[meteorite-list] Tektite fields and rotation

From: Göran Axelsson <axelsson_at_meteoritecentral.com>
Date: Sat, 29 Mar 2008 00:49:55 +0100
Message-ID: <47ED8423.5000400_at_acc.umu.se>

You're right, that is a quite complex problem but solvable with
differential calculus and analytical mechanics. The problem is real and
any gunner that had to calculate projectile trajectories know that you
have to take latitude and direction into the equations.

As a simple example, imagine a cannon ball being shot straight up. When
it leaves the barrel it has some angular velocity (momentum) from earth
rotation. As it rises it loose kinetic energy and gains potential energy
but nothing affects the angular momentum and just as a skater that
extends her arms after a fast rotation it looses angular speed (but not
momentum), the earth rotates faster than the cannonball. When it falls
down again it will gain angular speed and hits the earth straight down
but a bit from the gunner.

Okay, that was a simplification that only works at the equator as the
coriolis effect have a real effect anywhere else on the earth.
Think of it as a satellite orbit, you can't create an orbit that stays
on a constant latitude except on an equatorial orbit. So the coriolis
effect will rotate everything. The cannon ball will drop at a latitude
closer to the pole/equator (strikeout the wrong answer, can't calculate
that in my head... my brain is hurting...) and a bit behind you as the
earth rotates... and we are only talking about a shot straight up.

Actually, there is two places on the earth where a cannonball will drop
down at the gunner when shot straight up.... guess where!

It is a complex problem but it can be calculated without too much
problem. But my gut feeling is that geological and topological
differences in the target area, wind patterns and impactor direction is
bigger factors in how the tektite field develops.

/G?ran

Chris Peterson wrote:
> That was my first thought as well. It's probably a fairly complex
> problem. At the least, Coriolis effects will be significant, and will
> distort the debris pattern.
>
> Chris
>
> *****************************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>
>
> ----- Original Message ----- From: <mexicodoug at aim.com>
> To: <epgrondine at yahoo.com>; <meteorite-list at meteoritecentral.com>
> Sent: Friday, March 28, 2008 12:11 PM
> Subject: Re: [meteorite-list] Tektite fields and rotation
>
>
>> Hi Ed,
>>
>> Since ejecta would start out with the same rotational motion as the
>> Earth, at what point and by what mechanism would you inferring that
>> it "decouples" from Earth and looses that rotational component of its
>> own motion? Good question, though!
>>
>> Best wishes,
>> Doug
>
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Received on Fri 28 Mar 2008 07:49:55 PM PDT