To maximize longevity, you might think it’s best to play it safe and stay cozy. But some scientists believe we should do the opposite, as exposure to extreme temperatures can trigger our bodies’ own defenses against the killer diseases of old age. Chris heads for the freezing Arctic with his brothers Liam and Luke to take on the ultimate cold therapy.

Episode 3 continues to show the obstacles faced with charging electric bikes in remote places, but Ewan McGregor and Charley Boorman start to learn and evolve their process. The risk of cold temperatures is high but they bravely do it anyway. The duo is having a hard time of it out there but, thankfully, the scenery is absolutely stunning. Heading through Patagonia, Ewan and Charley stay at an eco-lodge in one of the world’s remotest areas with people that live off the grid.

From a primate that’s no bigger than a mouse, to a chameleon that can fit on your fingertip, the natural world is full of fantastically small animals. Biologist Patrick Aryee explores the fascinating secrets behind these miniature marvels and shows that they’re not the underdogs you might think they are. Super Small Animals follows him as he meets the leading experts on these pint sized superstars, and finds out what makes them some of the most successful on the planet.
First up, he reveals the huge benefits that being small can bring. There’s the little lemur whose diminutive frame helps it to exploit a unique gap in the eco-system, the tiny hummingbird that uses its size to out-maneuver the competition, and the world’s smallest seahorse that never has to leave home. He also explores why small animals are proportionally the strongest in the world, and introduces a peanut-sized beetle that can pull over a thousand times its own weight.
Next he explores the challenges that animals face when they shrink in size, and the ingenious ways they overcome them. We find out how the smallest armadillo in the world manages to control its temperature in the searing desert sun, and the how the world’s smallest fish can survive in nothing more than a puddle, because it never really grows up. Patrick meets a secretive hippo that lives in the dense jungle, and looks like it’s been shrunk in the wash, and some of the world’s smallest snakes that give birth to enormous babies. He also meets a scientist that studies how really tiny spiders have a surprising trick that enables them to travel an incredible 40 miles per day, using almost no energy.
Then there are the animals that refuse to be pigeon holed as small, and manage to punch way above their weight. He puts some astonishing invertebrates to the test, to see how they work together to become much bigger than the sum of their parts and meets a pint-sized predator that takes on some of the largest and most dangerous creatures on the planet, getting hands on to discover how its build helps it to be brave. Finally he uncovers the incredible lengths that deep sea anglerfish go to in order to be big and small at the same time, and has an endearing encounter with a tiny carnivore that manages to be small in just one direction.
Whether their size helps them to hunt, hide or survive, all these remarkable animals prove that good things really do come in small packages.

The Arctic is the harshest environment on Earth: little food grows, it's dark for months on end, and temperatures stay well below freezing for much of the year. Yet four million people manage to survive here. Human Planet tells remarkable stories of extraordinary people who make their homes in nature's deep freeze. In springtime, Amos and Karl-Frederik set out across the sea ice with their dogs to catch a real-life sea monster: a Greenland shark! Inuit mussel-gatherers venture underneath the sea ice at low tide for a perilous race against time as they gather their food. And the children of Churchill, Manitoba, set out on the most dangerous trick or treating Halloween in the world: they risk coming face-to-face with deadly polar bears on the streets of their town. Who'll get the tastiest snack?

The German army launched Operation Barbarossa, the invasion of the East, with supreme confidence in its own superiority. High Command was sure that victory would come as quickly and as easily as in France. At the onset, the troops advanced rapidly and the Panzer forces under General Guderian were unbeatable. There were, however, far more casualties and more wear-and-tear on equipment than anticipated. The invading force got bogged down short of Moscow and the withdrawal from there was a severe psychological blow to the men. When an extremely severe winter set in, morale sank further. The soldiers were not equipped for such low temperatures and their guns and machinery could not cope. Hitler ordered his troops to stand firm.

This episode explores the nature of the greenhouse effect (discovered by Joseph Fourier and Svante Arrhenius), and the evidence demonstrating the existence of global warming from humanity's influence. Tyson begins by describing the long-term history of the planet Venus; based on readings from the Venera series of probes to the planet, the planet had once had an ocean and an atmosphere, but due to the release of carbon dioxide from volcanic eruptions, the runaway greenhouse effect on Venus caused the surface temperatures to increase and boiled away the oceans. Tyson then notes the delicate nature of the amount of carbon dioxide in the atmosphere can influence Earth's climate due to the greenhouse effect, and that levels of carbon dioxide have been increasing since the start of the 20th century. Evidence has shown this to be from mankind's consumption of oil, coal, and gas instead of from volcanic eruptions due to the isotopic signature of the carbon dioxide. The increase in carbon dioxide has led to an increase in temperatures, in turn leading to positive feedback loops of the melting polar ice caps and dethawing of the permafrost to increase carbon dioxide levels. Tyson then notes that humans have discovered means of harvesting solar power, such as Augustin Mouchot's solar-driven motor in the 19th century, and Frank Shuman's solar-based steam generator in the 1910's. Tyson points out that in both cases, the economics and ease of using cheap coal and oil caused these inventions to be overlooked at the time. Today, solar and wind-power systems would be able to collect enough solar energy from the sun easily. Tyson then compares the motivation for switching to these cleaner forms of energy to the efforts of the Space race and emphasizes that it is not too late for humanity to correct its course.