The story of how the dinosaurs disappeared is getting more and more complicated(economist.com)
economist.com
The story of how the dinosaurs disappeared is getting more and more complicated
http://www.economist.com/sciencetechnology/displaystory.cfm?story_id=14698363
8 comments
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?
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. :-)
I've always liked the Nemesis conclusion myself. Very chilling, considering we are due. :-)
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Abstract from the GSA:
http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_16019...
Better article that is more critical of Chatterjee's theory: http://www.space.com/scienceastronomy/091018-dinosaur-crater...
Better article that is more critical of Chatterjee's theory: http://www.space.com/scienceastronomy/091018-dinosaur-crater...
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.
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.
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.
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.
Not all scientific theories are equal. Some just manage to scrape by an explanation for the known facts without providing further testable predictions - while this isn't inherently bad, I place a lot more confidence in theories that explain facts that they weren't specifically invented to explain.
I think methane hydrates had a lot to do with it:
http://www.amazon.com/When-Life-Nearly-Died-Extinction/dp/05...
[deleted]
I think it likely that eventually they will find that the evolution of a new, better adapted animal caused the extinction of the dinosaurs.
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?