Requirements for Promoting a New Scientific Theory

25 04 2013

I have been reading some pretty strange stuff this week about Gravity recently. It seems there are some pretty odd folk out there who have taken thinking about physics to a new, possibly unhealthy, level.

Gravity: It's the Law

Basically, they are crackpots. Well I guess it’s a slippery slope – one day you wonder why the earth is sucking down on you, the next you decide to spend some time on the knotty question. Soon enough you think you’ve got it, it is clearly that the earth is absorbing space which is constantly rushing down around us dragging us with it. Or similar.

So yes, its true, Einstein did not ‘solve’ Gravity, and there is still fame and fortune to be had in thinking about gravity, so this is the example I shall use today.

The trouble with Gravity is that Einstein’s explanation is just so cool! He explained that mass warps space and that the feeling of being pulled is simply a side effect of being in warped space. It sounds so outlandish, but also so simple, that it has clearly encouraged many ‘interesting’ people to have a crack at doing a better job themselves.

So, as a service to all those wannabe physics icons, I offer today a service, in the form of a checklist – what hoops will your new scientific theory have to jump through to get my attention, and that of the so-called ivory tower elite in the scientific community?

Requirement 1: Your theory needs to be well presented

presentation counts!Yes, it may sound elitist to say, but your documentation/website/paper/video should have good grammar. Yes, yes, one should not use the quality of one’s english to judge the quality of one’s theory, and I know prejudice is hard to overcome, but this is not my point. My point is that in order to understand a complicated thing like a physics theory it needs to be unambiguous. It needs to be clear. It needs to use the same jargon the so called ‘elite’ community uses. Invented acronyms, especially those with your own initials in them, are out.

Requirement 2: Your proposal needs to be respectful

Image courtesy of Wikimedia Commons

Image courtesy of Wikimedia Commons

Again, this is not about making you bow to your superiors in the academic world. Indeed in the case of Gravity, the physics community is one of the most humble out there. While I agree academia is up it’s arse most of the time, this is about convincing the reader that you know your stuff. In order to do that, you need to show that you know ‘their stuff’ too. If you have headings like “Einstein’s Big Mistake” it is a bit like saying to the reader ‘you are all FOOLS!’ and cackling madly. Don’t do it!

Respect also means you need to answer questions ‘properly’. That means clearly, fully, and in the common language of the community. You cannot say “its the responsibility of the community to test your theory”. This is a great way to piss people right off. It is your responsibility to make them want to. This usually means dealing with their doubts head-on, and if you can do that, I promise you they will then want to know more.

Requirement 3: You need to develop credibility

Sorry, as you can see we have yet to consider the actual merit of the theory itself. I wish it were not so, but we are humans first and scientists second. We cannot focus our thoughts on a theory if we doubt the payback. And if you say that aliens came and told you the scientific theory, then people are unlikely to keep listening, unless, perhaps they’re from Hollywood.

But seriously, credibility is the hidden currency of the world, it opens doors, bends ears and gets funds. It takes professionals decades to build and it is really rather naive to waltz into a specialism and expect everyone to drop their tools and listen to you.

That said, the science world is full of incomers, it is not a closed shop as some would you believe. If you follow requirements 1 and 2, and are persistent (and your theory actually holds water) then you are very likely to succeed.

Penrose_triangleRequirement 4: Your theory needs to be consistent

I have seen some pretty strange stuff proposed. Gravity is a manifestation of the flow of information, or the speed of light is determined by a planet’s density. Find your own at crank.net. Let’s look at this peach as an example: http://www.einsteingravity.com/.

This exhibit is great example of how not to go about promoting your theory. “Monumental   Scientific   Discovery  !” it screams across the top, then the first claim is this:

1) The Acceleration of earth’s Gravity x earth orbit Time (exact lunar year) = the Velocity of Light.
(9.80175174 m/s2 x 30,585,600 s = 299,792,458 m/s)

Now this is rather remarkable. Can it really be that you can calculate the speed of light to 9 significant figures from just the earth’s gravitational acceleration and the length of a year? Intuitively I suspect you could (eventually), but then I started to think, well, what if the earth was irregularly shaped? The gravitational constant is actually not all that consistent depending on where you are either. So I checked, then I noticed he said ‘lunar year’. What? Why? What is a lunar year? Then I calculated that the time he used was 354 days, which isn’t even a lunar year. Add to that that he gives the acceleration of gravity on earth to 9-figures despite the fact that nobody knows it that well (like I said it is location dependent). Does he does the same test for other planets? No. Well what if they have no moon!

So, 0/4 for on our checklist for einsteingravity.com!

Requirement 5: The theory needs to be be consistent with well-known observationsevidence

Now if your theory has got past requirements 1-4 , well done to you, you will be welcome to join my table any time. Now is when you may need some more help.

Once a theory is consistent with itself, it now needs to agree with what we see around us. It needs to explain apples falling, moons orbiting, light bending and time dilating. This is the hardest part.

It cannot leave any out, or predict something contrary to the facts. It cannot be vague or wishy-washy. It needs the type of certainty we only get from the application of formal logic – and that old chestnut – mathematics.

No you cannot get away without it, there is no substitute for an equation. Equations derived using logic take all the emotion out of a debate. And they set you up perfectly for requirement #5.

crystal-ballRequirement 6: The theory needs to make testable predictions

If your theory has got past the 5 above, very nice job, I hope to meet you one day.

We are all set, we have a hypothesis and we can’t break it. It has been passed to others, some dismiss it, others are not so sure. How do you create consensus?

Simple, make an impressive prediction, and then test that.

Einsteins field equations for example, boldly provide a ‘shape’ of space (spacetime actually) for any given distribution of mass. With that shape in hand you should then be able to predict the path of light beams past stars or galaxies. These equation claimed to replace Newton’s simple inverse square law, but include the effects of time which creates strange effects (like frame dragging), which, importantly could be, and were, tested.

The beauty of these equations, derived via logical inference from how the speed of light seems invariate, and now proven many times, is that they moved physics forward. Rather than asking, ‘what is gravity’, the question is now ‘why does mass warp space’. It’s a better question because answering it will probably have implications far beyond gravity – it will inform cosmology and quantum theory too.

Conclusion

So if you are thinking of sharing with the world at last your immensely important insights, and want to be listened to, please remember my advice when you are famous and put in a good word for me in Stockholm. But please, if, when trying to explain yourself, and are finding it tough, please please consider the possibility that you are just plain wrong…

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Jarrod Hart is a practicing scientist, and wrote this to shamelessly enhance his  reputation in case he ever needs to peddle you a strange theory.

Further reading:

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L’Aquila Earthquake: Science collides with the law…

22 10 2012

Today we heard that a group of seismologists have been jailed over the advice they gave prior to the 2009 quake in L’Aquila in Italy which killed over 300 people.

Is this good and right?

Well let’s start by imagining you lived in l’Aquila and a series of tremors had the town worried. A group of experts comes to town, and after a long meeting, come out and declare the risk is miminal. So rather than evacuating, you go home, rest assured, only to lose your family two days later.

I would want blood. I would want to lash out. My family could have been saved!

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So at first glance this judgement may seem like a last sad ripple from a tragic event, however, it isn’t. Upon further reflection, this judgement has serious implications for the relationship between science and the law.

I have always been troubled by how a guilty verdict means ‘you did it’ even if you didn’t, turning ‘beyond a reasonable doubt’ into no doubt at all. I have previously blogged about pragmatism in law, and how you cannot be 80% guilty and thus serve 80% of a sentence.

With such pressures on the law to come to a clear conclusion, it was only a matter of time before a court was asked to decide on whether scientific advice was correct…

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So today, when a court decided that scientists were ‘too reassuring’ to the public, my alarm bells were set ringing and still haven’t stopped.

Armed with the hindsight that an earthquake in fact did occur, it is natural that the families of the victims are appalled by the advice they got. However, in this case it is critical to also put yourself into the shoes of the scientist – in the days before the quake.

They must have honestly doubted a quake would happen. If you had expected a quake you would surely have said so!

In their statements they confirmed a quake was possible but unlikely. So what we have to ask is this: based on the data they had, was that conclusion faulty?

To answer that you only need to ask – do all tremors lead to quakes? Well no, most don’t. So the quake was by no means likely, let alone inevitable. They were not covering up. None in the group was suppressed or censored. I can only conclude that they, after years of chasing  tremors, had come to discount the value of tremors as indicators.

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And today, a judge decided that their advice was not only wrong, but criminally wrong.

The problem here is that science is not a PR exercise. If scientists put spin on data, they lose credibility. If they cry wolf, they lose credibility. The only safe way to do science is to stick to the facts. The facts did not indicate an imminent earthquake. The judge does not seem to realise: scientists cannot, and do not claim to be able to, predict earthquakes.

Perhaps the judge should read Taleb’s treatise on rare events, and he’d seen that just because something is unlikely (as the scientists said) does not protect us from the possibility it may still happen.

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So what we have seen today is this: scientists, giving their edified analysis, have been thrown in jail. The mob are satisfied, but you should be distinctly worried.

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See also: Letter from the AAAS to the Italian president





Global Warming Canaries, Anyone? A short intro to why most scientists are worried about climate change…

18 08 2012

The current state of arctic sea ice (see graph below) sends a chill down my spine.

Image

So what it says is that the ice is melting furiously, and looks like it’s not yet slowing down even though the days have started to draw in.

However, any scientist will tell you that no single data point can be used as evidence of global warming, there are simply too many fluctuations for anything to be concluded over anything but the longest timescales. We cannot simply look at the mean temperature for a hot year and say, there you go, global warming!

Now, the issue is, there are well-known cycles over pretty much all timescales – this pretty much undermines all serious attempts at prediction.

So, what to do? Well all is not lost; there are still some clever little leading indicators we can look at to give us that sobering wake up call.

#1:  CO2

Firstly, we know CO2 concentration is up, no doubt or argument, this can be seen in the famous Hawaii data above, complete with the seasonal ‘breathing’ by global plant-life. The argument is about whether the greenhouse models that say this will result in warming will turn out right. I honestly don’t know, but I wouldn’t even have to wonder if the CO2 levels weren’t going up, would I?

#2: A Record Breaking Rate of Record Breaking

Secondly, rather looking at averages or ‘new records’, we can look at the frequency of records. So rather than saying, “we just had the hottest summer ever in some parts of the US, there’s the proof” we can look at how often records are set all over the world – hottest, coldest, wettest, dryest and so on. This approach creates a filter; if it shows there are more records being broken on the hot side than the cold side, could this be an indicator? I hope not, because there are.

Again, it could be part of a long-term cycle that could bottom out any time now. But on the other hand, if it was going the other way, I wouldn’t have to hope, would I?

#3: Sea Ice

Now the sea ice. The sea ice is another proxy for temperature. The reason it’s interesting to climatologists is because it is a natural way to ‘sum-up’ the total warmth for the year and longer; if ice is reducing over several years, it means that there has been a net surplus of warmth.

CryoSat – The European Space Agency’s Sea Ice Monitoring satellite launched in 2010 – (Image credit ESA)

Today we are seeing a new record set for minimal northern sea ice. And not only is there less area of ice, but it is thinner than previously realized and some models now suggest we could be ice-free in late summer in my lifetime.

Now if that does not strike you cold, then I didn’t make myself clear. This is not some political posturing, not some ‘big-business’ spin, nor greeny fear mongering. It’s a cold clean fact you can interpret for yourself, and it could not be clearer.

So is it time to panic?

Well it can still be argued the melting is part of a cycle, it could of course reverse and hey, no biggy. After all, what does it matter how much ice there is?

Well, yet again, I hate to rely on the ‘hope’ that it’s a cycle. Because if it continues, the next effect will be felt much closer to home…

Sea Level

Sea level is the ultimate proxy for warming. Indeed, sea level change can be so serious, maybe it is the problem rather than the symptom. If the ice on Greenland and Antarctica melt, the rise in sea level would displace hundreds of millions of people and change the landscape so dramatically it’s a fair bet wars and famine will follow. Now that is serious.

So have we seen sea level rise? Well, yes. Here’s the plot:

Now, it looks pretty conclusive but hold the boat. Some say’s it’s proof of warming but not everyone agrees. It’s true it could again be a cycle. Also, the sea level rise is fairly gradual; what people are really arguing about is whether we should expect it to speed up. If temperature goes up a few degrees it could go up 5 or 10 times faster. The speed is the issue. Humanity can cope if the level goes up slowly enough, sure, countries like Tuvalu will be in big trouble either way, but countries like Bangladesh and cities like New York and London will only be in real trouble if the rate increases.

Actual Canaries

Canaries taken into mines in order to detect poisonous gases; the idea being they would suffer the gas faster than the people and if the canary dropped, it was time to vacate. Do we have systems that are hypersensitive to climate change?

Yes! There are many delicately balanced ecosystems that can can pushed over a tipping point with the lightest of touch. Is there an increase in the rate of species loss, or an increase in desertification? Yes!

We can also look at how far north certain plants can survive, how high up mountains trees can live or how early the first buds of spring arrive.

Again, these indicators fail to give solace. Everywhere we look we see changes, bleached coral, absent butterflies, retreating glaciers.

The conservative approach is to ascribe these changes to the usual cut and thrust of life on earth; some take solace from the fact that humankind has survived because we are the supreme adapters and that the loss of species is exactly how the stronger ones are selected.

Yes, we are great at adapting, however, to kill any complacency that may create, consider the following: for humans just ‘surviving’ is not the goal, that’s easy, we also need to minimize suffering and death, a much tougher aim. We’ve also just recently reduced our adaptability significantly by creating ‘countries’. Countries may seem innocuous, but they come with borders – and mean we can no longer migrate with the climate. Trade across border also needs to be of roughly the same value in both directions.  While some countries will actually see productivity benefits from global warming, most will not, and without the freedom to move, famine will result. Trade imbalances mean inequality will become extreme. The poorest will suffer the most.

So for now changes are happening, and advances in agricultural technology are easily coping; however, because ecosystems are often a fine balance between strong opposing forces, changes may be fast should one of the ropes snap.

Conclusion

Looking at the long history of the earth we have seen much hotter and much colder scenes. We have seen much higher and much lower sea levels. We are being wishful to assume we will stay as we have for the last 10,000 years. It may last, or it may change. Natural cycles could ruin us. And mankind is probably fraying the ropes by messing with CO2 levels.

Can we predict if we are about to fall off of our stable plateau? No, probably not. But is it possible? Heck yeah.

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If you liked this, you may like these earlier posts on the subject of global warming:

  1. What does the earth’s history tell us about climate? And how can we find out if our house will be one that sinks should sea levels rise? Find out here!
  2. Can we  change the planet’s dangerous behavior? Read my call for a study in mass behavior.




Big Pharma: Heroes or Villains?

25 12 2011

What is ‘Big Pharma’?

Many people have argued that alternative and complimentary medicines are suppressed because they threaten the status quo for ‘big pharma’.  Before we accept this claim, let’s unpack the idea of big pharma a little to understand the incentives at play and when it may be right not to trust big pharma.

Let me start by making it clear – big pharma, as a label for the largest pharmaceutical companies, deserves a healthy dose of outrage; but before we toss the baby out with the bathwater, but lets see when – and why.

Big pharma is just another name for ‘big business’: a big business is an organism that has grown beyond the people that founded it, such that rather than having emotions, conscience or guilt, it has KPI’s like turnover, cashflow and return on investment. Big pharma is in the business of making money and as such should generally be expected to default to that option unless constrained by law. The collective conscience of shareholders only tends to kick in when dirty laundry is put out on show. Ok, so firstly, I think we can agree, a business is not a charity.

Next we take this lack of compassion and combine it with size and complexity – we see we now have an organism susceptible to plain outright crookery – from the white collar sort, like insider trading – to the very tangible – such as the dumping of toxic waste. These practices usually require the corruption of people – but not always – it is very easy for companies to do bad things without any individuals having malicious intent; it could simply be negligence or incompetence, or it could simply be that profit sometimes comes before fairness.

Take for example the problem of selling DVD’s in the world market. They are small and lightweight and easy to ship worldwide. This usually means that the price would be similar worldwide, if dealers in one country were to raise prices, residents would simply import the product. However, the enormous wealth differentials that exist between, say, the USA and Mexico, mean that the company could set a high price to extract maximum value from the US market, but then essentially price themselves out of the Mexican market. If they lowered the price, they would sell more product but with much reduced profit margins.

This problem is thrown into stark relief in the case of drugs, where the most profitable option is often to cater to the richer countries. This is sound business – set your price high, keep your factory trim, reduce shipping costs, keep high margins. However, if the drug can radically improve health outcomes, this policy could be seen as unethical.

This is the sort of problem big pharma face routinely; they are not selling entertainment, they are sometimes selling life itself, and often find they need to play profits against ethics in they way I describe above. It is thus hardly surprising that the general public have a distrust and general suspicion toward Big Pharma. In addition to drug import controls, there are many other situations where governments have had to step in to ensure the pharmaceutical companies ‘do the right thing’, such as the case with antiretroviral drugs (for HIV) coming into Africa.

Now think for a moment on this thought experiment: what would happen if a small publicly traded company discovered a cheap and easily reproducible cure for cancer? Would they really be able to hold on and extract full value for their shareholders? History actually suggests they wouldn’t – the drug would become public property, or would simply be nationalised if the company tried to resist. Inventions like the major vaccines and the first antibiotics were often not patented, and we see if we look at the pharmaceutical industry that their biggest profits come predictably not from miracle cures but from drugs that cater to the maladies of the richer classes. The top targets are heart disease, heart-burn, stroke, mental health and asthma. Once you  add disorders like diabetes you have accounted for the most profitable chunk of the industry.

This trend raises fresh concerns, because there are many severe ailments that are simply not attractive to profit making operations, the poster-boys being malaria, TB and HIV/Aids. Drug companies can be bullied into doing work in these areas, but it tends to fall to governments and charities to fund research in the afflictions of the poor, or on the so-called ‘orphan diseases’ – ailments that affect too few people to ever make a profitable market.

Economists will also argue that profit making businesses, being creatures under the strict control of incentives, will be unlikely to aim for ‘cures’ because cures are ‘one-offs’. While this criticism has some sad validity (in the board-room if not in the clinic), we have to remember that the big drug companies only exist because they make profits; in an imagined world where the first dollars were always spent on the most dire diseases and we only get to do botox and erectile dysfunction once those are all solved we would have no private industry at all, so far fewer trained scientists, far less public knowledge and certainly no map of the genome. We have to remember that to some extent at least, the aging american taking their cocktail of pills every day for the last 50 years has in some sense subsidized the field doctor in rural Africa. Yes, they also subsidized Wall Street excesses, but perhaps it’s a deal worth making.

Publication Bias

Another area where drug companies increasingly in need government intervention is in drug trials; specifically, they are presently allowed to pick and choose what to publish; this sounds OK at first, because, surely, you assume, the drug company has to make a bulletproof case before the drug is licensed? Well, if you do 100 trials, you may well find 50 good results, and publish those, and simply sweep the duds under the carpet. What’s more is those duds could have revealed possible side effects or interactions that could actually turn out to be real issues later on down the road. This is going to be a big one in the next few years.

The Big Picture

When criticizing the pharmaceutical industry it is easy to get caught up in the weeds, for there are weeds, but let’s also try to remember that this century has seen unparalleled improvements in life expectancy world-wide, and the improvements in child mortality in the third world do owe a lot to the sometimes cold-hearted business models intrinsic to western medicine.

Before I move on, and being a scientist, I wanted to make another point about big pharma. While it’s true that big money is involved, we have to remember that the Pareto principle applies here too – the majority of the profits come from the minority of the research. There are legions of perfectly good people, motivated by no more that the desire to help people in distress working in healthcare all around the world. Drugs are highly integrated with other therapies at the clinical level and the people actually running trials ‘in the trenches’ face-to-face with the patients (and often dealing with terrible trauma)  are rarely shareholders in big pharma, and many would not even think for a second they are part of what people would call big pharma. Yet it is they who have gradually built up our current understanding of the human body, not the men in suits.

Conclusion

To me, the idea of executives at the top 5 drug companies has become conflated with the idea of the ‘canon’ of western medicine. The idea that the whole world of ‘proven medications’, the result of countless years of hard graft (and the learnings from millions of deaths), can be dismissed because it’s under the control of ‘fatcats’ is a sick tragedy. Western medicine is simply a name for ‘what has been statistically been proven to help’, and the idea that even a tiny fraction of the scientists who developed it would be working to suppress good ideas from outside the ‘fold’ sounds frankly paranoid. Yes big pharma has some warped incentives that cause it to focus on the wrong things and leave the poor out in the cold, but all for-profit publicly-traded businesses do that! Ask yourself for a minute – even if a cure for heart disease were found that threatened the profits to Pfizer and friends, could they really recruit a worldwide network of conspirators who think a cure for cancer is something worth selling their very souls for to suppress?

It hard enough to run a real business, let alone running one so effectively in complete secrecy in the face of so much scrutiny. If they have that much skill and power, they should go legit, they would make a real killing!





Air Fresheners Exposed!

22 05 2011

Ok, so I know its not a conspiracy to take over the world, but my inner nerd has been provoked.

Have you ever wondered how air fresheners work?

Let’s take a sceptical look.

Nanobot

This cool pic is from hybridmedicalanimation.com

I’d love to think that AirWick / Glade / {insert preferred brand here} consist of an army of nano-bots that round up and deport any molecules without the right paperwork.

Although we aren’t there yet, it’s actually not too far from the truth!

Although many cheap deodorisers do simply mask the truth by overpowering our senses, I really like to give credit where credit is due, so I am happy to disclose that there are indeed certain substances that can detain odours – such as zeolites and silica gels, and there are also organic molecules that will react with a wide array or hydrocarbons rendering them odourless. These ideas are in fact used by several big brands today.

Hurrah!

But that’s not the whole story, is it?

No, because none of that really means the substance (or it’s source) is ‘gone’; all they have done is disabled our ability to detect all that foreign matter around us!

The last time I looked, our sense of smell, just like our sight and hearing, was there to help us survive – to detect when there is something unsavoury in the vicinity and force us to deal with it. If your bed or sofa stinks, you should probably take it outside and try to remove to 5 lbs of skins flakes and  other sundry bodily oozings rather than spray the bed with an extra long burst of febreze.

You wouldn’t season rotten meat in curry then serve it to your in-laws, would you?

Now, to be fair, the purveyors of these products do not intend for you to use their product to allow you to live in filth disguised with the scent of lavender, and their scientists are smart people – however, there marketing departments do need to be brought to book for giving a few misleading impressions.

The world ‘fresh’ for example is used universally. I don’t know about you, but to me this should mean clean, pure and new. It may certainly allow for some sweet floral aroma, but it certainly doesn’t include ‘complex organics we cannot smell’.

Some solutions – like Resolve carpet cleaner, where an absorbent powder is applied liberally then hoovered up, deserve a break – but, as far as I can see there are the exception – most odour control is still in the form of the old “cover up”.

What we have to remember is that in order to claim a product is ‘absorbing’ an odour, one only need prove it absorbs ‘some’ odour – not necessarily the majority and very rarely “all”. Thus it can be that it absorbs 2% of the odour and the other 98% of the odour is still there but overwhelmed by the scent of a pine forest. The same is true with biocidal deodorisers (like Lysol) which may kill bacteria – a common source of odour. These products can actually kill germs – however the impression that a quick spray will effectively sterilise is falsely reassuring.

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I sign off now by pointing out that the best way to avoid odours is by good hygiene, though not too good: remember that we humans co-evolved with this slimy little planet!





Hysteresis Explained

1 04 2011

Hysteresis (hiss-ter-ee-sis). Lovely word. But what on earth does it mean?

Hysteresis is one of those typically jargonny words used by scientists that instantly renders the entire sentence if not lecture lost on its audience. Sure, you can look it up on wikipedia, but you may die of boredom before you get to the point, so I am going to explain it here.

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Hysteresis on the way to school

Let’s go for a walk. Let’s say we are ten years old and we are walking to school. The route is simple. The school is a few hundred yards down the hill on the other side of the road. Now consider the question: at what stage do we cross the road? Immediately? Or do we walk all the way to opposite the school before crossing – or somewhere between?

Assuming there are no ‘official’ crossing points, I bet you cross immediately, then walk down the far side of the road.

How can I make this prediction? Well, I assume that crossing the road requires there to be no traffic, so if there is no traffic as you start the journey, it is a good time to cross. If there is traffic, you just start walking down the road until a gap appears, then you cross. This strategy allows you to cross without losing any time. If your strategy had been to cross at the school there is a real risk you will need to wait, thus losing time. So it turns out the best strategy to avoid any waiting is to cross as soon as you can.

So now picture your walk home. Again, it makes sense to cross early on. The result is that the best route to school is not the same as the best route from school. This is an example of hysteresis – or a ‘path dependent phenomena’.

Hysteresis  everywhere

The dictionary will drone on about magnetism and capacitance and imaginary numbers. A much nicer example is melting and freezing of materials – some substances actually melt and freeze at different temperatures. This shows that the answer to the question: “is X a solid at temperature Y?” actually depends – on the path taken to that temperature. Just like what side of the road you are halfway between home and school will depend on whether you are coming or going.

It seems to me that falling asleep and waking up also bear some of the hallmarks of hysteresis; although they could be considered a simple state change in opposite directions, they feel very different to me – I  seem to drift to sleep, but tend to wake to alertness rather suddenly.

Now think of a golf club in mid swing. As the golfer swings, the head of the club lags behind the shaft. If the golfer where to swing in reverse, the club head would lag in the other direction – thus, you can  tell the direction of movement from a still photograph. We can therefore say the shape of a golf club exhibits hysteresis – and again you see see why it is so-called “path dependent”.

This logic can be taken further still – wetting is not the opposite of drying and likewise heating is rarely the inverse of of cooling. Let’s imagine for example that you want to make a chicken pie warm on the inside and cool on the outside. This is best done by warming the whole pie and then letting it cool a little. The temperature ‘profile’ inside your pie thus depends not only on the recent temperature but has a complex relationship with its more distant temperature history. This particular point is somewhat salient at the moment as we ask the question: is the earth heating up? 

So what?

Good question. I’m not a fan of jargon, and hysteresis is not a word I hope to need to use in my smalltalk. However, you can see that it encapsulates a rather specific and increasingly important concept that is pretty hard to replace with two or three simpler words; thus it passes my test of “words a scientist should understand that most don’t”. Please let me know your own additions to such a list!

 

 





Educational way to spend four minutes…

2 01 2011