Hey guys I have an issue I was wondering if you could help me with. There was a book in my high school library about the theory of relativity and time travel. I'm trying to find it again but the fact that I don't have a title for it is making things difficult. (For the record I'm long graduated from the school so asking the librarian isn't an option). I was wondering if anyone here would know the book. The book seemed to be aimed at high school students. It discussed the possibility of time travel both forwards and backwards (I don't remember what it said about backwards). I'm pretty sure it discussed mass changes as the speed of light approaches as well. Tachyons are discussed in the backwards time travel part. The book has equations in it but the math was pretty simple. Nothing higher than algebra 2 math. Imaginary numbers were used, but I don't quite remember how. It might have been imaginary mass for faster than light stuff. Anyway, that's what I know about the book. It seemed to be pretty low level, just a friendly guide for a high school student. The book would have had to have been published before 2009-2010ish. Oh, and it also uses frames of reference a lot. If anyone knows a book that fits that description it would be great because I've been trying to find that book for a while now.