4 ms·

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 li

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 17y ago
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 17y ago
  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 17y ago
    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 17y ago
      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 17y ago
        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.

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 17y ago

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 17y ago
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 17y ago
  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 17y ago
    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 17y ago
      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.