Wednesday, September 22, 2010

Looking for Aliens

So I feel like I've kind of digressed from the original purpose of this blog recently, but I intend to get back to it today.  Earlier this week, I saw this interesting article regarding one of the Vatican's astronomers and his feelings towards extraterrestrial life (often abbreviated ETI for ExtraTerrestrial Intelligence).  Considering I took a class called "Life Beyond the Earth" last semester and wrote my final paper on the potential religious implications of finding ETI, this really caught my eye.  

However, the religion aspect is not really my focus today.  What I am going to talk about is the statement made by Guy Consolmagno, the astronomer in the article, when asked about finding ETI-- "The odds of us finding it, of it being intelligent and us being able to communicate with it – when you add them up it's probably not a practical question".

This reminded me of my very first "Life Beyond the Earth" lecture, where we went over the formula known as the Drake Equation.  Now Frank Drake takes a lot of flak for this formula, such as in this xkcd comic.  
And yes, if you're trying to solve the equation mathematically to give the exact odds that ETI is out there, it is a little ridiculous.  However, that's entirely overlooking its true purpose; the equation is meant to act more as a mathematical description, a way of laying out all the factors that matter when looking for ETI.

The real equation (minus the extra variable included above) looks like this:
And each variable can be described as such:
N= the number of civilizations in our galaxy with which we might communicate
R*= the rate of star formation in the galaxy

fp= the fraction of stars with planets
ne= the average number of planets capable of supporting life per star with planets
fl= the fraction of planets on which life actually develops
fi= the fraction of planets on which intelligent life develops
fc= the fraction of lifeforms that develop the technology and a desire to communicate
L= lifetime as a communicating civilization

This last factor, L, is seen as the most uncertain term in this equation, mostly because we have no civilization off which to base it other than our own.  Some SETI scientists have been remarkably pessimistic about this, often saying that any civilization capable of communicating is also capable of destroying itself, and therefore we will never find ETI.  They often assign L a value in the hundreds, which causes N to be extremely low as well. (SMBC has a great comic about this.)  In contrast to this, others take a more optimistic view and say that civilizations could communicate until the evolution of their star makes their planet uninhabitable.  This would give L a value of about 109,which would clearly yield a much higher N value.  

Regardless of what their numerical value may be, however, these variables are considered to be the key components of whether or not we will find intelligent life elsewhere in the galaxy.  Hopefully as we continue to explore space we'll get a better idea of what it looks like and be able to calculate our odds of finding ETI.  I know xkcd and I are both excited about the recent discoveries of extra-solar planets (exoplanets), or planets orbiting stars outside our solar system.  We'll have to see what happens!

(Yes, I'm aware there's a large number of comics linked in this post.  That's part of what made me think of writing it.  That, the article and hearing a talk by an Apollo astronaut last week, to be specific.  Don't complain-- comics are one of the best ways to learn things.)


  1. Haha great post Amanda! And I hope that Guy Consolmango is wrong because the Universe is a huge place and it would be awfully lonely if we were the only "intelligent" life here (I say "intelligent" because that could definitely be disputed :-P). Although I do agree with him that it would be tough to communicate with any alien race because we can hardly communicate with each other. What do you think? Are we alone in the Universe? :-P

  2. I'd have to agree with the theory which has grown from our understanding of the actual size of the universe and just how much space is out there.
    I'm really only coming from seeing some show on tv at some point...... but the basic theory behind it was that space is SO large, that it is difficult to comprehend. The idea was that even our largest forms of measurement and distance were but fractions of the units you would need to describe the whole thing.

    And when thinking the universe is THAT big, the probability of there being a planet with life, that developed in exactly the same way as ours, with extremely similar people, talking about the same pretty high.

    Chances of meeting them though? Abysmally low

  3. What do I believe personally? I think it's pretty arrogant to assume that we're the only things in the universe capable of intelligent thought. After all, it's a pretty big place.

    Of course, this sentiment of mine is informed less by science than by a comment my brother made once, when he said that the universe is such a large place that, at some point in time, everything we can imagine will occur somewhere in the universe. I thought that was a really cool way of looking at things, and it really appealed to the dreamer/imaginative side of me.

    Will we encounter the rest of them? Not in my lifetime, I don't think. Especially if our space program continues to shrink (but that's a rant for another day). But maybe someday, as long as the pessimists aren't right about us destroying ourselves!

  4. Interesting that you made this post on the 23rd because on the 29th this article came out:

  5. I know, I saw that! Very exciting. I feel so current with this post.