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Old 22-07-2020, 03:48 PM posted to uk.rec.gardening
Martin Brown[_2_] Martin Brown[_2_] is offline
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On 22/07/2020 12:53, AnthonyL wrote:
On Tue, 21 Jul 2020 13:20:29 -0000 (UTC), (Nick
Maclaren) wrote:

In article ,
AnthonyL wrote:

When I hear them arguing and disagreeing with eachother the thought
that immediately comes to me is "You are scientists. If there is not
a proof there that satisfies all then shut up and go seek it".

It somewhat reminds me of what I learnt as an engineer "Safety factor
is simply ignorance factor".


The former shows your misunderstanding of complex issues - why do you
think there IS a single, explicable, complete answer? There very
often isn't - and, in some cases, there are questions that are quite
simply unanswerable in such terms.


So they may as well believe in a god and argue about that? They may
theorise one thing and it is in pursuit of theories that more becomes
known but to argue that one belief is better than another is the
anathama of what I understand science to be. What's the point in


Science is a progressive approximation to describing reality using the
best mathematics available. The more a scientific theory can explain and
the more experimental tests of its predictions that do not refute it the
stronger that scientific belief in that theory becomes.

The fundamental conservation laws are close to being an immutable core
set of beliefs and firmly believed by all as anything in physics.

But there is always a possibility that some clever experiment done
tomorrow will refute something that until now has been considered a
sacrosanct law of physics. Groundbreaking experiments with unexpected
results tend to break open whole new areas of physics for study.

Radioactivity, superconductivity, general relativity, lasers for
instance. You can never tell in advance what will be important.

Each advance in physics includes all the existing results as some weak
field limiting case of a more complete and complicated theory. It is
still not known if a grand unified theory of everything is even
possible. Certain pure mathematical proofs hint that it may not be.

believe a heavy stone will fall to the ground faster because it is
heavy?


Allowing for air resistance it does fall ever so slightly faster. But
shape will make a big difference too. Experiment trumps elegant theory
every time - nature is the final arbiter of every scientific theory.

A flat plate will fall more slowly than a sphere. Shape really matters
unless you do the experiment in a vacuum.

And the second is effectively ********. You cannot design for all
possible events - ships are designed only against (say) 'once in
a millennium' storms, not the worst possible storm, let alone such
things as Cumbre Viejo or the Storegga shelf collapsing.


That is not how engineering builds in safety factors. At least not in
the aviation (airframe and engine) environment I started off in.


They do basically look for the worst case loading that the airframe
might be expected to encounter in service and then choose a suitable
multiple of that as a safety margin. Victorians tended to err on the
side of caution with a factor of 7 so their sewers still work whereas
the cheap and nasty blocks of flats built in the 1960's used a safety
factor of 1.0 which is why Ronan Point collapsed like a deck of cards.

--
Regards,
Martin Brown