spotted something new: The arrows point to denser knots of material that are somehow causing the
reverse shock to move even more rapidly, and that material appears to be moving inward, not outward.
see WATCH THE EXPANSION OF THE CAS A SUPERNOVA REMNANT WITH YOUR OWN EYES!
https://www.syfy.com/syfy-wire/watch-the-expansion-of-the-cas-a-supernova-remnant-with-your-own-eyes