[meteorite-list] Newbie with questions

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 17 Jun 2010 03:55:23 -0500
Message-ID: <9A399E23773645D3B123762EE7F8221D_at_ATARIENGINE2>

Chris, List,

The "glowing" fragments still have plasma around them;
they're moving more slowly and plasma isn't shed back.
But when the light goes out, THAT'S when you're seeing
(or actually not seeing) the bare fragment, flying cold --
dark flight, it's called.

It's the light you're seeing -- not the object. All bright light
on a dark background produces a diffraction flare that
makes it seem to have a measurable dimension to the eye,
but it's (VERY) unlikely the object was big enough to be visible
on its own.

40 miles, you said? 211,200 feet away. Resolving power of
the human eye roughly 50" of arc (say one minute of arc).
If any object were 60 feet across, it would appear to the eye
as a pinpoint dot of no dimension at that distance (and in
practice, you never notice it at all). Can you see a jet liner
(200 feet across) at 40 miles?

Naaah.

> ...like a hawk seen from a mile away.

Assuming a small red-tail at one mile. The same angularly
sized object at 40 miles would be about 125 feet across, or
about 3 arc minutes. The fragments were not 130 feet across!
They were likely about 1/500th that size.

Interestingly, your choice -- hawk at one mile -- is very close
to the smallest object to be practically resolvable at one mile,
so your instincts are point-on... in the short range (where we
have the most experience).

Estimating size and distances in the sky, where there is no
referential framework is next-to-impossible for human senses.
It can be tackled by means of calculation and much training,
but it's still hard... and sometimes impossible.

I once asked someone who claimed to see an "object" in the
sky. (Yes, one of those.) I asked how big it was. After a moment's
thought he said it was about the size of a hat. I asked him, as big
as a hat how far away? At arm's length? Across a room? Across
a front yard? He said, what's distance got to do with it? A hat's the
size of a hat no matter what distance away it is.

No concept of angular size. Zero. Zip. Nada.

Say it again. What you're seeing is the light, NOT the object.


Sterling K. Webb
--------------------------------------------------------------------------
----- Original Message -----
From: "Chris Pagel" <catdoc at gmail.com>
To: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
Sent: Thursday, June 17, 2010 1:02 AM
Subject: Re: [meteorite-list] Newbie with questions


> I'll clarify to the list in a follow up: I saw 5 seconds of the
> blue-green plasma trail, let's call it "Northern Lights Blue-Green,"
> then the blinding flash-flash, then small glowing fragments with no
> tail shooting out and fading away.
>
> Like footage of a lava-bomb-spitting volcano, or burning leaves flying
> up from a campfire, the 10-15 fragments were white, then yellow, then
> orange, then red then dark all in 2 seconds, and very small.
>
> Smallest ones I saw were the size of a bright star, pinpoints, the
> larger ones were... well, bigger... like a hawk seen from a mile away?
> Non-pinpoint. None of these hot fragments had a plasma tail, they were
> post "flash-flash."
>
> Interesting!
>
> -Chris
Received on Thu 17 Jun 2010 04:55:23 AM PDT