Time travel features heavily in speculative fiction. It provides a useful means of foreshadowing and helps to heighten suspense as the characters try to avert a looming disaster or manipulate the future for their own ends. It appeals to all of us who have ever experienced guilt or loss and want to go back and fix it. It is rife with unintended consequences and can trigger exciting conflicts. However, it is also provides a great source of frustration for writer and reader alike as they try to contend with the plot holes, paradoxes, and skewed logic associated with tampering with the fundamental laws of our universe. In this post, I will address the most common problems and paradoxes associated with time-travel, and then discuss the science of time travel.