AT A ceremony in Brussels last week, governments representing more than half the world鈥檚 population 鈥� from China, the European Union, India, Japan and the US, among others 鈥� signed up to spend about $5 billion to build ITER, the world鈥檚 largest nuclear fusion machine. It should be the first fusion machine to deliver more energy than it consumes, and the optimists heading the programme say it will turn fusion power into a major energy source by mid-century.
Most scientists and engineers working on ITER are more wary. 鈥淭he current timetable is very, very, very ambitious,鈥� said one veteran last week. 鈥淚 think it will be 100 years before we have commercially viable energy.鈥� Such caution is not surprising. The reactor will heat plasma to temperatures 10 times those in the core of the sun. Harnessing such extremes in an engineered bottle will take many decades, and ultimately may not be practical.
The old joke, that practical fusion is 40 years away and always will be, is no longer funny. Last week, one senior scientist came up with a new version: 鈥淲e think it鈥檚 going to work. We have to, or the politicians wouldn鈥檛 give us the money.鈥� That is not good enough. If commercial fusion is viable, it may well be a century away. 杏吧原创s should say so and politicians should invest in it anyway. The climate-changing gases we are pouring into the air today persist for centuries. We need to search for solutions on a similar timescale.
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