A recent Scientific American article highlighted the work of two Canadian engineers. Todd Reichert and Cameron Robertson, who built the world’s first (and only) human-powered helicopter.
After they had completed their brilliant and imaginative work, they learned of a recent paper which showed that what they had just done was impossible.
Their achievement put me in mind of Lord Kelvin’s misguided pronouncement:
Heavier-than-air flying machines are impossible.
This is a popular meme: illustrious expert says something is impossible: ingenue shows it is not.
But nonetheless, there are (presumably?) things which, even though they may be imagined, are still either truly or practically impossible.
But how can you distinguish between ideas which are truly or practically impossible, and those which are just hard to imagine?
This is not a merely an academic question
The UK is currently committed to spending hundreds of millions of pounds on a nuclear fusion experiment called ITER which I am confident will never result in the construction of even a single power station.
Wikipedia tells me the build cost of the project is an astonishing $50 billion – ten times its original projected cost. Impossible projects have a way of going over budget.
I explained my reasons for considering the project to be impossible here.
And on reading this Jonathan Butterworth, Head of Physics at UCL tweeted that he:
could write a similar post on why the LHC is impossible. IMHO
But I don’t think he could. Let me explain with some examples:
1. The large hadron collider (LHC) where Jonathan works is a machine called a synchrotron, which is itself a development of a cyclotron.
The first cyclotron was built in a single University physics department in 1932 (History). If, back then, you had told someone the specification of the LHC, would they have said it was impossible?
I don’t think so. Because although each parameter (size, energy etc.) has been stretched – through astonishing ingenuity and technically virtuosity – the LHC is an extrapolation from something that they knew definitely worked.
2. A modern nuclear power station is an engineering realisation of ‘a pile of graphite bricks‘ that was first constructed beneath the stand of a playing field of the University of Chicago in 1942.
Within this ‘pile’, the first controlled nuclear reaction took place and worked exactly as had been anticipated. Would the people who witnessed the reaction have said a nuclear power station was impossible?
Definitely not. Everyone in the room was aware of the significance (good and bad) of what had been achieved.
Controlled nuclear fusion, is in an entirely different category from either of these stories of engineering success.
We have never created sustained nuclear fusion and the reasons for the failure of this achievement have always changed as we have understood the problem better.
The rationale for ITER is – cutting through a great deal of technical detail – that it is bigger than previous versions. This increases the volume of the plasma (where energy is released by fusion) in relation to the surface area (where it is lost).
I expect that ITER will meet its technical goals (or most of them). But even on this assumption, they would then have to solve the technical problems associated with confining a plasma at a temperature of 150 million ºC for 30 years rather than 10 seconds.
As I explained previously, I just don’t think solutions to these problems exist that would allow reliable operation for 30 years with 90% availability required for power generation.
So I think controlled nuclear fusion as a means of generating power is – while perfectly conceivable – actually impossible.
What if – in 50 years time – we make it work?
Then I will be proved wrong. If I am alive, I will apologise.
However, even in this optimistic scenario, it will be 50 years too late to affect climate change, which is a problem which needs solving now.
And we will have spent money and energy that we could have spent on solving the problems that face us now using solutions which we know will definitely work.