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

we're asked at 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.

One day we may retire our rockets and instead reach the heavens by ascending towers so tall they dwarf mountains, and rise above the sky itself.

The tallest structure in the world, at over half a mile or 828 meters tall, is the Burj Khalifa in Dubai.

It's not very far from the land of Shynar, the region of ancient Mesopotamia, where it

is said the Tower of Babel was built, seeking to stretch the heavens themselves.

That story is typically associated with pride and hubris, and that's often been true of many

projects for constructing

the tallest buildings or largest palaces or temples.

Even in modern times, these gems have often been financially absurd, and indeed the reason

the bullish caliphah is the tallest building isn't because we can't build taller, it's

because there's no compelling reason to build so high.

It is easy to forget that even the biggest and grandest of cities like New York or Tokyo only have a few hundred skyscrapers, while each place boasts over a million buildings,

and often even those values come only from using the most generous lowest mark for skyscraper,

which is unofficially viewed as

being at least somewhere between 100 to 150 meters tall, or 40 to 50 stories or more.

The reasons to build that high is partially for maximizing super-valuble real estate in packed

downtown regions, where your cost per acre might run a few million dollars, compared to a few

thousand in my own neck of the woods, and that alters the equation for usage, where the

cost of an individual floral level is actually less than the land in the city on, unlike

...