The Drake Equation Explained

The Drake Equation is used to estimate the number of communicating civilizations in the cosmos, or more simply put, the odds of finding intelligent life in the universe.  Basically, we solve for N, where N is the number of technologically advanced communicative civilizations in the Milky Way Galaxy.

This is equal to the rate of formation of stars in the galaxy multiplied by the fraction of those stars with planetary systems multiplied by the number of planets per solar system with an environment suitable for life multiplied by the fraction of suitable planets on which life actually appears multiplied by the fraction of life bearing planets where intelligent life emerges multiplied by the fraction of civilizations that develop a technology that releases detectable signs of their existence into space multiplied by the length of time such civilizations release detectable signals into space.
In short, the number of technological species that have formed over the history of the observable universe equals the number of habitable planets in a given volume of the universe multiplied by the likelihood of a technological species arising on one of these planets.  The number could be huge.

We know that the Universe is very, very large, and very, very old – so where is everybody?  There could be 100 billion Earth-like planets in the Universe, depending on how to adjust the numbers in the Drake Equation.  Current estimates have N = 156 million.  This is number is derived using many assumptions, but over time, it will become more accurate.

So the question is where are the Aliens and what is The Fermi Paradox

Enrico Fermi who gave us The famous Fermi Paradox wondered if, after millions of years of technological progress, an alien civilization should be capable of long-distance space travel.  So where are they?   How is it that we haven’t detected them?  There should be millions or billions of tech-savvy aliens with the ability to reach us, but there are none.

Here are some possible solutions to the Fermi Paradox:

    There are no signs of more advanced civilizations because we are alone in the universe.
    Super-intelligent life could very well have already visited Earth, but it occurred before humans.
    The galaxy has been colonized, we just live in some desolate rural corner where we can’t find anyone else.
    The entire idea of physical colonization is a backward concept to a more advanced species.
    There are predator civilizations out there, and most intelligent life knows better than to broadcast any outgoing signals that advertise their location.
    There is a super-predator species that keeps exterminating intelligent civilizations once they get passed a certain level.
    There’s plenty of activity and noise out there, but our technology is too primitive and we’re listening to the wrong things.
    They are using technology to spy on us.  They are around us, but we can’t detect their presence.
    We are receiving contact from intelligent life, but our governments are hiding it (not bloody likely because the temptation to leak would be massive… and too many people would need to be involved)
    Higher civilizations are observing us, but don’t interfere because they want us to evolve naturally (AKA, the “Zoo Hypothesis”).
    Our unique moon is necessary for maintaining stability, however its formation requires very unusual circumstances.
    We are all just completely wrong about the nature of reality.
    We are the first and it is going to take a long time before another civilization appears in our galaxy.
    Advanced civilizations may exist, but they only began a short time before us and haven’t yet developed superior technology.
    There is life everywhere, probably intelligent life too, but the distances are too huge to allow anyone to meet anyone else.
    Once a civilization develops the power to destroy itself, it does.  Therefore, the time frame for intelligent civilizations to find each other is very short.