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.

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In science fiction, we often see immense starships attacking planets, crushing or besieging them,

but in our own future, we may deploy powerful orbital fortresses to defend our world.

The Way back in the late 90s, when I was just starting college, one of my favorite

sci-fi TV shows, Babylon 5, was wrapping up its fourth season with the universe story

arc about a human civil war that had an attack on Earth.

CGI was just starting to let us have grand space battles between large fleets

instead of a handful of physical spaceship models, and so Babylon 5 and Deep Space 9

and some others were featuring episodes with dozens or even hundreds of ships flying around.

In this climatic episode, the good guys managed to trick the defending fleet out of position

and temporarily out of play and jump to Earth directly to begin the assault.

Classically in sci-fi, one or two ships are evenly matched against the planet, or even

have the upper hand.

But in the episode we suddenly see a whole

bunch of big orbital stations flick on, rotate into play, and begin firing high-energy

beams and follies of missiles and just start beating the heck out of the fleet.

It is a great episode to end the penultimate season of one of science fiction's best TV franchises, but it got

me rethinking a lot of classic space opera ideas about how space combat would work, and

challenged the tendency to think of planets as rare jewels in space that were terribly vulnerable

...