A constellation is a group of stars that are connected together to form a figure or picture. Explore some of the 88 official constellations and learn about some of the highlights of each.

The contests between predators and prey are the most dramatic events in nature. Taking an intimate and detailed look at the remarkable strategies employed by hunters to catch their prey and the hunted to escape. Sir David Attenborough narrates. "The Hardest Challenge" reveals the extraordinary range of techniques predators use to catch their prey - from a leopard using all its powers of stealth to stalk impala in broad daylight to wild dogs, whose tactic is to wear down their prey over long distances; from Nile crocodiles, the planet's most patient predators, to killer whales who use teamwork and intelligence to take on humpback whales. But even with these finely tuned strategies, the outcome is far from certain. Surprisingly, most predators fail most of the time.

Muhammad Ali was arguably the greatest boxer of the 20th century, and that rare fighter whose presence in the culture of the day was equal to (or perhaps even greater than) his remarkable skills in the ring. Ali was a superb fighter who squared off against a variety of gifted athletes during his career, and filmmaker Pete McCormack offers a new perspective on Ali through this documentary, in which some of his opponents speak about their experiences with the man. Facing Ali includes interviews with Joe Frazier, who speaks of the bitterness that still remains of his rivalry with Ali; George Chuvalo, a Canadian fighter who recalls that while Ali defeated him, he went dancing with his wife afterward while the winner went to the hospital; George Foreman, whose memories include a powerful punch that Ali chose not to land; Leon Spinks, whose 1978 upset victory over Ali thrust him into a level of fame he was not prepared to handle; Ernie Terrell, who discusses the technique and strategy behind Ali's approach; and many more.

American paleontologist Pete Larson and his team discovered the largest and most complete Tyrannosaurus rex ever found (nicknamed 'Sue') while digging in the badlands of South Dakota. However the skeleton was seized from Larson by the federal government, followed by a ten-year-long battle with the FBI, the National Park Service, the Bureau of Indian Affairs, and Maurice Williams, on whose property the bones were discovered. Pete Larson also spent 18 months in prison." After the film aired, The Society of Vertebrate Paleontology, a society of professional academic paleontologists, issued a statement of full support for legally protecting fossils on public land and criticized Dinosaur 13 for implying that government regulations impede paleontological science

Reptiles and amphibians look like hang-overs from the past. But they overcome their shortcomings through amazing innovation. The pebble toad turns into a rubber ball to roll and bounce from its enemies. Extreme slow-motion shows how a Jesus Christ lizard runs on water, and how a chameleon fires an extendible tongue at its prey with unfailing accuracy. The camera dives with a Niuean sea snake, which must breed on land but avoids predators by swimming to an air bubble at the end of an underwater tunnel. In a TV first, Komodo dragons hunt a huge water-buffalo, biting it to inject venom, then waiting for weeks until it dies. Ten dragons strip the carcass to the bone in four hours.

Ideas about time and space are explored in the changes that constellations undergo over time, the redshift and blue shift measured in interstellar objects, time dilation in Albert Einstein's theory of relativity, the designs of both Leonardo da Vinci and spacecraft that could travel near light speed, time travel and its hypothetical effects on human history, the origins of the Solar System, the history of life, and the immensity of space. In Cosmos Update, the idea of faster-than-light travel by wormholes (researched by Kip Thorne and shown in Sagan’s novel Contact) is discussed.