Just recently, a video posted by Big Think featuring Kaku suggested that aliens, assuming they're technologically advanced enough to travel to Earth, would be thoroughly unimpressed by what we’ve achieved so far. As highlighted by LiveScience, his Reddit chat follows much the similar theme – with a bold, additional prediction.

“Let me stick my neck out. I personally feel is that within this century, we will make contact with an alien civilization, by listening in on their radio communications,” he said in response to a questioner.

Although there’s increasing hope that microbial life – bacteria and, depending on your definition, viruses – will be discovered elsewhere in the Solar System, it’s deeply unclear as to how likely it is we’ll find any evidence whatsoever of alien life.

Although it’s generally seen as improbable that we’re the only intelligent life out there, the universe is a mind-blowingly huge place, and the chances of two civilizations crossing paths are incredibly low. So, any concrete or confident estimate as to when this will happen should be taken with a pinch of salt.

Kaku then went on to say that, even if we encounter them, “talking to them will be difficult, since they could be tens of light-years away. So, in the meantime, we must decipher their language to understand their level of technology.”

He added that we need to understand their intentions, how advanced they are, how aggressive (or not) they are, and so forth.

“Another possibility is that they land on the White House lawn and announce their existence,” Kaku adds. “But I think that is unlikely, since we would be like forest animals to them, i.e. not worth communicating with.”