Are We Alone?

We’ve all wondered if there’s other intelligent life out there, and we’ve wondered if we’ll ever make contact with them. But if there are hundreds of billions of stars in our galaxy, and each of these stars likely has a planetary system, and many of these planetary systems have Earth-like planets hospitable to life, then how come we haven’t heard from any of these aliens? How come there’s been no solid evidence at all of intelligent, extraterrestrial life capable of interstellar travel or communication up to this point?

In 1950, physicist Enrico Fermi was discussing this with some fellow physicists and famously asked, “Where is everybody?” This has come to be known as the Fermi paradox.

With the sheer number of Earth-like planets out there, it seems impossible for there NOT to be other intelligent life. Bill Nye comments on this:

Jodie Foster’s character in Contact, Dr. Ellie Arroway, says pretty much the same thing but with sentimental music and sexual tension:

One analytical exploration of the question is the Drake equation, a systematic formula by astrophysicist Frank Drake to propose an answer to this question. Check out Carl Sagan’s explanation of the Drake equation in his dated but nonetheless brilliant Cosmos (1980) documentary:

In a beautifully understandable way, Sagan walks us through the equation and gives us a way to make an estimate. He also suggests that life began quite quickly on Earth.

It’s been 40 years since that video was made, so where do we stand now? I’ve spent many hours watching more recent videos of lectures and arguments on this subject. Here are two of the more interesting ones I found recently.

In the first, professor David Kipping agrees that simple life appeared on Earth relatively quickly (within 900 million years at the latest, or about 20% into Earth’s existence), and that life appearing quickly is the most likely scenario on other Earth-like planets hospitable to life.

After doing a bit more research to collect more data points, here’s how things transpired on Earth:

If we use the end of Late Heavy Bombardment as a starting point, then life certainly appeared quickly on a habitable Earth. At most, it took 0.3 billion years for simple life to appear on a habitable Earth, but there is some evidence to suggest that simple life appeared almost immediately after the Earth became habitable.

But then it took another 2-ish billion years for simple life to evolve intelligence. If these numbers are the typical case on new planets, Kipping implies, then a majority of Earth-like planets out there might have life, but more likely simple life and not intelligent life.

Here, astrophysicist Brian Cox (one of the few public science figures today who approaches Sagan’s level of eloquence) makes similar points and suggests that there may be a few, intelligent, technologically advanced, spacefaring civilizations out there right now. Cox goes further and argues that we should consider the possibility that we ARE alone, because that will encourage us to more prudently safeguard our existence and care for our home and species.

So I’m on board with the assumption that, if there is life out there, most of it is probably simple, microbial, and not intelligent. But what about intelligent life? The way I see it, here are all the possible scenarios for intelligent life in the universe:

1. We are the only intelligent civilization in the universe…
   1. …and always have been and always will be (“rare Earth” hypothesis)…
      1. …because we are special
      2. …because some Great Filter barrier generally prevents life from developing intelligence [Brian Cox’s position]
   2. …but there may be others in the past or future that we will never have the opportunity to make contact with…
      1. …because intelligent, technological civilizations inevitably destroy themselves relatively quickly
      2. …because some Great Filter barrier prevents them from developing the technology
2. We are one of many intelligent civilizations in the universe right now… [Carl Sagan’s position]
   1. …but they can’t explore or communicate with other civilizations…
      1. …because their intelligence is social and cultural, not technological (like dolphins and whales) and therefore are unlikely to ever develop the technology
      2. …because they destroy themselves before they are able to make the technology
      3. …because they are hibernating until the universe cools off enough for them to fire up their megacomputers (“aestivation” hypothesis)
      4. …because some Great Filter barrier prevents them from developing the technology
   2. …and they can explore and communicate with other civilizations…
      1. …but don’t want to… [Michio Kaku’s position]
         1. …out of disinterest (they are so advanced that they have nothing to gain)
         2. …out of fear (“dark forest” hypothesis)
         3. …because it’s easier to destroy us with autonomous and self-replicating von Neumann probes (“berserker” hypothesis)
      2. …and do want to…
         1. …but they are too far away to have heard from us yet (radio signals from Earth have only had enough time to reach about 75 stars, many of which do indeed have Earth-like planets)
         2. …but we are not listening properly [Bill Nye’s position]
         3. …and we will detect their signals soon [SETI researcher Seth Shostak’s position]
         4. …and they have heard from us and they are coming…
            1. …and they will be nice
            2. …and they will destroy us
         5. …and they already found us…
            1. …and they left…
               1. …because they weren’t interested
               2. …but gave us the gift of technology and Egyptian pyramids
            2. …and they’re here…
               1. …and are silently watching us (“zoo” hypothesis)
               2. …and are hiding the presence of intelligent life from us (“planetarium” hypothesis)
               3. …and are doing a sloppy job of hiding themselves (UFOs)
               4. …and have made contact and are being covered up by governments
3. We are not intelligent, it is only an illusion as we exist in a simulation created by other intelligent beings (“simulation” hypothesis) [Elon Musk’s position]

Honestly, I don’t know where I stand. With a complete absence of concrete evidence for any intelligent life other than our own and so many unknowns, any one of these positions would be a wild guess. But it sure is fun to think about.