Question: What is space? What is it that can expand, warp, etc. — Doug
Answer: This is a very difficult question to answer. Space is not a “thing” or something that you can associate with “substance”. One way to describe space is to think of it as a three-dimensional construct within which the Universe exists. A perhaps more practical definition of space would be that which you can measure with a distance measuring device (like a tape measure), such as the distance between two objects.