The Physics of Motorcycling

Since I wrote a post on the Physics of Driving (March 2014), it seems only logical and fair to write one on the physics of motorcycle riding. The physics is more complex and counter-intuitive, but it’s also more intriguing.

In both cases the driving force (excuse the pun) is gyroscopic dynamics, though, in the case of a motorcycle, it’s both more central and more controlling. I can still remember the first time I went round a decent corner (as opposed to a street intersection) on a motorcycle and felt the inherent weightlessness it generates. This is the appeal of riding a bike and what separates the experience viscerally from driving a car.

As I’ve already explained in my previous post on driving, it’s the muscle strain on our necks that tells us how hard we are cornering, whether we are in a car or on a bike, though the effect is reversed from one to the other. In the case of a car we lean our heads into the corner to balance the semi-circular canals in our ears, and our neck muscles subconsciously tell us what the lateral force is in a subjective sensory manner. In the case of a bike we lean our bodies and keep our heads upright - because we feel effectively weightless - but the strain on our neck muscles is exactly the same, even though it is reversed.

So that explains how it feels but it doesn’t explain how it all works. The physics is not easy to grasp, but the effect is relatively easy to explain, even if one doesn’t understand the dynamics behind it, so please persevere with me. There is a second law of angular momentum, which effectively says that if you apply a torque around an axis perpendicular to the rotating axis, you will get a rotation around the third axis, called precession. One usually draws diagrams at this stage to demonstrate this, but I can do better: I will give you an example that you may be able to perform at home.

A surveyor’s plumb bob works best to demonstrate this, but a bicycle wheel can work as well. Take a plumb bob with its string wrapped around it, hold it horizontally so the wound string is vertical, then let it go while holding the end of the string. As it falls the unwinding string makes the plumb bob spin about its horizontal axis, but when it gets to the end of the string, it doesn’t fall over.  It precesses, giving the impression of weightlessness. This YouTube video demonstrates what I’m talking about rather dramatically with a heavy flywheel, and its sequel demonstrates it even better, and explains the so-called weightless effect. And this video explains the physics concerning the 3 axes using an ordinary bicycle wheel on the end of a rope (which you may be able to do yourself) .

So what has all this physics got to do with riding a motorcycle? It’s what gets you around a corner – as simple as that – but the way it does it is completely counter-intuitive. To get the bike to lean over we apply a torque, via the handlebars, perpendicular to the rotational axis, only we apply it in the opposite direction to what we might think. Basically, if you push on the bar in the direction you want to turn, it will lean over in that direction. By ‘push’ I mean you push on the left bar to lean left and on the right bar to lean right. This is the counter-intuitive part, because we would think that if we pushed on the left bar the wheel would turn right. In fact, I’ve argued about this with people who ride motorbikes, but I know it’s true because, I not only understand the physics behind it, I put it into practice in over a decade of riding.

Now, when the bike leans over, it behaves exactly the same as the fly-wheel in the videos, and, under the force of gravity, the bike precesses around the corner, generating a feeling of weightlessness at the same time.

So that’s the core of the physics of riding a motorcycle but there’s more. In a car you can swerve and brake at the same time, as any advanced driving course will teach you. But on a bike you can do one or the other but not both. If you brake in a corner, the bike will ‘stand up’ and there is nothing you can do about it. This is different to simply closing the throttle, when the bike will tighten its line (turn tighter). Now, why this quirk of physics may seem catastrophic, it’s what allows you to brake in a corner at all. You see the bike will still follow the same curved trajectory while it’s slowing down, and it does it without any intervention from you except for the application of brakes.

The other laws of physics I explained in my last post, regarding the inverse law of speed versus rate-of-change of direction, and the braking distance following the speed squared law still apply. In other words, it takes twice as long to change direction at double the speed, and it takes 4 times the distance to brake at double the speed.

Why consciousness is unique to the animal kingdom

I’ve written a number of posts on consciousness over the last 7 years, or whenever it was I started blogging, so this is a refinement of what’s gone before, and possibly a more substantial argument. It arose from a discussion in New Scientist  24 May 2014 (Letters) concerning the evolution of consciousness and, in particular the question: ‘What need is there of actual consciousness?’ (Eric Kvaalen from France).

I’ve argued in a previous post that consciousness evolved early and it arose from emotions, not logic. In particular, early sentient creatures would have relied on fear, pain and desire, as these do pose an evolutionary advantage, especially if memory is also involved. In fact, I’ve argued that consciousness without memory is pretty useless, otherwise the organism (including humans) wouldn’t even know it was conscious (see my post on Afterlife, March 2014).

Many philosophers and scientists argue that AI (Artificial Intelligence) will become sentient. The interesting argument is that ‘we will know’ (referencing New Scientist Editorial, 2 April 2011) because we don’t know that anyone else is conscious either. In other words, the argument goes that if an AI behaves like it’s conscious or sentient, then it must be. However, I argue that AI entities don’t have emotions unless they are programmed artificially to behave like they do – i.e. simulated. And this is a major distinction, if one believes, as I do, that sentience arose from emotions (feelings) and not logic or reason.

But in answer to the question posed above, one only has to look at another very prevalent life form on this planet, which is not sentient, and the answer, I would suggest, becomes obvious. I’m talking about vegetation. And what is the fundamental difference? There is no evolutionary advantage to vegetation having sentience, or, more specifically, having feelings. If a plant was to feel pain or fear, how could it respond? Compared to members of the animal kingdom, it cannot escape the source, because it is literally rooted to the spot. And this is why I believe animals evolved consciousness (sentience by another name) and plants didn’t. Now, there may be degrees of consciousness in animals (we don’t know) but, if feelings were the progenitor of consciousness, we can understand why it is a unique attribute of the animal kingdom and not found in vegetation or machines.

How should I live?

This is the 'Question of the Month' in the latest issue of Philosophy Now (Issue 101, March/April 2014). Submissions need to be 400 words or less, so mine is 400 words exactly (refer below).

How should I live?

How I should live and how I do live are not necessarily the same, but having aspirations and trying to live up to them is a good starting point. So the following is how I aspire to live, which I don’t always achieve in practice.

The most important point is that no one lives in isolation. The fact that we all, not only speak in a language, but also think in a language, illustrates how significantly dependent we are on our milieu. What’s more, from our earliest cognitive experiences to the remainder of our lives, we interact with others, and the quality of our lives is largely dependent on that interaction.

Everyone seeks happiness and in modern Western societies this universal goal is taken for granted. But how to achieve it? A tendency to narcissism, tacitly encouraged by the relatively recent innovation of social media, can lead to self-obsession, which we are particularly prone to in our youth. Socrates famously said (or so we believe): ‘The unexamined life is not worth living.’ But a thoughtful analysis of that coda, when applied to one’s own life, reveals that we only examine our lives when we fail. The corollary to this is that a life without failure is a life not worth living. And this is how wisdom evolves over a life’s experiences: not through success or study but through dealing with life’s trials and tribulations. This is reflected in virtually every story that’s been told: how the protagonist deals with adversity, be it physical or psychological or both. And this is why storytelling is universally appealing.

So how should I live my life? By being the opposite to narcissistic and self-obsessed. By realising that every interaction in my life is an opportunity to make my life more rewarding by making someone else’s life more rewarding. In any relationship, familial, work-related, contractual or whatever, either both parties are satisfied or both are dissatisfied. It is very rare that someone achieves happiness at someone else’s expense, unless they are competing in a sporting event or partaking in a reality TV show.

There is an old Chinese saying, possibly Confucian in origin: If you want to know the true worth of a person, observe the effects they have on other people's lives. A true leader knows that their leadership is not about their personal achievements: it’s about enabling others to realise their own achievements.

Pitfalls of a Democracy

The latest issue of Philosophy Now has as its theme, ‘Democracy’, with a number of articles on the subject covering Plato to contemporary politics. In particular relevance to this post, Anja Steinbauer ‘explains why Plato had problems with democracy.’ I won’t discuss her article at length, but early on she points out that ‘…it all comes to a head with Socrates: Athenian democracy didn’t like Socrates, which is why the troublesome thinker was democratically put to death.’ The reason I paraphrase this is because it has dramatic relevance to current political events in Australia.

On a recent issue of 4 Corners, whistleblowers and video footage tell us what the government was unwilling to reveal regarding not so recent events at a detention centre for refugees on Manus Island, Papua New Guinea, where an asylum-seeker was killed during a riot. The programme reveals the deeply flawed inhumanity of this particular government policy which was originally introduced by the previous (Labor) government and is now being brutally pursued by the incumbent (Liberal) government. Both sides of politics endorse this policy because it’s a vote-winner and, in fact, the last election campaign was dominated by who could be more successful in ‘stopping the boats’ (containing asylum-seekers) as if we are suffering from a wartime invasion.

The relevance to Steinbauer’s insightful commentary on Plato and Socrates is that, with the explicit support of the general public, a government can execute policies that directly contravene the human rights of people who have no political representation in that country. In essence, we are guilty of inflicting both physical and emotional trauma on people; an action we would condemn if it was being done somewhere else. In short, a democratic process does not necessarily provide the most ethical and moral resolution to a dilemma.

The other side to this, is the airing of the programme itself. Only a healthy democratic society can foster a journalistic culture that can openly criticise government policies without fear of retribution.

The physics of driving

This is quite a departure, I know, but one of my hobby-horses is how little people know about the physics of driving. Unlike our man-made road rules, the laws of nature are unbreakable, so a rudimentary knowledge can be useful.

But what prompted me to write this post was a road test I read of the new, upmarket Infiniti Q50 in EVO Australia (March 2014). The big-selling feature of the Infiniti Q50 is its so-called ‘direct adaptive steering’; a world first, apparently for a production car (as opposed to a prototype or research vehicle). It’s a totally ‘fly-by-wire’ steering system, so there is no mechanical connection between the helm and the front wheels. Personally, I think this is a dangerous idea, and I was originally going to title this post, rather provocatively, “A dangerous idea”. Not surprisingly, at least to me, the road-tester found the system more than a little disconcerting when he used it in the real world. It was okay until he wanted to push the car a little, when the lack of feedback through the wheel made him feel somewhat insecure.

There are gyroscopic forces on the front wheels, which naturally increase with cornering force and can be felt through the  steering wheel. The wheel weights up in direct proportion to this force (and not the amount of lock applied as some might think). In other words, it’s a linear relationship, and it’s one of the major sources of determining the cornering force being generated.

I should point out that the main source of determining cornering force is your inner ear, which we all use subconsciously, and is why we all lean our heads when cornering, even though we are unaware of it. It’s the muscle strain on our necks, arising from maintaining our inner ear balance, that tells us how much lateral g-force we have generated. On a motorcycle, we do the opposite, keeping our heads straight while we lean our bodies, so the muscle strain is reversed, but the effect is exactly the same.

Therefore, you may think, we don’t need the steering wheel’s feedback, but there is more. The turn-in to a corner is the most critical part of cornering. This was pointed out to me decades ago, when I was a novice, but experience has confirmed it many times over. Yes, the corner can change radius or camber or both and you might strike something mid-corner, like loose gravel, but, generally, if the front wheels grip on entry then you know they will grip throughout the rest of the corner. This is the case whether you’re under brakes or not, wet or dry surface. It’s possible to loosen traction with a heavy right foot, but most cars have traction control these days, so even that is not an issue for most of us. The point is that, if the front wheels grip on turn-in, we ‘feel’ it through the steering wheel, because of the gyroscopic relationship between cornering force and the weight of the wheel. And cornering force is directly proportional to the amount of grip. The point is that without this critical feedback at turn-in, drivers will be dependent on visual cues to work out if the car is gripping or not. What’s more, the transition from grip to non-grip and back won’t be felt through the wheel. If this system becomes the engineering norm it will make bad drivers out of all of us.

While I’m on the topic, did you know that at twice the speed it takes four times the distance to pull up to a stop? Perhaps, you did, but I bet no one told you when you were learning to drive. The relationship between speed and braking distance is not linear – braking distance is proportional to the speed squared, so 3 times as fast takes 9 times the distance to stop. This is independent of road surface, tyres and make of car – it’s a natural law.

Another one to appreciate is that at twice the speed, changing direction is twice as slow. There is an inverse relationship between speed and rate of change of direction. This is important in the context of driving on multi-lane highways. A car travelling at half the speed of another – that’s overtaking it, say – can change direction twice as fast as the faster car. This is also a law of nature, so even allowing for superior tyres and dynamics of the faster car, the physics is overwhelmingly against it. This is why the safest speed to travel on multi-lane highways is the same speed as everyone else. An atypically slow car, in these circumstances, is just as dangerous (to other motorists and itself) as an atypically fast car.

Addendum: I also wrote a post on the physics of riding a motorcycle.

Afterlife belief – a unique human condition

Recently I’ve been dreaming about having philosophical discussions, which is very strange, to say the least. And one of these was on the topic of the afterlife. My particular insight, from my dream, was that humans have the unique capacity to imagine a life and a world beyond death. It’s hard to imagine that any other creature, no matter its cognitive capacity, would be able to make the same leap. This is not a new insight for me; it’s one my dream reminded me of rather than initiated. Nevertheless, it’s a good starting point for a discussion on the afterlife.

It’s also, I believe, the reason humans came up with religion – it’s hard to dissociate one from the other.  Humans are more than capable of imagining fictional worlds – I’ve created a few myself as a sometime sci-fi writer. But imagining a life after death is to project oneself into an eternal continuity, a form of immortality. Someone once pointed out that death is the ultimate letting go of the ego, and I believe this is a major reason we find it so difficult to confront. The Buddhists talk about the ‘no-self’ and ‘no attachments’, and I believe this is what they’re referring to. We all form attachments during life, be it material or ideological or aspirational or through personal relationships, and I think that this is natural, even psychologically necessary for the most part. But death requires us to give all these up. In some cases people make sacrifices, where an ideal or another’s life takes precedent over one’s own ego. In effect, we may substitute someone else’s ego for our own.

Do I believe in an afterlife? Actually, I’m agnostic on that point, but I have no expectation, and, from what we know, it seems unlikely. I have no problem with people believing in an afterlife – as I say, it’s part of the human condition – but I have a problem when people place more emphasis on it than the current life they’re actually living. There are numerous stories of people ostracizing their children, on religious grounds, because seeking eternal paradise is more important than familial relationships. I find this perverse, as I do the idea of killing people with the promise of reaching heaven as a reward.

Personally, I think it’s more healthy to have no expectation when one dies. It’s no different to going to sleep or any other form of losing consciousness, only one never regains it. No one knows when they fall asleep or when they lose consciousness, and the same applies when one dies. It leaves no memory, so we don’t know when it happens. There is an oft asked question: why is there something rather than nothing? Well, consciousness plays a big role in that question, because, without consciousness, there might as well be nothing. ‘Something’ only exists for ‘you’ while you are alive.

Consciousness exists in a continuous present, and, in fact, without consciousness, the concepts of past present and future would have no meaning. But more than that, without memory, you would not even know you have consciousness. In fact, it is possible to be conscious or act conscious, whilst believing, in retrospect, that you were unconscious. It can happen when you come out of anaesthetic (it’s happened to me) or when you’re extremely intoxicated with alcohol or when you’ve been knocked unconscious by a blow. In these admittedly rare and unusual circumstances, one can be conscious and behave consciously, yet create no memories, so effectively be unconscious. In other words, without memory (short term memory) we would all be subjectively unconscious.

So, even if there is the possibility that one’s consciousness can leave behind the body that created it, after corporeal death, it would also leave behind all the memories that give us our sense of self. It’s only our memories that give us our sense of continuity, and hence our sense of self.

Then there is the issue of afterlife and infinity. Only mathematicians and cosmologists truly appreciate what infinity means. The point is that if you have an infinite amount of time and space than anything that can happen once can happen an infinite number of times. This means that, with infinity, in this world or any other, there would be an infinite number of you and me. But, not only am I not interested in an infinite number of me, I don’t believe anyone would want to live for infinity if they really thought about it.

At the start, I mentioned that I believe religion arose from a belief in the afterlife. Having said that, I think religion comes from a natural tendency to look for meaning beyond the life we live. I’ve made the point before, that if there is a purpose beyond the here and now, it’s not ours to know. And, if there is a purpose, we find it in the lives we live and not in an imagined reward beyond the grave.