What will happen tomorrow is not random. Well, not entirely random, because we know that some things will happen for certain, and some things will definitely not happen. This means we can predict that tomorrow the sun will rise, water will freeze at 0 °C, and you won’t have suddenly morphed into a chocolate labrador.
The Universe is in some ways predictable because everything in it is made up of 12 fundamental particles - divided into two groups of six quarks and six leptons - and they interact with each other in four predictable ways. So what if we could figure out the positions and velocities of every single one of these particles in the Universe? Well then we’d know the entire future of the Universe, which means nothing in it is random.
But where does human behaviour fit into all of this? Watch Derek and his guest Michael Stevens from Vsauce tackle this conundrum in the latest episode of Veritasium, and find out how everything we've ever done and ever will do is determined by the information in the state of the Universe at any one time.