Scientists estimate that there may be as many as 100 trillion stars in the Milky Way galaxy alone. If we assume for a moment that one out of every star has an Earth-like planet with intelligent life, and if we further assume (perhaps improbably) that these aliens are capable of interstellar travel and communication, then the chances that we’re actually alone in the universe are very small.

What are the chances of alien life?

Scientists aren’t even sure if there is any other intelligent life in the universe. They’ve looked for it by scanning stars and planets with radio telescopes, one possibility being that advanced alien civilizations may be using radio waves to communicate, but so far they haven’t heard anything.

“When we’re talking about looking for life beyond Earth, even if it’s just microbial life, the context always is that you’re looking at stars like the Sun,” said Jill Tarter of the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, California.

“There are about 200 to 400 billion stars in our galaxy, and at least 100 billion galaxies in the universe. So really it’s logical to ask “what fraction of stars will have a planet where life has gained intelligence?” And from that perspective, we’re still talking about very small numbers.”

Tarter is an optimist though, saying she believes there may be life out there somewhere, “based on what we know about the dynamics of planets.”

Some scientists think it’s likely that other planets could evolve into something like Earth where complex forms of life eventually evolved.

What would alien life look like?

That’s a big question that astronomers are trying to answer. The first step is really figuring out what alien life might be like.

So far, they haven’t found it. But many experts are confident that alien life exists. They say there are at least two reasons to believe in alien life.

First of all, scientists estimate that Earth is one of billions of planets in the universe. That means that if you multiply the number of planets by the number of stars, there are probably billions and billions of planets out there.

Some scientists say this means it’s almost certain that alien life exists somewhere in the universe.

Second, researchers say they’ve found many places on Earth where conditions could support very different forms of life than we have here. They think it’s possible that some of those forms of life may have developed intelligence, just like humans have.

So what would alien life look like? That’s a really hard question to answer because we don’t know for sure what life here on Earth looks like either. But some scientists think that intelligent alien beings might be very different from us in ways we can’t even imagine right now.


Although scientists have exhaustively searched for signs of extraterrestrial life, they’ve never found any evidence that life exists beyond Earth. However, this doesn’t mean there isn’t life somewhere else in the universe; it just means we haven’t detected it yet. Many scientists are confident that in all the vastness of space, there’s at least some other intelligent life.

Since we don’t have any evidence of intelligent alien life, the best we can do is guess how probable it is that they exist. We can say with some confidence that if intelligent aliens exist, they almost certainly live somewhere in the Milky Way galaxy because our galaxy contains a few hundred billion stars