The distances separating the stars are so vast that it would take a very advanced civilization—perhaps thousands or even millions of years more advanced than ours—to bridge those distances. In other words, any extraterrestrial civilization that visited us, hypothetically or in reality, would be using a technology that we can only dream about here on planet Earth.

Most life forms in outer space are probably microbial, but a handful of them may be advanced enough to actually reach us. Now, from their perspective, we humans are the microbial life and we would simply not be that interesting to them. I think this is one reason aliens don’t come here and say, “Take me to your leader, Earth man.” An extremely advanced civilization visiting humans would almost be like humans going down to an ant hill and telling them: "I bring you computers, I bring you nuclear power, I bring you knowledge…" Most of the time we simply step on them instead.

Stephen Hawking’s recent statements in his new series “Into the Universe” on the Discovery Channel have stirred up quite a few news stories in the past week. In fact, I will be appearing on Larry King Live tonight (4/30) at 9 p.m. EST to speak about these statements. In the series, Hawking says: “If intelligent alien life forms do exist out in the vastness of space, they might not be the friendly cosmic neighbors the people of Earth are looking for. Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they could reach. If so, it makes sense for them to exploit each new planet for material to build more spaceships so they could move on. Who knows what the limits would be?” Hawking adds: “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet. I imagine they might exist in massive ships…having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach.” In closing, he says that all of our efforts to search and contact aliens could ultimately end in our own destruction.

So how many advanced civilizations could there possibly be? Back in the 1950’s and 60’s, astronomer Frank Drake had the idea of searching for radio signals from intelligent life (intelligent enough to make radio broadcasts, that is) in outer space. Drake's equation is taught in every elementary astronomy course as a reasonable scientific estimate of the probability of intelligent races throughout the galaxy. It tries to estimate (N), which is the number of civilizations in our galaxy with which communication may be possible.

In order to calculate this number, a variety of factors come into play, such as:

  • The average rate of star formation per year in our galaxy
  • The fraction of those stars that have planetsThe average number of planets that can potentially support life per star that has planets
  • The fraction of the above that actually go on to develop lifeThe fraction of the above that actually go on to develop intelligent life
  • The fraction of civilizations that develop a technology that releases detectable signs of their existence into space
  • The length of time such civilizations release detectable signals into space

As Carl Sagan explained the Drake equation in his series "Cosmos," the number of technological civilizations should literally number in the millions (in our galaxy alone). This view is challenged by the Fermi paradox, which contrasts that expected number with the fact that ET hasn't phoned us yet, and perhaps suggests that technological civilizations tend to destroy themselves rather quickly.If Hawking's predictions haven't scared you off, there are a variety of projects which allow you to aid in the search for extraterrestrial intelligence.

One of the most popular is that of SETI@home which is a scientific experiment that uses Internet-connected computers in the Search for Extraterrestrial Intelligence (SETI). You can participate by running a free program that downloads and analyzes radio telescope data, "donating" your idle computer time to the task. Originally intended as a short-run project with hopes of attracting 50,000 participants, it ended up achieving over 5 million downloads, with 1/3 of those users using it at any given time. Thanks to this program, SETI can use millions of computers around the world to analyze data from telescopes in real time—a feat it could never have performed otherwise because its researchers are limited by the computing power they have on site. If you are interested in helping narrow down the search and using your home computer to help analyze signals from outer space, please download the BOINC program and start searching today. Who knows, your computer could be the one that discovers the signal that ultimately proves the existence of advanced life forms in the universe.

So why haven't they visited or conquered us? No one knows, but I think:

  • There are plenty of uninhabited planets with valuable resources to exploit, so they will likely leave us alone.
  • They might be benevolent since they have had thousands to millions of years to work off their aggressive tendencies.
  • Most likely, we are not on their radar screen. We may be too insignificant for them to make formal contact.

We’ve all seen the portrayals of aliens in the movies—including "Close Encounters of the Third Kind," "Fire in the Sky," "The Alien Trilogy," "Predator," "Independence Day," and "War of the Worlds"—and how most are unpleasant, making for much more interesting plots on the big screen. Let’s hope that if in fact we have a visit from an extraterrestrial civilization, it’s more like the one in Stephen Spielberg’s "E.T." than one in which aliens try to blow up the planet and consume all our natural resources before we even have a chance to finish eating our popcorn.