¡SkyCaramba! Weekly astronomy blog for the week ending September 30, 2014
How can intelligent beings from very different civilizations communicate with each other? If they’ve never had previous contact, they would have no agreement about gestures, sounds, symbols, and their meanings. They would have to construct understanding by interpreting the context everything is said and done in.
It’s possible they wouldn’t even recognize each other’s mode of communication. The first Europeans to see 
American Indian smoke signals saw just smoke on the horizon. Some people familiar with old Central American ways keep financial ledgers that look like knotted threads to everyone else.
Humans have always found enough in common with each other to get their point across and start learning each other’s words. Sometimes a warm smile conveys meaning. Unfortunately, so does cold blooded killing. Civilizations have come to know each other through both.
During the late 1800s, people started thinking there may be inhabitants of Mars. There was no hope of traveling to the red planet to find out for sure. Radio hadn’t been invented yet either. Some imaginative thinkers came up with the idea of planting or cutting back vegetation in patterns that don’t occur naturally.
They hoped Martians could observe cultivated areas on Earth through telescopes the way we can observe the ice caps on Mars. If you saw several perfectly crafted squares, circles, and triangles carved on a stone slab in the middle of a desert, you would know someone put the shapes there intentionally. Likewise, a Martian could have seen such things on Earth and concluded we meant to communicate.
We have yet to find any life on Mars, let alone any advanced enough to look back at us. But that doesn’t mean it isn’t out there somewhere else. Many modern scientists still want to know how we can communicate with 
extra-terrestrial beings and how to recognize their communication with us. First off, any radio signal they send our way had better stand out over all the naturally occurring radio noise the universe offers. And it had better not look too much like any signal we generate on Earth.
In 1977, a researcher in Ohio received a signal that was very strong, lasted for the entire 72 second period his equipment searched that part of the sky, and it came in on a narrow frequency band. Jerry Ehman was so excited, he wrote Wow! on the computer printout. It’s now called the Wow Signal.
Those searching for extra-terrestrial life marked its anniversary this month. But to their regret, no one has heard the Wow Signal since. So we don’t know if beings who live far away in the stars of Sagittarius created it or if a signal made right here on Earth bounced into Ehman’s equipment.
Suppose we do receive it again or any other signal. Without context, we could understand the other society’s symbols and words no better than historians can understand ancient marks without a Rosetta stone. Perhaps, like smoke signals, an important message for someone else will look meaningless to us.
¡SkyCaramba!