[Below is the original script. But a few changes may have been made during the recording of this audio podcast.]
The sun pumps out some 383 quadrillion watts of energy every second thanks to fusion. So, it's not surprising we've been trying for the last 50 years to harness the abundant clean energy from that process.
But it takes the Sun's powerful gravity and temperatures of around 14 million degrees Celsius to get these hydrogen atoms stripped down to just their nuclei and able to fuse inside an ionized gas known as plasma.
In fact, it will take temperatures of 100 million degrees C to get fusion going on a scale that could fit on our planet. Plus, there's the issue of turbulence.
Like the Earth's atmosphere, plasma likes to swirl because of temperature and pressure differences from point to point. The result is storms that can cool the plasma and halt fusion.
The International Thermonuclear Experimental Reactor or ITER to be built in Cadarache, France will rely on magnetic fields roughly 100,000 times stronger than the Earth's to contain the plasma and hold in its heat. At the right density, pressure and temperature, voilà, fusion!
Unfortunately, all existing fusion machines require more energy to operate than they produce. And ITER will cost at least $15 billion to build.
Fusion may have been going on in the Sun for more than four billion years but it still remains just out of reach here on Earth.