# There Have Definitely Been Advanced Alien Civilizations in Our Galaxy, Study Says

Most of the conversation surrounding the probability of alien life asks whether intelligent extraterrestrials exist right now (and if so, where are they?). We don't know the answer to that yet, but according to a new study, there's one thing that's relatively certain: there have definitely been advanced alien civilizations in our galaxy at some point in the past.

Last month, astrophysicist Adam Frank and astronomer Woodruff Sullivan published a paper in Astrobiology which mathematically "proves" that we are not the first technologically advanced civilization in the Milky Way. For the study, the researchers used the Drake Equation, which measures the chances that there are alien civilizations in our galaxy that will make contact with us. This equation uses seven different variables, three of which are now known to astronomers: the number of stars born each year, the percentage of stars hosting planets (approximately 100%), and how many of those planets are in the star's habitable zone (up to 25%).

As for the other four factors, they are still unknown, but they can be worked around by changing the question. Rather than asking whether there are civilizations now, the researchers used the equation to determine whether one has ever existed (aside from ours). This eliminates the variable of the average lifetime of a civilization, and the researchers then combined the final three factors into a "biotechnical probability," which essentially boils down to the likelihood that technologically advanced life will arise on any given habitable planet.

There are many different estimates for this number, which vary wildly and are somewhat dependent on a person's level of optimism. But even with that variable unknown, the likelihood that there has been such a civilization at some point in our cosmic history is very high, virtually 100%.

And yes, technically the number is unknown, so it could very well be less than one in 10 billion trillion. But to put that number in context, a probability of one in ten billion per planet is considered to be extremely pessimistic in the astrobiology field. So in short: there have been aliens.

Last month, astrophysicist Adam Frank and astronomer Woodruff Sullivan published a paper in Astrobiology which mathematically "proves" that we are not the first technologically advanced civilization in the Milky Way. For the study, the researchers used the Drake Equation, which measures the chances that there are alien civilizations in our galaxy that will make contact with us. This equation uses seven different variables, three of which are now known to astronomers: the number of stars born each year, the percentage of stars hosting planets (approximately 100%), and how many of those planets are in the star's habitable zone (up to 25%).

As for the other four factors, they are still unknown, but they can be worked around by changing the question. Rather than asking whether there are civilizations now, the researchers used the equation to determine whether one has ever existed (aside from ours). This eliminates the variable of the average lifetime of a civilization, and the researchers then combined the final three factors into a "biotechnical probability," which essentially boils down to the likelihood that technologically advanced life will arise on any given habitable planet.

There are many different estimates for this number, which vary wildly and are somewhat dependent on a person's level of optimism. But even with that variable unknown, the likelihood that there has been such a civilization at some point in our cosmic history is very high, virtually 100%.

"Unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first," Frank wrote in a New York Times op-ed.

And yes, technically the number is unknown, so it could very well be less than one in 10 billion trillion. But to put that number in context, a probability of one in ten billion per planet is considered to be extremely pessimistic in the astrobiology field. So in short: there have been aliens.

In other words, given what we now know about the number and orbital positions of the galaxy's planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational.