The third episode looks at anxiety and explores why it is so common. It talks to neuroscientists who explain the physiological and evolutionary basis of anxiety. Although it can help animals escape predators, anxiety can cause serious problems for human beings. It talks to sufferers of anxiety and examines the different types of anxiety people can feel. It also looks at how social media can cause anxiety.

This episode covers the nature of how life may have developed on Earth and the possibility of life on other planets. Tyson begins by explaining how the human development of writing systems enabled the transfer of information through generations, describing how Princess Enheduanna ca. 2280 BCE would be one of the first to sign her name to her works, and how Gilgamesh collected stories, including that of Utnapishtim documenting a great flood comparable to the story of Noah's Ark. Tyson explains how DNA similarly records information to propagate life, and postulates theories of how DNA originated on Earth, including evolution from a shallow tide pool, or from the ejecta of meteor collisions from other planets. In the latter case, Tyson explains how comparing the composition of the Nakhla meteorite in 1911 to results collected by the Viking program demonstrated that material from Mars could transit to Earth, and the ability of some microbes to survive the harsh conditions of space. With the motions of solar systems through the galaxy over billions of years, life could conceivably propagate from planet to planet in the same manner. Tyson then moves on to consider if life on other planets could exist. He explains how Project Diana performed in the 1960s showed that radio waves are able to travel in space, and that all of humanity's broadcast signals continue to radiate into space from our planet. Tyson notes that projects have since looked for similar signals potentially emanating from other solar systems. Tyson then explains that the development and lifespan of extraterrestrial civilizations must be considered for such detection to be realized. He notes that civilizations can be wiped out by cosmic events like supernovae, natural disasters such as the Toba disaster, or even self-destruct through war or other means, making probability estimates difficult. Tyson describes how elliptical galaxies, in which some of the oldest red dwarf stars exist, would offer the best chance of finding established civilizations. Tyson concludes that human intelligence properly applied should allow our species to avoid such disasters and enable us to migrate beyond the Earth before the Sun's eventual transformation into a red giant.

How does light escape from the sun? We take a journey from the center of the sun, following the path of light. We witness its fiery birth from in the core, its 430,000 mile battle against gravity and magnetism, and its escape from the solar surface.

Mysterious lights shine out from the edge of space, brighter than a trillion suns. They had to be the brightest objects we've ever seen in the universe, putting out amounts of energy that we couldn't possibly explain. So powerful, they can incinerate planets and rip stars to pieces. These are among the most mysterious and most energetic phenomenon in the universe. They can destroy galaxies, but may also be the key to their survival. These objects are a hotbed of all kinds of crazy physics. These celestial powerhouses are called quasars, and we may owe them our very existence.

Rainforests face more threats than ever before, but remain the last stronghold for some truly astonishing animal families. Today we know rainforests are some of the most wondrous and important habitats on Earth. It is the richest habitat on earth, teeming with millions of dramatic plants and animals. From giant landscape gardeners to a whole family supported by a single leaf, there are surprises at every turn.

Told by the activists and leaders who live and breathe this movement for justice, Whose Streets? is an unflinching look at the Ferguson uprising. When unarmed teenager Michael Brown is killed by police and left lying in the street for hours, it marks a breaking point for the residents of St. Louis, Missouri.
Grief, long-standing racial tensions and renewed anger bring residents together to hold vigil and protest this latest tragedy. Empowered parents, artists, and teachers from around the country come together as freedom fighters. As the national guard descends on Ferguson with military grade weaponry, these young community members become the torchbearers of a new resistance. Whose Streets? is a powerful battle cry from a generation fighting, not for their civil rights, but for the right to live.