We float along the river of time. But does that river have a source? Where did time come from? Some believe time and space are one thing, and the Big Bang started the cosmic clock. Others believe the universe existed for almost half a million "years" before light could move and time began. Still others say time is older than our universe. But what if time itself is an illusion? Incredible new experiments may hold the answer. One groundbreaking experiment gives us the power to punch holes in time…and another may create a machine that operates outside time’s boundaries!
We are all at the mercy of the Sun. Its glowing disc sustains nearly all life on Earth. But the Sun also holds a dark secret: someday, our aging, expanding star will bathe the Earth in a fiery holocaust. Everything we know will turn to hot, bubbling, plasma.
It's called the speed limit of the universe. Einstein blew all of our minds when he worked out the Theory of Relativity, and showed that space and time were malleable substances. He also theorized that we as humans can never travel faster than the speed of light, which leaves the stars and other galaxies almost impossibly out of our reach. But the dreams of Star Wars and Star Trek are not dead. In fact, there could be ways to travel faster than the speed of light - and some of them are already being tested in labs around the world.
Quantum theory, the best explanation of how atoms and anything smaller behave, is so weird even scientists who have mastered it find it baffling. But bit by bit scientists are finding maybe it's not so weird as comparable behavior is discovered in our every day world. It's just that no one noticed before.
Our universe seems real. But what if it’s a videogame? Scientists in a variety of fields are taking seriously the possibility that we live in a virtual reality. Maybe the Big Bang was just the moment someone flipped the switch and turned on our universe. Maybe what looks random has already been programmed to happen. If some advanced civilization did design and program our universe, would we ever know? Scientists are looking for glitches in the laws of the universe that may uncover its hidden code.
Sharks are more than just hunters. Only now are discoveries revealing a hidden side to their character. They have an intricate social life, complex courtship rituals, surprising ways of bringing up their young and extraordinary powers of navigation. They can forge relationships with the strangest of partners, even humans.
While most of the series has focused on conflict, this episode is all about co-operation. The suitably named social spiders spin one enormous, 30m web for the whole colony, a queen bee rules her hive with a strict hierarchy and some green ants show great team spirit to help build a nest together. There are no broken societies here. David Attenborough shifts the focus to bugs that prefer cooperation rather than conflict. They include burrowing cockroaches, the suitably named social spiders - which share a 30-metre web.