Slashdot Mirror
Galactic Origin For 62M-Year Extinction Cycle?
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."
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.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
What an incoherent rant. Perhaps you should lay off the vino before posting to slashdot.
you're so f**king right man. this article is f**cking stupid. i get you cause i drank a barrel of wine earlier too. OBVIOUSLY, the gas cloud is orbiting the milky way at 62 million year intervals and we're the ones standing still. IDNTRTFAWIDTBYDE (i don't need to read the f**king article when i'm drunk too because you didn't either)
Its actually the Infinite Improbability Drive in action. Research my ass. Before you ask any more questions, 42.
Real men read Slashdot articles at -1, bottom up.
Which is precisely why Coke kill a pony for every can they make ;)
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.
Which is precisely why Coke kill a pony for every can they make ;)
Ah, the well known Pony Preservation Principle.
We live, as we dream -- alone....
theory about 20 years ago. However that one suggested the reason for the mass extinctions was because the stars in the galactic plane are much closer together so the likely hood of being in close proximity to a supernova and all the incumbent radiation that entails is much higher. This also explains why occasionally mass extinction skips a beat. Of course the 2 scientists who postulated this theory were promptly laughed at and ridiculed by the scientific community in that very grown up way that scientists do.
Cold fusion anyone?
Build a Man a Fire, and He'll Be Warm for a Day. Set a Man on Fire, and He'll Be Warm for the Rest of His Life.
All this has happened before and will happen again.
Take a look at wikipedia's graph of extinctions from the article about the history of life. 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.
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.
Shut down the mass relays!
I would say encountering a star would definitely fit the description of "hitting the bottom of bioversity"
Why not just put it in your Low Budget HDV Filipino Horror Movie in NYC.
The interval between extinctions is 62 million years only if you accept ~30 millions of year of error margin. The current downfall of biodiversity is really fast compared to the time scale mentioned here. Its most likely reason has two legs, two arms, a big brain and a various set of forest-destroying machines as well as a bad habit of dumping various materials into the ocean.
You're right! It's people that is the problem. Please write your congressman and tell them to expand Cap'n Trade to cover Humans. All that human breathing is producing unacceptable levels of CO2.
We could put a life clock on everyone's hand, and only allow a few people selected by lottery to live past age 35. That should keep the population down enough to save planet Earth!
"Somebody has to do something. It's just incredibly pathetic it has to be us."
--- Jerry Garcia
The sun at this point is well over halfway through its yellow-phase lifetime. Earth only has a few billion more years left to reach whatever culmination it's going to. There's not really enough time to evolve another species to our level from scratch. A mere 95% extinction wouldn't be as bad, but if it's only 60-some-odd million years from now the next sentient species is going to have to make due with dramatically fewer energy reserves left on the planet to bootstrap its civilization.
In short, if you value sentience we're a pretty valuable resource for the solar system.
E pluribus unum
There's not really enough time to evolve another species to our level from scratch.
Well, perhaps not from scratch, but even the most massive of mass extinctions wouldn't destroy all life. There'd be plenty of bacteria, amoebas, and various other "simple" organisms around. Given that the majority of evolutionary time was spent developing these basic organisms, life would start out with a rather large head start as compared with starting from nothing.
A mere 95% extinction wouldn't be as bad, but if it's only 60-some-odd million years from now the next sentient species is going to have to make due with dramatically fewer energy reserves left on the planet to bootstrap its civilization.
Well, not necessarily. Fossil fuels aren't completely nonrenewable - they're just nonrenewable on any sort of human timescale. 60 million years is about the age of the coal and oil we're burning now. If there was a 95% extinction today, then the next sentient species would start out at with about the same amount of fossil fuel reserves that we had.
We all know what to do, but we don't know how to get re-elected once we have done it
Is it really flamebait to say that humans are the most likely cause of biodiversity downfall?
No; it's only considered flamebait in political/religious circles. ;-)
In scientific circles, it's conventional to attribute most of the current extinction event to human activity. Thus, we don't really know when humans first arrived in the Americas, and there are estimates at high as 30,000 years ago for the first. However, it does seem fairly clear that humans were rare on those continents before about 12,000 years ago, when there was a huge increase in the human population. At the same time, large numbers of large animal species went extinct. Some of those would have died out anyway, but the mass extinction is generally attributed to humans. After all, if you introduce a new major predator, you'd expect that the sort of prey it likes (large, meaty critters in this case) would start to disappear.
So the human-caused extinction has long been the default hypothesis. There are other possibilities, but if you want to argue for them, you should have some pretty good evidence, and such evidence doesn't seem to exist. Death at the hands of a new, powerful predator is just too reasonable to be dismissed without evidence, and it quite properly the primary hypothesis when there is evidence of such a predator. And, unlike in political discussions, there is rather little scientific argument about this. Rather, there are lots of scientists looking for evidence wherever they can find it. Other contributing factors have been reported, but so far nothing much that seriously challenges the primary hypothesis.
(Actually, there is a good recent example of the opposite process. Starting about 500 years ago, there was a mass extinction of humans in the Americas. It is common to attribute this to the introduction of a different human subspecies that had better weapons. But we have the evidence, and it shows that weaponry was a minor factor in the extinction, and only in the eastern coastal areas. It turns out that most of the people in the interior died from the diseases that the new humans unknowingly brought along, long before the newcomers reached the interior. Both groups of people attributed the plagues to acts of various gods, since neither had any understanding of microorganisms at the time. It wasn't until the 1800s that "germs" were understood, and the newcomers started using biological warfare in a controlled fashion against the original inhabitants. This produced a second extinction event, but it was much smaller than the one in the 1500s.)
(And it'll be interesting to see whether this gets any "flamebait" mods. There's gotta be at least a few people who'll read it that way. I've already got both "flamebait" and "insightful" for one post; now I'm trying for "flamebait" + ("informative" || "insightful") + "funny". ;-)
Those who do study history are doomed to stand helplessly by while everyone else repeats it.