The question of life in the universe really is an either/or issue: Either life is just on Earth and nowhere else, or it's everywhere.

Searching for life elsewhere in the universe is not an easy thing to do. The sheer size of the place we're looking (that would be the entire universe), kind of leaves you slack-jawed and mute. It's really hard to know where to even start.

At least when you're looking for your keys, you can start by re-tracing your steps and think about where you've been and narrow down the area you have most likely laid them down. You have a frame of reference from which to work. When you're looking for something that could could be, well, literally anywhere, the task is a little more intimidating. Especially if you're not even sure that what you're looking for even exists.

I've already established that the universe is a pretty big place, I know you knew that already, but at least now we have some perspective. Given that the universe is so mind-numbingly large, what is the best way to try and find life in it (that is, life somewhere that's not on Earth)? Where do we start? I made a video to get you thinking about it:



OK, so now we've defined the problem. Let me belabor the point by going through an example: What would it take for the crew of Battlestar Galactica to find us?

It's Gonna Be Real Hard for Captain Adama to Find Us
Let me just start by saying that I want the Battlestar Galactica to find us as bad as many of you do, I'm dying to meet Starbuck. I just don't think it's gonna happen. Nevertheless, let's pretend for a moment that the BSG guys are out there and that they are trying to find us. Here's what they are up against:

First off, let's forget about the entire universe, let's just say they are focusing their search on our galaxy, the Milky Way. Let's say Caprica is in our galaxy - and that they don't have The Prophecy to guide them (they forgot it on the coffee table at the house, then one thing led to another and the Cylons came and they couldn't go back for it - it was a pretty bad day).

The problem, as with all things related to astronomy and the universe, is one of scale. There are 500 billion stars in the Milky Way galaxy. Here, let me write that down another way:

There are 500,000,000,000 stars in our galaxy, or as I like to say Five Hundred Thousand Million (sounds way cooler).

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Quick note: this is an estimate. Astronomers do this a lot, they estimate, especially when it's just not feasible to actually count something. This number is plenty close enough for our discussion. I can promise you no one has ever actually counted them.

If astronomers know something about the universe to within 20%, they consider themselves extremely lucky.

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While we're pretending, let's say that the Battlestar Galactica crew have a way to look at every star in the galaxy through a special telescope (probably developed by Baltar to stare into Number Six's window).

So if they looked at each and every one of those stars through the telescope, and they looked at each one for only one second, it would take 500 billion seconds to search our galaxy. If we do the math (and you know we will), that turns out to be 8,333,333,333 minutes, 138,888,888.90 hours, 5,787,037 days, or (drumroll please) 15,854.9 years to search all the stars in our galaxy.



But that's not all. Life doesn't exist on the stars themselves does it? If it did, it would one robust form of life. No, life probably evolves on planets, or maybe frozen on asteroids and minor bodies, and there are usually several planets in a solar system.

So now you gotta multiply all those numbers above by some average number of planets in a solar system - and we don't even have a good number for that. That's why the Kepler mission is so important. It's going to hopefully find a lot of Earth-sized planets and give us some idea of how many are out there.

Sure, we could narrow the search down by looking for only those planets likely to have life, but how can we say what's likely when we haven't found any yet? All we know about is what's on this planet. For all we know, we may not be a representative example of how life develops. What's our standard of reasonableness? You could also have many people doing it all at once to shorten the time. Even so, it's a huge task. It would take thousands of years of hard, intensive searching for a culture even one as advanced as the Capricans.

And I'm talking about finding any form of life, such as microbes or bacteria. Finding an actual civilization is orders of magnitude harder.

Finding a Civilization Borders on Impossible
I don't want to be Captain Bringdown here (remember her? She was in command of the Pegasus), but think about it. If it's going to take at least 15,000 years to find any kind of life in our galaxy, and civilizations are only on a tiny fraction of the total planets that harbor any kind of life, it'll take that much longer to find a civilization.

And you need to be quick about it because civilizations (using ours as guide) are only around for a fraction of the time a planet is around. Humanity has been on this planet for about 35,000 years. Our civilization, about 7,000 years (if you're generous about what you call a civilization). That's literally a blink of an eye compared to the lifetimes of stars.

To find a civilization, you need to be very, very lucky. You need to be in the right place (on sort of a galactic hilltop overlooking the galaxy), looking at the right time (while the civilization is still alive), looking in the right place (planets that could harbor a civilization).

Let's Take Baby Steps
We should start this whole search by looking at the simplest question: Is there life outside of earth, AT ALL? We haven't even established if there is life elsewhere, much less other cultures or alien beings. Since answering that one simple question will take enormous resources, we should start by trying to find simple forms of life, like microbes.

If life is common in the universe - and it would help our search dramatically if it is - then we should see it as fossilized remnants of bacteria on asteroids, or even as simple microbes living on a distant planet. And if we can find that bacteria or microbe or whatever, then we've answered a burning question humanity has had for a long time: Is there life elsewhere?

And given the scale of the universe - the number of stars, the number of planets, the number of galaxies - if we find that one microbe on a rock somewhere that didn't come from Earth, then LIFE IS EVERYWHERE.

I'll explore this later in more articles/videos, so please subscribe to my feed if you're interested in being notified of any updates. For now, go and mess around with the Drake equation.

Keep Looking Up!