ParadoxBy: Jim Al Khalili Jim Al Khalili is about to untangle the world's greatest science conundrums ___________ How does the fact that it gets dark at night prove the Universe must have started with a big bang? Where are all the aliens? Why does the length of a piece of string vary depending on how fast it is moving? Our subject is 'perceived paradoxes' questions or thought experiments that on first encounter seem impossible to answer, but which science