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NNTP-Posting-Date: Wed, 06 Sep 2017 13:38:40 -0500
Message-ID: <59B040CE.429@mindspring.com>
Date: Wed, 06 Sep 2017 14:39:10 -0400
From: Ron Hardin <rhhardin@mindspring.com>
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Subject: Re: Hourglass Question
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Ron Hardin wrote:
> 
> An old question from the 1970s that I never
> figured out.
> 
> What governs the speed of flow of an hourglass?
> 
> I mean what principle.  What's going on.
> 
> It's not viscosity (no transport of x momentum in
> the y direction etc.)
> 
> It seems like it's the time it takes something to
> call out of a lockup condition and clear the mess,
> leaving it up to the next lockup condition, but
> what the hell equation is that?


Try this start: the sand above the hole consists of locked up unstable structures, each 
stabilized by the structure below it.

The one at the bottom goes unstable and falls, freeing the one above to begin going 
unstable.

So there a distance between structures, an instability growth time to collapse.
-- 
rhhardin@mindspring.com

On the internet, nobody knows you're a jerk.