Of Kepler and Fermi

Last time I left off talking about the cosmic lottery. We are pretty lucky to be around, and just how widespread that luck is. Estimates say there are roughly 500 million planets in our galaxy residing in habitable zones, 500 million chances for life to arise at any given time. And not all these might seem obvious at first; a few might turn out to moons orbiting giant planets.

The number of planets that will actually have life will turn out to vary from this a bit. There is a great diversity in planets and the right conditions need to be there. In our own solar system, it is accepted that Venus is at one end of our habitable zone and Mars is at the other. If conditions were different on these planets, life might have taken hold, and it might have even been there in the past. In our search of these 500 million candidates, we will find lots of planets like Venus and Mars. Either too small to retain an atmosphere against the solar wind, or to thick of an atmosphere with a runaway greenhouse effect. A lack of a protective magnetic field or plate tectonics. Objects like the Moon and Jupiter that protect against asteroids and comets. And a stable, long living star.

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Those are just a few of the conditions needed for life to develop into a complex form. And some people talk about colonizing other planets, but planets that we will be looking for will have these conditions, and native life. How we would handle that native life if we got there to colonize is just one of many problems to figure out. To we become hostile to it, do we study it, do we leave it be? Those are questions for the future.

But in the search for these ideal places to live, we will probably find less then ideal, but still great places. On these planets we will likely encounter our first alien life forms. Bacteria and Archaea like lifeforms, probably reminiscent of the extremophiles found all over Earth. Extremophiles live a variety of environments that might otherwise be considered inhospitable. They live in thermal vents under the ocean, in radioactive cooling pools, under kilometers of dirt, in sulfur or arsenic rich bodies of water. They are unique and amazing lifeforms, and likely the first that even developed on Earth. These little guys helped to shape and change the environment of the Earth, producing oxygen and changing the surface so that life could further grow and flourish. They also have an amazing tenacity for life, making them the ideal candidates to look for out in space.

The existence of extremophiles also does something to the idea of the habitable zone, it makes it all but defunct. It may prove that life is capable of sustaining itself in a dark ocean locked under ice on one of Jupiter's moons (Europa). Or even in the far flung space between stars, deep in the surface of planets cast off from their parent star, near radioactive heat sources.

So that's all fine and dandy for our first encounter with alien life and the exploration of colonize-able planets. But the idea of intelligent life is still one of the most argued questions. It is shown now that there is good cause to believe its out there. Though, it might turn out we did hit the 1 in 500 million lotto odds for our galaxy, or even larger odds for the Universe. So let's start with what it would mean if we are the only ones.

If we are it. If human kind is the only intelligent life form in the Milky Way, then we have come from amazing odds. We also have a whole Galaxy, at least 100 billion stars, to do what we want with. The first thing is that we should immediately preserve our home. It has become the precious jewel of our galaxy. In addition, we begin populating the galaxy. Use all of its resources to great potential. The human race may then long outlive the death of the Sun, and with it the Earth. But that flourishing will be humanities ultimate achievement, to escape their planet and become a galactic civilization. Research then would go to unbelievable new levels, the ideas of which are probably beyond our comprehension now, like our thoughts would be to the neolithic man. Life would be special in this scenario, and humans would be its gardeners throughout the cosmos.

Now, I don't really agree with that, but its a certain possibility. More likely, I feel that intelligent life is out there, and they may be roughly around the same level as we are. Super-intelligent civilizations, or those unrecognizably advanced beyond our own, are for another time. So if they are out there, where are they then? We raise the 'Fermi paradox,' with the contradiction between the high estimates of in the probability of extraterrestrial civilizations, and that there is a lack of evidence or contact with them.

My answer to the Fermi paradox is that the estimates aren't so high as to negate the immense size of the Milky Way. Much like to the ancients considering the celestial sphere and motions of the stars, arguing heliocentric versus geocentric theory. In that case of early astronomy, the stars were much to far away to measure parallax (an interesting subject on its own); now it may turn out that the distance between intelligent civilizations is to great to get a message across. Sorry, but here I am about to drop some math on you.

I am going to assume that the distance of the Sun from the center of the galaxy is roughly where most life is distributed, and that number is 26,400 light years (lys). I won't burden you with the circumference equation, but this region comes out with a circumference of roughly 166,000 lys. If we assume intelligent life to be 1 in a million chances, that gives us 500 civilizations, a pretty reasonable seeming number for any galaxy, right? Well, dividing our circumference up by 500, assuming they are roughly equally apart in distance, these civilizations would be about 350 lys apart. Imagine sending a message at the speed of light, waiting for someone to receive it, and then respond, That would take 700 years at minimum! No wonder we haven't found anyone yet, we might have even missed the message, or it might not have even gotten here yet.

We are just on the cusp of being able to detect messages from outer space, we may have to wait another half a millennium before we even hear from another civilization at our own level. Who knows, we might be surprised by some bright guys out there though. In the mean time, humans ought to just keep expanding, we have a good couple hundred light years to work with. We might as well expand into the stars. This post was much longer then I anticipated, but I hope you enjoyed it, I enjoyed writing it. I'm probably taking tomorrow off.

Posted in astrobiology,Astronomy,Kepler,Planets 25 comments