Alone in the universe

Andromeda Galaxy as taken by NASA's Swift spacecraft.

GeekDad had an interesting article on life in the universe recently. It starts with a quote from my favorite comic artist of all time:

“Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us.” – Bill Watterson

In order to understand or even comprehend the probability of our existence, much less the existence of others, we can turn to the probability theory suggested by the famous British mathematician Roger Penrose. Penrose supposed that the odds against the existence of life on this planet were on the order of (10 to the power of 10¹²³) to 1. That’s so massively unlikely it’s almost impossible to fathom, but there it is. That’s like rolling 20 on a 20-sided die a bazillion times in a row.

Let me put it this way, our own galaxy–the Milky Way–is about 100,000 light years across. That’s pretty small in the cosmic scheme of things. The Andromeda Galaxy, the closest galaxy similar to our own, is two million light years down the road. So let’s assume that there is intelligent life in the Andromeda Galaxy, and two million years ago they decided that they’d send a message out into space to see if anyone answers. Well, two million years ago was around the end of the Pliocene age. We were still halfway hunched over monkeys then (bite me, creationists), but there would be no way for them to know that. So say we got the message today. First off, how do we respond? Second, they would already be two million years more advanced than us, and third, may not even exist anymore.

Even if we did have a way of communicating back, that would be a four million year round trip for the message. So we’d better have something damn good to say. How about a Chuck Norris fact?

To fully suppose the possibility of other life in the universe we can apply the Drake Equation. Formulated by SETI founder and astronomer Frank Drake in 1961, the equation consists mostly of supposition by Drake and his colleagues to predict life in the universe. Sadly, it is nothing but guesswork as some of the values cannot be known for sure. It is basically meaningless, but cool to look at. To wit, the equation:

N = the number of civilizations in our galaxy with which communication might be possible;
and
R* = the average rate of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fℓ = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time such civilizations release detectable signals into space.

The equation, with Drake’s assumptions in place:

R* = 10/year (10 stars formed per year, on the average over the life of the galaxy)
fp = 0.5 (half of all stars formed will have planets)
ne = 2 (stars with planets will have 2 planets capable of developing life)
fl = 1 (100% of these planets will develop life)
fi = 0.01 (1% of which will be intelligent life)
fc = 0.01 (1% of which will be able to communicate)
L = 10,000 years (which will last 10,000 years).
N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10.

So let’s pretend all those numbers are nothing but exact. That puts the final value at ten. There are ten civilizations in our galaxy that we might communicate with. Where’s Superman when you need him to fly around to all these planets and start knocking on doors? What this theory does is help to explain to our tiny mammal brains that perhaps we aren’t all alone, that there may be someone else out there just as curious and confused as we are.

For the sake of further argument and putting you at ease with how singular we may be in the universe, let’s do some further calculations based on assumptive theory. Let’s assume there are roughly 50 billion galaxies that we can see, which isn’t too far off from what we can see with modern telescopes. In each of those galaxies there are billions of stars. I know after hearing about our national debt for so long, that number value has less meaning, but stick with me here.

Now to borrow a bit from the movie Contact: take those billions of stars, actually somewhere around 70 sextillion as supposed by the General Assembly of the International Astronomical Union back in 2003, and suppose that one in a million of those stars is in a working planetary system. Then, let’s say that one in a million of those has a planet that supports life (an “M-Class” planet, as they’d say on Star Trek). So being lazy and not taking out my calculator, that’s what, in the tens of billions still? It’s all hyperbole anyway, but if you were feeling alone you can take those assumptions and feel a little better.

Posted by Andrew
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