

The story of how the dinosaurs disappeared is getting more and more complicated - cwan
http://www.economist.com/sciencetechnology/displaystory.cfm?story_id=14698363

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roc
_Second, they coincided with one of the largest periods of vulcanicity in the
past billion years. Third, one of them just happened to strike where these
volcanoes were active._

Is it not plausible that impacts that massive _caused_ the volcanic activity?
Wouldn't impacts that massive be expected to catalyze that sort of reaction?

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Evgeny
What's with the articles that start with "EVERYONE knows" ... I used to think
that the asteroid hypothesis/theory was just that, one of many others. Or is
it considered to be a proven fact?

~~~
run4yourlives
It's certainly considered the most likely explanation in the general public.
(This is the Economist, not Paleo-Geologist Daily.)

I've always liked the Nemesis conclusion myself. Very chilling, considering we
are due. :-)

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btilly
Not one but 2 large impacts? The coincidence sounds like evidence for the
Nemesis theory. See <http://en.wikipedia.org/wiki/Nemesis_(star)> for more.

~~~
staticshock
how would collisions 300k years apart be, in any way, evidence in favor of a
star with a 26 million year oscillation period? if you're going to say
something like that, back it up.

~~~
btilly
Ordinarily an impact on the size of either should arrive once every hundred
million years or so. That two would independently arrive 300,000 years apart
is an extremely unlikely coincidence.

The Nemesis theory says that every 26 million years Nemesis arrives and knocks
a bunch of stuff out of the Oort cloud. Most of it is swept up by Jupiter, but
the Earth goes through a period where large asteroid impacts are likely. It is
a much smaller coincidence to have 2 large impacts in a period where large
asteroid impacts should be common.

Therefore this result is more substantially likely under the Nemesis
hypothesis than it would be without the Nemesis hypothesis. Which implies that
the conditional probability of Nemesis given this observation is higher than
it would be without this observation. Which is a fancy way of saying that the
observation is evidence for the Nemesis hypothesis.

~~~
tdedecko
I disagree. This event does not support the Nemesis hypothesis. This might
only add evidence to suggest that there is periodicity to Earth impacts.
Although, it might not. As I understand it the idea of periodicity for impacts
is debated and is not statistically conclusive.

There are other hypothesizes besides Nemesis to explain the supposed
periodicity of impacts. Essentially, we need something to cause a
gravitational change to the Oort cloud. Other possibilities include Brown
dwarfs and black holes or precession in the rotation of the milky way.

~~~
btilly
Correction. This event doesn't _only_ support the Nemesis hypothesis.

More precisely it is evidence that something caused excess asteroid activity
65 million years ago. And therefore is supporting evidence for any theory
which could explain that. Nemesis is the best known possibility, but is far
from the only candidate.

~~~
tdedecko
The supposed impact is merely a data point that could be used to interpret
Earth impact periodicity. It can only contribute to our to our current
collection of data. Defining it as evidence in support or against periodicity
is premature.

~~~
btilly
Who said anything about periodicity?

I was saying that it is evidence that the dinosaur asteriod was not just a
random asteroid. Some external force disturbed potential asteroids and shoved
multiple ones into the inner solar system. That fits with Nemesis. But would
fit with other theories as well.

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tdedecko
Abstract from the GSA:
[http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_16019...](http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_160197.htm)

Better article that is more critical of Chatterjee's theory:
[http://www.space.com/scienceastronomy/091018-dinosaur-
crater...](http://www.space.com/scienceastronomy/091018-dinosaur-crater.html)

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tlb
Basically, they don't know squat. They had one crater and a theory. Then they
found a 2nd crater and a new theory emerges. Presumably there's a 3rd crater
somewhere that'll require another theory. I think I'll ignore paleontology for
another 20 years and see if the theories settle down.

~~~
thaumaturgy
Well, that's what science _is_.

First there's the observation. Then there's a guess. Then there are tests, and
sometimes more guesses. Then more observations come along, and everything gets
revised.

This is in contrast to faith, where the individual picks the conclusion that
they like, and then tries to fit the evidence to it.

~~~
philwelch
Yes, but there are questions where we apparently know a lot, so our theories
do not change very much, and then there are questions where we don't know
shit, so our theories radically change with each new data point. We have much
higher confidence in relativity (or in the limited-scope applicability of
Newtonian physics) than, for instance, any given theory about the extinction
of the dinosaurs.

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mleonhard
I think methane hydrates had a lot to do with it: [http://www.amazon.com/When-
Life-Nearly-Died-Extinction/dp/05...](http://www.amazon.com/When-Life-Nearly-
Died-Extinction/dp/050028573X)

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Tichy
I think it likely that eventually they will find that the evolution of a new,
better adapted animal caused the extinction of the dinosaurs.

