[meteorite-list] Re: Asteroid?

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Thu Apr 22 09:53:37 2004
Message-ID: <3E0813E7.2BF84F15_at_bhil.com>

Hi,

    Because of the great distance of the Sun from the Earth, the shadow of any object at
roughly the same distance from the Sun as the Earth is being projected by nearly parallel
rays. For all practical purposes, they are parallel rays. This means that the shadow of an
object, even one 10,000 miles away, is essentially the same size as the object itself.
    Of course, such a shadow will not have sharp edges because of scattered sunlight
entering the shadow cone. The shadow will have a dark center and a diffuse boundary. But
an area of shadow on a sunny cloudless day can hardly be attributed to anything else. Note
that an asteroid shadow from a round asteroid will only be round at local noon. At other
times, it will be elliptical because of projection on the Earth's surface at an angle.
    There are hundreds of such "shadow" reports from the eighteenth and nineteenth
centuries, but such a shadow is nearly impossible to document even with the full
electronic and optical resources of today. And they are fleeting phenomena.
    Don't hold your breath waiting for an asteroid to pass between you and the Moon or
watching for asteroid shadows. It's not that we don't have enough passing asteroids, it's
that the shadow path is a tiny momentary line on the Earth's surface. A few thousand feet
away and there would be no shadow. You have to be in exactly the right spot (and time).
    And, Ron is right, there are more planes flying over than there are asteroids... But
this is an argument in favor of the eighteenth and nineteenth century reports being
"real," at least some of them. Very few Boeing's flying in the year 1757!


Sterling K. Webb
---------------------------------------------
Tom aka james Knudson wrote:

> Hello List, I want to ask a weird question. I can't give an exact date, all
> I can tell you is it was in April or may of this year on a week day. At
> about 2:30 or 3:00 in the afternoon in Chandler AZ, I was waiting for my
> wife and child to get out of school (wife was an aid). I was sitting in my
> car and there was teachers and students everywhere. For a split second the
> hole area got darker like we were in a big shadow. It was like a large dark
> cloud passed over. I noticed a couple of the adults look up to see what
> caused this thing, Maybe a plane, a bird, Heck, maybe even superman! But
> there was nothing at all in the sky that could of caused this.
> Tonight, I was out looking at the moon with my telescope when a plane
> eclipsed the moon(I like it when that happens). Well, it got me thinking of
> how neat it would be if a large asteroid eclipsed the moon while I was
> looking.Thinking of what it might be like if that happened. It reminded me
> of that after noon in Chandler. Could something in space cross in front of
> the sun and cause this?
>
> Thanks, Tom
> The proudest member of the I.M.C.A. #6168
>
Received on Tue 24 Dec 2002 02:59:36 AM PST