42: The Answer to Almost EverythingHow to Time Travel
"Time travel is just a fantasy," says physicist Carlo Rovelli. However, he also explains that time is not the rigid, unchanging line we intuitively imagine it to be. When Albert Einstein developed the special theory of relativity, he realised that time is relative and passes more slowly the faster one moves relative to another person. This opens up the possibility of travelling a few days into the future by travelling at nearly the speed of light through space. However, travelling to the past is even more difficult. NASA astrophysicist Michelle Thaller and physicist Saskia Grunau explore the theoretical possibilities of using black holes, wormholes, and cosmic strings for time travel.