[LINK] Numbers limit how accurately digital computers model chaos

Bernard Robertson-Dunn brd at iimetro.com.au
Wed Sep 25 15:06:16 AEST 2019

On 25/09/2019 10:35 am, Roger Clarke wrote:
> Models of real-world systems of large scale (many entities) and high
> complexity (many inter-relationships among many entities) have
> notoriously large error-factors, and have error-factors that vary
> enormously depending on the circumstances and that defy attempts at
> prediction.

Non-linearity rears its ugly head when it comes to predictions. It is a
characteristic of non-linear systems that any errors will grow
exponentially, the only question is How Quickly?

Your reference to moon and Mars landings is a little off target.
Engineers did what engineers always do when faced with non-linearity -
they wrap the prediction system in a negative feedback loop. By
definition a negative feedback loop tries to minimise the error between
target state and actual state. If the target state is a moving state,
then it's called goal seeking. 

> A new round of AI enthusiasm is prancing its nonsense around the
> world. And this one has associated with it a wave of artefact-autonomy.
> Unless we use our language very carefully, we're inviting:
> (a)  simplistic scientists and engineers, and feeble-minded marketers,
>      to over-believe and over-sell, and deliver horrible outcomes
>      (of which Robodebt is merely a harbinger)

My experience is that "simplistic scientists and engineers, and
feeble-minded marketers", get into trouble when they make predictions
outside their areas of expertise. Which is why Health IT has been less
than successful. Technologists do not understand the problems of
healthcare but they insist on implementing their solutions.

> (b)  the media and the public will put up with the nonsense for a
>      period of time, but public backlash will in due course wash away
>      the hubris, and with it not just the badly-conceived and harmful
>      models and artefacts, but also some that are of value to humankind

Sometimes. This was published today:

Why the Myth of Period Syncing Won’t Go Away

"For decades, researchers have been poking holes in the study that
introduced the concept of “menstrual synchrony.” Many people believe in
it anyway."


"For a phenomenon that’s highly unlikely to be real, period syncing has
enjoyed an impressively long life in the popular imagination. Every now
and again, news stories and listicles pop up to inform the public that
no, actually, period synchronization as a result of prolonged proximity
is not a thing, but the fictional story lines and offhand jokes persist

How does all this relate to non-linearity?

Sometimes you only have to be a little bit wrong to totally stuff things up.



Bernard Robertson-Dunn
Canberra Australia
email: brd at iimetro.com.au

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