane galactic crossing.
And here's the bad news. According to their calculations, the Solar System will be passing through the galactic plane in the near future, and should see an increased risk of impact.
The Solar System moves up and down as it orbits the galactic core (see image at left). Mikhail Medvedev and Adrian Melott, taking that motion into account, factor in the motion of the Milky Way itself, hypothesizing that its leading, north side generates a shock wave that exposes the Earth to high-energy radiation every 64 million years or so. Here’s Melott on the matter:
“I did notice that not only did these time scales appear to be almost the same, but the drops in biodiversity coincide with the times when the sun is on the north side of the galactic disc. I already knew the north side of the galactic disc was the direction toward which the galaxy is falling.”
Originally posted by CHA0S
I actually had it wrong to start with, I thought one half a cycle took 62 million years, so we would pass through the galactic belt every 62 million years, but I see now that it's the entire up down cycle. This actually makes things a whole lot worse, as it isn't the passing through the galactic belt that we should be worried about...
I actually think, that on one side of the galactic belt, there is something that makes it hard for life to survive...not quite sure what...scientists say that when we go through the galactic belt, there are large amounts of radiation coming from the "shock-waves" that come from the movement of our galaxy, just like the bow shock caused by our solar systems movement through the galaxy.
Astronomers have known for a long time that, in its revolution around the central mass of our galaxy, the Solar System performs such an up-and-down motion quite regularly, like a horse on a merry-go-round. Material lying mostly near the galactic plane tugs with its gravitational force on objects only loosely bound to the Solar System, like the distant comets that occupy a vast halo far beyond the orbit of Pluto. Many of these shaken comets then rain down in a shower toward the Sun, much as ripe apples drop from a tall tree during a windstorm. Our Earth intercepts some of the infalling comets. The biggest gravitational disturbances of the outer comet halo are believed to be made by close encounters with very massive objects, like the huge clouds of gas and dust that lie between the stars.
To predict the length of time between the Solar System's crossings of the galactic plane, astronomers have had to gauge the up-and-down motion statistically, using the numbers and the velocities of many sample stars distributed above and below the plane. The mathematical analysis then yields as a final result both the period of the up-and-down motion and the space density of matter in the flat galactic disk. In the same way that a pendulum swings much faster on Earth than in a low-gravity environment, such as an Earth-orbiting spacecraft, the surprisingly large space density found in the galactic disk gives the Solar System an unexpectedly short up-and-down period of 30 to 35 million years. This new measurement agrees uncannily well with the known impact cratering period on Earth.