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Lemur
04-23-2007, 07:31
Every 62 millions years or so the Earth seems to experience a massive die-off. This has been known for about twenty years or so, and I've read all sorts of oddball theories for the timetable. I read an entire book about the "Nemesis" proposal, which suggested that an undiscovered planet on a broad elliptical orbit must be jostling asteroids into hitting Earth every 62 million or so.

Anyway, there's a new and interesting (http://news.nationalgeographic.com/news/2007/04/070420-extinctions.html) theory being bandied about. Just thought I'd share.

And for Adrian II, I just want to point out that the new theory shows a shocking anti-cosmic-radiation bias.

Ancient Mass Extinctions Caused by Cosmic Radiation, Scientists Say

Scott Norris for National Geographic News
April 20, 2007

Cosmic rays produced at the edge of our galaxy have devastated life on Earth every 62 million years, researchers say.

The finding suggests that biodiversity has been strongly influenced by the motion of the solar system through the Milky Way and of the galaxy's movement through intergalactic space.

Mikhail Medvedev and Adrian Melott, both of the University of Kansas, presented their new theory at a meeting of the American Physical Society earlier this month.

The theory offers the first explanation for a mysterious pattern previously noted in the fossil record.

"There are 62-million-year ups and downs in the number of marine animals over the last 550 million years," Melott said.

Until now, however, even the scientists who first discovered the cyclical pattern had not been able to explain it. (Read related story: "Mystery Undersea Extinction Cycle Discovered" [March 9, 2005].)

A number of possible explanations had been considered—including volcanic activity, comet impacts, and changes in sea level—but none could account for the phenomenon's regularity.

The Kansas researchers discovered that high rates of extinction in the cycle coincide almost perfectly with periodic "excursions" of the solar system outside the central plane of the Milky Way galaxy.

"Excursions to galactic north coincide with drops in biodiversity," Melott said.

During these periods, which include some of the largest mass extinctions known from the fossil record, Earth is bombarded with high levels of cosmic radiation.

The radiation may harm biodiversity by causing mutations or by triggering climate change, the researchers said.

Richard Muller is the University of California, Berkeley, physicist who first discovered the 62-million-year cycle with his graduate student Robert Rohde.

"We spent a year searching for possible mechanisms," Muller said.

"I was stunned when I learned that Medvedev and Melott had succeeded where we had failed, and I congratulate them."

Cosmic Cause

Our solar system travels through the disk-shaped Milky Way on a complicated circuit that takes about 225 million years to complete. (See an interactive map of the solar system.)

At regular intervals, the system's wanderings take it up and down through the thin central portion of the disk. The sun reaches its farthest distance from the central plane every 62 million years.

The entire galactic disk, meanwhile, is hurtling through the hot gas that surrounds it at about 125 miles (200 kilometers) a second.

"The movement [of the Milky Way] is not edge-on like a Frisbee," Melott noted. Instead, he said, it is flat, "like a pie in the face."

The new theory suggests that cosmic rays are continually generated in a shock wave produced where the galaxy's "northern" or forward side collides with surrounding gases.

As the solar system rises above the central plane it sticks out like a cherry on top of the flying galactic pie—closer to the source of the cosmic radiation.

"We're exposed to the shock front more when we're emerging on the north side of the galactic disk," Melott said.

At the same time, he explained, the solar system receives less protection from powerful magnetic fields that form a shield from cosmic radiation in the dense, central portion of the galaxy.

Impacts on Earth

Melott said his group applied their model to the largest existing fossil database, which reconfirmed the finding of a 62-million-year fluctuation in diversity.

In a paper recently accepted by Astrophysical Journal, the Kansas researchers discuss various possible mechanisms by which cosmic-ray exposure could result in mass extinctions.

One possibility is that organisms receive harmful doses of radiation from high-energy particles known as muons, which are produced by cosmic rays colliding with Earth's atmosphere.

"Cosmic rays themselves are not really that dangerous," said Medvedev. "They create [charged particles] that propagate down through the atmosphere—especially muons that can go below the sea level."

Changes in the chemistry of the atmosphere, and accompanying depletion of the ozone layer, may also cause increased mutations, he added.

In addition, charged particles produced by cosmic-ray bombardment may cause greatly increased cloud cover, leading to climate change.

The researchers said their model does not explain all major mass extinctions.

For example the demise of the dinosaurs, which is thought to have been caused by an asteroid impact, does not fit the 62-million-year cycle. (Read related story: "'Dinosaur-Killer' Asteroid Crater Imaged for First Time" [March 7, 2003].)

As for what lies ahead, the news is mixed. The solar system has recently passed the galactic mid-plane and is on its way up, Melott said, which could mean greater exposure to radiation.

But, he added, "the next cosmic ray effect is about ten million years ahead of us."

Samurai Waki
04-23-2007, 07:41
Somehow I think that in 10 million years We'll have advanced for beyond the affects of Cosmic Radiation, or Humanity will already be very very very dead. In our case I'd go with the likeliness of the latter rather than the former.

Interesting Article Though.

naut
04-23-2007, 07:41
Interesting.


it is flat, "like a pie in the face."
:inquisitive:

Husar
04-23-2007, 09:49
Do you think that's why all the bees are dieing?:inquisitive:

Hepcat
04-23-2007, 10:31
Somehow I think that in 10 million years We'll have advanced for beyond the affects of Cosmic Radiation, or Humanity will already be very very very dead. In our case I'd go with the likeliness of the latter rather than the former.

Interesting Article Though.

Shhhh, don't upset their scare mongering.

Louis VI the Fat
04-23-2007, 11:05
Interesting.

But correlation does not equal causation. There needs to be a sound explanation of just how these two cycles are connected. Even assuming both cycles are correct. Their explanation doesn't sound very rock-solid yet:
'During these periods, which include some of the largest mass extinctions known from the fossil record, Earth is bombarded with high levels of cosmic radiation. The radiation may harm biodiversity by causing mutations or by triggering climate change, the researchers said.'

Also, there are two identified cycles of mass extinctions, one of which doesn't correspond with the cherry on top of the pie pattern. There's a 62 and a 140 million year pattern of mass extinction.

Extincion cycles. (http://news.nationalgeographic.com/news/2005/03/0309_050309_extinctions_2.html)

As an aside, I read the last paragraph as anti-scaremongering.

HoreTore
04-23-2007, 11:39
There is no doubt in my mind that this is caused by Co2 emissions. We have to drive electrical cars, or this will happen!

I'm pretty sure Saddam had something to do with it too...

JR-
04-23-2007, 12:29
interesting articles, cheers.

Don Corleone
04-23-2007, 14:09
There is no doubt in my mind that this is caused by Co2 emissions. We have to drive electrical cars, or this will happen!

I'm pretty sure Saddam had something to do with it too...

And we must only use one square of toilet paper per visit, from now on...

Can you spare another square? (http://www.foxnews.com/story/0,2933,267783,00.html)

lars573
04-23-2007, 15:25
I have a much better explaination.

https://upload.wikimedia.org/wikipedia/en/2/25/Galactus_close_up.jpg
Galactus! :hide:

KafirChobee
04-23-2007, 18:35
Discovery Channel has a series on the various eras of life and their extinctions. Quite amazing series really (based on fossils and radiation dating, or 'created by god to fool us'); spiders as big as small ponies, centipedes that could raise up to the height of a man, and such - then gone. Five or six times life has come near extinction, only for new forms of life to appear and evolve - then gone.

Still, it is an interesting theory. But, isn't Earth the center of the universe - ergo our galaxy? Gah, someone inform the Pope - be careful though, remember what happened to the last guys.

Lemur
04-23-2007, 21:14
Still, it is an interesting theory. But, isn't Earth the center of the universe - ergo our galaxy?
It would be profoundly bad news for us if we were anywhere near the galactic core. For starters, there's the massive black hole (http://space.newscientist.com/article/dn11157). Then there are the supermassive star clusters (http://www.universetoday.com/am/publish/fountain_youth_core.html). All of this adds up to more gamma radiation than you would ever need to kill all life on earth. No, if there are things that live in the galactic core, it's safe to say that they are profoundly different from us.

We live in a sedate arm of the milky way, a galactic sleepy suburb. You are here:

https://img.photobucket.com/albums/v489/Lemurmania/060227_milkywaymap_bcol_10a.jpg

KafirChobee
04-23-2007, 21:23
EEEEEEEEK! I hate when my sarcasm is misread, or not. But, thx Lemur.

OK, so the outer rim is the center of the universe. J/K

Gawain of Orkeny
04-23-2007, 21:27
Wow looking at it now I never realized the universe was flat :laugh4:

Tuuvi
04-24-2007, 00:39
And we must only use one square of toilet paper per visit, from now on...

Can you spare another square? (http://www.foxnews.com/story/0,2933,267783,00.html)
Yay! I can stop global warming by only using one square! rrrrrrrriiiiiiiiippppppppppp

TevashSzat
04-24-2007, 00:45
Lemure, well you know that some people have theorized that you could travel through time if you can survive passage through a black whole so if earth happens to be near there anytime soon which is unlikely, maybe we can finally see if time travel is possible or.....everyone dies through a very humorous method of spaghettification where the gravity difference between your head and foot is so great that you get streched into a ever longer and thinner thread until you die.

AntiochusIII
04-24-2007, 08:03
Wow looking at it now I never realized the universe was flat :laugh4:Nice one. :laugh4:

The Bible is right after all. Frickin' short-sighted liberals don't know how to read a holy book.

some people have theorized that you could travel through timeThing is, though, what does it mean to "travel through time?" I mean, did you just somehow reverse everything in the universe, with planets and galaxies and all the spaceships moving backwards exactly in reverse from what happened before, and then come out on the other side looking at the real past? It's sort of not really that plausible when you really think about it.