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!