[Rockhounds] NW Meteor hunters, forget it

[Alan Goldstein]

I heard a meteor explode overhead in 1977. It sounded like a sonic boom at 
almost exactly 3 PM. I went out to look for a fast moving jet. Naturally I 
saw nothing, because the explosion occurred long before I went outside. It 
certainly exploded a few miles overhead because the meteorites were 
recovered over a pretty wide swath of town. The largest meteorite recovered 
went through the roof of a house in west Louisville lodging in a rafter. 
Smaller rocks punched a hole through a corrugated metal roof in a downtown 
warehouse and went through a pane of glass in someone's sun room. No telling 
how many were never found because they ended up in the street or in 
someone's garden!  I think they all ended up in the Smithsonian 
Institution - including a specimen that was supposed to be returned to our 
local museum, but those greedy SI meteorite folks reneged on their 
agreement!

Your typical fireball meteor is caused by a pretty small piece of rock. Most 
can't be tracked by FAA-type radar.  That's actually a good thing or 
migrating birds would wreak havoc in the spring and fall! I understand that 
a large flock of sandhill cranes can be tracked, because together they can 
be as large (or larger) as a 747 wingspan.

I have seen a bright green fireball go below the horizon. It looked like it 
hit a few miles away, but as most already know, it probably vaporized in the 
atmosphere hundreds of miles away and a dozen or more miles up in the 
atmosphere.

Alan


----- Original Message ----- 
From: "Lanny R" <lanny.r at roadrunner.com>
To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors" 
<rockhounds at lists.drizzle.com>
Sent: Thursday, February 21, 2008 1:38 PM
Subject: Re: [Rockhounds] NW Meteor hunters, forget it


> Yes, with a lot of data, the impact point can be determined. But it  can't 
> be done just by knowing where a few cameras were pointed. To  determine 
> impact from the path, you need precise data including the  location of the 
> camera, the direction it was pointed, the focal length  of the lens, the 
> angle of the lens from horizontal and the precise  time of each frame of 
> the images. Most likely the meteor was a long  way from the cameras, so 
> any error in the measurements can make a big  error in the results. With a 
> bunch of these measurements from the  track, one can create the track in 
> 3-dimensions and determine the  point of impact.
>
> As to the flash of the meteor seen over the Northwest two days ago, 
> triangulating it will not give you the location of impact. These  flashes 
> that are often seen are not impact flashes, they are the  meteor breaking 
> up in the atmosphere. Triangulating on that will only  give you the point 
> over the ground where it exploded.
>
> Only really large meteors make a big fireball all the way to the  ground 
> followed by a big impact, and these we won't need any  calculations to 
> find. Small meteors are slowed so much by the denser,  lower atmosphere 
> that they cool and don't have a fiery trail to  impact, and don't make a 
> significant crater. Most likely, the meteor  seen two days ago was not 
> seen after the flash of it's explosion.
>
> The eye witness accounts of the "impacts" are typically completely  wrong, 
> especially in the dark. People misjudge their ability to  determine the 
> location of a flash in a dark sky, or even of a lighted  moving object in 
> the sky. They can't judge the size of an object or  its distance from 
> them. There is almost nothing for reference to make  determinations in a 
> dark sky (most people aren't very good at it in  the light either). 
> Consider this meteor, a report from AP news stated  that a pilot for 
> Northwest Airlines reported to see the flash of the  impact of the meteor 
> in southeastern Adams County in eastern  Washington. Completely wrong.
>
> The news is finally out from scientists; the report from the  University 
> of Washington this morning, from data from a motion-wave  detector is that 
> the flash happened over La Grande, Oregon when the  meteor broke up 19 
> miles above the earth's surface. Now, break out all  that surveillance 
> camera data, make a lot of calculations to determine  that trajectory 
> before the flash and you will get the general area of  where some small 
> pieces might have impacted over a broad area on  sagebrush (and snow) 
> covered hills and/or forested snow covered  mountains of Oregon, not 
> Washington, unless of course the angle is low  enough that they reached 
> Idaho, or was the direction actually to Nevada?
>
> Regards,
>
> Lanny
>
>
>
>
>
> On Feb 20, 2008, at 1:35 PM, Kreigh Tomaszewski wrote:
>
>> If you have multiple pictures you could go the location each was taken
>> from and find the elevation and direction of the meteor in the sky.
>> Plotting them together should allow you to identify the track thru the
>> sky and come pretty close to the impact point.
>>
>> Kreigh
>>
>>
>>
>> Lanny R wrote:
>>>
>>> There is nothing to triangulate from. The security cameras show the
>>> usual flash of light or short term streak in the sky (all of them I
>>> saw on the local news looked like just about the same quality and  same
>>> few seconds the news shows us time after time to report an exploding
>>> transformer, person illegally lighting a cigarette, a car crash or a
>>> robbery). There is a streak of light or a flash, then it's gone  behind
>>> trees, hills or the building next door. There is no indication of the
>>> angle of decent. Thus one might be able to determine the heading, but
>>> how far did it go?
>>>
>>> The news reported the supposed witnessed impacts in Adams County, but
>>> also reported that the experts believed that if the meteor impacted,
>>> it was in the Pacific. After all, if it killed a jack rabbit in Adams
>>> County, how was it seen overhead in Washington?
>>>
>>> Regards,
>>>
>>> Lanny
>>>
> -- 
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