[LINK] Numbers limit how accurately digital computers model chaos

[Roger Clarke]

On 25/9/19 9:29 am, Bernard Robertson-Dunn wrote:
> Scientists and engineers hate non-linearity. Unfortunately the world is
> essentially non-linear.

A quibble about language.  (I'm enjoying the conversation).

All mathematics involves intellectual models / mind-stuff.
Mathematics is not, and not of, the real world.

Statements like "the world is essentially non-linear" blend words that 
apply in the two distinct spaces of the mind and the real-world.

Some scientists and engineers 'know all that'.

But the media, and the public, are very prone to confusion, because 
they've never heard Einstein's dictum 'God doesn't play dice with the 
world'.

Worse still, many scientists and engineers fall into the habit of loose 
language, and trap their own thinking into the assumption that model = 
system.

Here's an (inevitably flawed) attempt to avoid loose language:

Various kinds of mathematical models can be used to represent various 
real-world systems, and can achieve varying levels of approximations of 
real-world behaviour and outcomes.

We (all) believe that a wide array of physical phenomena are being 
approximated with workable error-factors (e.g. tides, and met forecasts 
in relatively stable conditions).  In some circumstances, physical 
phenomena are being approximated with incredibly small error-factors 
(e.g. solar system mechanics, as indicated by moon and Mars landings).

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.

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)
(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

</morning-pontification>

-- 
Roger Clarke                            mailto:Roger.Clarke at xamax.com.au
T: +61 2 6288 6916   http://www.xamax.com.au  http://www.rogerclarke.com

Xamax Consultancy Pty Ltd      78 Sidaway St, Chapman ACT 2611 AUSTRALIA 

Visiting Professor in the Faculty of Law            University of N.S.W.
Visiting Professor in Computer Science    Australian National University