Are Aliens Trying to Call Us on the Cosmic Radio?

When it comes to interstellar messaging, size matters. A bigger radio reaches further, and a bigger web catches more. This is why the Arecibo Observatory, a massive radio telescope in Puerto Rico, plays a crucial role. With a diameter of 1,000 feet, it has been a key communication link with the stars.

In 1974, a significant event happened—the first intentional broadcast from Earth to space. This three-minute stream of binary data was aimed at M13, a star cluster in the constellation of Hercules. If any intelligent aliens deciphered the message, they’d see a simple picture revealing basic information about us. Yet, even traveling at the speed of light, the message will take 25,000 years to get there, making any response a 50,000-year wait.

Impatience isn’t an option in space communication. It’s easier to receive than to send. Just like on Earth, where there are more radio receivers than transmitters, the cosmos probably works the same way. Advanced civilizations likely receive more than they send—either by choice or because it’s cheaper.

But suppose an alien civilization has been sending signals. Would we even recognize it? Imagine finding a message in a bottle washed ashore on a deserted island without knowing what a bottle is. That’s the challenge: distinguishing a cosmic message from the universal noise. It would need to be an unmistakably artificial signal standing out against natural radio waves.

Despite the vast number of stars, searching for extraterrestrial signals is a cosmic needle-in-a-haystack problem. While we may have very little in common with aliens, we share the same galaxy, structured in a way that determines the nature of potential signals. Both we and they would likely utilize the ‘microwave window’—a range of frequencies less disturbed by cosmic noise. This search narrows down to about 1 to 10 gigahertz.

In 1959, Philip Morrison proposed that the frequency of 1420 megahertz—a unique frequency of hydrogen, the universe’s most abundant atom—would be ideal for alien communications. Following this lead, the first radio SETI search began in Green Bank, West Virginia. Frank Drake’s project, although unsuccessful, kicked off a quest that continues with around 60 independent searches worldwide.

Advancements in technology like Harvard Professor Paul Horowitz’s Project META broadened the search parameters, though many signals turned out to be terrestrial interference. Nonetheless, breakthroughs like these keep the hunt alive.

Sometimes, surprises come from unexpected places. In 1967, Cambridge researchers discovered strange regular pulses while looking for signals, which turned out to be not from aliens, but from a pulsar—a type of spinning collapsed star.

Yet, the search for alien signals persists. In 1977, Ohio’s Big Ear telescope recorded an intriguing one-minute signal that fit all the criteria but was never repeated, leaving it an enigma known as the “Wow! Signal.”

Close encounters, even ambiguous ones, stir emotions ranging from ecstasy to frustration among researchers. They know that real contact would bring a unique blend of discovery and elation, a feeling that, when it comes, will be shared by many.

Till then, we keep our ears to the sky, hoping to catch that elusive signal from the stars.