As you read this, two Voyager spacecrafts are traveling through the darkness of space at nearly twenty times the speed of the fastest airplane ever built. On board, they each contain a golden record. These records contain pictures of our home planet, greetings in many languages, the sound of a mother kissing her child and music from all over the world.

The idea is that one day these spacecrafts will come in contact with another civilization that can learn about us through these records. 

Nobody expects this to happen anytime soon.

Even at the extraordinary speeds that they’re traveling, the two spacecrafts couldn’t make it to our closest solar neighbor, Proxima Centauri, in less than 70,000 years.

But neither one is actually going in that direction.

So this is probably not the best option, at least for discovering aliens during our lifetimes. Or our children’s. Or their children’s. Or possibly any Homo sapien’s. We do have other methods for potentially establishing first contact, however. 

The strongest effort comes from the Search for Extraterrestrial Intelligence (SETI) Institute, which scans the skies using radio telescopes in the hopes of detecting alien signals. So far, they haven’t found anything suggestive of life.

But, before we throw in the towel, let’s keep in mind there’s still plenty of universe where we haven’t looked.

The truth is that we don’t have any idea of how worthwhile the SETI effort is. In 1961, the astronomer Dr. Frank Drake came up with a formula that should predict the number of detectable alien civilizations . Unfortunately, we still don’t have definite data for many of the formula’s parameters, so its estimations vary wildly.

And, while it’s hard for most of us to imagine that we are truly alone in the universe, hope may be blinding us. In the book “Rare Earth,” authors Peter Ward and Donald Brownlee play devil’s advocate, noting that, yes, the universe is very big, but there are very few places where life can actually inhabit it. In our solar system, for example, there’s only one small planet in the Goldilocks zone (not too hot, not too cold).

Also, even if life exists elsewhere, it needs to be smart enough to contact us or receive our signals. Intelligence is by no means guaranteed by natural selection. Humans have occupied the Earth for less than a percent of a percent of the planet’s lifetime and have only had the technology to send messages to other worlds for the past hundred years or so. With the way we are running things, many question how much longer we’ll be around.

The biggest problem with estimating the probabilities of extra-terrestrial contact is that we’re making predictions using a sample size of one. We know that intelligence can evolve, but we have no clue if Earthlings are slow at it or if it was a complete fluke that our brains got so big in the first place. We understand one kind of life, but we don’t know how specific the requirements may be for others — are our requirements for living (oxygen, temperate climate) universal, or specific to humans?

Life can be very resilient: 30 years ago, we found species of bacteria in conditions we didn’t think could sustain life (temperatures as high as 250 degrees, for example, or very acidic environments). These “extremophiles” didn’t just survive in these environments — they thrived — maybe our ideas of inhabitable environments are too limited.

Bacterial life isn’t the same as human life, however, and it’s unclear as to whether the observations we make about extremophiles could scale up to something as advanced as a human. Even if they can’t, intelligent beings still have a whole lot of space to potentially exist in, even considering how uninhabitable most of the universe is. There are more stars out there than there are grains of sand on Earth: with those kinds of numbers it seems almost impossible for us to be truly unique. But until we receive a signal, we can’t know for sure. 

In the meantime, all we can do is impatiently sit by the phone, imagine other life-forms out there and wonder what’s taking them so long to return our call.

Printed on Thursday, February 7, 2013 as: Alien invasion unlikely until E.T. phones home