I was wondering about going back in time. Are we allowed to change our past if we can travel back in time, and if so, will it affect our future? There's always that paradox of what happens if you kill your mum when she hasn't given birth to you? Will you cease to exist?

But perhaps we have long assumed the concept of free will. This may all already be predetermined, so you will never be able to kill your mother back in the past for example, simply because you exist. Or perhaps time travel is not possible.