Frank Drake is best known for developing the Drake equation, which is a mathematical equation that was developed to estimate the number of detectable alien civilizations residing in the Milky Way. In his equation, Drake took many things into consideration.

For example, the rate of star formation, the fraction of stars that have planets, the number of habitable planets circling each star, the fraction of planets that remain habitable long enough for life to evolve, etc. And even with this number of variables (and a host of others) the numbers were rather clear: in all probability, alien life does exist.

But of course, probability and reality are two very different things. Ultimately, the Drake equation is just an estimate, not a fact; and this leaves us with an important question: are aliens really out there?

This is the question that is always in the back of our minds. And even more so now, as Kepler and other telescopes daily (it seems) announce the discovery of new Earth-like worlds. Ultimately, the numbers suggest our galaxy could have billions of habitable planets and thousands of alien societies. Our search for these potentially habitable worlds has just begun, but there are still questions related to where all the aliens are. If our universe is really teeming with life, as most scientists seem to think…where is it?

We have yet to uncover proof that intelligent life exists beyond Earth, which is where the Fermi Paradox comes in. It attempts to address the apparent contradiction between the calculations that say our galaxy may have hundreds of thousands of intelligent alien civilizations, and the lack of proof.

Recently, the Director of SETI (Search for Extraterrestrial Intelligence), Seth Shostak, sat down to try to tackle the question of intelligent alien life. Watch the video below to hear him weighing in on the potential for alien life and whether or not we will ever actually contact it.