Far Away Suns
River knows sunlight is one of the few things Kaylee misses about living planetside. The eye-squints and bone deep warmth of a hot and dusty day.
She also knows Serenity's engine warms Kaylee well enough, but nothing about the cold dark of space can conjure the light of a sun.
River thinks Kaylee is like sunshine, burning yellow at the center of Serenity and her crew, holding the ship together with her tools and skills and laughter and warmth and brightness.
River tries not to remember that too much sunlight can drive a body to madness, a topic close to her heart. Once, she knows, when Kaylee was little, she had a run in with an old settler, a grizzled creature with cracked lips and veiny skin, his brain all sun-addled and confused. He thought Kaylee was his daughter and tried to make her do daughterly things. Later, he tried to drink too much water all at once and drowned in the rushing currents of the muddy river.
River doesn't want to be a daughter; she only wants to be a sister.
Some people think the opposite of sunlight is moonlight; River thinks this is silly, for only poets and children and the insane think the moon can shine on its own. It's all reflected sunlight. Book knows that the opposite of sunlight is nothing but freezing blackness, all dark and lonely.
His knowledge makes River's head ache.
Simon sees stars and poetry and pretty growing things when he looks at Kaylee, and this is well and good; everyone knows a star is just a sun from far away.
Sometimes River looks out into space and stretches her arms and fingers out, blocking each star from her vision one by one.