Where is everyone? We have been listening for messages from outer space for more than half a century, and so far... silence, why? Are we truly alone in the universe? Or is everyone else acting like us and just doing a lot of listening? Maybe we need to be louder. Maybe we need to send more messages out there. But how do you write a letter to an extraterrestrial whose language and culture and biology and mind we have no concept of? And what do you say? Given all of the unknowns about what they might behave, should we say anything at all?
Exoplanets, strange worlds outside our solar system. We're discovering the cosmos is full of alien planets. Alien worlds that challenge our understanding of planetary systems. Hellishly hot worlds, violently colliding worlds, worlds getting eaten by their stars. There's much, much more out there than we had ever imagined. Exoplanets are shaking up our understanding of the universe. The cosmos is a chaotic array of the odd, the weird, and the wonderful. The more we find, the less we know.
Episode 7 focuses specifically on first contact and the search for intelligent life in the vastness of the cosmos. Are humans ready to make first contact with other intelligent beings? Is our technology even sophisticated enough to detect communication signals from another world? Who are we to search for alien intelligence when we can't even recognize or respect the consciousness all around us, or even beneath our feet. Neil deGrasse Tyson reveals the hidden underground network that is a collaboration of four kingdoms of life, and a true first contact story between humans and beings who communicate in a symbolic language and have maintained a representative democracy for many tens of millions of years.
Most planets we know of are so hellish, it seems impossible that anything could live. But it's amazing where life can take hold in the Earth. Astrobiologists look for simple single-celled microbes known as extremophiles in places as Danakil Depression, known in Ethiopia as 'The Gateway to Hell.' In Episode 2, the fictional world is Janus, a planet in such a close orbit than its rotation is locked by the star's gravity and it always shows the same face to its sun. On one side of the planet, it's always daytime, a searing desert. On the other side, it's forever night, a frozen shadowland. Squeezed between the two, a sliver of perpetual twilight. Freezing meltwater flows from the cold side, carving canyons through the landscape. Deep in these canyons lives an extraordinary five-legged creature.
Planets beyond our solar system are known to astronomers as exoplanets. They are at trillions of miles from Earth and yet, it might be possible to detect a faint signature of life in them. From the light of the stars they orbit that passes through the atmosphere of an exoplanet, it is possible to capture the chemical fingerprint of the elements in that atmosphere. The fictional world Eden is orbiting not one star, but two. The light from its twin stars powers photosynthesis, pumping more oxygen into the atmosphere than in Earth, allowing life to thrive. Grazers are constantly alert to danger, because the canopy is home to predators perfectly evolved to live among the trees. In Episode 3, another topic are fungi and the role they could play on exoplanets. Ecologist Thomas Crowther talks about the role mycelial networks play in the Rothiemurchus forest in Scotland.
What sort of alien civilizations might exist in the vastness of space? Terra is the fictional world imagined in Episode 4, a planet nine billion years old, twice as old as Earth. Old enough that a truly advanced intelligence could evolve. It was once a fertile world, now it is barren. But life can still thrive here in artificial domes. Over time, they've evolved not to need their bodies. They exist only as neural tissue. They never age, they never die. They're monitored and maintained by robots. If alien civilizations are statistically so likely, why haven't astronomers found any sign of them? Where is everyone? Every time we look at an individual star, that's like dropping a bucket in the ocean. We're going to have to look at a lot of stars and to search through a lot of data until we find the clue that leads us to another civilization.
Given all of the unknowns about what they might behave, should we say anything at all?