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Friday, 29 July 2011


Late one night, half a lifetime ago when I was a student, I was repairing an old valve oscilloscope rescued from a skip at the back of Imperial College.  I decided that I'd had enough and that it was time for bed.  I poured a bowl of cornflakes and set it on the top of the bedside fridge (Peltier, so silent) that had the milk in for the morning, and went to sleep.

At about three a.m. I was woken by a crunching noise.  I turned on the light to find my nose about 20 centimetres from the nose of a mouse holding a cornflake in both hands.

The mouse didn't stay long.  I spent a few minutes chasing it round the room, until it ran into the scope, which still had its casing off.

I then had a really good idea: I turned the scope on.  After a few moments it had warmed up, and I clapped my hands.  I heard scampering noises from inside the works.  Another clap, another scamper, then a squeak followed by silence.

I could see the corpse lying in the wiring.

I then had a really bad idea: I reached in to extract the mouse.

I found myself on the opposite side of the room.

Either directly, or via the mouse, I had touched the final anode.  I estimate that this must have been at about 6,000 volts DC.  I was fortunate that I hadn't instead touched the main positive power line at around 300 volts; that might well have finished me.  The final anode supply was, of course, severely current-limited.

I said I found myself on the other side of the room, and that is exactly what the experience was.  I remember the shock, and I hadn't lost consciousness at all.  But, because what passes for my brain hadn't told my muscles to move, that brain deduced that an external agency had thrown me across the room.  In reality I had jumped, but my brain said thrown.

The next day I got to thinking, like all inventors, about better mousetraps.

Now, as a mousetrap, an oscilloscope is perhaps over-complicated.  But its principle is simplicity itself.

So I took a square of cardboard about 30 centimetres on one side and glued a 10 centimetre disc of aluminium cooking foil in the middle.  Around this I glued an annulus of aluminium foil with a 2 centimetre gap between it and the disc.  I put a dollop of peanut butter (crunchy) in the middle of the disc, wired the two pieces of aluminium across the mains, set the trap on the floor, left a note saying "Beware Electric Mousetrap" for my flatmates, and went back into IC to do a day's research for my PhD.

On my return that evening there was another dead mouse.  This time I turned off the mains before I picked it up to dispose of it.  It was a bit cooked...

But, now I'm older, I don't think I would use HT electricity in a mousetrap.

Better would be a strong gamma source such as 60Co in a small depleted uranium labyrinth with no line-of-sight from the source to the outside.  A DU cup dropped over the source should allow you to put peanut butter in and to take dead mice out...

Saturday, 23 July 2011


"Even the most powerful man on Earth, Barack Obama,...": thus some MP on a political TV show the other day that I flipped into by mistake.

This struck me as a decidedly ill-informed and parochial view.  It was rather as if Itzhak Perlman were to say, "Even the most powerful man on Earth, Sir Simon Rattle,..."

If politicians regard Barack Obama as the most powerful person in their field of endeavour, that is fair enough.  But that doesn't make him the most powerful person on Earth.  The most powerful person on Earth is the one who has changed it most.

Look at how people change things and what resources and constraints operate when they try to do so.  Those resources and constraints work at four different levels, each overwhelmingly stronger than the one that preceded it.

The bottom, least important, level is the level of rules.  That is to say, instructions said or written down by some people in the hope (a hope sometimes backed up by main force) that others will do as they say.  They are instructions like, 'You shall not eat pork,' or, 'Here you may not drive faster than 50 kph.'

The next level up is that of economics.  Money is more powerful than rules.   Or, to put it another way, the system of rules has to strain every last clause to have even a small effect on the world of money.  For example, possessing and trading in the alkaloids produced by the poppy Papaver somniferum are against the rules just about everywhere in the World.  And yet that trade is one of the World's most enduring, sustainable and profitable industries.

The next level up is biology in general, and human biology in particular.  Consider a teenage boy spending $200 on a pair of training shoes.  There's a perfect functional equivalent available for $50, and conventional economic theory says that those cheaper ones are the pair that he should buy.  But he is not buying shoes.  He is buying a peacock's tail.  The purchase is part of his breeding strategy, albeit probably a completely unconscious one.  Biology trumps money, and recently economists (to their credit) have recognised this and introduced a whole new branch of their subject - behavioural economics - to apply corrections to economics from the biology that overrules it.

The top level is that of physics - the substrate upon which all this other activity is played out.  No organism has ever evolved a perpetual motion machine; if one had, the results would have so out-competed everything else that all living things would work that way.  This omission might be because mutation had never chanced upon the right arrangement.  But the true reason is more profound: a living perpetual motion machine would break the Second Law of Thermodynamics, which is just about the most solid physical law that we have ever discovered.  Physics trumps biology.

Now we can see the depth of the MP's mistake.  Both he and Barack Obama are operating at the bottom level - they create and modify the rule book.  When they try to influence the next level above them - the world of money - it is as if they are operating a machine using levers made from jelly.  And they cannot hope to have any influence worth speaking of in the worlds of biology and physics.

To imagine that "the most powerful man on Earth" could be a politician is to make a category error.

The person who has made the biggest change to the world in our lifetimes - the most powerful man on Earth - did so by working at the biological and physical levels.  He used electronics to satisfy the innate biological need of people to communicate.  He is Sir Tim Berners-Lee.

The engine of history is engines...

Sunday, 10 July 2011


Mountains are not really very tenable objects.  They get thrown up by tectonic plate collisions or volcanism, but gravity and the weather then flatten them pretty quickly.  That is to say, quickly if you are a stone.  The longest-lived mountains tend to be ones that are made of low-density rock, or that float on a low-density area of plate.  Those are more-or-less in equilibrium, like ships on the sea.

This gives a clue how to make an artificial mountain.  You make it from bricks filled with helium.  The bricks would be tough rectangular plastic bags with aluminised interiors to retain the gas.  Each brick might be about the size of a house, and it would come with tabs on the edges to allow it to be attached to all its neighbouring bricks in the same sort of very strong bond pattern that you find in an ordinary brick wall.  Instead of the tabs, you might even be able to do something clever with Velcro on the surfaces.

As the mountain of bricks gets higher, you reduce the pressure of the helium in the bricks to match that of the surrounding atmosphere.  Some reasonably straightforward calculations should allow the entire structure to have neutral buoyancy as a whole, and also at every horizontal slice at all altitudes.  The individual bricks, whilst piled kilometres high, would not be being compressed by those above them, and would be almost completely unstressed.

If you made the helium mountain big, it would probably be a good idea to anchor it to something reasonably substantial in order to resist the wind.  For example, you could build it round an existing natural mountain.

You could then build your helium mountain right up to space.

Once you had done that, you could run a linear accelerator up the side and launch payloads into orbit electrically for a few dollars a kilogram...