Are we alone in the galaxy? Over recent decades, scientists have debated signaling our presence to potential extraterrestrials. But not everyone views this outreach positively. What if our quest for cosmic neighbors backfires?
Michio Kaku, professor of theoretical physics at the City College of New York and a leading proponent of string theory, is renowned for making complex physics accessible. You've likely seen him in documentaries or read his bestselling books.
In a recent interview with The Guardian, Kaku discussed his research and shared his views on encountering extraterrestrials.
Kaku estimates our chances of contact are strong, especially with the James Webb Space Telescope (JWST) launch slated for October 31, enabling unprecedented exoplanet observations. Yet, he urges caution. "Some of my colleagues think we should contact them," he notes. "I personally think it's a terrible idea."
The search for extraterrestrial intelligence began in the 1960s with astronomer Frank Drake. Using the National Radio Astronomy Observatory in Green Bank, Virginia, he targeted stars Tau Ceti and Epsilon Eridani—prime candidates for habitable worlds. After 150 hours over four months, no signals were found.
This effort birthed the SETI Institute (Search for Extraterrestrial Intelligence). SETI assumes advanced life might evolve similarly to Earth life, scanning for technological signals. Since 2015, Andrew Siemion, director of the Berkeley SETI Research Center and lead on Breakthrough Listen, has monitored the cosmos for such emissions.
In contrast, the METI Institute (Messaging Extraterrestrial Intelligence), founded in 2015 in San Francisco with private funding, advocates active transmission. Past efforts include the Pioneer Plaque, Arecibo Message, and Voyager's golden record. METI is the first organization dedicated to crafting and sending messages to potential aliens.
While SETI listens passively, METI broadcasts proactively. "Imagine if all civilizations just listen without transmitting… it would be an incredibly quiet universe," says METI President Douglas Vakoch.
Not all agree on transmitting signals into space.
"I personally think aliens would be friendly, but we can't bet on that," Kaku cautions. "So if we make contact, we should do it very carefully." The late Stephen Hawking echoed similar warnings before his passing.
Even within SETI, METI's approach draws criticism. "The ethical problem is they are taking a great risk on behalf of all humanity without permission," says astronomer John Gertz, former SETI board president, in Inverse.
Siemion warns that advanced civilizations may not be benevolent. "There are probably malevolent civilizations elsewhere," he explains. "We must consider this as we explore."
Vakoch counters that any threatening civilization likely already detects us. "What people forget is it's too late to hide," he says. "If they're coming, better to show we're good conversationalists, not lunch."
