Science, Friction:A Journey Below The Surface?

My first Skeptics in the Pub - Online of 2022 was an unusual one. I mean, many of them are. But this one was unusual in a different way. The subject matter seemed particularly niche yet it really wasn't. Surfaces, friction, stickiness. They're all quite important things. Things that are vital to everyday life. But how much time do we spend thinking about them?

In my case - very little. But in the case of Laurie Winkless, the physicist and author of Sticky:The Secret Science of Surfaces, ever such a lot. In fact, Laurie went as far as saying that friction, specifically, was her favourite topic (don't worry there was plenty of crude laughter in the chat boxes, the Skeptic community likes a smutty joke as much as any other) so she seem overjoyed to be up at 8am (Laurie's Irish but is now based in New Zealand so my Thursday night was her Friday morning) to give an enthusiastic talk, hosted by a very enthusiastic Brian Eggo from the Glasgow branch of the Skeptics, called Science Friction:How Surface Interactions Shaped The World.

Laurie's book touches (see what I did there?) on subjects ranging from adhesives and paints to hydrodynamics and ice and on to earthquakes, geckos, and Formula One racing (the tyres and brakes being of particular interest) but for her Skeptics talk she didn't want to simply rehash what's in the book but talk a little about our human relationship with 'surfaces'.

As with so many stories, we began with ancient rock art. The sort often found on cave walls. On the Indonesian island of Sulawesi there is cave art dating back forty-four thousand years (and there is still work being done to decide if Neanderthal cave art in Spain is over sixty thousand years old) which just goes to show that we have been interacting with surfaces for a very very long time.

This cave art gives us a fascinating glimpse into our ancestors and what they cared about (hunting buffalo primarily, it seems) but beyond the initial act of making impressions on surfaces to create primitive art there is also the question of how we move, both ourselves and objects - specifically ones too large to carry, across various surfaces.

During the twelfth dynasty, the ancient Egyptian governor Djehutihotep commanded so much power and hoarded such wealth that he was buried in a tomb worthy of a pharaoh. Inside his tomb is a famous mural, the 'colossus on a sledge', that shows Djehutihotep in statute form (a statue over 22ft high) being transported by 'workers' (probably slaves). Look at the dude stood near Djehutihotep's foot at the front of the sledge.

He's pouring some kind of liquid in front of the sledge's path. It was long believed that this was part of some kind of ceremonial act but, far more likely, the liquid is some kind of lubricant that is being used to ease the egotistical governor's statue across the desert sand of Egypt. Laurie then took us down what for me proved something of a cul-de-sac (it was too complicated for me, basically) in which she talked about, and showed us a few graphs to demonstrate, how there's an optimal level of water to apply sand to ensure movement.

It can't be too little - but it can't be too much either. I can't say I fully grasped the science bits about pascals and coefficients of friction but I, at least, got the general idea. It wasn't just in the twelfth dynasty of ancient Egypt that lubricants to ease movement were developing. Elsewhere in the world other products were developed from natural soaps, animal fats, and olive oil byproducts.

These were added to boat rudders and the axles of chariot wheels, things that needed to move as quickly and smoothly as possible. By the time of the industrial revolution, many individual mill owners had their own special 'recipes' for creating their own lubricants.

In 1872, Elijah McCoy, a Canadian born inventor of African American descent who took US citizenship, invented and patented an automatic railway locomotive lubrication which meant that trains didn't have to keep stopping to have grease manually applied. This, of course, led to much quicker train journeys and, ultimately, to the railways becoming the dominant transport form of the era.

A much underappreciated individual, Mr McCoy, it seems. I should learn more about him. Needless to say, development of lubricants (I'm sure I have never typed that word so many times) didn't stop there and today we have all manner of new lubricants used not only for assisting motion but as corrosion barriers and thermosyncs.

Whatever they are! Some of these modern lubricants don't even come in the standard form of gloopy liquids but instead we now use solid material like graphite and molybdenum disulfide. The mere mention of molybdenum disulfide again took me into a sphere in which I know, or understand, very little. Thankfully, Laurie Winkless realised not everyone would be as clued up as her on this subject and whenever it got too deeply into the science pulled the talk back with something a layman such as I could grasp.

For instance, what happens if we don't want to minimise friction but to maximise it? Early wheels were made of wood and the basic tyres they had consisted of not much more than a thin strip of leather that would act, essentially, as a sacrificial layer of protection to the wheel. If not for long.

The black rubber tyres we all know and love (or is it just me?) today came much later. Rubber had been harvested in Mesoamerican communities (in present day Colombia) for centuries but it wasn't until the eighteenth century invention of vulcanisation, adding sulphur to rubber, resulted in more rigid and durable rubber being available that an early form of modern tyre came into being.

These new tyres were used on the first ever cars and though new cars use tyres made from fossil fuel based polymers the technology is, more or less, the same. Rubber generates friction as the tyre rolls along the surface when it deforms to take in the bumps in the road and then, slowly, reverts to its original shape. Sometimes during motor sport events you'll see rubber marks left on the track. This helps in that when the cars pass over it again the meeting of rubber (on the tyres) and rubber (on the track) creates even more friction and, thus, even more speed.

But it wears down the tyres faster so that's why, in F1 for example, we have so many pit stops. Why pit stops have become such an integral part of the sport. I used to love Formula One (and even attended the Italian GP back in 2017) but I find it quite boring now (truth be told, it often sent me to sleep if I watched more than the highlights) and the farce which allowed Max Verstappen to become world champion at the expense of the deserved winner Lewis Hamilton last year has put me off the sport even more.

So let's not linger on Formula One and instead, as Laurie Winkless did, move quickly to violins, earthquakes, and ice. The three topics which formed the coda of her talk. Violins are played by dragging the hairs of the bow across the instrument's string to create vibrations in the form of sound but, unbeknown to me but common knowledge to all catgut violators no doubt, rosin is also used to keep that movement swift and fluid.

Rosin, also called colophony or Greek pitch, is a resin obtained from pines and is used to maintain the violin strings so that the bow hairs do not meet with too much resistance. I'm not really sure how the talk jumped so quickly to earthquakes but as we were running out of time these final sections were a little rushed.

Geologists had known for a long time that tectonic plates caused huge stresses that after decades, centuries, or even longer would fracture rocks and cause earthquakes but, later, 'stress drops' were measured by scientists and it was discovered that frictional sliding along fault places caused periods of slip that would last just a few seconds, or in the case of very severe earthquakes - minutes, but were enough to do lots of damage to the Earth's surface and the human built environment that now dominates it.

Ice presents a less severe problem than earthquakes but nevertheless can be difficult to navigate. Why is ice slippery? The temptation is to say, simply, "because it is" but that's not the way of science. We know we deal with it by wearing grippy footwear, or in extremely cold parts of the world like Canada, using snow chains on tyres and that's because we know, instinctively, that we need to increase friction when moving on ice.

That much I understand but when Laurie Winkless described the scientific make up of ice and how that makes it slippery it made me realise just how much I was lacking in science know-how. I talk a good game when it comes to science, and I bow down to scientists when it comes to all sorts of subjects from vaccines to biology, but I struggle to understand it.

That's one of the reasons I attend these talks and I'm glad I do. Because I learn stuff. Normally with these blogs I try and pass that knowledge on to you but in this one I feel I've not really managed to do that. Or at least not much. Instead, hopefully, I've shared my sense of wonder about just how much there is still to learn. Even about the everyday things that surround us.

I applaud Skeptics in the Pub, Laurie Winkless, and Brian Eggo (and his incredible wallpaper and tankard) for providing me with yet another opportunity to realise that. Any evening that ends with a Q&A session tha takes in Teflon, spaceships, Wetherspoons carpets (which a wag in the audience suggested were the stickiest things in the world), Nazi experiments on geckos, and a crocheted model of Prince can't be all bad.

If I didn't understand everything I did learn at least one important lesson. If an absolutely giant treadmill was built and an aeroplane placed on it, no matter what speed the treadmill was able to move at the plane would still not take off. That seems a fairly decent analogy for me trying to understand scientific concepts that absolutely do take off.. Even when I don't fly with all of them. I did, at least, point to the huge flying metal birds and marvel at them. Anyone up for joining a cargo cult?