I am flabbergasted, I have no explanation for this situation.
If this comet is really that big and has approximately said flyby orbit, how frequent are those? If one every thousand years, there were 60000 of those since the TC event. How come we had only one collision of this magnitude?
Maybe they are less frequent. How lucky we are then to witness one of them right now? Too lucky, I guess.
As on the other hand, it looks we are just too lucky to have no major collision of that kind relatively recently, if they were quite common.
Maybe I am missing something odd. Like an unexpected gravity or other effect, by which an actual collision is much more difficult. Something in line with this. What makes sense, but only after a careful consideration.
Maybe a planet like Mars or Earth repels comets somehow? Dodge them somehow? Some weird effect like this?
I recommend Taleb’s The Black Swan. The major premise is that people tend to underestimate the likelihood of weird events. It’s not that they can predict any particular weird event, it’s about overall likelihood of weird events with large consequences.
Another way of stating it in this circumstance: there are so many different things that we would consider ourselves lucky to see or that we would notice as unusual that even if the probability of any one of them is low the probability that we see something isn’t that low.
If you are randomly shooting a rock through the solar system, “close approach of mars within 100,000 km” is 870 times as likely as “hitting mars”. That brings a ‘once in 100 million years (really roughly guessing based on what I know of earth’s geological history)’ event down to the order of ‘once in a hundred thousand years’, and the proper reference class of things we would be considering ourselves this lucky to see is probably more like ‘close approach of a large comet to a terrestrial body’ rather than singling out mars in particular. I don’t know enough about distributions of comet orbital energies to consider different likelihoods of comets having parabolic orbits that bring them closer to the center of the solar system versus further away to compare the odds of things going near the different terrestrial planets with different orbits.
The gravity of a planet actually slightly increases the fraction of randomly-shot-past-them objects that hit them over just sweeping out their surface area through space, but for something with a relative velocity of 55 km/s (!) that effect is tiny.
If so, we are indeed very lucky to observe an event, which happens every 100 000 years or so.
OTOH, I’ve conclude, that it is in fact less likely for a planet to be hit by a random comet than it is for a big massless balloon of the same size, to be hit by the same comet.
Why is that? Roughly speaking, if the comet is heading toward some future geometric meeting point, the planet will accelerate it by its own gravity and the comet will come too early and therefore flies by. It’s a very narrow set of circumstances for an actual collision to take place.
A bit counter intuitive but it explains why we have so few actual collisions, despite of the heavy traffic. Collisions do happen, but less often than a random chance would suggest. The gravity protects us mostly.
I am flabbergasted, I have no explanation for this situation.
If this comet is really that big and has approximately said flyby orbit, how frequent are those? If one every thousand years, there were 60000 of those since the TC event. How come we had only one collision of this magnitude?
Maybe they are less frequent. How lucky we are then to witness one of them right now? Too lucky, I guess.
As on the other hand, it looks we are just too lucky to have no major collision of that kind relatively recently, if they were quite common.
Maybe I am missing something odd. Like an unexpected gravity or other effect, by which an actual collision is much more difficult. Something in line with this. What makes sense, but only after a careful consideration.
Maybe a planet like Mars or Earth repels comets somehow? Dodge them somehow? Some weird effect like this?
I recommend Taleb’s The Black Swan. The major premise is that people tend to underestimate the likelihood of weird events. It’s not that they can predict any particular weird event, it’s about overall likelihood of weird events with large consequences.
Another way of stating it in this circumstance: there are so many different things that we would consider ourselves lucky to see or that we would notice as unusual that even if the probability of any one of them is low the probability that we see something isn’t that low.
I second the book recommendation by the way.
Flabbergasted no more! There was no collision, of course.
Should have known it, immediately!
If you are randomly shooting a rock through the solar system, “close approach of mars within 100,000 km” is 870 times as likely as “hitting mars”. That brings a ‘once in 100 million years (really roughly guessing based on what I know of earth’s geological history)’ event down to the order of ‘once in a hundred thousand years’, and the proper reference class of things we would be considering ourselves this lucky to see is probably more like ‘close approach of a large comet to a terrestrial body’ rather than singling out mars in particular. I don’t know enough about distributions of comet orbital energies to consider different likelihoods of comets having parabolic orbits that bring them closer to the center of the solar system versus further away to compare the odds of things going near the different terrestrial planets with different orbits.
The gravity of a planet actually slightly increases the fraction of randomly-shot-past-them objects that hit them over just sweeping out their surface area through space, but for something with a relative velocity of 55 km/s (!) that effect is tiny.
Should we bring Shoemaker-Levy into this discussion?
If so, we are indeed very lucky to observe an event, which happens every 100 000 years or so.
OTOH, I’ve conclude, that it is in fact less likely for a planet to be hit by a random comet than it is for a big massless balloon of the same size, to be hit by the same comet.
Why is that? Roughly speaking, if the comet is heading toward some future geometric meeting point, the planet will accelerate it by its own gravity and the comet will come too early and therefore flies by. It’s a very narrow set of circumstances for an actual collision to take place.
A bit counter intuitive but it explains why we have so few actual collisions, despite of the heavy traffic. Collisions do happen, but less often than a random chance would suggest. The gravity protects us mostly.