Static Electricity

What do lightning conductors and Global Warming have in common?

Recently when covering Static Electricity we looked at how lightning conductors work, but we also discussed why they took so long to catch on.

Try answering the following questions without looking at the answers (I know you’re not actually going to do this, but it gives you a sense how the conversation went in class).

Me: Give me some examples of what you can NOT insure your house against.
Students: Floods, hurricanes, earthquakes

Me: What are these collectively known as?
Students: Acts of God

Me: Why are they referred to as Acts of God?
Students: Because you can’t predict when or if they’re going to happen.

Me: But why would you call those events ‘Acts of God’?
Students: Because you can’t predict when or if they’re going to happen.

Repeat three times.

Me: But why would you call those things ‘Acts of God’?
Student: Because God must have wanted those things to happen – or at least that’s what the people believed back then.

Me: Exactly. And before you all laugh at how ridiculous that sounds remember that it’s not that they were any less intelligent than we are now, it’s just that life in the 16th and 17th century was incomparably different to today. We live in a so-called age of reason. We know you can’t say ‘well that’s obviously what God wanted’ every time something bad happens. And I’m pretty sure that if our civilisation survives another century or two the people who are around then will look back at some of the rather bizarre belief systems that we subscribe to. The United States contains approximately 5% of the world’s population yet in incarcerates 25% of the world’s prison population. Enlightened?

Even Newton himself fell into this way of thinking. When he found out that the orbits of the planets didn’t quite match his mathematical equations his response was to say that God obviously needs to step in and give them a nudge every so often. It took Einstein to explain that the problem was that Newton’s equations weren’t exact enough and it needed his (Einstein’s) Theory of Relativity to sort out the anomaly.

The point is that, as with so much of the Church’s teachings, its beliefs can be traced back to either St. Augustine or St. Thomas Aquinas. In this case both believed that the air was filled with seriously questionable characters. Aquinas wrote that “Rain and winds, and whatsoever occurs by local impulse alone, can be caused by demons. It is a dogma of faith that the demons can produce winds, storms, and rain of fire from heaven.”
And so, presumably, can God.

So when Franklin suggested that his lightning rod could save  church buildings he naturally thought that this would be well received (in fact he considered it to be one of his greatest accomplishments, which is no mean feat when one considers that he was also one of the founding fathers of the United States.) It turns out that his suggestion went down like the proverbial lead balloon.

If a building struck by lightning was an Act of God, then interfering with this process was akin to thwarting God’s plan. And that, in the eyes of the Church authorities at least, couldn’t be a good thing. So they simply refused to put them in.

But there was one small problem. The church building was invariably the tallest structure in every village and town. So it was also the most likely to get hit. Now as you can imagine this confused people greatly. Not only that but the bell-ringers whose job it was to alert the townsfolk about the impending storm also tended to become the first victims of any lightning strike. In Germany alone approximately 300 bell-ringers lost their lives in the last 30 years of the 19th century.

So slowly but surely Church authorities began to relent and accept that maybe it was time to accept that there was something to be said for these so-called ‘blasphemous devices’ after all. Lucky for them it wasn’t too late.

So what’s all this got to do with Global Warming?
According to one 2006 study, 76 percent of Republican citizens profess a belief in the Second Coming (the so-called ‘Apocalypse’). They also represent one of the largest groups who oppose scientific teaching on Global Warming. They simply refuse to accept that Global Warming has the potential to change the world irrevocably. Why? Because the end of the world will come at a time of God’s choosing, not ours, so whatever mankind is doing right now, it’s certainly not going to bring about the destruction of civilisation.

These religious conservatives have become a very powerful force in American politics in recent decades (how that came to be is an equally fascinating story, but not for today).

Add to this the lobby group for oil and other fossil fuels and you have a voice that is both loud and very difficult to dislodge.

Now for fun throw in optimism bias which is evolutionary hardwired into all of us. Optimism Bias is the belief that the future will be better than the past. So for example 10% of Americans expect to live to be 100 when in fact only 0.02% are likely to live that long.We all experience optimism bias. It’s why none of us mention Global Warming when political canvassers call to our door. We all just assume that it will get sorted somehow. It may even explain why we are all so reluctant to engage with the concept of our own mortality; deep down we all think we’re going to live forever.

So you can see why Global Warming remains low on everybody’s radar.

And it will most likely remain that way – until it’s too late.

Unlike lightning conductors.

This is a link to resources I use when teaching about Global Warming and The Apocalypse in Transition Year.


The precautionary principle gone mad


This sign now seems to be appearing regularly in petrol stations across the country. Presumably it’s because the owners are afraid that the mobile can somehow cause a spark, even though there is not the slightest bit of evidence that this can happen. Maybe it’s related to the demonstration involving mobile phones cooking pop-corn. We seem to be approaching the day when it’s not even Wikipedia we have to worry about as the source of all knowledge, but YouTube.

For the record, there is also no possibility that mobiles can cook popcorn, so yes, some of those videos may just be hoaxes.

There does seem to be something not quite right about banning the use of phones while on the same pump having a picture of a big juicy hot-dog – I guess the heart attack you get in a few years’ time can’t be attritubed back to the station.

Oh, and don’t rub your bum on the car seat either.

Secrets of the Van der Graff


The philosopher of science Michael Polyani referred to it as ‘personal knowledge’, sociologist of science Harry Collins called it ‘tacit knowledge’ and your local gardener would simply know it as ‘green fingers’. It is the knowledge which we possess as experts in any given field but which is difficult to articulate. A certain ‘je ne sais quoi’ if you will. I suppose it’s why these cookery programs are so popular. All these wonderful chefs giving the impression that ‘there’s nothing to it’ is music to our ears – until we try to repeat the exercise ourselves.

In fairness to cookery programs, they are so much better than cookery books because there are so many vital steps which would never appear in print, partly because the chef simply can’t think of everything, but also perhaps because some of the essential steps would be considered ‘too obvious’ by the expert.

Needless to say, the same applies to teaching, and even more so when teaching a practical subject.

So with this caveat, here are a few tips when using the Van der Graff generator in a physics lesson.

  1. Don’t make the mistake of waiting for a sunny summer’s day. Yes the air needs to be dry to prevent the machine discharging into the air, but if you think about it there is likely to be less moisture in the air in a cold, dry winter’s day than in a warm dry summer’s day (warm air holds more moisture).
  2. I say that like it’s the most natural thing in the world for a physics teacher to know, yet it was only pointed out to me last year. You see you don’t need to know everything to be an expert – you only need to know a little more than your neighbour.
  3. You must have a hair-dryer to hand. Ideally have a student spend 10 minutes warming up all the belt in advance of any demonstration, and if necessary continue to use it on and off throughout (but obviously have it off while speaking).
  4. You will also need to hair dryer when trying the hair-raising demo with a volunteer student. There isn’t any danger here (unless the student has a pace-maker!) and greatest chance of accident is if someone gets a shock accidently and falls and bangs their head.
  5. Here you will need to give the student a helping hand. Again it’s the hair-dryer to the rescue – use another student to help here (if the volunteer is a girl then the person with the hair-dryer should also be a responsible female, for obvious reasons). Get her to use the hair-dryer to ‘fluff-up’ the volunteer’s hair and the Van der Graff should keep it up there.
  6. Volunteer needs to be well insulted – standing on plastic box usually does the trick.
  7. Have another student hold up a mirror so the volunteer can see herself – it adds to the fun.
  8. Remember that not only can the volunteer be touched, but the electrons can ‘jump’ through the air, so you can’t even come close to her.
  9. When discharging, ask her to simply touch the wooden bench and she will discharge sufficiently slowly to prevent shock. The effect is most noticeable if there is contrast between the hair and the background, so ideally have the lights on and dark blinds on the windows.
  10. Don’t forget to try some of the other old reliable like aluminium trays, fluorescent light bulbs and even blowing bubbles at the dome.

Hope this helps.
Have fun!

Fun with the Van der Graff and Animoto

A study of concentration

We had the usual fun with the Van der Graff today. The weather was rather accommodating, and it tallied nicely with the last class before the long weekend.

I have never got a student’s hair to stand up dramatically, but i was drying the canvas belt with a hairdryer when I realised I could help things along a little by aiming it upwards into Fania’s hair. It loosened up the hair very nicely and the show was much more impressive as a result. I also got a student to hold up a mirror so Fania could see for herself what everyone else was laughing at.

I have seen a few examples of Animoto and how it does a pretty cool job of presenting photos, so I thought I’d head on over and check it out.

It really is pretty impressive, and very user-friendly. There might be a couple of thinks I would change, but then again that may just be me not familiar with the program.

It allows for automatic uploading to youtube, which was a pleasant surprise. The free version limits the clip to 30 seconds, so I might just invest in the longer version to check it out.

This is a clip I uploaded last year