Tuesday, June 22, 2010

The Drake Equation

Although recently criticized, the Drake equation offers a jumping-off point for discussions concerning possibilities for life in the universe. It goes like this:

Out of all the stars in the galaxy (n), only a fraction will have planets (fp). Only some out of those planets will be habitable (H). Out of the habitable planets, a fraction will develop life (fl). From those, another percent will develop intelligent life (fi). Then, out of those, only a fraction will develop technology (ft) sufficient for space travel. (N) becomes the estimate for the number of technological civilizations in the galaxy (N) that are capable of being our little green men. Here is the equation:

N = n × fp × H × fl × fi × ft

There are about 100 billion stars in the Milky Way so use that for (n). We can only guess what fraction of stars have planets, but it can be a qualified guess. If we are optimistic, then we choose a fraction near one, essentially saying all stars have planets. Then we must estimate the number of planets per star that would be habitable. Such planets must be located at a distance from their star that is neither too hot nor too cold (in our current understanding of what constitutes life). In our solar system there are three candidates: Venus, Mars, and the Earth. But we can say some stars would support fewer, or no, habitable planets. So, we can say, on average, only one in 10 stars with planets has one planet that could support life. Plug in the values and we have the following:

N = 100,000,000,000 × 1 × 0.1 × fl × fi × ft

Next, if life can develop, does it develop? Opinions differ on this point. This is where the recent Life on Mars issue has some application. If this development holds up, then life developed on both Mars and the Earth and it becomes much more problematic to say that life is incredibly difficult to get started on any given planet. If you believe life is inevitable, given habitable conditions, then fl =1.

Now, if life forms, does it become intelligent? If we can agree that life has been on Earth for billions of years and modern humans came on the scene only in the last 100,000 years, then take the ratio of 100,000 years of humans to 1 billion years of life. That gives us 1 in 10,000 planets with life that develop intelligence.

Finally, we must consider whether intelligent life inevitably develops technology? Rather than debating the point, let's cut to the chase and assume that intelligence leads to technology (based on our history of development, it's a fair assumption). Ergo, ft = 1. The upgraded equation becomes:

N = 100,000,000,000 × 1 × 0.1 × 1 × 0.0001 × 1

With the plugged-in numbers, N = 1,000,000. That's one million planets with technologies sufficient for space travel.

OK, we slanted the equation by choosing optimistic numbers. If you like, plug in your own numbers. Keep in mind that even if you consider that Earth is the only life-bearing planet in the galaxy, there are still more galaxies in the visible universe than there are stars in our galaxy. So, statistically speaking, if there were only one life bearing planet in each galaxy there would still be trillions of life-bearing planets.

Thursday, June 10, 2010

The Problem With Teachers

So what is really wrong with public schools in the good 'ole USA? Listen to the media and you're led to believe it's lousy teachers, or not enough funding, or racism, or any of a half dozen other red herrings.  If you don't know what's going on, read this article. If you want to help your child with his/her education, get involved.

Tuesday, June 1, 2010


Great site for readers of any genre to keep track of books you've read, find books, explore & meet other readers, and swap books. Check it out. www.goodreads.com