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.

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This episode is sponsored by Audubal.

I think we can all agree, 2020 has been a heck of the year.

Hopefully the rest of the century will go smoother, but if it doesn't, how will we survive it?

Nuclear weapons, viruses, artificial intelligence, technological singularities, asteroid impacts, earthquakes, supervolcanoes, 3D printing, automated factories, gray goo, genetic engineering,

unemployment, virtual reality, deforestation, desertification, changing climates and vases, species, antibiotic

resistant superbacteria, ultra-addictive designer drugs, solar storms and flayers, designer babies,

and uplifted lions and tigers and bears, oh my, the future is going to be quite a challenge.

Welcome to Science and Futurism with Isaac Arthur, and I am your full-mentioned host,

Isaac Arthur.

In general I tend to be known for my optimism about humanity's future, but the point

I always feel obliged to bring up when accused of being optimistic is that it's not optimism

that arises from being unable to see all our problems, but from being able to see a lot of

the potential solutions too, and that we can meet and overcome these challenges.

We have a lot of challenges coming up in the next century, many of which could cripple

or even obliterate us, and what we're going to do today is go through those, ask how we

can avoid the pitfalls, and how we can mitigate the damage or recover if we still

trip into one of those potentially cataclysmic scenarios.

Of course normally the one thing guaranteed about surviving the next century is that

...