Lightening the load on weighty issue of physics
Linguistically, during the evolution of modern English, the words mass and weight have been synonymous, not only colloquially, but also in learned publications.
However, physics, quite independently, unilaterally redefined "weight" as "a quantity which results from gravitational action".
After spending 39 years earnestly preaching to generations of captive adolescents the essential differences between mass and the gravity force, using at least that number of different methods of explanation, I have suffered a Pauline conversion. My Damascene moment occurred when I was marking a straightforward question addressed to Intermediate level pupils.
Essentially, it asked "what is the weight of a mass of 25kg?"
It will come as little surprise to experienced teachers that about a third of the responses said 25kg and that about another third said 250kg.
Only 5 per cent of the responses gave the correct answer of 250 N.
After firstly banging my head against the nearest mass, (the wall), my response was to ask myself, "Why do I bother?"
I have had successes with the teaching of weight. Unfortunately, these have been limited to the scholastic academics, who can accept anything coming from authority, and the natural physicists, who need few linguistic guidelines to appreciate the fundamental ideas of mass and force. The mass of my pupils, upon whom we also depend for our future, do try hard, and multiply any number with the unit "kg" after it by ten with gusto - but often completely out of the correct context.
My disappointment has been ameliorated by the realisation that this is not a physics problem, nor should it be my problem.
Years and years of usage from outside the physics universe, from the general public, the media, and from mathematicians and chemists (who should perhaps know better), have engendered a climate where the meaning of the word "weight" produces linguistic tension in most of our pupils.
Our poor pupils not only have to cope with the demands of an intellectually rigorous topic, motion, which is full of demanding concepts, but also have to try to model the concept of gravitational force through the fog of obscure and unfortunate nomenclature, after having suffered inculcation from birth with the "commonsense" equivalence of mass and weight.
Yet physics encourages and perpetuates the continuing use of an everyday word for a technically explicit concept, completely at odds with its everyday meaning.
The present English word "weight" derives fairly directly from the old German word wegan, meaning to carry, or convey, and was used often in relation to balances. Up to the end of the 16th century, the word was synonymous with mass.
Galileo, the father of controlled experimental physics, accepted this usage. In his discourse on the nature of motion, De motu, 1590, he persistently uses the old Italian gravita, meaning having gravity, instead of using a term for inertial mass. However, the great man could not be expected to anticipate Newtonian ideas on gravity, and hence the new definition of weight as the force of gravity. With Galileo Galilei, the 10,000-year struggle of civilised man to understand motion had made a quantum leap of progress.
Fourteenth century savants such as the mathematician and theologian Thomas Bradwardine of Oxford, and polymath Nicole Oresme of Paris, had already realised that the theories of the pagan ancients such as Aristotle did not describe reality, but their work on improving the fundamentals of kinematics basically led up a blind alley, having to satisfy elements of metaphysics and theology as well as what we now call physics.
Galileo was the first to see through this fog of obscurity, so let us forgive his imprecision of language at this stage in classical development.
But now, despite another 400 years of usage by the physics community, the word "weight" is no longer fit for purpose; it has failed its 21st century MOT.
Ipso facto, it follows that the solution to the problem is very clear.
Let us consign the W word to the oubliette, to whatever is the physics equivalent of the Vatican's Index Librorum Prohibitorum, (the list of forbidden books). Requiescere in pace - let it rest in peace with other words of the devil such as centi*ugal, suc*, hea* of ovens, siz*, rea*ing, po*ndal, g-*orce and *ig-*ags (known as graphical lines).
We should reject it, ignore it, leave it to the province of the scientific illiterate, to the editors of the national tabloids.
And its replacement?
Our customers appear to like the word "gravity", judging by its frequency of usage.
So would anyone object to "gravity force"?
We seem to have persuaded our pupils fairly easily at SQA Higher Grade to use the idiosyncratic term "buoyancy force", (and even occasionally to spell it correctly).
"Gravity force" is at least accessible and its meaning is unambiguous. Setters of national exams could improve the true assessment of physics, by removing the weighty (sorry) linguistic impedimenta associated with the W word, simply by not using it.
As a Janeite would have it, it is a word lost to respectability; let no decent person have anything more to do with it.
• Charles Buchan is head of physics at Fraserburgh Academy. He has held many SQA posts, including science panel convener and advisory group member, and has had national and regional development roles in Standard Grade and Higher Still. He is a former teacher-researcher in medieval science at New College, University of Oxford.