Where Grey Matter meets Dark Matter

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Episode 18 - 11 October 2009

As the name suggests, electricity is about the movement of electrons. Whenever you switch on the TV you're plugging into the awesome power of bazillions of electrons. That should make you think twice about squandering your time in front of the idiot box – every second the TV's flickering you should be staring in open-mouthed wonder at the forces of nature that you control.

'Aarrgh! Where are these electrons coming from? How do we stop them?!' Well there is no stopping them, but they come from atoms. Atoms, as you should have learned in school, are little nuclei (that's more than one nucleus) surrounded by buzzing electrons. The electrons are negatively charged and the nucleus is positively charged, so the electrons don't bugger off. But like a youngest child that is allowed to drift into waywardness by jaded parents, not all electrons are kept on a tight leash - some of them can be induced by the bright lights of the wide world to abandon the nest.

So now if you have some material that conducts electricity, call it a metal for the time being, then there is a whole bunch of atoms all stuck together, and they bring with them a lot of these delinquent electrons. In the metal, these electrons all hang out with each other and cause trouble. Well, they don't really cause trouble - these electrons are what gives metal its useful properties of strength and flexibility. And they also make electricity.

Think of all these electrons as like the Blob from the movie (conveniently titled, 'The Blob'), only coloured blue, with cool sparks and an echoey, static hissing sound. This electron blob is smeared out all over the metal. If there is some strong positive charge nearby, then all of the blob will tend to flow towards it, until enough electrons build up there to neutralise the charge. As the blob moves, it picks up energy, just like anything that moves. This is the beginnings of electricity - you can tap into that energy to get it to do stuff, like play repeats of JAG.

If only you could somehow convince the electrons to keep moving. Well, with a circle of wire and a battery that is exactly what happens. One side of the battery is positively charged, so it attracts electrons, and the other side is negative, so it repels them. Connect the wire to both ends of the battery and watch the fireworks (there probably won't be any for a small consumer drycell battery, but don't do it, since it will discharge quickly and might explode - battery acid not cool). If you could watch the electron blob, then you would see it moving around the wire, from the negative side of the battery around to the positive side, then going through the battery and out the negative side again.

Source: http://www.todaysolar.com/html/pv_cells.html

But you would be waiting a while to see the electrons move. Their speed is a gastropodan 1.8 millimeters per hour. But that's not their fault - there's a whole lot of the little buggers in there and they keep crashing into each other when they try to move. They only get about 40 nanometers (that's nanometers folks) before they get stuck again. No wonder they don't like being around each other.

'So how does the light come on so fast?' Well, you're not waiting for the electrons to get there, that's for sure. Think of what would happen if you had a hose full of water connected to a tap. When you turn on the tap, you don't have to wait for the water to run all the way to end, because it's already full - water will start pouring out straightaway. It's exactly the same for electrons. Metal is totally FULL of electrons. So the light comes on as soon as the pressure from the light switch gets to the lightbulb, which is almost the speed of light.

There'll be more electrical goodness coming soon. In the meantime, you could watch the following video. Beware: although it's mostly accurate, it's concerned with safety, and with no foul language you'll be surprised to learn it's quite dull. It seems that most youtube science vids have this problem. But if you're into moving picture, go for it.


  • The first book we go to for all things physics is Halliday, D., Rescnick, R. & Walker, J. (1997), Fundamentals of physics: 5th edition, John Wiley & Sons, New York.
  • Really, any first year university textbook will have all this info and heaps more, but there'll be a stack of equations (at least there should be). For those that don't like equations, there's bound to be a tonne of info in the internet about electricity. Start with Wikipedia.
  • Also, don't forget YouTube. Of course, they usually aren't nearly as entertaining or engaging as we are. But we can't reference ourselves.
  • On YouTube there's a lecture course from MIT about electricity. Given that it's recordings of actual lectures, it's exactly like being there. Not for everybody, but it gives you a good introduction to electricity and magnetism, and he explains the important equations.


To truly understand an alien, one must become an alien.

If aliens do finally make contact (of sorts), what will be their purpose? War? Trade? The betterment of humankind? Or will it be hopelessly unclear? If somebody came into your house and just stood there, staring into space despite your questioning how the hell they managed to pry the lock on the gate, what would you assume?

District 9, for those who have yet to see it, tells the story of an alternate world, where aliens have arrived on Earth. Aside from the ridiculous notion that humans would treat the aliens with fear, suspicion and xenophobia merely because they look, act and smell different from us, it's an excellent film.

One of the key plot points is that the alien technology can only be used by the aliens themselves. Why would that be? Good question.

Is it for security? You can imagine that an alien race that moves into a planet containing semi-intelligent creatures would want to prevent the locals from getting into their store of weapons, or taking off in their spaceship.

If it is security, perhaps there's some sort of DNA scanning device in the handle of the weapon, like in GATTACA. Or perhaps there's some chemical on the skin of the aliens that catalyses (ie. starts) the chemical reaction that gets the gun going.

Or is it some more fundamental part of the gun? Maybe the energy of the gun comes from the aliens, or maybe it requires brain signals to aim and fire it. This is especially believable when it comes to flying the spaceship. Perhaps the driver needs to think about the direction they want to go in order to get the thing to move at all.

Then there is the whole question of combining the genetic material of aliens with humans - like a horrible medical science experiment gone awry. At the risk of manhandling our MacGuffin , it seems unlikely that the genetics of our human protagonist, Wikus, would merge neatly and tidily with that of an alien species. But with a slight tip of the hat to our good friend carbon, we may envisage an alien biology that may be compatible with humans. We could all just get along, replicators and vehicles alike! At least on a molecular level, anyway.

Lots of interesting questions. But in the end it was a political and social commentary wrapped in sci-fi. I don't know if the engineers writing the script knew the answers to these questions.

But then again..


  • You want references? Maybe go and see the film.
  • Here's the website for it: http://www.d-9.com/

Oops. Mistakes we shouldn't have made but did anyway:

  • When Nadine asked Anthony about whether only metals conduct electricity, he said 'yes', which is a blatant falsehood. His excuse is that he was trying to avoid a difficult topic for the time being. We plan to cover it in a future episode, but for the time being - lots of stuff can conduct electricity. And often something can conduct at one temperature but not at a different temperature. It's complicated: conductors, semi-conductors, low-temperature super conductors, high-temperature semi-conductors... We'll get onto it
  • Anita implied that guns work by a mechanical process, not a chemical one. This, however is not correct - the burning of gunpowder is pure chemisty. Also, she said that nuclear energy is the breaking of bonds. Bond breaking and forming is chemical energy, nuclear energy is the decay of the nucelus of an atom, or sticking two of them together.
  • Anthony said that 1 Ampere was the current required to generate a force of 1 Newton between 2 conductors separated by 1 meter. Actually, it's 2x10^(-7) Newtons. But let's not go into that.


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