Star power

The Sun is a huge nuclear reactor. Under extreme pressure and heat, hydrogen is fused together to produce helium and energy.

For over 70 years, scientists have tried to copy this fusion reaction. An artificial sun could create a limitless supply of energy.

Last week, a groundbreaking experiment ran for a record-breaking 403 seconds. China's Experimental Advanced Superconducting Tokamak (EAST) uses magnets to control superheated plasmaa gas charged with electricity, found in stars such as the Sun. Physicists regard it as a state of matter, along with gas, liquid and solid..

The potential is vast. A litre of seawater contains enough fusion material to produce the same energy as 300 litres of petrol. And without any greenhouse gasesGreenhouse gases, which increase the atmosphere's capacity to hold heat, are vital to life on Earth: without them the planet would be freezing. But human activity is disturbing the delicate balance that created the conditions for life as we know it. Carbon dioxide is responsible for 60% of the manmade greenhouse effect, but we also produce smaller quantities of methane, ozone and nitrous oxide, which are even more damaging..

Critics say the technological challenges are too great. Starting a fusion reaction is very difficult. It needs temperatures ten times hotter than the Sun and powerful lasers and magnets to contain it. All of this is very expensive.¹

Physicist Arthur Turrell disagrees. Building these "star machines" is humanity's greatest challenge. A global effort "could provide millions, perhaps billions, of years of clean energy". Limitless power everywhere would change the world, ending energy poverty and wars over fuel.

Many are betting big on a fusion future. The International Thermonuclear Experimental Reactor (ITER) in France is a joint project of 35 nations. It will use the most powerful magnet ever built.

The word nuclear makes people think of nuclear accidents and radioactiveSomething that has or produces radiation. waste. But fusion is much safer. Splitting atoms in nuclear fission sets off dangerous chain reactions. "In fusion," says expert Chris Warrick, "we have the opposite problem". Fission is difficult to stop, fusion is hard to start.

But if we can keep it running, Turrell says fusion rockets will be our "best hope" for space travel. Humanity's future may depend on building stars on Earth.

Yes: Fusion is the longest of long shots - the hardest thing we have ever done. It may take decades to perfect, but this ambition and foresight will give future generations the gift of limitless energy.

No: Fusion is science fantasy. Physicists and governments are wasting time and money on a pet project while the world burns. We already have the technology of the future in wind and solar power.

Or... No single technology will decide our future. Optimists always believe new technology will change everything and fix all our problems. In reality, we will need a variety of inventions working together.