Are we alone? SETI--the Search for Extraterrestrial Intelligence--is a privately funded project using radio telescopes and optical telescopes to scan the stars for signals.

The Universe as we know it is condemned to death. Space, matter and even time will one day cease to exist and there's nothing we can do about it. Harsh realities are revealed about the future of our Universe; it may collapse and burn or it might be gripped by a galactic ice age. Either of these scenarios might be a long way off. However, our Universe could suddenly be destroyed by a "random quantum fluctuation", a bubble of destruction that can obliterate the entire cosmos in the blink of an eye. No matter how it ends, life in our Universe is doomed.

As the early June sun begins to set over a calm river in Central Hungary, masses of ghostly shapes emerge from their larval cases to take to the air for the first time. They are mayflies and in a spectacular display, thousands of them demonstrate how the very first wings were used. From the stunning aerobatics of hoverflies in an English garden to the mass migration of purple crow butterflies in the valleys of Taiwan, this episode tells the tale of the first animals ever to take to the air. Unique footage reveals the lightning fast reactions of bluebottles and hoverflies, filmed with one of the world's fastest cameras, and Sir David Attenborough handles the world's largest (and perhaps most ferocious) insect - the Titan beetle.

The world of invertebrates exists in a web of relationships with plants and other animals. Unique footage of the world's smallest insect (a fairy wasp only quarter of a millimetre long) shows it flying underwater to find the eggs of water beetles in which to lay its own brood. Some ants 'farm' the trees that give them shelter, creating areas known as 'Devil's gardens'. To make sure these grow without competition, they kill off other seedlings in the surrounding vegetation. The blister beetle's larvae huddle together on the end of a piece of grass and mimic a female bee. When a male bee tries to mate with the 'female', the larvae grab on to his belly. Confused, he flies away and searches for a real female. When he eventually finds her and mates with her, the beetle larvae hurriedly swap from his front on to her back, and hence get carried back to her nest where they eat her pollen supplies.

Invertebrates don't always operate alone. True society was the last feature to evolve in invertebrates, as recently as the time of Tyrannosaurus. In the last programme see the tensions below the surface in some of the great social structures built by insects, and witness the carnage when an ant colony and a termite colony wage war.

The episode begins with Tyson describing how pattern recognition manifested in early civilization as using astronomy and astrology to predict the passing of the seasons, including how the passage of a comet was often taken as an omen. Tyson continues to explain that the origin of comets only became known in the 20th century due to the work of Jan Oort and his hypothesis of the Oort cloud. Tyson then continues to relate the collaboration between Edmond Halley and Isaac Newton in the last part of the 17th century in Cambridge. The collaboration would result in the publication of Philosophiæ Naturalis Principia Mathematica, the first major work to describe the laws of physics in mathematical terms, despite objections and claims of plagiarism from Robert Hooke and financial difficulties of the Royal Society of London. Tyson explains how this work challenged the prevailing notion that God had planned out the heavens, but would end up influencing many factors of modern life, including space flight. Tyson further describes Halley's contributions including determining Earth's distance to the sun, the motion of stars and predicting the orbit of then-unnamed Halley's Comet using Newton's laws. Tyson contrasts these scientific approaches to understanding the galaxy compared to what earlier civilizations had done, and considers this advancement as mankind's first steps into exploring the universe. The episode ends with an animation of the Milky Way and Andromeda galaxies' merging based on the principles of Newton's laws.