Sure, we aren’t alone, but should we be seeking company?

Michio Kaku, a theoretical physics professor at City College of New York, has warned humans about reaching out to extraterrestrial beings. “I think it’s a terrible idea,” Kaku said.

The astrophysicist, best known for his work on the string theory, recently spoke to the Guardian about his latest book, The God Equation. However, he also shared his thoughts on extraterrestrials or commonly referred to as aliens.

Kaku believes that humans might make contact with the aliens within this century; however, the idea sounds more terrifying than exciting to the theorist. “We all know what happened to Montezuma when he met Cortés in Mexico so many hundreds of years ago,” he said, referring to the death of the 16th century Aztec emperor, which was instigated by his friendship with Spanish conquistador Hernán Cortés.

Kaku believes that aliens might have a friendly approach, although they could have nefarious intentions. “Now, personally, I think that aliens out there would be friendly, but we can’t gamble on it. So I think we will make contact but we should do it very carefully.”

Kaku also points out the possibility of making contact will be much higher as NASA will have its James Webb telescope up in the orbit and will look at thousands of planets. It will make the chances of contact with alien civilization higher than ever.

The 74-year-old astrophysicist also predicted self-replicating robots. In a recent video, he discussed sending clone bots to Mars to help build a galactic colony faster.Speaking about Elon Musk’s plans to colonize the Red Planet, Kaku said, “You have to have fleets of workers to begin the process of building things — unless you create the first self-replicating robot … until you have an army of these robots that can build cities on Mars.” He envisions that these robots “can make copies of themselves by mining the minerals that are already on Mars.”