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With the possible exception of Hulkamania, there is no force mightier than nuclear fusion. Pound for pound, it releases more energy than any fuel source ever used on Earth. It sustains the stars themselves, bringing the daytime and filling the night sky with the light of fusion fires so brilliant they can be seen light-years away. It is the furnace in which all but the simplest elements were forged, from the oxygen in your lungs that fuels your metabolism to the silicon in your computer that lets you read this article to the protactinium that just sits uselessly next to uranium on the periodic table doing nothing to justify its sorry existence.
Want to tap into that same power yourself? It couldn't be simpler.
First, gather up around 1.989x1030 kilograms of hydrogen. Just call it "one nonillion, 989 octillion" if you need to say it out loud for some reason. Heat the core to a temperature of 15 million degrees Kelvin (roughly 25 million degrees Farenheit, for those who want a conversion), enough to get all those hydrogen atoms moving fast enough to overcome their natural mutual repulsion from each other and collide. Hydrogen atoms will fuse together into helium, releasing energy in the process, and you've got nuclear power!
Then, keep the reaction going by tightly confining this hellstorm in place despite its natural desire to blow outward. Conveniently enough, the tremendous gravity produced by the mass of an entire star will do both of these things for you. You now have a power source that releases enormous amounts of energy and produces virtually no pollution.
Then just do the same thing again, except this time replace the mass of an entire star with a metal donut about 50 feet across. Oh, and since you won't have the density and sheer size of the solar core to work with, you'll need even higher temperatures; a hundred million or so degrees ought to do it.
That's what a group of scientists in Germany have been working on with the Wendelstein 7-X, a type of experimental fusion reactor called a stellarator. Gas is injected into a torus-shaped chamber, where it is bludgeoned with microwaves and particle beams into a plasma with a temperature of millions of degrees. Superconducting magnetic coils ringing the chamber confine the plasma, controlling its flow and preventing it from touching anything in the interior of the stellarator that would react badly to contact with the core of a star.
Which is everything, so you really don't want to cut corners on those magnets.
It's still in its early days. The Wendelstein hasn't even caused a fusion reaction yet, just shown promise that it can. On December 10th, 2015, the Wendelstein's first successful test produced a helium plasma with a temperature of about one million degrees Kelvin. Its builders hope to eventually achieve temperatures of 60 to a 130 million degrees, over eight times hotter than the core of the Sun.
End even if the Wendelstein 7-X design does turn out to be the road to practical fusion power, there's still a long way to go. Artificially causing nuclear fusion is one thing; that's been possible for decades. (Over half a century, actually, though for a while it could only be done through laboratory-unfriendly means like setting off a nuclear bomb.) Causing fusion efficiently enough that you actually get more energy out than you put in is another, and doing that efficiently enough to make it economically viable as a source of electric power is yet another.
Still, it may well be possible, quite possibly within our lifetimes. What would some of the implications of that for our world be?