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.

Astronomers make an extraordinary discovery out in deep space when they uncover a cosmic mega-structure that's one billion light-years long. Now, investigators race to decode the hidden forces that shape the most massive and mysterious structure known in the Universe.
We dive into this space great wall's fiery birth and hunt for the weird cosmic glue that holds it together to reveal how this megastructure rewrites our understanding of the universe on an epic scale.

The white hole is a region of spacetime and that cannot be entered from the outside, although energy-matter, light and information can escape from it. In this sense, it is the reverse of a black hole. Einstein predicted strange cosmic phenomena known as white holes, but scientists have yet to prove they exist.
Today, astronomers race to find the clues that can unlock the secrets of white holes. They investigate the tiny black holes that hide in the most ancient parts of the universe to finally find the smoking gun.

Brian takes a fresh look at the concept of gravity, revealing it to be far more than just the force that makes things fall to the ground.
In the last three years, we've made profound discoveries about the nature of gravity and the way it behaves, and how this relates to the origin of the universe and strange things like black holes. Our theory of gravity has become the attempt to understand the nature of space and time.

The centre of our galaxy is home to an invisible monster of unimaginable power – a supermassive black hole named Sagittarius A star, with four million times the mass of the Sun. Recent astronomical breakthroughs have confirmed not only that black holes like Sagittarius A star exist, but that these bizarre invisible objects may be the ultimate galactic protagonists.
Stunning CGI takes us back to witness the fiery origins of our galaxy’s black hole 13.6 billion years ago, when the early universe was home to colossal blue stars, and when they ran out of fuel, they collapsed under their own enormous mass, crushing down into an object so small and so dense it punched a hole in the fabric of the universe. Over billions of years, Sagittarius A star feasted on nearby gas, stars, and through cataclysmic mergers with other black holes. A breakthrough discovery by Nasa’s Fermi gamma-ray telescope has shown that our black hole had the power to sculpt the entire galaxy, creating vast bubbles of gas above and below our galaxy and even protecting stars systems as ours.
In a mind-bending conclusion, Brian Cox reveals how our modern understanding of black holes is challenging our concepts of reality to the breaking point. In trying to understand the fate of objects that fall into Sagittarius A star, scientists have come to a stunning conclusion: space and time, concepts so foundational to how we experience the world around us, are not as fundamental as we once thought.

The meteoric rise of renewable energy has consequences for our electricity supply. While coal and gas fired power stations can generate electricity whenever you need it, renewables are intermittent by nature. So we need a backup plan for when the wind stops or the sun goes down.
All over the world, engineers and scientists are racing to solve one key problem; how to safely and efficiently store electricity at a huge scale but at a low cost. The quest is producing some truly remarkable ideas and this episode details three of them.