Surface tension

I don't know why I have never dealt with surface tension here: it is in at least two of my books. Here is how I have dealt with it in What On Earth?

Water has a property called surface tension. The why of surface tension is hard top explain, so the simple explanation is that surface tension is caused by polar water molecules all pulling each other together. Don’t worry too much about the why: the main thing is that the effects are amazing.

For example, water forms drops that stick together. Without surface tension, there would be no raindrops. Next, lots of insects and spiders can walk across a water surface. In fact, you can even make a paper clip sit on a water surface, but it isn’t floating, not as we usually mean ‘float’!

Many of the strange things that water does depend the effects of surface tension. This is a complicated idea, but you can see surface tension in the way wet hair clings together or the bristles of a paint brush stick to each other, but better, you can demonstrate it this way. 

You need two paper clips and a glass of water. Follow the pictures that you see here: bend one paper clip into an L shape. Use this clip to gently lay another paperclip on the top of the water. The surface of the water bends under the weight of the paperclip like stretched rubber, but doesn’t let it through.

You need to pick up one paper clip with the other. The next part needs a steady hand, or it won't work. You are going to lower the unbent paper clip onto the water surface like this:

The next step is to push the supporting paper clip down. With any sort of luck, the supported paper clip will 'float'. Let me say again, this is not really floating.

If the trick doesn’t work, pull the paperclip out, dry it carefully and rub a tiny bit of grease on the paperclip before trying again.

If you look closely at the reflections coming off the water in the photo on the right, you can see how the water surface is bent. To push the water surface out of shape you must use force.

If the paperclip can’t exert enough force, it can’t stretch the surface enough to let the paperclip slip through. All the same, one drop of detergent in the water, and all the magic goes! (No, I won’t explain why!)

The Two Cultures and strange circles

This is another selection from my book Playwiths, available from Amazon or through Polymoth Books. The apparent supplier is really just me, trading as Polymoth Books, but I set the firm up so I can supply booksellers and libraries more cheaply (note that some conditions apply).

This bit is free, and it probably is not for the faint-hearted

1. The Two Cultures

In very early 1959, I argued with a pompous headmaster who had a Master of Arts degree, because I wanted to continue my studies in Latin, and also study physics. He rejected my request with a crushing dismissal: “Boys who do physics do not do Latin.” That was how I became the victim of something neither of us would have heard of back then, the notion that learned society was made up of “two cultures”, the Arts culture and the Science culture.

The divided cultures had been around for a century or more, but the name “two cultures” was only proposed in 1958 by C. P. Snow, a physicist who wrote fine novels, making him a member of both cultures. Snow said that, as the Arts people saw it, the “Arts Culture” contained all the witty, urbane and articulate people.

The “Science Culture” was, according to the Arts people, made up of scruffy men (and just a few equally scruffy women back then) who were incredibly clever about extremely difficult things, but who were absolutely useless when it came to dealing with people. Scientists were stolid and uncreative manipulators of objects, lacking in personal skills.

The scientists were often absent-minded, we were told, where the Arts culture people were clear-thinking. Leave us to do the ruling, puffed the Arts people. The scientists and engineers let this go, but in their turn, they puffed that the Real Work should be left to them.

According to this divisive pair of stereotypes, creativity is only found in the Arts people, and practicality lies only with the Science people. Fuelled by these notions, the two camps are encouraged to regard each other with a less than friendly contempt. My regard for people who accept that view is far less polite. To survive and do well, it helps to have a foot in each camp. To work in STEM, you badly need the art of debate, the ability to write clearly, sketch neatly, take photos and more. You need STEAM, and the M is important.

2. Strange circles

Some non-standard round shapes. 

Once upon a time, astronomers were certain that all the moving bodies in space travelled in circles, “because circles are perfect”. In many ways, modern science began when Johannes Kepler saw that the orbits of planets were ellipses.

Or maybe science emerged when Isaac Newton proved that the orbits had to be that shape, because of the way gravity worked. Whichever way it happened, those odd squashed circles called ellipses were involved. 

 

A 19th century engraving of a Gatling gun: notice the shape of the wheels. 

To me, ellipses are important, because in perspective, circles look like ellipses, but I am no artist, and I need help to get my ellipses right. When I am drawing on paper, I use plastic templates to draw my ellipses, but with a simple graphics program like Paint.Net, I can draw ellipses of any shape and size.

If you want to work on shading and stippling geometric shapes, use a colour printer to print out pale sky-blue ellipse outlines. Make just enough fine black points on the paper to show the outline, then photocopy it: pale blue (often called “dropout blue”) usually fails to show in a photocopy, and away you go.

We will meet Piet Hein again in chapters 15 and 20 of my book (and I may get to them here, one day), but now we need to look briefly at his superellipses, which were adopted as a suitable shape for rounding-off a space in the centre of Stockholm, rather more nicely than the rounded rectangle above. If you look online for <Sergelstorg>, you can see the result in maps and aerial photos of Stockholm.

By an odd chance, Hein came up with his solution in 1959, the year in which I encountered the two cultures, and C. P. Snow published a book about his them. Surely, if anybody ever showed how the Two Cultures notion breaks down, it must be Hein. And now, we need to venture into mathematics of a Heavy Kind. 

There is a whole family of curves with this formula:

As a group, they are called Lamé curves, after Gabriel Lamé, who discovered them. If n is between 0 and 1, the figure is a four-pointed star. If n= 1, it is a parallelogram, and for n between 1 and 2, it is a rounded-off rhombus. If n=2, we get an ellipse or a circle (depending on the values of and b), and above that, we get squircles, or superellipses.

Sergelstorg has n=2.5, and a/b=1.2. Over to you, but look around on the internet for 3D supereggs and ellipsoids…

The pendulum and the shape of the planet

The 'researchers' of the Internet, the climate clowns who cherry-pick data to prove their dopey obstructionist theories, commonly demonstrate how little they know of the ways that scientists can measure and discover things.

With the exception of the Flat-Earthers (and even climate clowns hate it when they are treated as latterday Flat-Earthers!), we all believe that the Earth is pretty much a sphere, but pretty much leaves wiggle room, and strange as it may seem, it was an upgraded version of a playground swing that revealed the precise shape of our globe, which some people likened to a watermelon stood on end, while others thought was more like a pumpkin.

This is the story of how they did it, almost three centuries ago.

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In some parts here, the main measurements have been converted to their modern equivalents. The unconverted unit called the ‘line’ is 1/4 of a barleycorn, a twelfth of an inch, or about 2 millimetres.

The barleycorn measurement turns up in the oddest of places. Edward I, King of England, decreed in 1305 that “three grains of barley, dry and round, make an inch”, and if you change from a size 7 shoe to a size 8 shoe, the difference in length is one barleycorn.

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Now to our story:

In 1672 Jean Richer reported that the period of a pendulum varied with latitude, and Isaac Newton said that Richer’s variation of pendulum was due to equatorial bulge, a comment offended the French. By this time, nobody thought the world was a perfect sphere any more, but France and England disagreed, and national honour was at stake.

Isaac Newton had proposed that the Earth was an oblate spheroid. If this were so, argued Newton, the precession of the equinoxes (we may or may not come to those later) could be explained. French scientists had taken some sloppy measurements, getting results which suggested that the Earth was more like a watermelon on its end than a pumpkin.

The French Académie set out to determine the truth of the matter by experiment, measuring a degree of latitude in Lapland and in Central America. Among those who went to Lapland was Pierre de Maupertuis, while the American group included Pierre Bouguer and Charles La Condamine.

Richer’s pendulum clock had been accurate in Paris but it lost two and a half minutes each day at Cayenne in Africa, closer to the equator. Clearly, more data were needed, and scientists were rushed to different places in 1735, mainly in South America, a mere 63 years after the comment. Newton had died in 1727, but the French still wanted to show him up, the insolent upstart!

We know Pierre Bouguer’s name today mainly in the form of Bouguer anomalies. This name commemorates his pioneering work in the Americas. When the acceleration due to gravity is measured very accurately, small local fluctuations can indicate equally local deposits of high or low density mineralisation — these fluctuations are the Bouguer anomalies.

Bouguer spent much of his life studying gravitational effects. In 1740, he estimated the value of G, the universal gravitational constant, using a mountain as an attracting mass. A method such as this can only be as accurate as the information the enquirer has about the interior of the mountain, and there were other problems which Bouguer could not have known about. We will ignore those for now, but the key word is isostasy, if you want to know more.

The French work in Central and South America between 1735 and 1743 was to measure the length of an arc of one degree of latitude at the Equator. Other scientists went to Lapland to measure a close-to-polar degree. Any difference in the lengths would reveal whether France or Britain had the right shape.

Inserted without comment.

Here, from the French Académie des Sciences Memoirs, is part of a letter from Bouguer to René de Réaumur in 1735, followed by part of Bouguer’s 1749 report of his findings.

I have made here [in San Domingo] a simple pendulum of steel which I have made as invariant as possible. It has a bob of [12 kilograms], about [12 centimetres] in diameter and [3 centimetres] deep. To keep it swinging true, I have put on the rod a crossbar of iron to serve as an axis, at right-angles to the rod. The instrument is mounted on a tempered steel knife-edge on two steel springs. These two springs are mounted on a copper plate in which there is a hole for the rod. The plate rests on a stool [1.5 metres] high, and is levelled by three screws…

We used the barometer that we set up to study the balance between the weight of the mercury and the air in all the accessible parts of the atmosphere. We saw how many feet we had to rise or descend to make the mercury change height by one line. It is then necessary to find the specific weight of air that balances other bodies. In this way, I have found by comparison with copper that on the top of Pichincha, there is a loss from unity of 1/11 000. Now it follows that the weight of my simple pendulum also loses 1/11 000 part of its weight. This loss produces a similar reduction in the restoring force, and naturally, I found the pendulum to be slow by 1/11 000. To correct this loss, it was necessary to adjust the pendulum’s length by 4/100 of a line…

Translation of the translation: Bouguer had an accurate pendulum, mounted on a wooden stand (the stool) and it was adjustable. He used a barometer as a way of measuring altitude. By timing the pendulum, he could get a measure of g at different heights above sea level.

The degree-measuring expeditions succeeded in proving Newton correct, but one of the more lasting effects came from La Condamine’s explorations while he was there, travelling over a large part of South America, and then 5000 km down the Amazon.

When he returned to Europe, La Condamine brought with him what the locals called cauchu, and the French still call caoutchouc. Thanks to Joseph Priestley, we still call it ‘rubber’, because it can be used to rub out pencil marks, and what is an eraser in some English-speaking countries is still called a rubber in others.

Benham's colourful tops.

 Charles E. Benham (1860-1929) was a journalist and inventor, and he deserves more than this, or what his Wikipedia entry, offers. I was triggered to go here this morning because of a comment Stew made about my last entry: there may be more, later.

When I first discovered the Benham disc, I was delighted, because I am colour-blind. The Benham disc is a black and white patterned circle, which looks coloured when it is spun around. I had heard of these things but I had never tried them, and I thought it would be interesting to see whether they had the same effect on a colour-blind viewer. Being colour-blind does not mean that you “see everything in black and white”, as David Brewster said. It simply means you see colours differently. It occurred to me to wonder if maybe I would see different colours in the disc from those other people see.

Benham described his illusion in an article published in Nature  back in 1894. In those days, if you wanted to see the disc, you would look for the design on a children’s top, known, predictably, as ‘Benham’s top’. The first account was a brief and anonymous one, noting that the ‘disc’ on the top was a black semi-circle, with the white half of the circle divided in four, and with black arcs painted in.

As the disc is rotated, people see different colours from the different black arcs. And, as the reporter noted, if “. . the direction of rotation is reversed, the order of these tints is also reversed. The cause of these appearances does not appear to have been exactly worked out.”

An ‘Artificial Spectrum Top’, devised by Mr. C. E. Benham, and sold by Messrs Newton and Co., furnishes an interesting phenomenon to students of physiological optics. The top consist of a disc, one half of which is black, while the other half has twelve concentric circles drawn upon it. Each arc subtends an angle of forty-five degrees. In the first quadrant there are three such concentric arcs, in the next three more, and so on; the only difference being that the arcs are parts of circles of which the radii increase in arithmetic progression. Each quadrant thus contains a group of arcs differing in length from those of the other quadrants. The curious point is that when this disc is revolved, the impression of different colours is produced upon the retina.

(Nature , 51 (1309), November 29, 1894, 113–114.)

There followed an animated correspondence, during which Benham stepped in. Illuminate the top with a bright sodium flame, he said, and you will see a very clear blue, and a very clear red. And now the controversy heats up: immediately underneath, in the same issue, Professor Liveing retorts that he has seen no such colours: the phenomenon is obviously a subjective one. Clearly there is room for more research here.

It is unclear whether Nature  thought so too, for they go on in the same column to publish next a letter from F. G. Donnan in Leipzig, suggesting that we need a new word in chemistry: ‘solute’, and the discussion seems to have died there. Well, as far as I can judge, I see the same colour effects as other people, which means we won’t learn anything about colour blindness from the Benham disc. But how about trying to learn about colour vision? What causes the colour effect as the disc slows down?

Most explanations seem to speculate rather than to explain, but here is the official version as found in psychology text-books. We have three kinds of light receptor in our eyes, in the same way there are three kinds of phosphor in a colour TV. Speaking crudely, these receptors, the cone cells, are all sensitive to just one of red, green and blue.

According to the theory, you need all three kinds of cone in the retina of your eye to see colours normally. Somehow, the cones which pick up one of the colours (red, for example) must react differently to flashing lights of a particular frequency. So with different size black bits on the disc, we get different frequency effects, and so our eyes are stimulated to ‘see’ different colours.

Well, that’s what the theory says. Some time in the future, a careful and critical look at it, will reveal once and for all whether and how this official explanation operates, and where it breaks down. There is probably a Nobel Prize in this for somebody, though they will need to acknowledge Gustav Fechner, and that's a hint.

Water wheels

Left, an overshot waterwheel in Poland, right, an undershot waterwheel, Den Gamle By, Denmark.

The water wheel was the start of a whole, and rather serious set of simple machines, devices that used power. The water wheel gave more power more cheaply (once a mill was built), it helped feed a lot of people, but more importantly, it set people to thinking about the mechanical works of a mill.

Water mills probably started in Greece, some time before 80 BCE, because that was when a Greek poet called Antipater of Thessalonika mentioned young women being relieved of the work of operating a hand-mill, now water had taken over the hard work.

Soon, waterwheels began to spread into other areas where there was plenty of rainfall, all year round, places where slaves were hard to get. It was the first labour-saving device. The water wheel may have got its start, though, as a device used to raise water from a river to fields, high above the river bank, and that requires some explanation.

Today, if a moored paddle steamer sits in a current and the paddle wheel is disconnected from the engine, the wheel will turn. Something similar would happen to a water-raising wheel (usually powered by humans, working it as a treadmeill) when it sits in the current of the river. This is the simplest of water wheels, the undershot wheel, where water passes under the wheel, making it turn.

Then there is the more efficient overshot wheel where water drops onto the front side of the wheel and carries the front of the wheel down. Both the undershot and overshot wheel need at least two gear wheels to transfer the rotation through 90°.

Waterwheels were not as good at gathering energy as the efficient turbines in modern hydroelectric stations. Still, when there were no animals to feed, all you had to do was have a big enough mill, and enough fall to get enough energy from it.

This was a special problem with overshot wheels, where mill owners needed to take water out of the river, somewhere upstream, and run it through a channel that wound around the contours on a gentler gradient than the river bed.

Sometimes this would be helped out by a weir or a dam that raised the water level, but if there were several mills along a river, they would sooner or later start to interfere with each other. The Domesday Book was completed in England in 1086. This inventory of what the Normans had taken when they invaded England listed 5624 waterwheels in England, about one for every 50 households.

Bread was a staple food, and so mills were needed, all over the country. The Domesday book also records two mills in Somerset which paid their rent, before 1086, with blooms of iron, which makes it fairly clear that those mills were being used to forge iron. 

Cistercian abbeys in 12^th century France commonly used waterwheel power to grind grain, to sieve flour, to full cloth and to tan leather.

At other times, water power crushed olives and operated bellows for forges and the fires used to brew beer. A paper mill powered by water existed in Spain in 1238, and seven such mills were to be found in Italy by 1268. Paper was made by pounding linen, either by hand, or by foot, or by water power. Guess which one was more popular with the workers?

Water power was easier. when you could get it. In France, a tributary of the Seine River, the Robec, had two mills in the 10^th century, four in the 11^th, ten in the 13^th and twelve at the start of the 14^th century. Before long, the medieval world was running out of space for mills, and disputes began to break out as dams and weirs grew higher, backing water up to the next dam upstream, reducing the fall at the upper dam.

At peak times, the Garonne River at Toulouse in France has a flow of up to 9000 tons of water a second, about a fifth of a cubic mile or 780 megalitres of water a day. Damming something like that meant driving thousands of 6-metre oak logs into the river bed in two rows and then filling the gap between with rocks, gravel, oil and wood to make a water-tight wall.

There were three Garonne dams: Château-Narbonnais, La Daurade and Le Bazacle, and between 1278 and 1408, various acts of dam-raising led to lawsuits and orders to demolish dam extensions and pay damages that were mostly ignored. By 1408, the La Daurade company had ceased to exist, its last shares snapped up by the shareholders of Le Bazacle, ending the dispute.

In later times, windmills took over part of the task, simply because they could be located where there was no reliable flow of water, but windmills were not as powerful. The early Industrial Revolution grew up near rivers, but with time, the waterwheels were replaced by steam engines. The world was ready for them, because the mechanical skills needed to build and fix mills driven by water and wind were very much the skills needed to make early steam engines.

The art of estimation

Like the previous entry, this comes from my (now) out-of-print volume, The Speed of Nearly Everything.  I may get around to releasing it as an e-book, if enough people think it's a good idea.

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To a physicist, the notion of an immortal rabbit is quite acceptable. As a boy, my English teacher encouraged me to psychoanalyse Macbeth, even though I objected that we shouldn’t, since Freud hadn’t been invented when Shakespeare was writing. Ever a historically-minded cuss, I argued that it would be more relevant to look at the political situation in London, with a Scot sitting on the throne. Exasperated, he exhorted the class to engage in the willing suspension of disbelief.

And well he might, if he wanted us to accept some of the artifices and conceits of coincidence found in the 19th century novel, but we scientific types were subjected to much hardier fictional nonsense than that.

We routinely solved problems that involve a steel girder of negligible mass, suspended at its centre of gravity by a silken thread, and before we were too far advanced, we heard our first physics joke. It was about the three scientists who were trying to pick the winner of Australia’s premier horse race, the Melbourne Cup, which is held each November.

The mathematician gathers a wealth of data on weather, rainfall, wind, pollen counts and other possible influences, and three years in a row, fails dismally to pick a winner. At the end of those three years, the geneticist has just finished drafting a plan for a breeding program that should, in five generations, produce a winner, but the physicist has got it right, three times in a row.

The others ask him how he did it. He reaches into his pocket and produces an envelope which he turns over. Then he draws a circle on it. “Consider,” he says, “a spherical horse running in a vacuum…”

In fact a spherical cow or spherical horse can be a useful starting point to explore ideas, to get a first approximation that can be extended. Take the yarn about the bumblebee that was shown not to be able to fly: this is usually trotted out as evidence that scientists are thick, but there is a little more to it than that. In 1934, a French entomologist called Antoine Magnan tried to apply an engineer’s equation to bumblebees, and showed that according to that equation, designed for aircraft that did not flap its wings, the bee could not generate enough lift.

A bumblebee, coming in to land (or fall?)

There is a great deal of folklore wrapped around this “event” and who actually was involved, but it appears that the equation was worked out by André Saint-Lagué, and while the incident is often dressed up as “a scientist proving that bumblebees can’t fly”, all that was really shown was that the equation was inadequate to describe the flight of the bumblebee.

Magnan had shown that you can’t apply that particular equation to bumblebees, rather than proving that spherical bumblebees can’t fly, even if real ones, flapping their wings at 130 times a second, move happily along at 3 metres/sec, 11 km/hr or 7 mph. Like Zeno’s paradox (which will be in the next blog entry), Magnan’s calculation merely showed that there was a faulty assumption in there somewhere. The mathematical model was flawed.

When we escaped from the English classroom to the lab, we learned of marvels that could be done with simple apparatus. The muzzle velocity of a bullet could be measured with nothing more than a block of wood, a piece of string, a protractor and a measuring tape.

Our physics teacher, equally as at home with fiction as our English teacher, explained how, in the days of gunpowder and muzzle-loading firearms, slight variations in the ingredients, their amounts and proportions, could make a lot of difference. The most obvious measure was the speed at which a cannon ball or musket ball left the barrel of the gun, or in physics-speak, the muzzle velocity.

The idea was quite simple. You suspend a large block of wood and fire a bullet at it from close range. The bullet lodges in the block, and the energy of the bullet is transferred to the block, which swings like a pendulum. Then one simply has to measure the swing angle and calculate the height the block reaches.

This device even has a name: it is called the ballistic pendulum, and it has been around since the 1742, when it was invented by Benjamin Robins. From the swing, or so we were told, it is a fairly elementary calculation to estimate the energy and hence the velocity of the bullet. Unfortunately, this explanation ignores the 800-pound spherical horse which is rolling around the room.

Some of the energy goes into deforming the bullet and the wood, some is wasted as friction, and to do any calculations, we have to assume that the bullet stops instantaneously (which is as likely as a girder with negligible mass). Of course, if you are trying simply to compare different grades of gunpowder, rather than measuring the muzzle velocities, the losses will be similar in each case, and can be ignored. Whichever powder produces the biggest swing is the best, if everything else is kept constant — and in fairy physics, that always applies.

Robins was born to Quaker parents, but as a mathematician, he tried to make gunnery a science. Along the way, his ballistic pendulum probably showed that Indian saltpetre made the best gunpowder. He died in India in 1751, supervising the construction of forts, and a few years later, the British drove the French out of India, which let them have all that excellent saltpetre for their own use.

Curiously, the pursuit of novel sources for saltpetre during the Napoleonic wars led a French chemist, Bernard Courtois, to discover iodine, but that's another story...the next story, in fact.

That speedy botfly

I revived this excerpt from my out-of-print book The Speed of Nearly Everything when the image on the right turned up in my Facebook feed, coming from Science Humor.

In case you don't look out for details, the hole that the fly was caught in (or poked into) was actually made by a projectile coming from the other side, so the accompanying question about the fly's speed is, at the very least, just a bit misleading, but somebody is going to cite a legend.

When you enquire about fast animals, more often than not, you will read that the fastest animal of all is the deer botfly, which is credited with an amazing 1287 km/hr, though if you convert this to miles per hour, it comes out as a round 800 mph, a figure that smells a little bit like fudged science—and rightly so.

The story begins with a 1927 article by an entomologist called Charles Henry Tyler Townsend, who reported a speed like this in the Journal of the New York Entomological Society. He actually claimed that the fly was clipping along at 400 yards per second, which works out at 818 mph or 1316 km/hr in metric units. As we will see shortly, any preciseness in the conversion is hardly justified.

Townsend reasoned that these flies passed in a blur, and so must have been travelling very fast. On that scientific basis and no other, he credited them with a nice round 400 yards/second.

That story should have been questioned right away, but people wrote it down, passed it on, quoted it uncritically, and never stopped to wonder what would happen if flies were tearing around at supersonic speeds.

As we will see later (next entry in this blog), some people would stop to prove that the bumblebee could not fly, but nobody stopped to consider and demonstrate the impossibility of the botfly claim until 1938, when Irving Langmuir, a Nobel laureate in chemistry, having given it some thought, tested the assumptions.

First, the air pressure on the fly at that speed would be more than half an atmosphere, surely enough to crush it. The energy needed to maintain the flight would be 370 watts, half a horsepower, which would be quite an ask. Aside from anything else, the botfly would use up its own weight in fuel every second, so it would need to be a voracious feeder.

Next, Langmuir had been hit by these flies, and while it hurt, that weight of fly at 1300 km/hr would have left a significant hole, rather like that of a soft bullet, and the fly would have been mashed inside the wound. Instead, the fly bounced off.

Langmuir mocked up a model of the botfly, using solder to make a pellet that was 1 cm long and 0.5 cm wide. He attached this to a string, and whirled it around his head, timing it so he could work out its velocity. He reported that at 13 mph it was a blur, at 26 mph it was barely visible, at 43 mph an observer could not tell which way it was going, and at 64 mph, it was completely invisible.

He concluded that the blur Townsend had seen came from a fly travelling at 25 mph (40 km/hr). His results were published in Science and reported in Time magazine, but legends are tough things, even when they are debunked by Nobel Prize winners. So even today, the same old values keep emerging from the woodwork.

By a curious chance, Langmuir’s name crept into the record books in an entirely different way in 2006 when plasma physicists used a specially designed holographic-strobe camera to capture pictures of matter waves that were travelling at 99.997% of the speed of light.

Known as Langmuir waves, they are generated by intense laser pulses, and may one day lead to “tabletop” versions of high-energy particle accelerators. One step along the way was taking photographs of the waves to see if they behaved the way scientists thought they would. They did, which is more than we can say about the botfly's behaviour.

What is a day?

When does the day start? The ancient Greeks said the day began at sunrise, and ended at the next sunrise. The Babylonians held that the day began and ended at sunset, while up until 1925,

astronomers worked on a “day” which began and ended at noon, and so did the Royal Navy in the days of Captain Cook. Now the astronomers, like us, and the ancient Egyptians, have a day which commences at midnight. Islamic tradition has a day which begins at sunset.

By definition, noon is when the Sun is at its highest point in the sky, so it is always noon somewhere in the world, with a noon zone sweeping along through a degree of longitude every four minutes. Logically, you should be setting your clock forward or back by a minute for each 15-20 kilometres that you go east or west!

This would be far too confusing, and to make life easier, we have split the world into time zones, usually (but not always) 15 degrees across, where everybody keeps the same “official time”. If you are trying to set up a very accurate sundial, you need to make allowance for your position east or west of the true time in your zone.

Some points to ponder: Clockwise is a word used to describe the direction of the shadow of a northern hemisphere sundial. What way does the shadow travel in the southern hemisphere?

If you stop and think about it for a moment, you may be able to deduce where the word “dial” comes from, especially if you know anything about the Latin word dies. If you lack this knowledge, look up “dial” in a good dictionary, and find out where it comes from. From this knowledge, can you say what the most appropriate use of the word “dial” is?

We probably had the idea of the two ways, even before clocks. Widdershins is an old word meaning counter-clockwise. The equally old word which means “clockwise” is deasil.

Somewhere along the way, something happened to humans that made them start using art, that made them start communicating with each other, and generally showing signs of being human, rather than hominid. Could it have been the discovery of time which caused these changes?

It is probably time to look at the things we first used for time-keeping and calendars, the stuff that is out there, beyond our atmosphere, the stuff that even a century ago, people knew was forever unreachable — and rather hard to see in any case.

The barman says, “We don’t serve time travellers in here.”

A time traveller walks into a bar.

Macedonio Melloni, a forgotten genius

This is just a filler to say I aten't dead yet. I'm just fairly busy.

Macedonio Melloni (1798 - 1854) is little-known, which is why this is a brief account. Still, what there is seems quite interesting, and it sets the scene for several other stories, so I will share it with you.

First, some background. William Herschel did many things in astronomy. Among other things, he took the temperature of different parts of the spectrum, and found that the hottest part of the Sun’s spectrum was beyond the visible range. Using a thermometer, he discovered the infrared part of the spectrum.

Now back to Melloni: if you heat a junction between two different metals, you generate a very small current. In order to be able to measure the current, you need to multiply it by linking a number of these junctions together, to make a battery of them, like the pile of cell units that Alessandro Volta made. This is why we call Melloni’s invention a thermopile.

Source: https://muxindia.wordpress.com/2014/11/06/passive-infrared-sensor-pir-sensor/

As well, Melloni developed ways of concentrating the heat from distant sources, and he found out how to use rock salt to make lenses to focus the heat rays, in the same way we use glass lenses to focus light rays. He established that the infrared rays were in every way like light: they could be refracted, reflected, polarised and made to interfere with each other, exactly like light.

Melloni really deserves to be better known, for while Herschel’s discovery of the infrared is a commonplace, few people realise that Melloni’s investigations laid a practical framework within which James Clerk Maxwell could propose the existence of a continuous electromagnetic spectrum.

Everything in science is connected, which is why we can usually spot fraudulent science at a glance. It doesn't connect with all the other bits...

Does thermodynamics matter?

To put it another way, do ordinary folk need thermodynamics, or an understanding of it? C. P. Snow, later Lord Snow, certainly thought they did, because, as he saw it,  thermodynamics is an area that matters intensely.

As a scientist who also wrote literary novels (as did his wife, Pamela Hansford Johnson), Snow was very aware of how ‘the other side’ saw science, and vice versa. Here, Snow is characterising the attitude of scientists to the ‘arts culture’, in his first entry into this arena, his lecture called The Two Cultures:

…the whole literature of the traditional culture doesn’t seem relevant…They are of course, dead wrong. As a result, their imaginative understanding is less than it could be. They are self-impoverished.

But what about the other side? They are impoverished too—perhaps more seriously, because they are vainer about it. They still like to pretend that the traditional culture is the whole of ‘culture’, as though the natural order didn’t exist. As though the exploration of the natural order was of no interest either in its own value or its consequences…

As with the tone-deaf, they don’t know what they miss. they give a pitying chuckle at the news of scientists who have never read a major work of English literature. They dismiss them as ignorant specialists. Yet their own ignorance is just as startling. A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought to be highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists.

Once or twice I have been provoked and asked the company how many of them could describe the Second Law of Thermodynamics. The response was cold: it was also negative. Yet I was asking them something which is about the scientific equivalent of: Have you read a work of Shakespeare’s?

I now believe that if I had asked an even simpler question—such as, What do you mean by mass, or acceleration, which is the scientific equivalent of saying Can you read?—not more than one in ten of the highly educated would have felt that I was speaking the same language.

Sir Arthur Eddington thought thermodynamics mattered very much to scientists:

Eddington was always at his best when he was having fun with science: “Electrical force is defined as something which causes motion of an electric charge; an electrical charge is something which exerts an electrical force.”

That, however, was bettered by this comment, also from his book, The Nature of the Physical World:

The law that entropy always increases—the second law of thermodynamics—holds, I think, the supreme position among the laws of Nature. If [your pet theory of the universe] is found to be contradicted by observation—well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.

So, yes, thermodynamics matter. It would be worth asking a climate change denier who babbles (as they all do) some drivel about the uncertainty of science, one of Snow's questions.

Oh, and if you aren't sure what the second law says, try this: In any spontaneous process, there is always an increase in the entropy of the universe.

Another way of saying this is to assert that there can never be a 100% efficient (or perfect) heat engine. Another form of the law states that heat flows spontaneously from a hot object to a cold object. Heat will not flow spontaneously from a cold object to a hot object.

If you understand thermodynamics, you can answer this:

You have a perfectly insulated room, and inside it, there is a refrigerator. It has been switch on, and the door had been wedged open. Now:

• Does the room get cooler? or
• Does the room get hotter? or
• Does the temperature stay the same?

This one tricks a lot of people, and the odds are that it will fool climate change deniers as well.  Nobody who is unable to answer this should speak about climate matters.

There may be a small delay in transmission

I went to the ophthalmologist to say I needed new glasses, because I could no longer read 4-point type, not even in bright sun.

Now I know enough physics to know that the reason for using bright light is that the pupils constrict, and this makes focusing easier.

Given that, I should have realised that this was not just a matter of new spectacles. He knew what the problem was, of course, because he is used to seeing it, and he had diagnostic scans up on his screen.

I have been growing cataracts, a milkiness of the lens that can only get worse. So to cut a long story short, I had the first eye done today, and I will have the second done in three weeks.

Until I take the patch off tomorrow, wearing glasses is hard, so I may not be at the keyboard as much. Then again, perhaps I will drift back, because there's a list of things I must not do, like gardening, leaping, jumping and stuff.  Bang go most of my hobbies.

The only consolation is that I have a great pic for Talk Like a Pirate Day, coming up next month.

They say that getting old is a pain in the proverbial.  But as the clever ones say, the alternative is worse.

Anyhow, please make allowance for gaps, if they happen between now and Talk Like a Pirate Day.

Curtiosity about atoms

First, a note about "curtiosity": it is the key attribute of Rudyard Kipling's 'Elephant's Child. It isn't a typo. The curtiosities were collected originally as possible epigraphs, and then as a possible book in their own right, but it all seemed too hard.

Most collections of "quotes" on the web lack the necessary details of chapter and verse and are commonly spurious. You get my notes, so you know where they came from, and any agile mind will recognise the occasional traps laid for mindless plagiarists. Verb. sap. (Look that up, if you need to!)

Mind you, the lack of a full source may just mean I was busy the day I collected that quote, but such information as I give should be reliable.

Atoms move in the void and catching each other up jostle together, and some recoil in any direction that may chance, and others become entangled with one another in various degrees according to their shapes and sizes and positions and orders, and they come together and thus the coming into being of composite things is effected.

— Simplicius (c. 400 BC), De Caelo

To understand the very large, we must understand the very small.

— Democritus (470 - 380 BC

The Atoms of Democritus

And Newton's Particles of Light

Are sands upon the Red sea shore

Where Israel's tents do shine so bright.

— William Blake (1757 - 1827), Complete Blake (Oxford Paperback, 1974), page 418.

1. From nothing comes nothing. Nothing that exists can be destroyed. All changes are due to the combination and separation of molecules.

2. Nothing happens by chance. Every occurrence has its cause from which it follows by necessity.

3. The only existing things are atoms and empty space; all else is mere opinion.

4. The atoms are infinite in number and infinitely various in form; they strike together and the lateral motions and whirlings which thus arise are the beginnings of worlds.

5. The varieties of all things depend upon the varieties of their atoms, in number, size, and aggregation.

6. The soul consists of fine, smooth, round atoms like those of fire. These are the most mobile of all. They interpenetrate the whole body and in their motions the phenomena of life arise.

— Robert Andrews Millikan quotes these (translated) words of Democritus in his book The Electron, saying that they are from [Sir John] Tyndall.

When any body exists in the elastic state, its ultimate particles are separated from each other to a greater distance than in any other state; each particle occupies the centre of a comparatively large sphere, and supports its density by keeping all the rest, which by their gravity or otherwise, are disposed to encroach upon it, at a respectable distance.

Chemical analysis and synthesis go no further than to the separation of particles one from another, and to their reunion. No new creation or destruction of matter is within the reach of the chemical agency. We might as well attempt to introduce a new planet into the solar system, or to annihilate one already in existence, as to create or destroy a particle of hydrogen. All the changes we can produce consist in separating particles that are in a state of cohesion or combination, and joining those that were previously at a distance.

— John Dalton, A New System of Chemical Philosophy, 1808.

They may say what they like. Everything is organised matter.

— Napoleon Bonaparte (1769 - 1821

We shall never get people whose time is money to take much interest in atoms.

— Samuel Butler (1835 - 1902), Notebooks

The first support of the isotope theory among non-radioactive elements was given by the anomalous behaviour of the inactive gas neon, when analysed by Sir J. J. Thomson's method of positive rays . . . This peculiarity was that whereas all elements previously examined gave single, or apparently single, parabolas, that given by neon was definitely double. The brighter curve corresponded roughly to an atomic weight of 20, the fainter companion to one of 22, the atomic weight of neon being 20.20.

— Francis Aston (1877 - 1945), address before the Royal Institution, 1921. This established the existence of isotopes.

No one has ever seen, nor probably ever will see, an atom, but that does not deter the physicist from trying to draw a plan of it, with the aid of such clues to its structure as he has.

— Maria Goeppert Mayer (1906 - 1972), 'The Structure of the Nucleus', Scientific American Reader (1953), page 116.

In fact it may be logically impossible for anyone to be able to correctly visualize certain physical systems, such as atoms, because they contain features that simply do not exist in the world of our experience.

— Paul Davies, The Mind of God, Penguin Books, 1990, p. 18.

There have been almost innumerable attempts to reduce the differences between atomic weights to regularity by contriving some formula which will express the numbers which represent the weights with all their irregularities. Needless to say, such attempts have in no way been successful.

— Sir William Ramsay (1852 - 1916), address to the British Association, Toronto, 1897.

Some thoughts on educational research

I found a reply that apparently never went to an email list. It was written some years ago, but it remains valid today.  The matter under consideration was an item of research that concluded that "who" your parents are, as in being better educated, high socio-economic status etc etc was more important than what they "do" with their children in their formative years and so "proved" that success is dependent on those factors.

One of my good friends (her name is Barbara, which will identify her to a few) commented:

I am ... very sceptical about a lot of  "research" because, as we know,  much of it is undertaken by parties with vested interests in the results and these can be skewed to reflect those interests and sell their product.

I agreed with this, but from an expert viewpoint. My reply began by saying that my science teacher wife and I had been entertaining a rather delightful US environmental activist, writer and illustrator who had been staying with us for a few days, so I had not been reading my email, but oddly enough, reading to children was a topic of conversation that arose several times as we clambered around Sydney's many Aboriginal engravings sites.

We agreed that reading was a key, because we shared that sort of mind-set.  We even debated, not the truth of what we saw as self-evident, but how reading to small persons could be encouraged more, because we took its central role as a given. This is what tends to happen when educators meet: they agree on what is good, or potentially good, and look at ways to foster it.

I must say that I agreed strongly with Barbara about educational research -- and in the 1980s, I had more than my fill of contact with educational researchers seeking access to certain classes of data that were under my management in the NSW Department of Education. If they wanted our data, or access to our schools, they had to get past me.

This is Peter the ADHD, who is almost indistinguishable from Rikki-Tikki-Tavi who always had to run and find out: I care passionately about Aboriginal engravings, I care about wee beasties, rocks and stuff — and I am a dab hand at educational research, among other things. I also know a fraud when I see one, and I saw a few.

I will be blunt: I moved on to other and more engaging things when I found that most educational research is the codification of the bleeding obvious, and some journals are amazingly able to be worse than others. At one point when I was no longer with the NSW Dept of Education, I acted as the external member of a panel to select somebody who needed expertise in research methodology.

After hearing the applicants I argued for one bright young person getting the position, because I had asked about the Journal of Educational Research, probably the most popular "journal" in the Directorate where he was working and where I had once worked.

Most of the other applicants, when I asked them about their preferred sources for information, immediately named the  Journal of Educational Research, praising it for its lucidity and relevance.  The bright young person was different.

He had mentioned other journals, but not the JER, and when I asked him about it, he declared that he wouldn't touch it with a barge pole.  This was in contrast to the other suckers, who had all declared, unprompted, that it the best thing since sliced bread.

The BYP's answer accorded with my judgments of JER, based (among other bizarre things) on a learned piece that demonstrated that children took longer to read longer passages (the author did have the grace {or tail-covering skills} to admit that this result was unsurprising!)  The others on the selection panel saw other values in him, and he got the job by unanimous consent.

Surely the key thing with the alleged research on determining factors is that many of the variables are correlated. I used to be one of those austere number-crunching types who would engage in statistical jiggery-pokery to partial out confounding effects of inter-correlations, but that is probably even rarer now than it was then.  You have to do that, and do it the right way around.

I suspect that the better-educated and higher status etc etc parents are also the ones who take it for granted that they should read to their children.  Maybe some of them are too busy earning Nigel and Nigella's school fees, but others are right in the thick of it.

In the same way, some parents take it as a given that they will sit and watch television with their children -- and I suspect that this style of TV watching would not be counted as different from unsupervised watching by most "researchers".

"All science is either physics or stamp collecting" said Lord Rutherford, a little unkindly. Well, some educational research is stamp-collecting, and some of it barely makes it to the level of a sincere form of philately.  Please remember that, next time you see a report that research has shown that something is good while all competing forms are incontrovertibly bad.

Remember: research in education nearly always states the bleeding obvious — or at least that which was the bleeding obvious for the "researcher" when the "research" took place. There are, I have to concede, rare exceptions, but these are vanishingly rare.

Batteries included

Some more bits from my quotations collection:The world changed in a curious way in 1800, when Alessandro Volta wrote to Sir Joseph Banks about his piles. Voltaic piles were batteries, though. Once the pile was common, people could discover electrolysis, chemistry got a leg-up, and in time, teenagers would be able to share boom-tish and doof-doof with their fellow passengers on train and bus.You can't win them all.  Mind you, the fellow on the right was a bigger loser than most.

Sixty or more pieces of ... silver, applied each to a piece of tin or zinc ... and as many strata of cardboard, soaked in salt solution, interposed between every pair of metal discs, and always in the same order, constitutes my new instrument.

 . . . an apparatus having resemblance in its effects . . . to an electric battery . . .

— Alessandro Volta, in a letter to Sir Joseph Banks, 1800.

Having a few pet plants which slugs and snails are particularly fond of as food, I have devised the following simple and efficacious mode of protecting them against their and my enemies ; and as this plan may be useful to some of your readers, I herewith send you a description of my galvanic circle. Procure a flat ring of zinc, large enough to encircle the plant; make a slit in the ring after the manner of a keyring, so that it can be put round the stem of the plant and then rest upon the ground.

Now twist a copper wire into a ring very nearly of the same circumference as the flat zinc ring, and putting it round the plant, let it rest upon the zinc, as in the illustration. No slug or snail will cross that magic circle; they can drag their slimy way upon the zinc well enough, but let them but touch the copper at the same time and they will receive a galvanic shock sufficient to induce them at once to recoil from the barrier.

— Septimus Piesse in Scientific American May 2, 1863, p. 276.

For the sake of portability, many forms of Leclanché cell have been constructed in which there is no free liquid present. In most of these there is a paste containing manganese dioxide surrounding a carbon rod. This is in contact with a layer of sawdust, or in some cases, plaster of Paris, saturated with sal-ammoniac. The whole is contained in a zinc case which forms the negative electrode.

— J. Duncan and S. G. Starling, A Text Book of Physics, Macmillan, 1918, p. 912.

. . . the magnetic needle was moved from its position by the help of the galvanic apparatus when the galvanic apparatus was closed, but not when open . . .

— Hans Christian Oersted (1777-1851

Oersted would never have made his great discovery of the action of galvanic currents on magnets had he stopped in his researches to consider in what manner they could possibly be turned to practical account; and so we would not now be able to boast of the wonders done by the electric telegraphs. Indeed, no great law in Natural Philosophy has ever been discovered for its practical implications, but the instances are innumerable of investigations apparently quite useless in this narrow sense of the word which have led to the most valuable results.

— Lord Kelvin (1824-1907), quoted in R. A. Gregory, Discovery (1916), p. 241-2.

Electric relay

The quantity of electricity requisite to deflect a magnetic needle is so inconsiderable, that if the current of a moderately-sized pair of plates were sent into one end of a wire, and only one-hundredth part of it came out at the other end, it would still be sufficient.

— Edward Davy, (1806-1885), inventor of the electrical relay.

Few of our readers have heard of the name of Edward Davy in connection with the history of the telegraph . . . nothing has been published of his labours. Yet it is certain that, in those days, he had a clearer grasp of the requirements and capabilities of an electric telegraph than, probably, Cooke and Wheatstone themselves . . .

— J. J. Fahie, The Electrician, July 7, 1883.

Curtiosity about (scientific) education

Another collection if unused epigraphs and pithy comments from past times.

My schoolmaster had been a little too crude in his instructions. He had not been a scientific man, but only a teacher of science.

— H. G. (Herbert George) Wells (1866 - 1946), The Work, Wealth and Happiness of Mankind, Heinemann, 1932.

As a schoolboy in London I learnt how sulphuric acid is manufactured, how time is measured at Greenwich, how soap is made, and how glass is blown — entirely from the teacher or the book, although all of these could have been seen at first hand within half an hour of the school. Adam saw the animals in the garden before he named them, but we (as Whitehead has said) named them before we saw them.

— Professor Eric Ashby, The Place of Biology in Australian Education, inaugural lecture, Sydney, 1939.

The true aim of the teacher must be to impart an appreciation of method and not a knowledge of facts. This is far more readily achieved by concentrating the student's attention on a small range of phenomena, than by leading him in a rapid and superficial survey over wide fields of knowledge. Personally, I have no recollection of at least 90 per cent of the facts that were taught to me at school, but the notions of method which I derived from my instructor in Greek grammar (the contents of which I have long since forgotten) remain in my mind as the really valuable part of my school equipment for life.

— Karl Pearson (1857 - 1936), The Grammar of Science, Everyman edition, p. 12n.

I find not any science that doth fitly or properly pertain to the imagination.

— Francis Bacon (1561 - 1626), Of the Advancement of Learning, second book, XI, 3, 1605..

In the circle where I was raised, I knew of no one knowledgeable in the visual arts, no one who regularly attended musical performances, and only two adults other than my teachers who spoke without embarrassment of poetry and literature — both of these being women. As far as I can recall, I never heard a man refer to a good or a great book. I knew no one who had mastered, or even studied, another language from choice. And our articulate, conscious life proceeded without acknowledgement of the preceding civilisations which had produced it.

— Shirley Hazzard, Coming of Age in Australia, Boyer Lectures, 1984, ABC Books, 1985.

In every respect but one, in fact, the old Mathematical Tripos seemed perfect. The one exception, however, appeared to some to be rather important. It was simply — so the young creative mathematicians, such as Hardy and Littlewood kept saying — that the training had no intellectual merit at all. They went a little further, and said that the Tripos had killed serious mathematics in England stone dead for a hundred years. Well, even in academic controversy, that took some skirting around, and they got their way.

— C. P. Snow (1905 - 1980), The Two Cultures and the Scientific Revolution, Rede Lecture, 1959.

T H Huxley, British Museum of
Natural History

Again, there is a fallacy about Examiners. It is commonly supposed that any one who knows a subject is competent to teach it; and no one seems to doubt that any one who knows a subject is competent to examine in it. I believe both these opinions to be serious mistakes . . . Examination is an Art, and a difficult one, which has to be learned like all other arts.

— Thomas Henry Huxley (1825 - 1895), 'Universities: Actual and Ideal', 1874, quoted in Cyril Bibby (ed.) The Essence of T. H. Huxley, Macmillan, 1967, p. 225.

Its so-called equipment is dirty and disorderly beyond description. Its outfit in anatomy consists of a small box of bones and the dried-up, filthy fragments of a single cadaver. A cold and rusty incubator, a single microscope, . . . and no access to the County Hospital. The school is a disgrace to the state whose laws permit it to exist.

— Abraham Flexner (1866 - ??), Medical Education in the United States and Canada (1910), page 190, quoted in Blaine Worthen and James Sanders, 'Educational Evaluation', New York: Longman, 1987, page 101.

My friend Tom Smith and I made it a rule - and in this we were encouraged by his father - that, so far as was possible, we ourselves should actually make the acids and other substances used in our experiments. We were not to buy them ready made, as this would have taken the zest out of our enjoyment. We should have lost the pleasure and instruction of producing them by aid of our own wits and energies. To encounter and overcome a difficulty is the most interesting of all things. Hence, though often baffled, we eventually produced perfect specimens of nitrous, nitric, and muriatic acids. We distilled alcohol from duly fermented sugar and water, and rectified the resultant spirit from fusel oil by passing the alcoholic vapour through animal charcoal before it entered the worm of the still. We converted part of the alcohol into sulphuric ether. We produced phosphorus from bones, and elaborated many of the mysteries of chemistry.

The amount of practical information which we obtained by this system of making our own chemical agents was such as to reward us, in many respects, for the labour we underwent. To outsiders it might appear a very troublesome and roundabout way of getting at the finally desired result. But I feel certain that there is no better method of rooting chemical or any other instruction, deeply in our minds. Indeed, I regret that the same system is not pursued by young men of the present day. They are seldom, if ever, called upon to exert their own wits and industry to obtain the requisites for their instruction. A great deal is now said about "technical education"; but how little there is of technical handiness or head work! Everything is bought ready made to their hands; and hence there is no call for individual ingenuity.

— James Nasmyth, James Nasmyth: Engineer, An Autobiography, 1883.

 The true aim of the teacher must be to impart an appreciation of method and not a knowledge of facts. This is far more readily achieved by concentrating the student's attention on a small range of phenomena, than by leading him in a rapid and superficial survey over wide fields of knowledge. Personally, I have no recollection of at least 90 per cent of the facts that were taught to me at school, but the notions of method which I derived from my instructor in Greek grammar (the contents of which I have long since forgotten) remain in my mind as the really valuable part of my school equipment for life.

— Karl Pearson, The Grammar of Science.

Mrs. Sanger's pamphlet on birth control, which is addressed to working women, was declared obscene on the ground that working women could understand it. Dr. Marie Stopes' books, on the other hand, are not illegal, because their language can only be understood by persons with a certain amount of education. The consequence is that, while it is permissible to teach birth control to the well-to do, it is criminate to teach it to wage-earners and their wives. I commend this fact to the notice of the Eugenic Society, which is perpetually bewailing the fact that wage-earners breed faster than middle-class people, while carefully abstaining from any attempt to change the state of the law which is the cause of this fact.

— Bertrand Russell, Marriage and Morals.