Today's episode is brought to you by the letter "L".
[music playing] Astronomers reckon there might be tens of billions of planets out there that are at least a little bit like this one, but we've only found life on one of them. Here on Earth, life popped up pretty much as soon as it could. Around three and a half billion years ago, after comets had bombarded Earth with water, and volcanoes had belched out an atmosphere, it was POOF, life!
Maybe, out there in the universe, wherever the ingredients for life are right, it might just happen. Eventually, and I'm fast forwarding through just a little bit of Earth's history here, some of that life became intelligent. As intelligent species go, humans are the only ones capable of having an existential crisis. We just very badly don't want to be alone in the universe.
Now we're looking for other intelligent life out there. But what exactly are we looking for? What would intelligent life look like? Well, no. Yeah, but no. Let's pretend we launch a spacecraft to fly by a rocky planet that sits int eh habitable zone of its star. The first thing we'd see is that it's covered in water, on the surface and in the air. And there's way too much oxygen and methane in the atmosphere. It gets weirder. There's something covering the land that's absorbing a ton of red light. And this planet is screaming with radio signals. We've discovered a planet with life!
This space mission actually happened. Back in 1990, when the Galileo spacecraft flew by Earth on its way to Jupiter, Carl Sagan had an idea. To give us an idea of what we'd see if we found a planet that holds life, we should start by looking at our own. But life out there might not look like life on Earth. Assuming that everything out there is just like us, would be like an alien landing on Earth and finding a platypus, and deciding that everything down here looked like the result of a beaver's late-night encounter with a duck.
The nearest Earth-like planet might be twelve light years away, that's a 200,000 year one-way trip for a spacecraft like Voyager. The key to finding life on other planets, might be zipping through the air all around you. Now, civilization could probably live happily ever after without radio. It worked for the Aztecs. But no matter intelligent a life form is, without radio signals they might as well be invisible to the galaxy.
Luckily, we are not invisible. We've been beaming out signals to the universe for over a century. Now, it hasn't all been good [voice clips] Luckily, some humans have been trying hard to make a better first impression on the universe.
In 1974, Frank Drake shot an electronic greeting card toward the M13 star cluster using the 300 meter Arecibo observatory in Puerto Rico. To say it was powerful would be an understatement.
If you had eyes that could see radio waves, for a brief instant, it would have been brighter than the sun. That coded message is currently 230 trillion miles from Earth. In it, it lists the elements that make up life here, a DNA helix, a picture of a man, and the radio dish that sent the signal.
Anything that receives and decodes that message would also know that they weren't alone. If there's other intelligent life out there, hopefully they'd also be curious to know that there are worlds beyond theirs, and they'd be looking and listening for us. So . . . hi, I guess! I come in peace.
