Fact vs Opinion

As with many other technical writers worldwide, I have cut back on answering questions on Internet forums.

Whilst the CMCA’s forum is at most times an exception, a lot of respondents on many others seem unable to distinguish between facts and opinions. The resulting postings can tie one up for hours trying to explain something that is totally basic and can have only one valid answer.

An example of a fact is that half the population is below average intelligence. An example of an opinion is in which half I might think the above respondents belong.

It is a fact that, on average, people have less than two legs. It may be your opinion my statement is wrong, but for it to be wrong there needs to be an exactly corresponding number of people with more than two legs.

But not every decision can be based on facts. Doctors must often assess the limited facts available to them (increased blood pressure, heart rate etc) to arrive at what can only be an opinion. So another doctor given the identical information may well arrive at a different opinion.

By and large though, established technologies do not work this way. They utilise long established and proven knowledge about (say) the elastic elongation of a bridge’s steel beam under load, or the shear strength of a pivot. It’s essentially a factual process. Where opinion may come in however is this. A bridge is designed to carry a certain load, but there will be a safety factor inbuilt: opinions may differ about the desirable size of that safety factor – and the final decision may well be made on financial as well as engineering grounds.

This occurred whilst I was a motor industry research engineer (back when safety had yet to become a paramount issue). We made changes to brake design that reduced heat-related fading. But the bean counters worked out that the original braking performance could then be achieved using smaller brakes. And that’s what happened. The engineers provided the facts, but it was the bean counters’ opinion that lower price (and higher profit) was more important than safety.

Here’s an actual Internet example (not from the CMCA). A posting noted that “my fridge doesn’t work properly”. Querying disclosed the 120 litre three-way fridge was drawing 10 amps through 10 metres of 1.5 square millimetre copper cable. I responded that the fridge was losing about 1.1 volts along that cable - and whilst that may not be the only problem that fridge could not work properly until that matter was fixed.

This resulted in a barrage of responses to the effect that my response was only an ‘opinion’ and that Fred up the road says it’s nonsense etc. But my response was not an opinion. The relationship between voltage, current and resistance has been known since 1827. It is a fact.

I was then called on to defend my claim that it was a fact. I foolishly mentioned Ohms Law and copped another salvo. One response was: “what would that fellow Ohm know about it - the real world’s different mate”. Life is too short to get involved in stuff like that. There are just too many things I’d like to achieve.

Prejudices at Eighteen
Commonsense is also often drawn upon to defend technical absurdities: as Albert Einstein famously pointed out, “commonsense is the collection of prejudices acquired by age eighteen.”

An often heard example is: “people need exercise to be healthy – it’s just plain commonsense then that lead acid batteries need exercise.” But that anthropomorphic belief is totally unfounded. Indeed, the opposite is closer to reality. Lead acid battery heaven is to be fully charged and kept at float voltage with close enough to zero load. If retained as a sort of lead acid Labrador they live for ever.

This ‘commonsense’ approach manifests at CMCA Rallies. It may seem commonsense that it’s safe to join power cables as long as the join connectors are kept dry. But it’s not. Here again, my ongoing writing on this matter is not, as is sometimes suggested, an opinion. That the practice is unsafe (and illegal) is a fact.

What’s wrong here with the ‘commonsense approach’ is that it is based on safety practices that are no longer relevant. The problem of connecting power cords together nowadays (particularly to extend overall length) is to do with an issue known as loop impedance. Loop impedance is the resistance to the flow of alternating current in a circuit. If increased beyond a certain critical amount (by extending cable length) the time required for a circuit breaker and also an RCD (Residual Current Device) to respond by cutting the current flow is slowed.

For these to save life they must react within an obligatory 0.4 second. The revised cable rules ensure this happens. If you join cables together to extend length you extend that reaction time. In some circumstances, protective devices may not even work at all.

But raising this issue on an Internet site only too often results in any number of “I’ve been doing that for fifty years mate – the #@%^$ electricity regulators don’t know what they are talking about.” And any number of respondents may then reinforce such almost terminally silly views.

This seems to be a particularly Australian characteristic and could be a factor in our having one of the highest death rate/per capita from electrocution in the world: with Queensland and the Northern Territory virtually double that of the other States.

It is often hard for lay people to evaluate what appear to be conflicting answers about technical matters. They do not know whom to believe but, unless the background and record of a technical respondent is known to the respondent, this puts that individual’s reputation at risk.

Whatever else, be hugely distrustful of campfire mythology. Our field is absolutely rife with it and a great deal relates to what may have just worked in unique circumstances. The classic example is the bicycle wheel or tin dunny roof which just happened to suit a freak TV reception area – but is thereafter promoted as the panacea for all TV reception problems.

Collyn Rivers is an ex- research engineer. His books, available directly from the CMCA, are written in plain English but based on his extensive engineering background.

By Collyn Rivers, W8045