List of extraterrestrial volcanoes

Transcription

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. Listening and looking are literally mankind's only hope for the future. Maybe not tomorrow, but we're running out of time. I don't want to be a downer here, but life on Earth has an expiration date. You might already know this, but one day, billions and billions of years in the future, our sun will swell up into a red giant, engulfing Earth in BURNINATION! That is going to be a very bad day. But it won't matter, because life down here on Earth will be gone long before that. As our sun gets older, it's getting hotter. So in 500 million to maybe a billion years, our oceans will have boiled away, along with our atmosphere, and anything that hasn't evolved back into bacteria by that time, well, sayonara. Life on Earth is already in old age. Maybe. If you've seen my Sagan-tastic Valentine's Day episode, you know that Frank Drake is also famous for the equation that he came up with to estimate how much intelligent life is out there in the universe. The most important variable in that equation is the last one, big L. L tells us how long a civilization lasts.How long it is that we could be found, and we don't know what our L is. It might be very small, maybe we're doomed to go extinct, or maybe after thousands of years of trying, we'll finally destroy ourselves. But L could also be very big ,maybe we'll figure out warp drive, or Mars colonies, or world peace! The thing is L is not fixed, it's up to us. First, that will mean surviving on Earth, but eventually it will mean surviving out there, or all we'll leave are dead satellites that speak of a world that doesn't exist or TV reruns beaming through the universe like electric fossils of an extinct species from a black and white land. We have to do more than just look, we have to keep listening, and we aren't willing to do that here, then how can we expect anyone else out there to do the same. Here's where I could try to inspire you with beautiful words to give you goosebumps and all those feelings, but I'll never do better than this. Stay curious. The fence we walked between the years Did balance us serene; It was a place half in the sky where In the green of leaf and promising of peach We'd reach our hands to touch and almost touch the sky, If we could reach and touch, we said, 'Twould teach us, not to, never to be dead. We ached, and almost touched that stuff; Our reach was never quite enough. If only we had taller been, And touched God's cuff, His hem, We would not have to go with them Who've gone before, Who, short as we, stood tall as they could stand And hoped by stretching tall to keep their land, Their home, their hearth, their flesh and soul. But they, like us, were standing in a hole. O, Thomas, will a Race one day stand really tall Across the Void, across the Universe and all? And, measured out with rocket fire, At last put Adam's finger forth As on the Sistine Ceiling, And God's hand come down the other way To measure Man and find him Good, And Gift him with Forever's Day? I work for that. Short man, Large dream. I send my rockets forth between my ears, Hoping an inch of Good is worth a pound of years. Aching to hear a voice cry back along the universal Mall: We've reached Alpha Centauri! We're tall, O God, we're tall!