[OldNavyVet]

From "Darwin's Ghost," a modern update on each and every chapter in Darwin's "Origin."

From the chapter titled "On the geographical Succcession of Organic Beings" (page 218) we have ...

"A trillion comets orbit the sun. The gravel that surrounds them appears, should it hit our atmosphere, as a shower of meteors. The Earth gains a ton in weight every hour from their dust. Two thousand asteroids big enough to destroy civilization orbit nearby."

[SunkenCiv]

They drop in once in a while, too. :’)