S4F: Can Anyone Intelligent Communicate with Me? Other Than My Earthling Friends. Part II

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By David Siegel Bernstein, PhD

In my last S4F, I asked: does intelligent life exist outside our solar-system and, if so, could they (if they wanted to) communicate with us. Using the Drake Equation and a certain set of assumptions, I calculated 600 communicating civilizations in the Milky Way galaxy. If you haven’t read it Part I, shame on you!

This time I’m asking, if there really are 600 extra-solar civilizations in our galaxy, why haven’t we heard anything from them? This question is known as the Fermi Paradox, which addresses the contradiction between the high probability (Drake Equation) of extraterrestrial life capable of communication and the absence of evidence of such life.

To tackle the paradox, I’m going to present an Anti-Drake(ish) argument called the Rare Earth Hypothesis, which seeks to demonstrate how unlikely the existence of Earth-like planets— populated by complex intelligent communicating life—may really be.

It all begins with a star.

  1. An Earth-like planet needs a host star residing in the galactic habitable zone. If it is too close to the galactic center, then there will be black hole and radiation problems. If it is too far away from the galactic center, then there won’t be enough metals in the sun to form planets. Approximately 10% of all stars in our galaxy appear to reside in a habitable zone.
  2. The host star must be a singleton. Life under a binary system is tricky. I’m not saying impossible, but very unlikely. That said, a long long time ago, the population of Tatooine thrived with two suns.
  3. The host star has to have lived long enough for life to form on the planet. We have a nice 4.5 billion year old G-type star. It took about 1 billion years for life to kick-off on our planet. Our sun should make it to the ripe age of 10 billion. However, we must get off the planet by about 1 billion years from now or we will become extinct (more on this in a future post dedicated to endings). Only about 9% of stars in the Milky Way are G-type.

    Now that we know what kind of sun is needed for life, let’s get down to life’s planetary needs.

  4. An Earth-like planet must have liquid water for chemical reactions to occur. As we currently understand it, liquid water must exist for life to exist.
  5. A large planet must be close enough to our Earth-like planet to deflect meteors attracted by the sun’s gravity, but it must be far enough away to not affect the Earth-like planet’s orbit. For us, Jupiter plays this supporting role. It protects us from asteroids—most of the time (sorry dinosaurs).
  6. The Earth-like planet must have a magnetic field to protect life from cosmic rays. Mars doesn’t have such field, which might be why we aren’t regularly invaded by Martians.
  7. The Earth-like planet must have plate tectonics to circulate CO2 (in the carbon cycle).

    As they say, it takes a village to make a planet hospitable for life. We already know it needs a sun, but did you know it also needs a moon?

  8. For intelligent life to develop, the planet probably needs a long period of stable climate as a result of stable orbit and rotation. So the Earth-like planet needs a large moon to hold its rotational axis constant. Without such a moon—a planet’s axis can vary widely.
  9. Keep in mind, it is very rare for a moon as large as ours (relative to our planet’s size) to exist.  Our moon was created after a Mars-sized planet collided with the Earth.  An estimate I’ve come across states that only 8% of Earth-like planets may have such a moon.

Given all these conditions, I estimate a one-in-a-billion chance for an Earth-like planet to exist. So yes, our Earth is indeed rare.  Now, for the important bit—my estimate is only for the existence of habitable planets. I have not calculated the chances for intelligent life to actually evolve on them. I’ll leave that to you. However, I suspect that only a fraction of the rare Earth-like planets will have such life.

If you’re worried that all this can make the extraterrestrial life in your fiction sound implausible, then stick with having your character spout off bits from the Drake Equation.  Now, a savvy fiction writer might attempt to include parts of the Rare Earth Hypothesis, but come up with other kinds of plausible life that may evolve under other conditions (e.g., evolution of life without water). I have a few ideas on this, but I’ll save them for a future post.

If you are interested in speculative flash fiction, or curious about speculative flash fiction, or have 30 seconds free, I encourage you to read my story Textual Relations in this month’s issue of AntipodeanSF—a science fiction magazine and podcast out of Australia.  When you read the story, I think you’ll scratch your head at how it could be read during a podcast. When asked to record it, I politely declined in favor of one their professional readers.

Do you like good science fiction (and you must if you’re an Abandoned Towers fan)? I suggest you check out Subversion: Science Fiction & Fantasy tales of challenging the norm!  It’s an original anthology by the gang who publish the sleek Crossed Genres magazine, edited by (dare I say) the visionary Bart Lieb. Click here to see my work in Crossed Genres.

See you in time and space… and S4F

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3 Responses to “S4F: What’s the Matter with Antimatter?”

  1. William Haloupek Says:
    March 8th, 2012 at 6:43 pm

    Interesting article!

    Stealth is easier than cloaking, and we already have the technology.

  2. David Siegel Bernstein Says:
    March 30th, 2012 at 7:41 am

    William you are absolutely correct. Invisibility (a descendant of Stealth) is not only easier to achieve, but a future topic. I thought I’d go over invisibility first to please those who enjoy Harry Potter, but want to write hard science fiction.

  3. donnagalanti Says:
    April 5th, 2012 at 5:39 am

    Fascinating post. We are so much empty space and mostly water. Amazing to think how we can be beings of intelligence and creativity.

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