Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asking the reason alien civilizations might be rare is because most aliens are huge.

To hear it and every episode early and ad-free, plus hours of bonus content,

check out go.nebola.tv slash Isaac Arthur and use my code, Isaac Arthur.

There's an old joke that Fusion is the energy technology of 20 years from now, and always

will be, and yet that technology may finally be on the horizon.

Welcome to Science and Futurism with Isaac Arthur, and I am your aforementioned host,

Isaac Arthur, bringing you hopefully accurate glimpses into the future for the last decade,

and now with 90% more letter R's, though there are subtitles available on all our episodes.

Besides having a stubbornly lingering speech impediment and a science show, I am also a physicist,

and one of the things that attracted me to the field was energy production.

I grew up in the 1980s when fear of nuclear war was probably at its peak, fossil fuel concerns

were beginning to arise, and solar

was a distant dream.

Global population growth was very fast, and there was always a concern bordering on dread

that we were going to have a Malthusian catastrophe and all ended up living in the burned

out ruins of a deforested, toxic, and irradiated planet.

This was all about the time that nuclear fusion was getting its first developmental disappointment

phase with the public, as it had started getting talked about as an option that we might have

in a couple decades in the 1950s and 60s and seems still almost entirely theoretical. Add to it, we would soon

get inundated with a lot of cold fusion designs, and were some were at least reasonably

sincere and sane, many more were utter scams and hoaxes. At the same time, even nowadays

...