Tyson describes the discovery of cosmic rays by Victor Hess through high-altitude balloon trips. Swiss Astronomer Fritz Zwicky, in studying supernovae, postulated that these cosmic rays originated from these events instead of electromagnetic radiation. Also tells how Vera Rubin observed that the rotation of stars at the edges of observable galaxies did not follow expected rotational behavior leading to consider the existence of dark matter. This further led to the discovery of dark energy to account for the increasing rate of expansion of the universe. Tyson then describes the interstellar travel of the two Voyager probes. Tyson tells the Carl Sagan's role in the Voyager program, including creating the Voyager Golden Record to encapsulate humanity and Earth's position in the universe. Tyson concludes the series by emphasizing Sagan's message on the human condition in the vastness of the cosmos, and to encourage viewers to continue to explore and discover what else the universe has to offer.

There is a strange and mysterious world that surrounds us, a world largely hidden from our senses. The quest to explain the true nature of reality is one of the great scientific detective stories. Clues have been pieced together from deep within the atom, from the event horizon of black holes, and from the far reaches of the cosmos. It may be that we are part of a cosmic hologram, projected from the edge of the universe. Or that we exist in an infinity of parallel worlds. Your reality may never look quite the same again.

Sir David Attenborough explores the incredible diversity of Britain’s woodlands, taking us on a seasonal journey through our forests, and revealing a host of spectacular animals and the hidden dramas that rule their lives.
In an ancient pine tree in the Cairngorms, two eagle chicks are on the verge of fledging their gargantuan nest. In winter in the Forest of Dean, the reintroduction of wild boar has given the robin a lifeline. As they root through the thick snow, the boar unearth the worms with their snouts, which the robins otherwise couldn't find.
Back in Scotland, a male capercaillie displays to gathering females. These birds are on the edge. With only around 500 left, they are some of the rarest and most threatened in the British Isles. In a beech woodland outside London, the deciduous trees burst to life in spring, and huge colonies of wood ants awaken and go looking for food. Also looking for sustenance is a female roe deer. With no large predators left in our woods, the deer are free to browse on new growth to the extent that they can damage the woodland itself.
In Sussex is an ancient-looking landscape, but one that has only been recreated in the past 20 years. This is the wood pasture of Knepp, created by using old grazing methods that generate a mix of scrub, open areas and ancient trees. In the Scottish Highlands, red squirrels battle it out for access to ripe pine cones at the top of a tree. It’s an acrobatic and energetic encounter, with more than a little cunning required to win the day. As the summer finally fades, we encounter a honey buzzard nest, where two chicks feast on wasp grubs, squabble between themselves and grow up before our eyes.
Autumn brings the fallow deer rut. The woods resonate with their calls, and bucks fight for supremacy. The season also brings colour, both in the leaves but also in the fungi that fruit at this time of year. The mushrooms are just a tiny part of their story, however, and we travel underground to see how the wood-wide web connects the whole forest together.