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Have Milky Way's Cycles Influenced Earth's Biological History?

113055588_ff2318338b_2Horoscope enthusiasts will be happy to hear that a grand cosmic force does indeed seem to be responsible for controlling the direction of all life on Earth. However, this grand cosmic cycle has more to do with extinction than finding a tall, handsome stranger.

Early last year, research revealed that the rise and fall of species on Earth seems to be driven by the undulating motions of our solar system as it travels through the Milky Way. Some scientists believe that this cosmic force may offer the answer to some of the biggest questions in our Earth’s biological history.

The University of California, Berkeley found that marine fossil records show that biodiversity increases and decreases based on a 62-million-year cycle. At least two of the Earth's great mass extinctions-the Permian extinction 250 million years ago and the Ordovician extinction about 450 million years ago-correspond with peaks of this cycle, which can't be explained by evolutionary theory.

Elsewhere, a team of researchers at the University of Kansas came up with an out-of-this-world explanation for the phenomenon. Their idea hinges upon the fact that stars move through space and sometimes rush headlong through galaxies, or approach closely enough to cause a brief cosmic tryst.

Our own star moves toward and away from the Milky Way's center, and also up and down through the galactic plane. One complete up-and-down cycle takes 64 million years- suspiciously close to the Earth's biodiversity cycle.

Once the researchers independently confirmed the biodiversity cycle, they then proposed a novel mechanism whereby which the Sun's galactic travels is causing it.

It’s no secret that the Milky Way is being gravitationally pulled toward a massive cluster of galaxies, called the Virgo Cluster, which is located about 50 million light years away. Adrian Melott of the University of Kansas and his colleague Mikhail Medvedev, speculate that as the Milky Way rushes towards the Virgo Cluster, it generates a so-called bow shock in front of it that is similar to the shock wave created by a supersonic jet.

"Our solar system has a shock wave around it, and it produces a good quantity of the cosmic rays that hit the Earth. Why shouldn't the galaxy have a shock wave, too?" Melott asks.

The galactic bow shock is only present on the north side of the Milky Way's galactic plane, because that is the side facing the Virgo Cluster as it moves through space, and it would cause superheated gas and cosmic rays to stream behind it, the researchers say. Normally, our galaxy's magnetic field shields our solar system from this "galactic wind." But every 64 million years, the solar system's cyclical travels take it above the galactic plane.

"When we emerge out of the disk, we have less protection, so we become exposed to many more cosmic rays," Melott has said.

The boost in cosmic-ray exposure may have a direct effect on Earth's organisms, according to paleontologist Bruce Lieberman. The radiation would lead to higher rates of genetic mutations in organisms or interfere with their ability to repair DNA damage. In this way, the process could lead to new species while killing off others.

Cosmic rays are also associated with increased cloud cover, which could cool the planet by blocking out more of the Sun's rays. They also interact with molecules in the atmosphere to create nitrogen oxide, a gas that eats away at our planet's ozone layer, which protects us from the Sun's harmful ultraviolet rays.

Richard Muller, one of the UC Berkeley physicists who co-discovered the cycle, said Melott and his colleagues have come up with a plausible galactic explanation for the biodiversity cycle.

If future studies confirm the galaxy-biodiversity link, it would force scientists to broaden their ideas about what can influence life on Earth. "Maybe it's not just the climate and the tectonic events on Earth," Lieberman said. "Maybe we have to start thinking more about the extraterrestrial environment as well."

Posted by Rebecca Sato.

Related Galaxy posts:

Mysterious Outburst from the Edge of the Milky Way
Cataclysmic Clockwork -Our Solar System's Deadly Orbit Through the Milky Way

GAIA -Mapping the Evolution of the Milky Way



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Wow, you do bring up some very valid points here!


Article: "Our solar system has a shock wave around it, and it produces a good quantity of the cosmic rays that hit the Earth. Why shouldn't the galaxy have a shock wave, too?" Melott asks.

I once looked at intergalactic vs. galactic density out of curiosity - my recollections tell me that the answer to this question is:


There are many other bad things that could be synchronous with one lap around the black hole, though.

Does passing through the galactic plane not create noticeable shifts in the strength of gravitational force we feel?

Does this have any effect on the earths crust? (it is rather weak, relatively.)

So could deformations due to alterations of centripetal force cause the kind of flooding and coastline adjustments we've noted in historical past?

daaamnn yooo thats strayt buggin

I know I can proboblly find this some were else but, in correlation to say that north side (the bow) our solar system lies in our galactic orbit currentlly?

Intresting ideas, what makes up for the 2 million year difference though?

Agree with these theories.

Even though we (alltogether) do not have the minimum idea about the intergalactic medium.

Do not understand the notation made above on density and black holes.
Our galaxy has a supermassive black hole in the center and likely also oscillates in its rotation.

Collateral mini or normal (size-mass) black holes are created by giant exploding stars (e.g. 1987A in LMC)....BUT none of this is was available near us...nor was available at the times of the two main ELEs.

The continent movement is however another periodic ELE factor....the next Pangea in 250MY from now or similar age ...will destroy all the living species on this very planet.

Therefore even IF I tend to agree with the oscillation of the solar system up and down the galactic plane (the average of angle of the the galatic plane that also oscillates) as the main factor for the past ELE, the continents movements is not a negligible factor......

Then somebody may also theorize some asteroids hit us of the size of Xiculub or larger....at the time of those ELE.

HENCE We alltogether , DO NOT KNOW what created the 2 large mass extictions said above....but I like better the theory of the galactic plane.

Regards to the galatic plane that is oscillating and to the solar system oscillation above-below the average of the galactic plane.

Do bears shit in woods? Why do you think we go through ice ages every few hundred thousand years, and why do you think all the water on Mars evaporated?

And it's happening to us too and it's only a matter of time, so we better start fixin' it NOW!



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