It’s statistically pretty likely that there are plenty of planets which support life.
In fact, there are between 1 and 4 billion planets pretty much like Earth just in the Milky Way alone – and there are 100 billion galaxies out there, each with 100 to 1000 billion stars. Which means trillions and trillions of habitable planets. Right? There’s a thing called the “Fermi Paradox” that basically lays out the possible reasons why. (Yes, the Fermi Paradox came from physicist Enrico Fermi. Part of it — the odds that life exists elsewhere — is closely related to the Drake Equation). The first aspect of the Fermi Paradox is that sheer numbers concept above. The second aspect is that life tends to do well despite adversity, and it tends to colonize new habitats, pretty much all the time. So … why haven’t any E.T. types come and said hello?
Here are a few of many possible reasons:
1) Maybe it’s actually pretty difficult for complex life like that on our planet to develop. We don’t know yet. Maybe we’re unique or one of the first civilizations that’s made it this far.
2) It’s also possible that there’s a hard stop that means that any planet that supports life eventually stops supporting life and everything dies off — or kills itself. In other words, it’s possible that civilizations on all worlds hit a point where they destroy themselves, or are eliminated naturally. Always. Just as an example, 99% of all species that have ever lived on this planet are gone now.
3) This one’s scary but fascinating. Maybe there’s an ancient civilization that monitors the universe and when all worlds hit a certain point where they’re getting too big for their britches, steps in and takes them out. Bam.
4) There might be some extremely intelligent life forms out there that have checked us out, but decided to stay the heck away because we’re entirely too dangerous. I recall a Kurt Vonnegut sub-story called “The Dancing Fool” within the novel “Breakfast Of Champions” that rather hilariously depicts a version of that. Paraphrased, an alien with the knowledge to end wars and cancer but communicates solely by tap-dancing and farting lands in Connecticut, where he discovers a house on fire. He rushes in, dancing and farting away to warn them of the danger. The head of the house grabs his golf club and pummels the alien in the head until he’s quite dead. Smart aliens could take one look at us and wisely decide to stay the heck away.
5) Maybe, just maybe, we are indeed alone in the universe. I mean, it seems unlikely that this is the case based on sheer numbers. But still … it’s possible.
Time is a big factor — compared to the life of most planets and stars, humans have been here and able to communicate beyond ourselves for just a tiny sliver of time. So if someone happened across our Blue Dot and checked in on what kinds of life forms might be here, it could have been before we were even a species.