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How Many Alien Civilizations Exist in Our Galaxy?

Exploring The Drake Equation


One of the greatest mysteries that plagues mankind is the question "are we alone in the Universe?" We study the heavens and we search for signals from alien life forms. To date we have never been in contact with a species not of this world. But should we expect to? The Drake Equation seeks to answer that very question.

What is the Drake Equation?

The object of this equation is to estimate the number of civilizations in our Galaxy with the capability of communication at any given time. The Drake Equation arrives at this number by multiplying together fractions that represent values ranging from:

  • The average rate of star formation per year in our galaxy.
  • The fraction of those stars that have planets.
  • The average number of planets that can potentially support life (per star that has planets).
  • The fraction of planets that can support life that actually go on to develop life at some point.
  • The fraction of planets that develop life that eventually develop intelligent life.
  • The fraction of civilizations that develop communication technology capable of reaching Earth.
  • The length of time for which such civilizations can attempt communications.

Controversy Over the Drake Equation

The problem is that, while some of the parameters are getting closer to being determined by scientific observation, most of them we really have little or no basis for.

We may very soon have a good grasp on the likelihood of a given star having an Earth-like planet around it. But we are far from understanding what the likelihood of life actually evolving there, and therefore just as unsure what percentage will develop intelligent life.

Current estimates of the Drake Equation spit out numbers ranging from far less than 1 (meaning we are assuredly along in the galaxy) to tens of thousands (meaning life would be rather common in the galaxy and we should expect contact at any moment). But, again, these values are based, for the most part, on very little data.

In fact the only Earth-like planet that we know of for which we can measure whether life exists is, well, Earth. So on that basis intelligent life seems to evolve 100% of the time on Earth-like worlds. But basing such an estimate on a single data point is not meaningful.

So what is a better estimate then? Truthfully, we have no clue. That is one primary reason why we get such a broad range of solutions to the Drake Equation.

The other parameter that makes this entire exercise worthless is the last one; estimating the time scale over which a civilization can send out communications into deep space. As has become apparent over the last century, evolved beings eventually will discover ways to annihilate themselves (such as nuclear weapons) and face devastating diseases (AIDS, resistant cold and flu viruses).

Their ability to overcome these obstacles and resist self-annihilation are key to a civilizations survival. In theory, a civilization could persist for billions of years, but that would probably require some level of luck. Conversely, the inhabitants of some world may not make it past the growing pains of technological revolution, and bring their existence to an end after a few thousand years.

And what might a reasonable average be for this, the most tenuous of parameters? Again, we have no idea.

So Does Life Exist Outside of Earth?

So, where does this leave us? With a very simple, yet unsatisfying conclusion. Could life exist elsewhere in our galaxy? Absolutely. Are we certain of it? Not even close.

The more we gather information about the heavens and the nature of other solar systems in our galaxy, the more we can begin to refine tools like the Drake Equation to, perhaps, give us a better idea of what might be out there. And even more importantly, where to look.

Of course, in spite of what may be statistically long odds we will continue to search, to seek out signals from deep space. All with the hopes that we may one day make contact with a people not of Earth.

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