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."

Comments

Not a new idea

[MichaelSmith]

I read about it in books which must have been published 30 years ago, though I think the theory than was than the gravitational field of passing stars was changing the orbit of comets in the Oort cloud and causing comet impacts.

Re:Not a new idea

[Cyberax]

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.

Re:Not a new idea

[Jaysyn]

Niven & Pournelle's "Lucifer's Hammer" started out with a nice description of this happening.

Re:Not a new idea

[Hognoxious]

It also ended with one.

Re:Not a new idea

[ErkDemon]

see also:

• The Poison Belt (Arthur Conan Doyle, 1913)
• The Black Cloud (Fred Hoyle, 1957)

Re:Not a new idea

[Anonymous Coward]

Unlikely? With, *currently*,
- Alpha Centauri A+B massing 1.100 + 0.907 solar masses 4.365 ly away, and
- Sirius A+B massing 2.02 + 0.978 solar masses 8.6 ly away,
I don't see what's so unlikely about having stars the size of our Sun passing within 2 light-years of the Sun once every 62 My.

Re:Not a new idea

[Ozmodium]

I am surprised that no one mentioned the theory of Nemesis? Oh wait, there was a Slashdot story (http://science.slashdot.org/article.pl?sid=06/01/21/0338234) on it, or at least on the possibility.

According to this site (http://www.bibliotecapleyades.net/ciencia/ciencia_nemesis07.htm) :

"Nemesis' existence was proposed in 1984 by American physicists Daniel Whitmire and Albert Jackson (The University of Southern Louisiana) and also by Richard Muller, Piet Hut & Davis M. in 1984 in order to explain an apparent 26-million year cycle in the occurrence of mass extinctions on Earth, like the one that killed the dinosaurs 65 million years ago, as noted by Raup and Sepkoski."

So, simplified, the other sun rotates in and drags a whole bunch of crap out of the Oort cloud and wipes out (almost) everything. Lather, rinse, repeat.

Re:Not a new idea

[mdwh2]

though I think the theory than was than the gravitational field of passing stars was changing the orbit of comets in the Oort cloud and causing comet impacts.

So in other words, it is a new idea, as the one you read about was a different idea.

Re:Not a new idea

[GodfatherofSoul]

"Sun-like stars (sic) are not that common."

Isn't the Sun a run-of-the-mill main sequence star? I thought it typified "common"?

Re:Not a new idea

[Cyberax]

Sun is more massive than an average star.

In fact, our Sun is more massive than 90% of stars (I might misremember this number, but it should be pretty close).

Re:Not a new idea

[Gilmoure]

Well, sure, if you're counting all the red dwarfs out there. They breed like rats!

Re:Not a new idea

[Daniel Dvorkin]

I read about it in books which must have been published 30 years ago, though I think the theory than was than the gravitational field of passing stars was changing the orbit of comets in the Oort cloud and causing comet impacts.

Which was, as it happens, a completely different idea from the one discussed in TFA.

Do you have any idea how different the scales involved are -- the movements of a few local stars in the scenario you're discussing, vs. the movements of galaxies and clusters of galaxies in this case? Do you have any understanding that comets, planets, stars, and galaxies are not the same thing? Or are astronomical terms just so jumbled up in your head that any idea regarding mass extinctions and the movements of anything beyond Earth's atmosphere just kind of seems the same to you?

I really despise the /. meme that dictates, whenever pretty much any science story is published, that a bunch of posters feel the need to say, "Oh, I heard about that X years ago." Almost always, they're dead wrong, and their wrongness is based on profound and nigh-aggressive ignorance. Everyone, before you post that comment or some variant of it, please think for a moment, okay?

Re:Not a new idea

[Jaysyn]

Thanks. Haven't managed to finish it yet. I hate disaster flicks, disaster books don't fare much better apparently.

Re:Not a new idea

[RockDoctor]

Thanks. Haven't managed to finish it yet. I hate disaster flicks, disaster books don't fare much better apparently.

Lucifer's Hammer is good - worth the investment of effort. I've heard it described as considerably better than "Footfall", from which it was a spin-off ; I'm re-reading Footfall for the first time while I've read Lucifer several times. ("Lucifer" was originally an idea for the alien attack novel which became "Footfall" ; the ETs dropped an asteroid on Earth as a softening-up tactic. Niven and Pournelle decided to split the themes into separate novels.)

Re:Not a new idea

[RockDoctor]

In fact, our Sun is more massive than 90% of stars (I might misremember this number, but it should be pretty close).

If you're looking to improve your estimate by a factor of about 2 at each degree of approximation, that's good enough for a first or second approximation.

The Sun is not an "average" star, but it's nothing unusual on a galactic scale. For a comparison, try counting the number of languages spoken in a household - most households use just one, but in excess of 10% of households would use 2 (the national language plus the family's traditional language) and several percent three languages (national, mum's language, dad's language). You very probably know at least one polyglot household, and it wouldn't be exactly surprising if you yourself came from a polyglot household.

When you're doing statistical analyses of data you have to be quite precise about what you mean by "unusual", expressed in statistical lingo as a "confidence level" (or a minor variant of this). Anything much lower than a confidence level of 15% really isn't giving much more than an indication of which way to direct further investigations - you've got a 1-in-3 chance of getting the same result by chance even if the hypothesis under test is incorrect and the null hypothesis is correct. A 5% confidence level is worth betting small change or the price of a pint of beer on. A 1% confidence level might be worth investing a day or two of salary. A 0.1% confidence level is a career-affecting decision.

YMMV, the cheque is in the post, etc, etc. To a confidence level of 10%.

Re:Not a new idea

[Grayswan]

The red dwarf star Gliese 710 is predicted to come within nearly 1 light-year of the Sun ... about 1.5 million years from now

Re:Not a new idea

[Hognoxious]

It doesn't affect the plot. Don't know if that's more or less of a spoiler. Life is hard.

Not news

[BigBadBus]

BBC documentary series Horizon, c.late 1980s

Clouds?

[TapeCutter]

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.

Re:Clouds?

[Jurily]

http://xkcd.com/326/

Re:Clouds?

[e2ka]

This should help our understanding.

Re:Clouds?

[Burnhard]

Mabye cosmic rays effect the ozone layer, I don't really know.

A recent paper shows that this may indeed by the case

However claiming that CR's increase cloud cover is stretching the science well beyond what is known.

Given that Svensmark's team has been granted an experiment slot at CERN, at least many of those in the Physics community believe it's a plausible hypothesis. There is research out there demonstrating some causal link between cloud cover and Cosmic Rays. Science is all about reaching beyond what is known. It would be pretty a pointless exercise otherwise.

Re:Clouds?

[TapeCutter]

Thanks for the informative update. I was unaware anyone had found evidence of an 11yr cycle, that has been a major crticisim of the idea. Not sure why you didn't post this when we last "debated" the idea. ;)

Re:Clouds?

[Burnhard]

Not sure why you didn't post this when we last "debated" the idea. ;)

All such theories should be described as tentative, in the absence of solid physical evidence (i.e. not just correlation). The CERN experiment will at least show what and how cloud condensation nuclei can be generated by Cosmic Rays. This may, or may not, be the start of a paradigm shift in Climate Science. We will wait and see.

Re:Clouds?

[TapeCutter]

Yep all science is tenative and it's models are constantly improving. As you probaly know the IPCC rate clouds as having a low level of scientific understanding, regardless of the outcome getting a better handle on the CR idea will assist in modeling cloud formation

Re:Clouds?

[rpresser]

Ironic considering cosmic rays were discovered by the use of Wilson cloud chambers.

Re:Clouds?

[Kismet]

How about calling them hypotheses?

Let's reserve "theory" for something that actually has solid evidence.

Re:Clouds?

[jc42]

How about calling them hypotheses?
Let's reserve "theory" for something that actually has solid evidence.

That would go over well in a scientific forum. OTOH, in the mass media and the general population, "theory" is used the same way that scientists use "hypothesis", for a guess that's consistent with known data but hasn't been tested.

So the question is: Is slashdot a scientific or a general-reader forum? The best answer is "both". There are lots of techie geeks here; there are lots of non-techie readers with an interest in tech stuff. So we get what you'd expect: Different people use the terminology differently, and most of them can't be bothered to make their definitions clear.

I get as annoyed as others here at the frequent blatant disregard for the proper scientific terminology. But I remind myself that this isn't really a scientific forum; it's a general-reader forum with an emphasis on techological issues. So getting our terminological act together here is probably hopeless. A large fraction of the readers don't understand such issues. And a small fraction are actively opposed to correct terminology. All this is quite normal for a mixed-level forum such as this. And we need such forums to get better information out to the public than the mass media can provide.

Still, it probably doesn't hurt to occasionally point out the technical definition of a term, for the benefit of non-tech readers who are amenable to such details. In this case, we could just point out that in scientific circles, "theory" refers to a hypothesis that has been fairly thoroughly tested, has passed the tests, and is generally accepted as the best explanation we have at present. Something that explains all known data but hasn't been tested much isn't a "theory"; it's a "hypothesis".

We have good theories of cloud formation in low-level weather phenomena. For clouds at higher altitudes (>10 or 20 km), we mostly have hypotheses. People have done a lot of mathematical modelling, which is interesting but doesn't qualify as scientific testing, so the results aren't proper (scientific) theories yet. But to the mass media, they are theories, since the media is using a different dictionary.

Re:Clouds?

[YenTheFirst]

wooooooosh. :)

Re:Clouds?

[Burnhard]

How about calling them hypotheses? Let's reserve "theory" for something that actually has solid evidence.

Yes, to quote self, "...Physics community believe it's a plausible hypothesis". But then of course you have to define what you mean by `solid evidence'.

Re:Clouds?

[onemorechip]

not to mention the misused apostrophe

Re:Clouds?

[MaxEvans47]

Good morning everybody! Thought i'd let you know a few of us do bother reading all this stuff and learn from it so, yes, we appreciate people like you give themselves the trouble of calling things by their proper names and set things right when/as needed. If the average joe doesn't mind about it, it's a problem of his own. As to us, keep leading, we'll follow and, hopefully, succeed on our quest for knowledge. Don't give up!

Re:Clouds?

[jc42]

One of my favorite examples of "popular" misuse of technical scientific terms is the way the media uses "quantum" with a meaning almost opposite to its scientific meaning. For example, a while ago I read a news article claiming a "quantum leap in income" for a certain company in the past year. My immediate thought was "The company's income was $0.01 more than the previous year, and it's a news story?" After all, the quantum of the US's monetary system is the penny, $0.01.

But of course the writer meant a very large increase. The curious thing here is the question of how the media adopted the term "quantum", which basically means the smallest change possible, and uses it to describe very large changes. It's easy to understand why they might not understand the actual technical definition as physicists use it, but how they could get the magnitude so wrong is a real mystery.

It turns out in this case that there's usually a clue as to which meaning is being used. A physicist would write "quantum jump", while journalists usually write "quantum leap". Why this change was made is also a linguistic mystery, but it helps decode what people are writing. If a physicist said he'd had a quantum jump in income, it probably would mean that his/her paycheck had increased by $.01 (or the equivalent in the local currency), and it might be written with a smiley. A journalist would read this and write an article stating that physicists in general are seeing a large increase ("quantum leap") in income.

Examples like this are useful to explain how hopeless it is. Physicists aren't about to change their definition of "quantum" to match the media's misuse of the term, and journalists aren't about to change their definition of an impressive-sounding technical term just because their definition isn't the same as the physicists' definition (which the journalists can't understand). So we just have to live with it.

The computer industry has lots of similar situations. Probably the funniest is the way that computer geeks still use "hacker" as a compliment, despite the media using it to mean "computer criminal". This term isn't as critical to computing as "quantum" is to physics, of course, so the two definitions of "hacker" are mostly just the basic of some geek humor.

But we computer geeks have seen enough of this sort of thing to realize that it's a hopeless situation. So more and more, we take the physicists' approach, and just continue to use terms with their technical meaning in private. The only real problem is in forums like this, that are sorta halfway houses between the technical field and the general population. In such surroundings, it can be tricky getting across which of the various possible meanings you're using. The term "theory" is one of the most common cases, since the techies here tend to use it in its scientific sense, and then are taken aback by the evidence that others read it in its media/political/religious sense.

Re:Clouds?

[RockDoctor]

But of course the writer meant a very large increase. The curious thing here is the question of how the media adopted the term "quantum", which basically means the smallest change possible, and uses it to describe very large changes. It's easy to understand why they might not understand the actual technical definition as physicists use it, but how they could get the magnitude so wrong is a real mystery.

There's a "law" of Usenet, that every dispute will inevitably result in one protagonist accusing the other of being a Nazi (or Hitler's love-child, or something equally disreputable) ; it has a corollary that when this occurs, there is no more useful content to the dispute. this is IIRC "Godwin's Law.

There's a similarly well-founded "law" which states that any post complaining about someone's spelling or grammar will itself contain significant spelling and/or grammatical mistakes. Sorry, "speelung" mistakes. I can't remember that "law's" name ; perhaps it has several.

Depressingly, there is a third similarly well-founded law, concerning the likelihood of introducing serious error when trying to explain technical concepts in public.

Your analogy between the physicist's use of "quantum" and money is OK to a degree, but has an important misleading effect which isn't present in a physicist's (or chemist's) use of the term. From what you say, a reader could draw the inference that a system at an energy level of 13.24 dollars (or electron-volts, eV) could change to a state of 13.23 eV, or to 13.25 eV, but not to 13.242456 eV. This inference would (generally) be false.

While the energy levels of some systems can be calculated ab initio (and as understanding improves, this can be done for more and more complex systems), for most, it cannot. Where ab initio calculations have been done, and where data has been recorded from nature, the spacing of energy levels is generally not even, as your monetary analogy implies.

It's a nice try as an analogy, but this incorrect implication is quite serious. The same can be said of the "Floors on a skyscraper" analogy, unless you get quite explicit about the irregular spacing of the floors. It's not an easy concept for some people.

Not the First Post

[scum-e-bag]

Imagine the earth floating on a sine wave. The sine wave passes though the zero point. The zero point is a plane which contains the hot gasses. Are going to be other civilisations outside this cycle? Are there other civilisations who thrive inside the plane? Do some humans need to grow a brain?

Re:Not the First Post

[fractoid]

The end is near! IT'S A SINE!

So the milky way is falling sunny-side up?

[Anonymous Coward]

from TFA: It turns out that the biodiversity minima of the 62-million- year cycle happens when the Sun is âoebobbed upâ on only one side of the galaxy, when the solar system is on the diskâ(TM)s upper, âoenorthâ side...These [cosmic rays] should be showering the north side of the galaxyâ(TM)s disk. We are protected by the galactic magnetic field, much as the Earthâ(TM)s magnetic field protects our planet. When we rise to the north side, we are less protected.

Re:So the milky way is falling sunny-side up?

[zombie_monkey]

I remember reading about this decades ago in a book by Stanislaw Lem.

Re:So the milky way is falling sunny-side up?

[Vectronic]

Yeah, I remember reading this a few minutes ago, it was even on Slashdot I believe, only there wasn't any Unicode to ASCII fuck ups.

Re:First Post

[Anonymous Coward]

Every 62 million years, a giant goatse monster appears and sucks 95% of life on this planet into it's anus.

Better find something strong to hold on to!

Its also possible...

[bmgoau]

Its also possible that my opening of a coke can will unsettle the quantum state of the water molecules vaporized in the air consequentially causing a pony to spontaneously appear. But as much as i wish it to be true, it aint going to happen (at least not for a really long time).

The whole point of the 65 million year cycle was not only the extinctions, but also the discover of elements in the ground only found as a result of asteroid impacts. Tha'ts why researches spend to much time trying to find a large mass that could disturb the Kuiper belt.

Re:Its also possible...

[CarpetShark]

Its also possible that my opening of a coke can will unsettle the quantum state of the water molecules vaporized in the air consequentially causing a pony to spontaneously appear.

Which is precisely why Coke kill a pony for every can they make ;)

Re:Its also possible...

[macshit]

Its also possible that my opening of a coke can will unsettle the quantum state of the water molecules vaporized in the air consequentially causing a pony to spontaneously appear.

Which is precisely why Coke kill a pony for every can they make ;)

Ah, the well known Pony Preservation Principle.

Re:Its also possible...

[dna_(c)(tm)(r)]

OMG Ponies?

Re:Its also possible...

[Anonymous Coward]

Get it right. Its ...

OWM Pwnies

http://www.thinkgeek.com/tshirts-apparel/womens/a078/

Re:Its also possible...

[powerlord]

Its also possible that my opening of a coke can will unsettle the quantum state of the water molecules vaporized in the air consequentially causing a pony to spontaneously appear.

Which is precisely why Coke kill a pony for every can they make ;)

Ah, the well known Pony Preservation Principle.

Precisely.

Re:What a f**king dick

[boot_img]

What an incoherent rant. Perhaps you should lay off the vino before posting to slashdot.

Re:What a f**king dick

[adamchou]

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)

Brain full?

[clickclickdrone]

As others have noticed, this is hardly new. 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. It's effectively impossible for people to fully grasp the entire sum of knowledge in their field with the result we're starting to spend time 'reinventing the wheel' to a depressing level.

Re:Brain full?

[dna_(c)(tm)(r)]

I'm starting to think we just have too much knowledge these days.

Certainly too much data, perhaps too much knowledge, definitely too little insight.

Isn't it the same problem popping up in the IP arena? You know, patents and such.

Re:Brain full?

[feepness]

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.

Re:Brain full?

[Kjella]

People have always been reinventing the wheel, that is when we haven't had dark ages and lost the wheel in the first place. It just shows the importance of putting knowledge in a context. By all means I'm not saying wikipedia is perfect in content, but the basic idea of hyperlinking up documents to related concepts makes it 1000% user-friendlier than the dead tree encyclopedias I grew up with.

We do have a few books like that too, trying to give a bird's eye view of a topic. I remember using one of those in my master's degree, it was 8-900 pages thick, basicly shortly put a topic in context and listed central works. They referenced literally hundreds of works and basicly told us enough to say whether it was relevant or not for the thesis.

Yes, it's impossible to know the whole width of human knowledge or even within a single field. I think you'd have a helluva time trying to get through the Library of Alexandria, so it's hardly a new thing. But knowing every wheel is different from not finding the one wheel you seek and end up reinventing it. The former is impossible, the latter takes structure.

And there's a cost to overstructuring. You mention IT as an example - yes, but how long does it also take to find a library that does what you want, is it documented properly, is it of good quality, is it still developed so people will fix issues, can you adapt it to your needs, will upstream want your changes, in short reusing the wheel is not free either.

Re:Brain full?

[kjllmn]

So the next thing would be an area of knowledge which deals with precisely this. Not philosophically, but more in terms of optimizing knowledge acquisition and management - or something like that. Or, speaking of reinventing the wheel, perhaps there already is?

Re:Brain full?

[mdwh2]

As others have noticed, this is hardly new.

Citation needed?

The other posts have simply been ideas related to a galatic cycle, but claimed a different cause to what is discussed in TFA. We have a word for "same theory, except for this and this and this" - we call it "different".

I've lost count of the number of 'discoveries' that are already known, both in IT and the wider areas of science and beyond.

Well come on then, let's have some examples?

Whilst it's not inconceivable that researchers may overlap in their work without realising it, I find it hard to believe that a cosmologists is unaware of something that is apparently common knowledge on a random Internet forum...

Re:Brain full?

[GodfatherofSoul]

I've never read anything about gases and radiation causing the extinction cycles, I'd be curious to know where everyone has seen this before. What I have heard is that the same undulating motion of our solar system through the "denser" galactic plane brings us into contact with more asteroids.

Re:Brain full?

[delt0r]

this is /.

What where you expecting? Field expert reviewed news stories?

Re:Brain full?

[JuzzFunky]

Too true. As the saying goes:
"Experts know more and more about less and less."

Re:Brain full?

[dissy]

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 Simpsons.

*In comic book guys voice*

Season 10, episode 2, The Wizard of Evergreen Terrace

"Homer gets to work and develops several inventions, such as an alarm that beeps every three seconds when everything is OK, a shotgun which shoots make-up onto women's faces, a very difficult to control electric hammer, and a reclining chair which has a built-in toilet. But none of these inventions are well received. Feeling despondent over his failure to invent anything useful, his invention career is saved when he reveals he added two hinged legs to a chair making it impossible to tip over backwards. However, his hopes are dashed when he notices his poster of Edison shows his idol sitting in the same type of chair, which indicates Edison has already invented Homer's untippable chair. But Homer also finds out no one else has seen the extra legs on Edison's chair, and thus Edison has never received public credit for inventing it. So he sets out with Bart and his electric hammer to the Edison Museum in New Jersey to destroy the chair. Before he smashes the chair, Homer notices a poster of Edison's which reveals that Edison idolized Leonardo da Vinci in the same way Homer idolizes Edison."

Re:Brain full?

[sysrammer]

I think Library Science deals with this.

sr

Crap

[powerslave12r]

Its actually the Infinite Improbability Drive in action. Research my ass. Before you ask any more questions, 42.

Re:Crap

[Anonymous Coward]

Research my ass.

I've just got the research report about your ass, and you're not going to like the findings.

Re:Crap

[Amazing Quantum Man]

Let me guess... his ass is full of shit?

Re:Crap

[DinDaddy]

I hope you got £20,000 to even think about doing that.

Re:What a f**king dick

[MichaelSmith]

This is about the motion of our star relative to the disk. Because our orbital inclination around the galactic core is different from other stars in the galaxy we tend to drift above the disc, then we get pulled back by gravity and pop out the bottom of the disc. When we pass through the disc we encounter more objects such as stars and gas clouds.

Re:What a f**king dick

[silanea]

Those gas clouds are probably circulating at the same speed as us.

Nice assumption. TFA apparently assumes otherwise. Now I don't know which one of you is right, but at least they did not call people names without even bothering to read their text and without bothering to give any more of an explanation for their opinion other than "I mean, for Christ sakes [sic!]". Which leaves only one fucking twit here, as I see it.

Heard a similar

[Big Hairy Ian]

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?

Re:Heard a similar

[DJRumpy]

Why is the above post flamebait? Granted the wording in the last bit could have been a bit more..erm..politically correct and on-topic, but I found it actually interesting. I wasn't aware that someone else had proposed a similar theory, although I wish the above poster had included a link for handy reference.

Re:Heard a similar

[CRCulver]

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.

Nerds are likely to recognize a similar scenario from Larry Niven's 1966 short story "At the Core" (now in his collection Crashlander ), where the stars packed together near the galactic core set off a chain reaction of supernovas that would send a deadly wave of radiation towards the outskirts of the galaxy, killing off all life. Depressing reading.

Re:Heard a similar

[Anonymous Coward]

I disagree with the moderator of this post's parent comment. While he may have been poking fun at some scientists, he's correct that they're human and often overreact to ideas with which they disagree (much like the mod who marked the parent as flamebait). I too first heard an idea like this 20 or 30 years ago, but what I recall of it was the idea that, as the Solar system passes through the galactic plane, we're inundated with far more dust than while outside it. Additionally, gravitational tugs from nearby stars (of which there are a lot more when passing through the plane) have a better chance of knocking objects out of the Oort cloud and toward us. Also, there's always the chance that our sun could gravitationally tug objects from a neighboring star's Oort cloud toward us-- in other words, it's not just one mass of comets we're dealing with in such an event, it's two, plus all the itinerant dust in between.

Re:Heard a similar

[kjllmn]

I read "SPACE" by Stephen Baxter (from 2000) a couple of days ago, and was also built on the idea of periodical mass extinctions allover the galaxy (with a happy ending though). He proposed it as an explanation of Fermi's Paradox. Shortly put: "If they existed, they would be here."

Us living in a galaxy with periodic mass extinctions might explain why we have not been encountered by the alien species yet, even though they should, theoretically, be allover the place. No mention of Atlantis though.

Re:Heard a similar

[eyrieowl]

The grown-up way which involves invoking claims like, "extraordinary claims require extraordinary evidence"? I think it's a misunderstanding of science to think that scientists should throw up their hands in glee when someone comes along with a revolutionary idea. Science depends on a LOT of skepticism. Scientists wouldn't be doing their jobs if they didn't try to tear new theories to shreds. If you want to propose new theories and can't handle the scrutiny, either grow up, or find a different profession. Quite frankly, it's not enough to dream up the right idea, you have to prove it, and you have to make sure other people can prove it to.

Re:Heard a similar

[Gilmoure]

I read about this back in the 80's, and from what I remember, the theory was that passing through the galactic plane put more gravitational stress on the solar system and we got more kuiper/oort belts items falling in, and therefore, more impact events. I think it was Omni magazine but might have been Discover, if it was around back then.

Man, 40+ years on this rock and it's all a blur.

Re:Heard a similar

[relguj9]

TFA talks about some of the other similar theories as well. It's actually a really good read, maybe you guys should give it a go!

Re:Heard a similar

[JATMON]

but what I recall of it was the idea that, as the Solar system passes through the galactic plane, we're inundated with far more dust than while outside it.

I admit that I am not an astronomy expert, but I thought that we travelled around the center of the galaxy in the galactic plane and that we pass thru the spiral arms. It is the spiral arms that have the large concentrations of stars and dust.

Re:Heard a similar

[NotBornYesterday]

Not exactly. Our solar system is one little tiny node that makes up part of one of the spiral arms, and we move with those arms as they rotate around the galactic center. As the arms move through space, they do encounter dust and gas. Most of the collision there is at the leading edge of the spiral arms, and can birth new stars. However, as we rotate around the center, we also wobble perpendicular to the galactic plane, oscillating back and forth (or up and down, if you prefer) from one side of the galactic plane to the other.

Re:Heard a similar

[JLF65]

Our solar system is one little tiny node that makes up part of one of the spiral arms, and we move with those arms as they rotate around the galactic center.

Your grade school called - they've revoked your graduation certificate. The arms don't rotate around the galactic center. We don't move with the arms. We're also not currently in one of the arms. So you're batting a thousand there - got everything in your statement completely wrong.

All the stars in the galaxy orbit the center. The arms are merely a density wave in the disc. As stars enter the wave, they slow down and "bunch up", forming the "arms". As they leave, they speed up and spread out. It exactly the same phenomenon as traffics jams on the freeway, and scientists use the same math when doing calculations on both.

Anywho, our solar system passes through the arms about once every 200 million years, and the last one we passed through was about 60 million years ago. Scientists don't think it's a coincidence that the last time we passed through an arm was also when the dinosaurs went extinct.

Re:Heard a similar

[fractoid]

The grown-up way which involves invoking claims like, "extraordinary claims require extraordinary evidence"?

Actually, no, no they don't. Not scientifically. Just plain old every day garden variety ordinary evidence is perfectly good for supporting claims, no matter how extraordinary. Of course, if there's a much simpler, more widely accepted claim, then your data need to support the extraordinary claim better than the widely accepted claim, otherwise Occam's Razor comes into play - but if it doesn't, then it's not evidence of any sort for the extraordinary claim, now, is it?

The problem with cold fusion wasn't the nature of the claim, it was the lack of reproducibility. If I figured out a way to fuse deuterium by simply giving heavy water an electric shock with a platinum stick, and when I told you and everyone else about it you could reproduce it, then I'd need no more evidence than "push button, water gets really hot, even though I'm only putting a few Watts of electricity into it". If I tell you I can do it but when you try replicating my method all you get is some little bubbles, then you have every right to question my original data.

Re:Heard a similar

[vikstar]

Wow, you learned that at grade school? Which school did you go to? Also, how old are you. When I was at school we learned that the earth orbits the sun, and the sun orbits the centre of the milky way.

From a Galactic Origin

[Toutatis]

All this has happened before and will happen again.

Re:From a Galactic Origin

[kjllmn]

Read a lot of Nietzsche, do you?

Re:From a Galactic Origin

[dodobh]

The wheel of time turns ...

Re:From a Galactic Origin

[Toutatis]

I think you read more Nietzsche than me.
My message was about Battlestar Galactica (2004).

Re:From a Galactic Origin

[jedidiah]

Either that or Gilgamesh...

        On the subject of old ideas being suddenly declared new.

Examine It For Yourself

[TerribleNews]

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.

Re:Examine It For Yourself

[Late Adopter]

I don't know that I'd expect that much consistency. The actual effects are indirect, cosmic ray flux leads to climate change leads to decreased biodiversity leads to ecological collapse. I would expect large amounts of variation in the timing in any one of those steps, just due to their chaotic nature.

So, statistically speaking, the case loosens up quite a bit. I would need to see more evidence of the mechanisms to be persuaded one way or the other.

The reapers are coming!

[Redlite]

Shut down the mass relays!

Re:The reapers are coming!

[mcgrew]

No, it's the Vogons. But due to the vast bureucracy the project always seems to be cancelled right as demolition is beginning.

See? Sometimes bloated, inept, confusing, mismanaged, out of control bureaucracy is a GOOD thing!

Re:What a f**king dick

[jarleih]

I would say encountering a star would definitely fit the description of "hitting the bottom of bioversity"

Re:What a f**king dick

[captainpanic]

This is about the motion of our star relative to the disk.

OCIADBTRTFA (Of course I also didn't bother to read the f**king article), but what the hell has the Discworld to do with this???

What if the Great A'tuin would change course? Huh? We wouldn't even know, because we're not ON the f**king Discworld. It's fiction.

[/deliberately off-topic]

awesome

[circletimessquare]

can't wait to see it in action the next michael bay movie

Re:awesome

[CrashNBrn]

Why not just put it in your Low Budget HDV Filipino Horror Movie in NYC.

Re:awesome

[jollyreaper]

can't wait to see it in action the next michael bay movie

Why not just put it in your Low Budget HDV Filipino Horror Movie in NYC.

He said "low-budget", not "no talent".

Re:awesome

[mcgrew]

CTS's movie is the DNF of film.

Re:First Post

[Dan541]

The real question is; and so what if we're gone?

After reading some of the contributions on /. I completely agree.

Re:Just no

[Curunir_wolf]

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!

faster pussycat, kill, kill

[tverbeek]

'[W]e are on the downside of biodiversity, a few million years from hitting bottom,'

Ha! With good ol' human ingenuity, I'm sure we can hit bottom a lot faster than that!

Re:What a f**king dick

[MichaelSmith]

The Galactic disk.

On a related topic I recently rented a movie of The Color of Magic. The elephants were shown standing motionless on the turtle with their heads pointing out and their tails pointing in. I had always assumed that the elephants were lined up around the turtle head to tail so to speak so that they could rotate the disk while the turtle kept pointing the same way.

Re:So what keeps the globular clusters alive?

[jarleih]

1st m94 is a galaxy at a distance of 15-33 mio ly not a globular cluster 2nd) globular cluster form sperical halos around the galaxies at distances several times the diameter of the host galaxy 3rd you are right, m94 is definitely out of the plane of the milky way, so at least your post is not total nonsense

Mayan Calendar

[elkto]

Chime in here with any information on this.

I was lead to believe at one point that the Mayan Calendar's "Beginning of time/End of time", December 21 2012, corresponded to when our Solar System transverses the plane of the Milkway.

Where these people a few million years off? (Amongst other things)

Re:Mayan Calendar

[Guido von Guido]

Chime in here with any information on this. I was lead to believe at one point that the Mayan Calendar's "Beginning of time/End of time", December 21 2012, corresponded to when our Solar System transverses the plane of the Milkway. Where these people a few million years off? (Amongst other things)

I think that's something some new age nutjob added after the fact in order to sound more authoritative when they made their doomsday predictions.

Re:Mayan Calendar

[mcgrew]

Wikipedia is your friend.

Adrian Melott

[Anonymous Coward]

Not to be anal, but his name is spelled Adrian Melott , with one L. This spelling will help if you google his name.

I attend the University of Kansas (where he teaches), and know this guy is associated with some pretty far out ideas.

Re:First Post

[maxwell demon]

Actually the true danger is in white holes. You never know what will come out of them.

Re:What a f**king dick

[jandoedel]

but why would they rotate the disk if the sun is rotating around the disk?

Re:What a f**king dick

[MichaelSmith]

Showing my unfamiliarity with discworld physics here. I assumed that the sun around turtle+elephants+disc is one year, while one turn of the disc is one day.

We need to talk about this! Re:Not news

[Snaller]

Remember how many people on the planet think that just *believing* something is ok ("I believe in a god", "I blieve there is no global warming" etc etc) - it will take 5 million years to get everybody to accept this and start working on a solution!

Re:We need to talk about this! Re:Not news

[JLF65]

Remember how many people on the planet think that just *believing* something is ok ("I believe in a god", "I believe in global warming" etc etc)

FTFY

Re:Just no

[Copperhamster]

There is no sanctuary!

Re:Sorry, m92, not m94

[Hognoxious]

yo mama.

Cthulu?

[gijoel]

Maybe it wasn't radiation that killed off all those critters. Maybe the stars were just right.

Re:Cthulu?

[fractoid]

So you're saying that these cosmic rays that are more common when we're on 'top' of the galaxy are actually cosmic manta rays? As in Great Old Ones?

Re:Deflation

[sigxcpu]

Your mixing moonshine, which is only about 40% pure with moonlight, which is the real thing.

Re:Sorry, m92, not m94

[jarleih]

old it might be, especially since science nowadays dates the age of the Universe at ~13.7bn years.

Well, i always wondered what was before the Big Bang; now I know: m92, ah m94, ah whatever...

Congrats, I hereby nominate you for the 2009 (IG) Nobel Prize

yeah i really have to finish that thing

[circletimessquare]

no time ;-(

Re:Just no

[Elrond, Duke of URL]

All right, Carousel!

Woo!

Re:First Post

[vertinox]

Well there will be the damn dirty apes!
But they won't give a damn either about us.

gah lak tus

[discogravy]

Sure, but where's the silver surfer come to warn of Galactus? Maybe Jack Chick was right all along

And also:

[markov_chain]

Nightfall (Isaac Asimov, 1941, and Isaac Asimov & Robert Silverberg, 1990)

Re:What a f**king dick

[CTalkobt]

>> IDNTRTFAWIDTBYDE (i don't need to read the f**king article when i'm drunk too because you didn't either)

I finally realized that, today, for the first time I've been on Slashdot too long.

I was able to understand your acronym without the explanation just by looking at the letters.

OMG.

Re:First Post

[samkass]

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.

We've got time...

[vwampage]

...to build the shield generators that will protect our ancestors from the rarified hot gases.

Re:We've got time...

[greyhueofdoubt]

that will protect our ancestors from the rarified hot gases

Wow, shield generators *and* a time machine all in one? Too bad your ancestors will take all the credit...

-b

Re:We've got time...

[vwampage]

Ooo... my bad, I did mean descendants, but if our ancestors built them then it would make for a wonderful sci-fi story.

Well damn

[CaseM]

Guess that means no Duke Nukem Forever this time around. Hopefully they'll time-capsule the source, at least.

Re:Gamma Ray Bursts Anyone!

[GodfatherofSoul]

No, that would just turn us all green and make us speak in broken english.

CTHULHU FHTAGN!

[Eli Gottlieb]

So when the stars are right, the living creatures of Earth all die. Sounds like it's nearly time for Cthulhu to rise again!

Re:CTHULHU FHTAGN!

[dissy]

I think they just found his children in the sewers of North Carolina

( Video link, and I should probably put a warning of some sort here.. Warning: Contents may include scary life form )

  http://www.wimp.com/lifeform/

Re:CTHULHU FHTAGN!

[Eli Gottlieb]

It just looks like a bunch of heaving meat to me. Are they going to zoom out to get a look at the whole thing or what?

Iridium anomaly

[janwedekind]

Interesting idea. But what about the Iridium anomaly then?

Re:Iridium anomaly

[janwedekind]

Sorry. The link to the Iridium anomaly got screwed up. The Wikipedia editors like special characters in their URLs :(

Re:Just no

[Yvanhoe]

Is it really flamebait to say that humans are the most likely cause of biodiversity downfall ?

Re:What a f**king dick

[nospam007]

But do we eat the pudding now or not?

Old idea: Read "Calculating God" by Sawyer

[KeithH]

This hypothesis is old and was used as part of the story "Calculating God" written by Robert J. Sawyer in 2000. It's an excellent book which I can heartily recommend. You might also be familiar with his work through the "Hominids" alternate earth trilogy.

Quick We need to start producing More CO2

[Blackdragonpkj]

Know that this paper has come out we need to increase the chances for all life to survive. By increasing C02 levels, we will trap more radiant energy which will negate the increase cloud cover. The additional CO2 and smog will create a "shield" against the cosmic rays! Come on everyone buy any American SUV and start driving! We will stimulate our economy and save the Planet!

Ohai-Thanks for the mindnumbing oversimplification

[Phizzle]

Usupported by actual data. If you look at the Phanerozoic biodiversity data, it doesnt validate the 62 million years extinction cycle theory. You cant just take a small subset, selectively ignore data points that don't fit into your theory and preach the end of the world. Admittedly that does seem to sell books.

don't 4get hhgttg;-)

[airdrummer]

when we finally figure it all out, it will completely change...and some maintain it already has...

Re:First Post

[quanticle]

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.

Human's not responsible?

[harl]

What?! I'm outraged!

Humans are responsible for all bad things! Humans are not part of nature! That's what the media tells me. How dare something else be responsible! How dare our actions not be as important as we think they are!

A Paleontologist's Take on This

[Anonymous Coward]

Hrm, I'm only glancing over the article in question, but I was just last week at a conference (North American Paleontological Conference, held in Cincinnati) where this work was presented.

As others have pointed out, cycles of diversity in the fossil record have been pointed out before, as have cycles in extinction rates. Dave Raup and Jack Sepkoski did some very important work in this. However, paleontologists have gone back and forth on whether that cyclicity really exists or not.

Melott and Bambach (Richard Bambach... a very very important paleoecologist!) presented work at NAPC that they have found the 62 mya cycle in a number of very different datasets of fossil diversity. This is important... it means the signal is very likely to be real.

I can't speak as to the astronomical mechanism they postulate; in the talk at NAPC, they suggested it might have to do with continental erosion rates (which is related to an idea Bambach has pushed many times before, particularly in a paper entitled "Seafood through Time" in the journal Paleobiology).

It will be more interesting, as Mike Foote (UChicago) pointed out at NAPC, to see if this cyclicity exists in the seperate origination and extinction rates, the combination of which produce the changes in diversity. Melott and Bambach were not at NAPC however, and the person they asked to substitute for them to present their paper (Eugenie Scott, head of an important science education taskforce) could not speak on the details of their work.

Not fault of galactic arms

[Nyrath the nearly wi]

Spiral Arms Did Not Cause Climate Change on Earth

A new map of the Milky Way galaxy proves that the sun's motion through the spiral arms could not have caused a well-known climate-change cycle.

http://www.technologyreview.com/blog/arxiv/23763/

Re:Just no

[jamstar7]

OK, so we're about due for another mass extinction, according to the theory.

Hopefully, it'll hold off until I've had my coffee...

Quantum, Heisenberg,...

[dna_(c)(tm)(r)]

And that was the one time Albert was wrong...

Re:Skeptics

[Anonymous Coward]

From their site:
"CNSNews.com is an alternative to the liberal media, focusing on stories that are unreported, under-reported, or misreported by the mainstream press."
They're pretty open about declaring their far-right bias, at least, but I wouldn't see them as a good source if you're interested in facts rather than worldview confirmation.
Although if you actually believe that there's a chance of the USA breaking up in the forseeable future you may be immune to facts.

Re:First Post

[amoeba1911]

amoebas will survive? awesome.

Re:Just no

[jc42]

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". ;-)

Does anyone think it could be related to...

[fabs8611]

..the Earth leaving the Sun's heliosphere? As described in this article a few days ago: http://www.newscientist.com/article/mg20227144.700-sun-leaves-earth-wide-open-to-cosmic-rays.html The (predicted) length of time for a cycle for this event, and the event described in the story is only a single order of magnitude off. Fairly common yet acceptable difference in in the field of Astronomy, I've been told.

Re:Skeptics

[rally2xs]

So, we can only read, watch, and listen to the (liberal) mainstream media about the global warming fraud? That would be convenient for the libs, I think, but I'm not gonna be there.

I basically believe I can tell when a liberal is lying by watching if his lips are moving. The global warming nonsense is the greatest lie ever perpetrated on mankind, and will result in horrors in human suffering paralleling the holocaust if we try to spend $50 trillion by 2050 to do something about it. The deprivation resulting from sucking that much money out of the world economy I believe will result in far more than 6 million deaths around the world.

As for the USA breaking up, there's some really unresolved problems, some fundamental disagreements with the approach to take in solving them, and the aforementioned deprivation that would result from an expensive attempt to cure the "global warming" non-problem could move people to armed resistance as jobs are carted out of the country, etc. - especially if they wake up and see that it doesn't matter who you vote for, the same things will happen.

And then there's the wild card - some bonehead takes a shot at the President, DOESN'T miss, and because he's black, we suffer a devastating race war. Yeah, I think that's really, really likely if such a trigger is pulled. That could break up the country, too.

Take your pick - newly impoverished middle class workers whose jobs and all our prosperity go overseas in a completely boneheaded effort to solve a non-problem, or millions of blacks that are P.O.'ed because someone just off'ed their hero - yeah, either could accomplish the demise of the USA as a country. I think the chances are way too high, too - I'd guesstimate it's maybe only a 20-1 shot against it happening. That "1" is way too high in a field of 20 other possibilities for me...

Re:What a f**king dick

[CrimsonAvenger]

Those gas clouds are probably circulating at the same speed as us.

Probably pretty close to the same speed, yes.

But, alas, not necessarily close to the same velocity.

To use a car analogy, two cars going 75 mph are both going the same speed. If one is eastbound on West Esplanade, and the other northbound on Power, they'll have a velocity differential of over 100 mph when they meet at the intersection of Power and Esplanade...

Re:Just no

[PiSkyHi]

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!

The IMF and the WTO wish to sue you for patent infringement.

20 Million Years Late...

[DynaSoar]

... and a dollar short.

This is twice in a week that someone has made assertions about mass extinctions, and both times their (different) numbers don't match the commonly accepted numbers http://en.wikipedia.org/wiki/Milky_way . (No, the Big W is not necessarily authoritative, but the sources referenced are.)

The solar system orbits the galactic center in 220 Myr. It oscillates through the galactic plane 2.7 times per orbit. That's a period of 81.5 Myr, and each crossing at half-period being 40.75 Myr. I doubt anyone would consider that an acceptable error margin.

Furthermore, the matter density in the galactic plane oscillates with a period 1/2 that of the galactic rotation, expanding out from the center in waves (density wave 25 Myr; spiral structure 50 Myr). Passing through the plane would have little effect unless these two coincide.

Re:Just no

[NotBornYesterday]

I'm trying to picture the world after you save it this way. Children of the Corn? Lord of the Flies?

Re:Just no

[mcgrew]

This isn't the first time a speices (or multiple species in that case) destroyed life on Earth. The anarobic bacteria were perfectly happy until they stupidly unleashed all that oxygen.

Variety

[Boronx]

We already know why one extinction event happened. The current one is caused by us. These leads me to believe that there may be some variety in causes of mass extinctions, and that no single theory will cut it.

Re:Variety

[RockDoctor]

We already know why one extinction event happened. The current one is caused by us. These leads me to believe that there may be some variety in causes of mass extinctions, and that no single theory will cut it.

Hmm, that logic doesn't stack up. "We know of the cause of one extinction event." Do we? which event? and what is the cause?
Then you seem to imply that we know that the cause of the current extinction event is "us", which is probably true but certainly not undisputed, let alone fully proven. So, are you counting this as a second data point, from which you impute a trend?

(NB : I'm a geologist by profession. So double check what you think is the accepted cause of some non-current extinction event. It's likely that I'm more familiar with the literature than you are.)

Re:Variety

[Boronx]

This is true. We appear to be in the middle of an extinction event caused by us, but it may peter out, and the true cause may still be hidden. I didn't mean to imply that we knew the cause of previous extinctions.

It seems to me, however, to be the most solid data point we've got. I'm not predicting any trend from it, just noting that it doesn't point to a galactic scale cause.

Re:Variety

[RockDoctor]

It seems to me, however, to be the most solid data point we've got.

(The "it" being that the present-day mass extinction event is human-caused.)

Yes, you're probably right that the present mass extinction is probably the best understood of the lot, in terms of causes. Over it's 0.05Ma (approx.) duration this mass extinction has closely coincided in time with the entry of humans to particular areas, as well as to anthropogenic effects on climate, landscape and habitats. Of course, being a continuing situation, it's also amenable to experimentation, which would give us the prospect of understanding it quite well by the time that it is over. Say, in another 0.05Ma.

Equally importantly is the valid question of whether there will be any humans around in 0.05Ma. That's not a question that gets as much visceral attention as it should, IMHO.

As for previous mass extinctions - we're very much in the dark about their causes.

• The P-E (Palaeocene-Eocene) extinction event - argued as the consequence of a global warming event of about 0.15Ma duration caused by discharging what has been described as "the methane clathrate carbon capacitor" into the atmosphere. Which may be true - we're doing experiments on that at the moment. We'll find the answer (or have a much better understanding of the question) in about 0.001Ma or less.
• The K-T (end-Cretaceous) extinction event was preceded by an asteroid impact event. By about 0.3Ma. Which leaves us uninformed about the causes of the mass extinction. The broadly contemporaneous occurrence of a flood basalt event may be related - and the presence of un-reworked dinosaur egg fragments in inter-lava soils strongly argues that the flood basalts did not follow the extinction of the dinosaurs, though it may have preceded the extinction - but we don't have sufficient precision of dating to be really sure. Nor do we know well what the pollution effects of the flood basalt were. Which is contrary to the impression you'd get from some popular science publications.
• The T-J (Triassic-Jurassic) extinction event was nearly coincident with the formation of the astrobleme chain that includes the 200+ km diameter multi-ring Mainicougain. Well, only about 12Ma away, according to some. Whether that's significant or not is not known. On the other hand, it's also approximately coincident with the CAMP flood basalt sequence, as well as can be determined. But no-one is really sure, in part because flood basalt events are sufficiently common that there is a good chance of there being one happening at any randomly chosen moment in time.

We simply don't have enough data to be sure what the origins of previous mass extinction events were. For some, we've got moderately good evidence, but no real "smoking gun" evidence. Even the best-characterised ones - the present day and the P-E events - don't get to a criminal level of proof ("beyond reasonable doubt"), and are little beyond the civil level of proof ("on the balance of probabilities" ; your jurisprudence standards probably vary in detail).

wider variety of bacteria now

[tizan]

Oil and coal formed as there were not enough species of bacteria to cause decay before they got fossilized Arguably this will not happen anymore as most organic (and even some non organic) have bacteria which will cause them to decay in very short period of time into CO2, methane etc etc...

Re:wider variety of bacteria now

[mhajicek]

Well then they'll just have to use the methane.

Only One Question Matters

[Nom du Keyboard]

Only one question matters: when is the next one due?

Re:Only One Question Matters

[Spy Handler]

2012, according to Mayans and Nostradamus. You have exactly 3 years left!

Past Climate Change Cannot Be Tied to Earth Pass..

[n3v]

From universe today:

Past Climate Change Cannot Be Tied to Earth Passing Through Galactic Plane
http://www.universetoday.com/2009/06/26/past-climate-change-cannot-be-tied-to-earth-passing-through-galactic-plane/

Re:Not a new idea Maybe the Sun-sized stars

[davidsyes]

will heed the galactic call to "Aboort! Aboort!"

Re:What a f**king dick

[oblivionboy]

Modding him up +1 FUNNY, was the other option. I quite enjoyed it. :)

we're floating down a river not plowing through it

[klossner]

From TFA:

This supercluster is so massive that its gravity pulls our galaxy toward it at a velocity of about 200 kilometers per second.

(Huh? Gravity pull is an acceleration, not a velocity.)

The space between galaxies is not empty. It's actually full of rarefied hot gas. 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.

I don't follow this. If the supercluster is pulling us in, it's also pulling in the intergalactic gas. We should be flowing along with that gas, not blasting through it.

Oh No!

[Un pobre guey]

How will the "We Have To Get Off This Rock wackjobs react to this? a) they will realize they are utterly out to lunch and give up, or b) they will now stridently insist that not only must humanity magically leave earth, but leave the galaxy as well!

You know which one they'll choose...

See also: Spider Robinson

[lennier]

"Melancholy Elephants". http://www.spiderrobinson.com/melancholyelephants.html

Re:First Post

[fractoid]

Humans will survive, too. Unlike dinosaurs, we know about things like 'lead plate stopping radiation'. If you're lucky, you amoebas will be inside the lead-plated bunkers with us. As our food source! Muahahahahaha*gasp*hahaha*cough*.

i will be in my

[chris.evans]

space ship snug and safe from the interstellar soup dust.

Re:What a f**king dick

[RalphTheWonderLlama]

BAWITDABADABANG...

-Kid Rock

(damn caps filter)

Re:You obviously fail to grasp...

[RalphTheWonderLlama]

Does that have crunch berries?

Re:First Post

[Bat Country]

You're assuming we're not going to be in the surviving 5%. Considering a substantial ability to terraform and a relief from ethical concerns regarding GM food stocks (plants and animals) we've got a survivability as a species just under that of the cockroach.

Re:Just no

[St.Creed]

Apart from the hypothetical extinction in a few million years, we're going to be hardpressed ensuring we have something to extinguish left over.

The newfoundland codfish collapse is about to repeat itself on a rather large scale. Climate change predictions are getting worse, now that more data is coming in it looks like the trend is accelerating. Noone really knows what will happen when the permafrost melts, but all indications are it's going to be very, very bad. Not for everyone though, just for enough people currently arming up with nukes or already armed that it's a pretty sure bet we all get to join in the fun.

Re:we're floating down a river not plowing through

[RockDoctor]

I don't follow this. If the supercluster is pulling us in, it's also pulling in the intergalactic gas. We should be flowing along with that gas, not blasting through it.

The inter-galactic gas of the Local Group will hit the inter-galactic gas of the supercluster (Virgo) resulting in shock waves which will be transmitted to gas within the component galaxies, with possibly significant effects within those galaxies.
Clearer now?