Nowadays, it's a universally accepted theory that the universe began 13.8 billion years ago with the Big Bang. But did you know that two radio astronomers unintentionally stumbled upon its discovery? In the 1960s, Robert Wilson and Arno Penzias were measuring the brightness of the sky with their radio telescope. No matter where they pointed it, they picked up an inexplicable droning sound. What initially sounded like a mistake ended up being the discovery of a lifetime.