Some of the world's leading physicists believe they have found startling new evidence showing the existence of universes other than our own. One possibility is that the universe is so vast that an exact replica of our solar system, our planet and ourselves exists many times over. These Doppelganger Universes exist within our own Universe; in what scientist now call "The Multiverse." If proof is found it will change our lives, our minds, our planet, our science and our universe.

We think of comets as beautiful glowing balls of light streaking across our skies with their long sweeping tails, yet comets are so much more than just a cosmic firework display. Comets have a uniquely important place in modern science. As time machines from the early universe, they could hold the key to unlock the secrets of the cosmos. Comets could even be the origin of life itself. We follow the incredible odyssey of a comet as it sails through the solar system, watching it's every move as it evolves from a dormant chunk of ice and rock into a tumbling, violently active nucleus engulfed in a gaseous haze. What we learn is a revelation; comets are even more mysterious and fascinating than we had ever imagined.

Earth’s oceans help make our planet different from every other planet in the solar system. As far as we know, no other place is the right temp for liquid water, the most essential ingredient for life to exist. The oceans are Earth’s primary stabilizing force, and their immense power helps to shape the appearance and behavior of the entire planet and everything living on it. And they are also the planet's great unknown - their deepest points have been visited less than the surface of the moon.

Does life exist on other planets? Astrobiology is a visionary new science that searches for life in space by combining the disciplines of astronomy, biology and geology. How did life evolve on Earth? What will life look like on other planets? These and other pertinent questions will be answered by a diverse group of scientists. Viewers will visit the Pilbara region of West Australia where the oldest evidence of life on Earth has been discovered. Travel to the moons of Jupiter and Saturn to test a theory that life could exist in the clouds of Venus. Finally, watch as experiments are done to see if life exists on exoplanets, earth-like planets beyond our solar system.

the final episode deals with plants that live in hostile environments. Attenborough visits Ellesmere Island, north of the Arctic Circle, to demonstrate that even in a place that is unconducive to life, it can be found. Algae and lichens grow in or on rock, and during summer, when the ice melts, flowers are much more apparent. However, they must remain close to the ground to stay out of the chilling wind. In the Tasmanian mountains, plants conserve heat by growing into 'cushions' that act as solar panels, with as many as a million individual shoots grouped together as one. Others, such as the lobelia in Mount Kenya, have a 'fur coat' of dense hairs on their leaves. The saguaro cactus in the Sonoran Desert flourishes because of its ability to retain vast amounts of water, which can't be lost through leaves because it has none. Many desert dwellers benefit from an accelerated life cycle, blooming rapidly within weeks after rainfall. Conversely, Mount Roraima is one of the wettest places on Earth. It is a huge sandstone plateau with high waterfalls and nutrients are continuously washed away, so plants have to adapt their diet if they are to survive. A bladderwort is shown invading a bromeliad. Inhabitants of lakes have other problems to contend with: those that dominate the surface will proliferate, and the Amazon water lily provides an apt illustration. Attenborough ends the series with an entreaty for the conservation of plant species.

Orbits are the dynamics that drive the universe. From the smallest asteroid to the largest super-cluster, everything in the universe is in orbit. We owe our very existence to the stability of earth's orbit — it gave us life and keeps us safe. But we are the freaks. Everywhere else we look we find orbits are chaotic, unstable, and violent. Beyond our solar system we find planets that are blow-torched, stars that eat each other, and black holes that destroy everything in their path. Yet on the very largest scale, orbits are also a creative force. clashing galaxies give birth to new stars and new worlds. on the galactic scale orbits even construct the fabric of the universe itself.