What happens when galaxies collide?

When we look up at the night sky, we are linked to our ancestors. Away from city lights, we can see what generations of people before us have wondered at and weaved stories around. But all that will change.

In this talk, astrophysicist Lisa Harvey-Smith tells us what will happen when the Andromeda Galaxy, which is hurtling towards us at 400,000 kilometres per second, collides with planet Earth in about 4 billion years time. Will the collision will form new stars, a hundred times brighter than the Sun? Or will it tear us away from the Milky Way, firing our solar system into space and leaving us floating into complete blackness?