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.nebler.tv slash Isaac Arthur and use my code, Isaac Arthur.

Our world is ancient, but the universe is far older.

What were those hot and dense,

they surpassed a supernova, and in under a minute, virtually every particle of hydrogen,

helium, deuterium, and lithium that now exists was formed.

Things grew less dense and cooler after that, and by 400,000 years after the Big Bang,

conditions since settled down to what the surface of a dim or star would be like.

It's ironic that folks think we have problems recreating fusion in the lab because we're

trying to replicate

the innards of stars, but we are not. Fusion of any given particle in the core of a typical

star is the sort of thing that happens less often than once in a billion years. People might

envision a house-sized fusion reactor replicating our sun's interior with 100 tons of stellar core matter inside

as some powerful joker not, but only be able to run a few light bulbs off the fusion

energy it was producing, albeit it would run them for billions of years.

No, to generate useful power from fusion, you need to replicate the conditions inside a dying

star, and those are the conditions that replicate the conditions inside a dying star, and those

are the conditions that forge the matter planets are made of, and those conditions lasted

only a few brief moments after the beginning of time.

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