Metaphysics is the study of reality, the study of the most basic questions that could be asked by any thinking human.
That definition alone as simple as it is goes way deeper than the uninitiated could imagine.
The field of metaphysics alone embodies the power of ideas, the principle that explains of how the most simple ideas could be manifsted to give birth to something truly life changing and extraordinary.
Legend has it that, the field of metaphysics originated from the archives of Aristotle. Aristotle was said to have named his first body of work Physics and left the remaing works of his unnamed.
The remaining unnamed were later said to come to be known as the The books after Physics later shortened to After Physics. The Greek translation for the word after is meta which is why we now have MetaPhysics.
Among the many subtopics under MetaPhysics, we have the study of space and time. Which is a whole new world unto itself.
The study of space and time is one that breeds an overlap between philosophy and science, so much of an overlap that it is hard to tell which parts is derived from which.
In some schools of thought, the reason for the science/philosophy combination in the study of space and time is due to the fact that the science and philosophy are basically the same fields tackling the same issues from different angles. It only makes sense that a hybrid topic such as the study of space and time employ elements from both ways.