According to the laws of physics we can never travel faster than the speed of light...or can we? Learn all about light speed, the ultimate constant in the universe.

The series explores the incredible universe inside each and every one of us. Through an examination of diverse personal stories from around the world, Human reveals how our everyday lives, our passions, and our goals are powered by the amazing systems that define our biology as a species.
The first episode goes on a journey with parents who are preparing for new life to see how our bodies create and sustain new life. Through their stories we learn about what is fundamentally shared and absolutely unique about the experience of birth.

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.

New technologies are making rockets cheaper and more powerful than ever before. As companies like SpaceX and Virgin Galactic make space more accessible, and NASA returns to crewed spaceflight, a new era of space exploration may be on the horizon.

Time is woven into the fabric of the universe as one of the dimensions in which we live our daily lives. But maybe it is only a brain state that we use to piece together events. Could it exist only in our minds? Your sense of time can be totally different than the person next to you. This and other theories illustrate that time is an illusion and does not really exist. The world's top physicists tackle this fundamental question, does time exist, and offer new ways to perceive the physical world.

In this second episode we travel from January to the March equinox. Kate Humble gets closer to the Sun than she has ever been before, whilst Helen Czerski visits a place that gets some of the biggest and fastest snowstorms on Earth.