Re: Possible evidence for Stone Age (Clovis) Cosmic Catastrophe?

Apparently on date Fri, 04 Nov 2005 16:09:13 -0800, Tom McDonald
<tmcdonald2672@xxxxxxxxxxxxxxxxxxx> said:

>nospam@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx wrote:
>
><snip>
>
>> Because comets are rare, i.e. I've seen only a few, combining the remote chance
>> 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.
>>
>> 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.
>
> Comets are not in the least rare. Here is the list of comets
>newly discovered in 2004:
>
>http://www.comethunter.de/2004.html

That's a list of comets *discovered* in 2004, not crossing earth's orbit in
2004.

I'd best explain how this works. Comets are numbered serially by type. So,
there are about 170 periodic comets, I think it was last time I looked. They
are numbered as per 1P, 2P, 3P and going all the way up to 170P or so.

There's a list of periodic and lost periodic comets here:
http://tinyurl.com/bt9db

What you are looking at in your reference is not the same thing. Most of the
list consists of SOHO discovered objects which are invariably objects grazing
the sun which can be called comets if you like but which are never anywhere
near earth's orbit.
http://sohowww.nascom.nasa.gov/

Most of the rest are objects out in the distant outer solar system that can be
detected as telescopes and techniques improve, e.g. LINEAR which is trying to
establish whether there are any threats up there potentially liable to hit the
earth at some point in the predictable future.
http://www.ll.mit.edu/LINEAR/
Also NEAT http://neat.jpl.nasa.gov/neofaq.html

The reason a lot of "comets" have been discovered in 2004, is that there are
lots of remote objects that, depending on your classification system, qualify
as comets is that a lot of searching of the skies has taken place in the last
few years looking for objects that potentially are threats. These are not all
objects that cross the earth's orbit, these are objects that orbit the sun and
can be checked to see *if* they cross our orbit. Regardless of this, they are
catalogued when they're discovered, not when they actually cross the orbit if
they ever will, and most of them aren't anywhere near doing this.

If you cut out all the SOHO, LINEAR, NEAT, etc designations, you're left with
160P, 162P, 163P, 164P, 167P.

Cross reference these to http://tinyurl.com/czd2s and you will find these five
comets discovered in 2004 are due to actually pass perihelion in 2012, 2010,
2012, 2011, and 2066. One of them, 163P did actually perihelion in 2005, but
wasn't crossing our orbit to do that, it's a remote comet that shouldn't be
considered when assessing the likelihood of comets impacting the earth. That's
true of many actual comets, but there are some which definitely can hit the
earth, and eventually, one will.

> Here is a list of comets named after their human discoverers.
>You will often see comets named Linear X, or SOHO Y; but these,
>and some others, are the names of comet-hunting observatories,
>not individuals:
>
>http://www.comethunter.de/discoverers.txt

Yes I realise this. I also realise that most of these people are finding the
comets by looking at SOHO images of the sun - which appear online somewhere or
other. They find objects very near the sun in the images and these are,
presumably, comets.

These are essentially not relevant to the risk of impact on earth, even less so
than the trillions of comets up out there which don't orbit into the inner
solar system. At least the latter have some prospect of being pitched down
sunwards at some future moment.

.

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