Carl sagan — contact. chapter 4 — prime numbers

Prime Numbers

The cold black vacuum had been left behind. The pulses were now approaching an ordinary yellow dwarf star and had already begun spilling over the retinue of worlds in this obscure system.

They had fluttered by planets of hydrogen gas, penetrated into moons of ice, breached the organic clouds of a frigid world on which the precursors of life were stirring, and swept across a planet a billion years past its prime. Now the pulses were washing against a warm world, blue and whit, spinning against the backdrop of the stars.
There was life on this world, extravagant in its numbers and variety. There were jumping spiders at the chilly tops of the highest mountains and sulfur-eating worms in hot vents gushing up through ridges on the ocean floors. There were beings that could live only in concentrated sulfuric acid, and beings that were destroyed by concentrated sulfuric acid; organisms that were poisoned by oxygen, and organisms that could survive only in oxygen, that actually breathed the stuff.
A particular lifeform, with a modicum of intelligence, had recently spread across the planet. They had outposts on the ocean floors and in low-altitude orbit. They had swarmed to every nook and cranny of their small world. The boundary that marked the transition of night into day was sweeping westward, and following its motion millions of these beings ritually performed their morning ablutions. They donned great-coats and dhotis; drank brews of coffee, tea, or dandelion; drove bicycles, automobiles, or oxen; and briefly contemplated school assignments, prospects for spring planting, and the fate of the world.
The first pulses in the train of radio waves insinuated themselves through the atmosphere and clouds, struck the landscape and were partially reflected back to space. As the Earth turned beneath them, successive pulses arrived, engulfing not just this one planet but the entire system.

Very little of the energy was intercepted by any of the worlds. Most of it passed effortlessly onward — as the yellow star and its attendant worlds plunged, in an altogether different direction, into the inky dark.
Wearing a Dacron jacket displaying the word “Marauders” above a stylized felt volleyball, the duty officer, beginning the night shift, approached the control building. A klatch of radio astronomers was just leaving for dinner.
“How long have you guys been looking for little green men? It's more than five years, isn't it now, Willie?”
They chided him good-naturedly, but he could detect an edge to their banter.
“Give us a break, Willie,” another of them said. “The quasar luminosity program is going great guns. But it's gonna take forever if we only have two percent of the telescope time.”
“Sure, Jack, sure.”
“Willie, we're looking back toward the origin of the universe. There's a big stake in our program, too — and we know there's a universe out there; you don't know there's a single little green man.”
“Take it up with Dr. Arroway. I'm sure she'll be glad to hear your opinion, “he replied a little sourly.
The duty officer entered the control area. He made a quick survey of dozens of television screens monitoring the progress of the radio search. They had just finished examining the constellation Hercules.