Or, Where is everybody?

The numbers are staggering; even in a place with little light pollution, when we star-gaze we are looking at only about 2500 stars, or a hundred-millionth of the stars in our galaxy, mostly within 1000 light-years of Earth. There are 100 to 400 billion stars in the Milky Way Galaxy, and roughly as many other galaxies in the observable universe. Although measurement is imprecise, there are likely 10^22 to 10^24 total stars in our universe. With the conservative assumption that possible life requires a sun-like star (estimated, at the low end, at 5% of total stars), that leaves us with 500 billion billion sun-like stars.

Of course, there is a debate about what percentage of such stars could foster Earth-like planets (with similar temperature conditions, and liquid water). The commonly accepted answer is at least 1-in-6. This means that roughly 1% of the sun-like stars in the Universe could have Earth-like planets orbiting them.

Assuming the mediocrity principle, the Earth (and its development of intelligent life) is not highly unusual. But even with a conservative estimate that 1% of our Earth-likes develop life, and .5% of that life achieves observable technological civilization, that would mean roughly 5 million billion civilizations in our observable universe. Even shrunk to our immediate neighborhood- the Milky Way Galaxy- there should be 50,000 communicating or traveling civilizations within it's 100,000 light year diameter.

So, where is everybody? This contradiction is known as the Fermi Paradox. A number of answers have been proposed:

• Extraterrestrial life is rare or non-existent
• No other intelligent species have arisen
• Intelligent alien species lack advanced technology
• It is the nature of intelligent life to destroy itself
• It is the nature of intelligent life to destroy others
• Periodic extinction by natural events
• Inflation hypothesis and the youngness argument
• Intelligent civilizations are too far apart in space or time
• It is too expensive to spread physically throughout the galaxy
• Human beings have not existed long enough
• Humans are not listening properly
• Civilizations broadcast detectable radio signals only for a brief period of time
• They tend to isolate themselves
• They are too alien
• Everyone is listening, no one is transmitting
• Earth is deliberately not contacted
• Earth is purposely isolated (planetarium hypothesis)
• It is dangerous to communicate
• They are here undetected
• They are here unacknowledged

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The Fermi Paradox Jam (#fermijam) is an invitation to make something (anything!) inspired by this problem. In addition to games, we welcome digital work, music, star charts, prose, comics, or things more alien. The jam will run from midnight September 2nd to midnight September 12th, 2016.

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API reference materials:

• http://sciencehackday.pbworks.com/w/page/24499518/APIs
• http://www.programmableweb.com/category/science/apis?category=20070
• http://www.projectrho.com/public_html/starmaps/catalogues.php

Image credit: Max Ernst and NASA