Over at *The Conversation*, they have been on something of a roll. There was the recent article trumpeting the ‘inquiry learning versus explicit teaching is all a false choice’ trope which I tackled here. However, in this post, I want to focus on an even more extraordinary piece that expands on why we should teach Einstein’s theory of general relativity to primary school students (except for the ‘scary equations’ which have ‘no place in the school curriculum’). Sensible as my readers are, I imagine you may think such a claim is too silly to warrant a response, but it does illustrate an important point about science that is not widely appreciated.

The Einstein article was written by Emeritus Professor David Blair of the Einstein-First Project. Einstein-First seeks to teach relativity and aspects of quantum physics using Lycra and Nerf guns. Why? Well, partly this is justified because ‘activity-based learning’ is fun (I discuss the idea of activity-based learning here). I do not doubt for a second that primary school children enjoy firing Nerf guns, although I would be interested to see the evidence that this leads to a long-term interest in science and a better understanding of the subject.

For many educational projects inspired by romantic notions of childhood, this would be enough. However, Blair adds another component to his argument. We must start with Einstein because, ‘Newtonian physics is wrong’. Blair is not alone in having received such a divine revelation. The internet is awash with clickbaity articles leading with the idea that Newton was wrong. Shock! Horror! WE WERE LIED TO AT SCHOOL!

But before we get carried away, let’s back up a minute.

Science is the process of formulating hypotheses, usually based upon mathematical or analogical models, and then testing these hypotheses against reality, either by conducting controlled experiments or, where that’s not possible, analysing observational data. The hypotheses involved have to be falsifiable - this means that we need to be able to make predictions that could conceivably be proved wrong by some set of data. A good model is one that makes accurate predictions. And yet, fundamentally, no model is ever proved right because there is always the possibility of some future observation that may conflict with the model.

The current state of play is that we have two sets of models - quantum physics and general relativity - that make accurate predictions about different areas of physics but that conflict with each other at a fundamental level. This is fine if we view them as models that approximate reality. The issue arises when we confuse them with reality itself. Which one is right and which is wrong, we ask? It is still an open question as to whether we will ever develop one consistent, full description of physics with no internal contradictions.

I frequently encounter the confusion between a scientific model and the reality it is meant to be modelling when attempting to discuss models of the human mind - such as that the mind consists of a limited working memory and an effectively limitless long-term memory. Everyone working with such a model knows it is a simplification. It stands and falls on whether it makes accurate predictions about features of human cognition to which the model is applied, such as how we learn. That is all that matters. And yet there are those who argue such models neglect sensory memory or cannot explain where working memory is located in the brain, neither of which is actually relevant to the value of the model. They think they are adding nuance to the discussion, whereas they are actually signaling a fundamental misunderstanding.

Was Newton wrong? Trivially, yes he was wrong in some circumstances. His theory of gravity could not, for instance, account for the perihelion of mercury. If you don’t know what a perihelion is, it doesn’t particularly matter, but it is worth noting that Newton’s laws predict a perihelion, it’s just that Newton’s prediction is a bit off. There is a peculiar pedantry about pronouncing Newton’s incorrectness on this basis. Newton devised the most complete model of motion ever constructed up until that point. Not only that, he subsumed planetary and terrestrial motion under one unifying model. And his model works extremely well. If you are an engineer, then unless you are working at the extreme technological fringe, Newton’s principles work really well. And I mean, *really* well. In contrast, you don’t want to be messing about with Einstein’s genuinely quite scary equations of general relativity when designing a forklift truck.

There is a similar phenomenon at play in the teaching of chemistry. A common trope is that models of the atom that consist of electron ‘shells’ are ‘wrong’. And again, at a certain pedantic level, this is true. But you can ultimately claim the same of the more sophisticated ‘orbital’ model that chemists typically replace it with. In fact, shell models of the atom are useful for explaining many chemical properties. They break down at some point. This is both inevitable and interesting. It is the bleeding edge of science where we make new discoveries.

Shell models of the atom are similar to models of the mind, biochemical models or basically *any* scientific model other than the grand, unifying model of physics that we have not discovered yet, in that they are all approximations that break down in the extreme. Nevertheless, applying those models that accurately predict what happens at these extremes to the situations for which the models were typically developed would be cumbersome and perverse - like using general relativity to design a forklift truck.

It almost seems unnecessary at this stage to note that Blair’s suggestion of modeling particles that have both a wave and a particle nature with a Nerf gun ‘bullet’ is, well, wrong. The bullet does not capture the wave nature of the particle at all. It’s a model that breaks down immediately. Similarly, Lycra sheets only approximate the curvature of spacetime. They don’t have enough dimensions to do otherwise. If we were being generous, we would recognise that these are analogies that have some value. But if we were being generous then we would extend that generosity to the far more deserving case of Newton’s laws.

Entertaining though these Nerf guns and Lycra may be - and we have all messed about with science toys during science week - they will not leave children with a somehow truer understanding of science because their deployment is based on a naïve misconception. There is no revelation here and no impending revolution. There’s the potential for some fun but when you strip away the clickbait veneer, you are left with the same romantic argument about experiential learning that has been failing since at least the nineteenth century.

It’s not cutting edge. It’s proper retro.

Right. I've taught relativity (at university, not in primary or secondary schools) and I agree. In fact, it's not only a misunderstanding it is also ignorance of many things at play here.

One interesting point is that the "correctness" of Newton's model is quite well-known and well-appreciated. Work continues on, but something for the interested reader to google (and anyone who would ever write the very embarrassing phrase "Newton was wrong") is "Newtonian limit".

Here is my oversimplification. Some things are approximations, but they are VERY USEFUL because we have a parameter that we can tweak to be as precise as we like. For example, think about the N decimal place approximation of Pi. We know that if we have N digits then we are with 10^-N of the true value of Pi. In applications, we just need to tweak our N to whatever we care about (for example, the machining accuracy or resolution of our device). We say that in the limit (as N approaches infinity), this approximation converges to Pi.

Now. If someone says to you Pi is 3.14159 to 5 decimal places, does it really mean anything to say "hey, you're wrong, it has infinitely many digits!" Of course not. Those first few decimal places will be correct no matter how much much more precise the approximation becomes. The same is true for Newton and Einstein. The intuition gained by studying Newton properly will remain valuable, even (especially) if the student does go on to study relativity.

When teaching kids about planets and the cosmos, yes, it is important to mention Einstein and Newton. But it should only be a mention. In high school perhaps Newton's model makes sense and can lead to interesting discussions. It could be said that it is an approximation, and that Einstein's model is more precise. But it should only be said, quickly, before returning to Newton. Anything more is gratuitous and a waste of time. And bad for learning.

You're right - total clickbait - it's a giveaway at the start: "We ... think we have the answer." So many correction points available indeed.

One missing piece (one might say important) is any evidence that this is more than fun and enjoyable.

A key nuance in my book is the fact that a key challenge in teaching secondary Newtonian physics lies in the fact that it is so counter to everyday experience. Newton was a genius in that he came up with something that was so counterintuitive but was a better model. We never experience frictionless motion in our normal lives etc etc. A key challenge in secondary physics is engaging with students so they learn a deeper understanding than just parroting it (very very hard indeed).

Re centrifugal force - this is similar to the point above. We shouldn't muddy the waters by validating everyday experience in this area. Our job as teachers is to engage and take students deeper to a better model!