## Mnemonics for the S.I. Prefixes

The S.I. System of Weights and Measures may be a bit of a dog’s dinner, but at least it’s a dog’s dinner prepped, cooked, served and — more to the point — eaten by scientists.

### A brief history of the Système international d’unités

It all began with the métre (“measure”), of course. This was first proposed as a universal measure of distance by the post-Revolutionary French Academy of Sciences in 1791. According to legend (well, not legend precisely — think of it as random speculative gossip, if you prefer), they first proposed that the metre should be one millionth of the distance from the North Pole to the equator.

When that turned out to be a little on the large side, they reputedly shrugged in that inimitable Gallic fashion said: “D’accord, faisons un dix millionième alors, mais c’est ma dernière offre.” (“OK, let’s make it one ten millionths then, but that’s my final offer.”)

Since then, what measurement-barbarians loosely (and egregiously incorrectly) call “the metric system” has been through many iterations and revisions to become the S.I. System. Its full name is the Système international d’unités which pays due honour to France’s pivotal role in developing and sustaining it.

When some of those same measurement-barbarians call for a return to the good old “pragmatic” Britsh Imperial System of inches and poundals, I urge all fair-minded people to tell them, as kindly as possible, that they can’t: not now, not ever.

Since 1930, the inch has been defined as 25.4 millimetres. (It was, so I believe, the accuracy and precision needed to design and build jet engines that led to the redefinition. The older definitions of the inch simply weren’t precise enough.)

You simply cannot replace the S.I. system, you can, however, dress it up a little bit and call a distance of 25.4 millimetres “one inch” if you really wanted to — but, in the end, what would be the point of that?

### The Power of Three (well, ten to the third power, anyways)

For human convenience, the S.I. system includes prefixes. So a large distance might measured in kilometres where the prefix kilo- indicates multiplying by a factor of 1000 (or 10 raised to the third power). The distance between the Globe Theatre in London and Slough Station is 38.6 km. Longer distances such as London and New York, NY would be 5.6 megametres (or 5.6 Mm — note capital ‘M’ for mega [one million] to avoid confusion with the prefix milli- ).

The S.I. System has prefixes for all occasions, as shown below.

Note also that one should convert all prefixes into standard units for calculations e.g. meganewtons should be converted to newtons. The sole exception is kilograms because the base unit is the kilogram not the gram, so a megagram should be converted into kilograms, not grams. I trust that’s clear. (Did I mention the “dog’s dinner” part yet?)

For perspective, the distance between Earth and the nearest star outside our Solar System is 40 petametres, and current age of the universe is estimated to be 0.4 exaseconds (give or take a petasecond or two).

A useful mnemonic for remembering these is Karl Marx Gives The Proletariat Eleven Zeppelins (and one can imagine the proletariat expressing their gratitude by chanting in chorus: “Yo! Ta, Mr Marx!” as they march bravely forward.)

But what about the little prefixes?

Milli- we have already covered above. The diameter of one of your red blood cells in 8 micrometres and the time it takes light to travel a distance equal to the diameter of a hydrogen atom is 300 zeptoseconds.

Again, there is an SI prefix for every occasion:

A useful mnemonic would be: Millie’s Microphone Needs a Platform For Auditioning Zebra Yodellers.

For the record, GCSE Physics students are expected to know the SI prefixes between giga- and pico-, but if you’re in for a pico- then you’re in for anything between a yotta- and a yocto- in my opinion (if you catch my drift).

### Very, very, very small to very, very, very big

The mean lifetime of a Z-boson (the particle that carries the Weak force) is 0.26 yoctoseconds.

According to our current understanding of physics, the stars will have stopped shining and all the galaxies will dissipate into dissassociated ions some 315 yottaseconds from now.

Apart from that, happy holidays everyone!

## IoP Energy for busy teachers

The first rule of IoP Energy Club is: you do not talk about energy . . .

. . . unless you’re gonna do a calculation.

— with apologies to Brad Pitt and Chuck Palahniuk

In the UK, the IoP (Institute of Physics) has developed a model of energy stores and energy pathways that has been adopted by all the exam boards. Although answers couched in terms of the old “forms of energy” model currently get full credit, this will almost certainly change over time (gradually or otherwise).

This post is intended to be a “one stop” resource for busy teachers, with suggestions for further reading.

Please note that I have no expertise or authority on the new model beyond that of a working teacher who has spent a fair amount of time researching, thinking about and discussing the issues. What follows is essentially my own take, “supplemented by the accounts of their friends and the learning of the Wise” (if I may borrow from Frodo Baggins!).

### Part the First: “Why? For the love of God, why!?!”

The old forms of energy model was familiar and popular with students and teachers. It is still used by many textbooks and online resources. However, researchers have suggested that there are significant problems with this approach:

1. Students just learn a set of labels which adds little to their understanding (see Millar 2014 p.6).
2. The “forms of energy” approach focuses attention in the wrong place: it highlights the label, rather than the physical process. There is no difference between chemical energy and kinetic energy except the label, just as there is no difference between water stored in a cylindrical tank and a rectangular tank. (See Boohan 2014 p.12)

The new IoP Stores and Pathways model attempts to address these issues by limiting discussions of energy to situations where we might want to do calculations.

Essentially, the IoP wanted to simplify “energy-talk” and make it a better approximation of the way that professional scientists (especially physicists) actually use energy-concepts. The trick is to get away from the old and nebulous “naming of parts” approach to a newer, more streamlined version that is fit for purpose.

### Part the Second: How many energy stores?

The second rule of IoP Energy Club is: you do not talk about energy . . .
. . . unless you’re gonna do a calculation.

— with apologies to Brad Pitt and Chuck Palahniuk

The IoP suggests eight named energy stores (listed below with the ones likely to be needed early in the teaching sequence listed first).

Many will be surprised to see that electrical energy, light energy and sound energy are not on this list: more on that later.

There are, I think, two very important points:

1. All of these energy stores represent quantities that are routinely measured in joules.
2. All of the energy stores represent a system where energy can be stored for an appreciable period of time.

For example, a rattling washing machine is not a good example of a vibration energy store as it does not persist over an extended period of time: as soon as the motor stops, the machine stops rattling. On the other hand, a struck tuning fork, a plucked guitar string or a bell hit with a hammer are good examples of vibration energy stores.

Similarly, a hot object is not a vibration energy store: it is better described as a thermal energy store. Thermal energy stores are useful when there is a change in temperature or a change in state.

Likewise, a lit up filament bulb is not a good example of a thermal energy store because it does not persist over an extended period of time; switch off the current, and the bulb filament would rapidly cool.

Note also that the electric-magnetic energy store applies to situations involving magnets and static electric charges. It is not equivalent to the old “electrical energy”.

The thread linking all the above examples is we limit discussions of energy to situations where we could perform calculations.

Thermal energy store is an appropriate concept for (say) the water in a kettle because we can calculate the change in the thermal energy store of the water and the result is useful in a wide range of situations. However the same is not true of a hot bulb filament as the change in the thermal energy store of the filament is not a useful quantity to calculate (at least in most circumstances). For further discussion, see this blog post and also this section of the IoP Supporting Physics website.

### Part the third: How many energy pathways?

The third rule of IoP Energy Club is: there ain’t no such thing as ‘light energy’ (or ‘sound energy’ or ‘electrical energy’).

— with apologies to Brad Pitt and Chuck Palahniuk

In the new IoP Energy model, there is no such thing as a “light energy store”. Instead, we talk about energy pathways.

Energy pathways describe dynamic quantities that are routinely measured in watts. That is to say, they are dynamic or temporal in the sense that their measurement depends on time (watts = joules per second); energy stores are static or atemporal over a given period of time.

It is not useful to talk about a “light energy store” because it does not persist over time: the visible light emitted by (say) a street lamp is not static — it is not helpful to think of it as a static “box of joules”. Instead it is a dynamic “flow” of joules which means its most convenient unit of measurement is the watt.

As an analogy, think of an energy store as a container or tank; in contrast, think of a pathway as a channel or tap that allows energy to move from one store to another. )

You can read more on the “tanks and taps” analogy here.

The cautious reader should note that the IoP describe slightly different pathways which you can read about here. (Mechanical and Electrical Working are in, but the IoP talk about “Heating by particles” and “Heating by radiation”; on this categorisation, sound would fit into the “Mechanical Working” category!)

The fourth rule of IoP Energy Club is: I don’t care what you call it, if it’s measured in watts, it’s a pathway not an energy store, OK?

— with apologies to Brad Pitt and Chuck Palahniuk

You can look forward to more ‘IoP Energy Club Rules’, as and when I make them up.

Important note: all of the above content is the personal opinion of a private individual. It has not been approved or endorsed by the IoP.

## Ohm From Ohm

Amongst the myriad inconveniences and troubles of a Physics teacher’s life, the choice of the symbols commonly used to represent voltage, current and resistance, must surely rank in the top ten.

### V is for voltage in volts, V

Well, OK, that’s sensible enough. On a good day, I may even remember to call it “potential difference”. The sage advice of Never use two words when one will do is commonly accepted by everyone; however, Physics teachers have, as a profession, decided to go it alone and completely ignore this tired old saw. Thus, voltage is become potential difference because of — erm, reasons (?)

One can only hope that everyone got the memo . . .

### R is for resistance in ohms, Ω

R for resistance? That’s fairly sensible too.

“But what’s that weird squiggly thing, Sir?”

“Ah, you mean the Greek letter omega? Because Physics is soooo enormous that the measly 26 letters of the Latin alphabet ain’t big enough for it…”

### I is for current in amps, A

“WTφ? Are you taking the πΣΣ, Sir?”

“I know, I know! Look, if it helps, think of it as short for intensité du courant . . . Wait, don’t leave! Stop, I have many more fun Physics facts to teach you! Look, here’s a picture of Richard Feynman playing his bongo drums — nooooooooo!”

# V = I R

Except, that’s not Ohm’s Law; it’s actually the definition of resistance:

# R = V / I

There is not a single instance where it is not true by definition. The value of resistance will always be equal to the ratio of the potential difference and the current.

Think of it like this. At room temperature, 1 V of potential difference can push (say) 0.5 A of current through the wire in a filament bulb. (I just love that retro 1890s tech, don’t you?)

This means it has a resistance of 1/0.5 = 2 ohms. However, bump up the potential difference to 6 V and the current is (say) 0.75 A. This means that is has a resistance of 6/0.75 = 8 ohms. Its resistance has changed because it has become hotter. In other words, its resistance is not constant.

Ohm’s Law is perhaps most simply stated as:

The potential difference is directly proportional to the current over a range of physical conditions (including temperature).

Using standard symbols:

# V α I

or, taking R’ as a constant of proportionality:

# V = I R’

You do see the difference, don’t you?

In the first example, R is not a constant value for a given range of physical conditions: for example it can get higher as the temperature increases.

In the second, R’ is constant over a range of temperatures and other physical conditions.

And so there we have it: V=IR can be a perfectly valid statement of Ohm’s Law, provided it is specified that R is constant. If one does not do that, then all bets are off…

In the meantime, here’s another picture of Richard Feynman playing the bongo drums. Enjoy!

## Markopalypse Now

AHT VAL: And once you’ve finished marking your students’ books and they have responded IN DETAIL to your DETAILED comments, you must take them in again and mark them a second time using a different coloured pen!

AHT HARVEY: A page that’s marked in only one colour is a useless page!

NQT BENJAMIN: Erm, if you say so. But why?

AHT VAL: It’s basic Ofsted-readiness, Benjamin. Without a clearly colour-coded dialogue between teacher and student, how can we prove that the student has made progress as a result of teacher feedback?

NQT BENJAMIN: But I’ve only got this red biro…

AHT HARVEY GRINS UNPLEASANTLY AND OPENS A CABINET FULL OF PENS OF MANY COLOURS.

AHT HARVEY: In this school we wage a constant battle against teacher sloth and indifference!

(With apologies to The League Of Gentlemen)

I have been a teacher for more than 26 years and I tell you this: I have never marked as much or as often as I am now. We are in the throes of a Marking Apocalypse — a Markopalypse, if you will.

And why am I doing this? Have I had a Damascene-road conversion to the joy of rigorous triple marking?

No. I do it because I have to. I do it because of my school’s marking policy. More to the point, I do it because my school expends a great deal of time and energy checking that their staff is following the policy. And my school is not unique in this.

Actually, to be fair, I think my current school has the most nearly-sensible policy of the three schools I have worked in most recently, but it is still an onerous burden even for an experienced teacher who can take a number of time-saving short cuts in terms of lesson planning and preparation.

Many schools now include so-called “deep marking” or “triple marking” in their lists of “non-negotiables”, but there are at least two things that I think all teachers should know about these policies.

1. “We have to do deep/triple marking because of Ofsted”

No, actually you don’t. In 2016, Sean Harford (Ofsted National Director, Education) wrote:

[I]nspectors should not report on marking practice, or make judgements on it, other than whether it follows the school’s assessment policy. Inspectors will also not seek to attribute the degree of progress that pupils have made to marking that they might consider to be either effective or ineffective. Finally, inspectors will not make recommendations for improvement that involve marking, other than when the school’s marking/assessment policy is not being followed by a substantial proportion of teachers; this will then be an issue for the leadership and management to resolve.

2. “Students benefit from regular feedback”

Why yes, of course they do. But “feedback” does not necessarily equate to marking.

Hattie and Timperley write:

[F]eedback is conceptualized as information provided by an agent (e.g., teacher, peer, book, parent, self, experience) regarding aspects of one’s performance or understanding. A teacher or parent can provide corrective information, a peer can provide an alternative strategy, a book can provide information to clarify ideas, a parent can provide encouragement, and a learner can look up the answer to evaluate the correctness of a response. Feedback thus is a “consequence” of performance.

So a textbook, mark scheme or model answer can provide feedback. It does not have to be a paragraph written by the teacher and individualised for each student.

Daisy Christodoulo makes what I think is a telling point about the “typical” feedback paragraphs encouraged by many school policies:

[T]eachers end up writing out whole paragraphs at the end of a pupils’ piece of work: ‘Well done: you’ve displayed an emerging knowledge of the past, but in order to improve, you need to develop your knowledge of the past.’ These kind of comments are not very useful as feedback because whilst they may be accurate, they are not helpful. How is a pupil supposed to respond to such feedback? As Dylan Wiliam says, feedback like this is like telling an unsuccessful comedian that they need to be funnier.

## When Harold Met William

Legend has it that in 1988, U.S. Presidential candidate Michael Dukakis opened an election rally in front of a huge crowd in a red state with the ringing words: “This joke will appeal to the Latin scholars amongst you…” He went on to lose decisively to George H. W. Bush.

On that note, this joke will appeal to all the Physics teachers (and other aficionados of the dot-and-cross convention).

For the non-physicists amongst you, this is an illustration of the dot-and-cross convention, which allows us to represent 3D objects on a 2D diagram. The dot represents a vector emerging out of the plane of the paper (think of an arrow coming towards you) and the cross represents a vector directed into the plane of the paper (think of an arrow going away from you).

I’ll get my coat…

## Room 808

It was a warm but overcast day in late August and the clocks were striking thirteen.

Mr Winston Smith, Principal of the Victory G+MINDSET Academy (formerly the Bogstannard Comprehensive School), woke to find himself lying on something that felt like a camp bed, except that it was higher off the ground and it seemed that he was fixed down in some way so that he could not move. Light that seemed stronger than usual was falling on his face.

He gasped as he realised that the infamous MiniEd interrogator, “Grammar School” O’Greening, was standing at his side, looking down at him intently. At the other side of him stood a man in a white coat, tapping an iPad.

“Tell me, Winston,” said O’Greening gently, but with a chilling undercurrent of steel in her voice, “how many buckets am I holding up?”

Winston swallowed fearfully as he realised that he had been deposited by mysterious forces into the deepest bowels of the dreaded MiniEd.

“Erm…two?” he quavered. The two buckets had “EBacc”and “More bloody EBacc” scrawled on them in crayon.

There were a couple of muffled metallic clangs as O’Greening did a rapid double take. “Nick!” she hissed furiously through clenched teeth. The other man ran to join her. He groaned as he strained to lift a third bucket. “Why do I always have to do the Maths and English bucket? It’s sodding well double-weighted, you know…” he muttered resentfully.

O’Greening ignored him. “How many buckets, Winston?”

“Three! I see three buckets!”

The man let the third bucket drop with an explosive gasp and rubbed his tired arms. “Thank God for that! We had that Sir Ken Robinson in here last week. Kept claiming that he could see a fourth bucket called ‘Unleashing Children’s Inner Demiurgic Muse’. I thought my arms were going to fall off…”

“Comrade Gibb!” snapped O’Greening. The man lapsed into sullen but acquiescent silence. “Now, Winston,” she said sweetly, “from whom have we taken our maths mastery pedagogy? From whom have always taken our maths mastery materials?”

Winston locked his dry lips nervously. “Eastasia…we get our maths mastery materials from Eastasia…” O’Greening nodded encouragingly​. “… but up until a couple of years ago, of course, we were encouraged — well, ordered, actually — to get them from Eurasia instead…”

Gibb had stuck his fingers in his ears and was humming “La la la! Not listening! La la la!”

O’Greening glowered at Winston. “Lies! Delusion! Comrade Gibb: take him to . . . Room 808!”

“Erm, this is Room 808, ma’am.”

“Oh. Then fetch me . . . the school’s RAISEonline report!”

Gibb placed the iPad so that it filled the trembling Winston’s entire field of vision.

“Currently, I have a ‘good pass’ set to ‘4’,” she said conversationally. Actually, thought Winston, it didn’t look too bad. The screen was mostly green with only the odd patch of blue.

“Now observe what happens as I now define a ‘strong pass’ as a ‘5’!” O’Greening twisted the dial from 4 to 5.

Winston screamed as the entire screen turned blue. “Arrgh! Don’t do it to us! Do it to another school! DO IT TO ANOTHER SCHOOL!”

O’Greening and Gibb patted him on the shoulder. “Oh, we will. We most certainly will.”

They left Winston Smith alone in Room 808. Tears ran down his face, but he smiled quietly to himself as he stared at the screen. Students, happiness, staff, well-being, people — none of that mattered any more. He had finally won the battle against himself. He loved Big Data.

## Still Working Away In Our Silos (Thank Goodness)

If a thing is worth doing, it is worth doing badly.

–G. K. Chesterton, What’s Wrong With The World (1910)

Why are teachers beavering away in their individual silos, each one of us spending hours reinventing each pedagogic wheel, crafting schemes of work and resources for the new GCSEs?

Wouldn’t life be so much easier and better if we simply shared…?

To which I say: NO!

To be honest, my favourite part of the job is designing, crafting and re-designing resources and teaching approaches. They’re not perfect, of course. I’m reminded of a line from the opening credits of South Park: “All celebrity voices are impersonated . . . poorly.” As Chesterton remarked, if a thing is worth doing, it is worth doing badly.

But the point is, my approaches and resources are a lot less imperfect than they used to be. I flatter myself that, over the years, some of them have become . . . quite good. I believe Michael Stipe once said that in the entire history of the world there were only ever five rock and roll songs; and that REM could play two of them quite well. There’s a parallel in that most teachers have a lesson or two (or three) that they — and they alone — can teach brilliantly.

I often think that, given the right context, most students prefer shabby, bespoke individualism rather than shiny mass-produced perfection.

As teachers, I think we sometimes overestimate the impact that we have on our students. There is no royal road to learning, and neither can all our craft and pedagogic arts construct a conveyor belt either.

As educators, the most we can hope to do is clear a few stones out of the way of our charges as they set out on the rocky path to learning.

In the end, the journey is theirs. Let us wish them well as we watch from our silos . . .

The difficulty of obtaining knowledge is universally confessed [ . . .] to reposite in the intellectual treasury the numberless facts, experiments, apophthegms and positions, which must stand single in the memory, and of which none has any perceptible connexion with the rest, is a task which, though undertaken with ardour and pursued with diligence, must at last be left unfinished by the frailty of our nature.

Samuel Johnson, The Idler, 12 January 1760

## Brownian Motion, Staff Rooms and Bromeliads

Individuals aren’t naturally paid-up members of the human race, except biologically. They need to be bounced around by the Brownian motion of society, which is a mechanism by which human beings constantly remind one another that they are…well…human beings.

— Terry Pratchett, Men At Arms

Happiness is . . . not having an office.

I had a job once where I had an office. It was a quite a nice office. And I had it all to myself. It was a quiet, pleasant little space with a small kitchen nearby. It even had natural daylight through a large window Perfect, you might think.

But I grew to hate that office. You see, I think that teachers — more than anyone, perhaps — need, occasionally, to be “bounced around by the Brownian motion of society”.

What is Brownian motion? Well, it was first observed by botanist Robert Brown in 1827, who noted that, under a microscope, pollen grains in water seemed to “jiggle” randomly. Brown at first assumed that this motion was due to the “life force” of the pollen grains; however, he dispensed with this idea when he saw particles of stone dust (reportedly taken from the Great Pyramid to make sure they were completely and utterly devoid of life) perform the same drunken, wiggly waltz that came to be known as Brownian motion.

And there the matter rested, for a while. And then in 1905, a young patents clerk, working in his spare time at a kitchen table in a very modest apartment in Geneva, suddenly discovered the explanation — and more, much more.

The patents clerk’s name was, of course, Albert Einstein. His explanation rested on the insight that the visible pollen or dust particles were being buffeted by invisible water particles. His mathematical analysis was not only the first verifiable evidence of the actual physical existence of atoms, but also established their size. Understanding the movement and nature of the unobservable by minute and careful scrutiny of the observable…

Looking back at the job with its own office, I think I missed the simple daily dose of teacherly Brownian motion that you get by simply stepping into a staff room. Are you a little too-full-of-yourself-by-half? Some friendly ego-puncturing banter is usually on tap. At your wit’s end with a difficult student or class? A sympathetic shared eye-roll can work wonders. Plus there might even a few good ideas thrown in for good measure.

A good school staff room is not always synonymous with a “good” school, but a good staff room can make even a “bad” school bearable — enjoyable, even! — and the lack of one can make even an “outstanding” school feel like a souless and joyless treadmill.

If you are being interviewed by more than one school, choose the one that has the beat-up, well-used furniture in the staff room, replete with dirty coffee mugs and tottering piles of unmarked marking whose lower layers are being spontaneously formed into sedimentary rock by the crushing pressure from above.

Sadly, I feel that that this type of staff room is a vanishing phenomenon. I suppose that I am like a dinosaur complaining that bromeliads these days don’t taste as nice as the bromeliads they had in the old days.

Teachers today just aren’t rubbing elbows as much as they used too. H’mmm. Maybe that’s why we don’t have to wear elbow patches any more…

But that does not detract from this universal truth that should, I feel, be more universally acknowledged: if a staff room is suspiciously neat and clean and looks like an airport lounge…RUN AWAY!

## It’s Not All Relative: Five Things That Einstein Never Said

We have all done it, haven’t we? Each and every one of us has, at some point, appropriated (or misappropriated) a quotation from a great thinker or writer to lend a spurious profundity to our own footling little thoughts.

While it may be well-nigh irresistible to wrap ourselves in the borrowed robes of literary or scientific genius, the temptation is fraught with dangers. To spare both our own blushes and those of our unsuspecting audience, it’s a good idea to check whether the Great Person actually said what they are reputed to have said.

For one reason and another, the life, career and reputation of Albert Einstein makes him an especially tempting target for spurious attributions.

This is my eclectic list of five things that Einstein did NOT say, and yet seem to be quoted and requoted again and again, especially in an educational context.

It is a melancholy truth that these particular memes will most likely be circulating on the internet until the last router rusts away to nothingness. However, on the principle that it better to light a candle than complain about the dark, I present this list (although, given their preternatural persistence, a flamethrower might be more appropriate).

Watch out, any one of them may well be coming to a CPD near you sometime soon…

Nein-stein No. 1

Everyone is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.

This, according to Quote Investigator [QI 1], was first attributed to Einstein as recently as 2004. The original allegory about animals attending a school and being judged against inflexible criteria, can be traced back to physicist Amos E. Dolbear who published it under a pseudonym in 1898.

Nein-stein No. 2

Everything is energy and that’s all there is to it. Match the frequency of the reality you want and you cannot help but get that reality. It can be no other way. This is not philosophy. This is physics.

Philosophy this gem certainly isn’t. Sadly, it bears no relation to any recognisable form of Physics either. (“Pass the bag labeled ‘New Age Quantum Claptrap’ please, Alice.”)

The original form of this quotation was penned by special effects artist Darryl Anka in 1998 — forty years after Einstein had shuffled off this mortal coil (or, at least, had become significantly less ordered).

Incidentally, Anka never attempted to attribute this thought to Einstein. In fact, he claimed that it had been obtained via “trans-dimensional channelling” from an extraterrestrial entity named “Bashar”. [QI 2]

Nein-stein No. 3

Two things inspire me to awe: the starry heavens and the moral universe within.

A beautiful quote, but Einstein? Naaaah. From Immanuel Kant’s Critique of Practical Reason (1788), actually. Highbrow enough for ya? [Ref 1]

Nein-stein No. 4

The definition of insanity is doing the same thing over and over and expecting different results.

Not Einstein. Not Benjamin Franklin. Not Rita Mae Brown either. The earliest instance tracked down by Wikiquote was from a Narcotics Anonymous publication from 1981.

Nein-stein No. 5

Two things are infinite: the universe and human stupidity. Actually, I’m not sure about the universe.

Einstein may or may not have said this, but the only evidence we have is from the works of therapist Frederick S. Perls, who credited the quote to a “great astronomer” in a book published in 1947. In later works, Perls specifically named Einstein as the originator of the quote which was said during a personal meeting with Perls. However, Perls did present different versions of the statement over the years. [QI 3]

## The F.B.I. and Gang Signs for Physicists

Those notions which are to be collected by reason . . . will seldom stand forward in the mind, but lie treasured in the remoter repositories of memory, to be found only when they are sought.

— Samuel Johnson, The Rambler, 7 April 1759

Sir John Ambrose Fleming (1849-1945) was the inventor of the thermionic valve, devices that formed the glowing (literally!) and pulsing heart of most electronic circuits until the invention of the transistor in the 1960s and the dawn of the Age of Semiconductors.

His part in most GCSE and A-level courses is small in extent but of significant and perhaps under acknowledged importance: he is the original framer of Fleming’s Left Hand Rule and Fleming’s Right Hand Rule. These respectively predict the direction of the force produced on a current-carrying conductor in a magnetic field (left hand) and the direction of induced current flow when a conductor cuts magnetic field lines (right hand). In short, they summarise the physics of everything from the humble electric motor to the Large Hadron Collider via the rail gun; not to mention the giant spinning generators that produce the humming electrical essence that powers our civilisation.

To use the rules, hold your thumb and first two fingers at right angles to each other. I tell my students that the left hand rule and right hand rule are physicists’ gang sign — it’s not too great a stretch of the imagination, at that. If you have ever invigilated a Physics exam, you can tell the point when the students have reached the Fleming’s Left/Right Hand Rule question . . . just look at their hands!

But I digress. I began this post because I was taught the following mnemonic for FLHR:

And to be honest, I have passed it on without thinking too hard about it. However, a student recently introduced me to the F.B.I. Mnemonic. Start with your thumb and say “F for force”, first finger and say “B for B-field” and then second finger and say “I for current”.

The great advantage of this is that F, B and I are the standard physical symbols for the quantities they represent, unlike the multistage hoop-jumping demanded by the traditional mnemonic.

I don’t know about you, but I think I will be using the FBI mnemonic from now on (which, incidentally, was developed by Robert Van De Graaff (1901-1967), of Van De Graaff generator fame).