I came across an article of interest on Facebook this morning.
http://themindunleashed.com/2017/07/scientists-accelerate-backward-time-travel-laboratory-conditions-first-time.html
It's about scientists accelerating backwards time travel for the first time and involves creating negative mass under laboratory conditions. Fascinating stuff!
So, this is the type of stuff I get to read to research time travel for my series. Neat, huh?