And there's the first "time window".
TRANSCRIPTION COURTESY OF JOSEPH HOUK - (CW continues – wearing her radiation suit with a Geiger counter) At first I was just trying to get the little rock to stabilize, and at about 90 degrees it did. The metal was greenish, slightly malleable, and had a faint glow to it. [Which explains why the time portal is a yellowish-green] When I took a Geiger counter to it, however, the radioactivity was surprisingly very low. Low enough, in fact, for me to not really need the radiation suit [which she removes]. I don't remember all the experiments that I performed... but there was one I would definitely never forget. [setting up a laser at the rock] Hoping for a cool color show, I focused a laser beam on one of the bumpy parts. The beam, bouncing off the rock, created green rings in the air... and through those rings I could see myself... FROM AN HOUR AGO. [Inside the ring is an image of Cassie putting ON her radiation suit!]