Professor Brian Cox concludes his exploration of humanity's place in the cosmos by examining what the future holds. In Florida, he learns about the latest efforts to protect Earth from potential catastrophic events and joins a team of Nasa astronauts who are in a submerged laboratory that simulates space as they train for a future mission to an asteroid - should one ever be discovered heading to Earth. At the National Ignition Facility in California, the physicist witnesses the world's most successful fusion experiment in action, one which he believes may unlock a way to the stars that will not destroy the planet in the process.

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Tags: BBC, Human, Universe, 5of5, What