Apparently on date Sat, 05 Nov 2005 11:29:45 +1300, Eric Stevens
>On Fri, 04 Nov 2005 19:17:07 GMT,
>>Apparently on date Fri, 04 Nov 2005 20:47:58 +1300, Eric Stevens
>>>>>>Sure, comets *can* hit Earth. But the situation is that a particular
>>>>>>comet will do it and it will be a very rare event.
>>>>>It all depends on what you mean by 'rare'. There are respectable
>>>>>astromers who believe it has happened in historical times.
>>>>I reject their opinion then, as I shall show with numbers.
>>>You should also consult the outside world. I suggest for a start you
>>Why would I want to read twenty year old, generally rejected popular books
>>I can do the same maths and get different sums, repeatedly and even see where
>>Clube and or Napier made mistakes in their books?
>Now there is a circular argument. How can you know that Clube and
>Napier made mistakes in their books if you never read the books?
I have. I just don't see any point in consulting catastrophist websites that
rely on Clube and Napier.
And I don't accept that these are more "real life" than comparing the
circumference and diameter of the earth using basic maths.
>>>>Now, how many comets have you seen? I've seen Hale-Bopp, and if memory
>>>>when I was a child there was one called Kohoutek, and later on, Halleys
>>>>came round in about 1986 was it?
>>>I doubt that your age is statistically significant in terms of the age
>>>of the solar system.
>>You realise that's squinking?
>Don't be bloody silly! It's mathematics.
The number of comets that cross our orbit in a decade is a fact, not maths.
>What you have proposed is that you can reach a meaningful conclusion
>about the behaviour of the solar system for a period of only a few
How many comets do you propose pass the earth in a given period then?
>>Because comets are rare, i.e. I've seen only a few, combining the remote
>>of an impact with the small number of comets in a typical decade, or whatever,
>>makes the likelihood of a cometary impact something that happens on average a
>>few times in a decade divided by a very small chance per decade.
>Your definition of a comet seems to be that if they don't have a tail
>which you can see with the naked eye, then it is not a comet.
>First, there are very many comets which are too faint to be seen with
>the naked eye. Second, there are many old comets which no longer have
>a visible tail at all. In short, you are vastly underestimating the
>number of comets in existence.
I'm not interested in, e.g. comets orbiting other solar systems, comets grazing
the sun, comets that only go from the hand of a child to miss another child and
strike earth in winter, comets that spend billions of years hanging about in a
2 light year orbit and never change.
The ones that are a threat, are the ones that cross the orbit of earth. And are
comets, i.e. they have a tail when the approach perihelion. Comets that are
small rocks that would have a tail that can only be detected close up, don't
really interest me.
Clube and Napier aren't interested in the other sort either, except when they
are estimating how many comets they should think there are, when calculating
how likely these are to hit earth. IOW counting cars that drive about Paris
when assessing the risk of being run over in Adelaide.
>>You need instead to show that comets are more common than historical records /
>>personal experience seem to show. Clube and Napier manage this by interpreting
>>anything remotely possible as a comet, and argue that we're living in a period
>>of remarkably few comets compared to the (unknown) rest of pre-history and the
>>unknowns of the future.
>It seems that you have read their book. In that case you will know
>that they propose a long period of terrestial bombardment as a result
>of the entry into the solar system and subsequent break up of the
>super-comet Encke. You should also know that this idea is now
>generally accepted by astronomers.
I should know that their ideas have been long discredited by astronomers, and
their predictions haven't turned out to be supported by events.
It is the equivalent of assuming most, if not all, accidental deaths in
Adelaide, were caused by motor cars and the current lack of motor car accident
deaths is due to a temporary, statistical lull in the accident rates.
And then assessing the number of cars in the world, multiplied by the chance of
a car in Adelaide causing an accidental death, provides the risk of being run
down by a car in Adelaide.