Note that different people have different research approaches. The two old ladies check that none of them can see herself and the problem is solved! ;-)
The other older lady makes an experiment with motion and rigorously determines that she is ... well ... unsichtbar. :-)
How the Universe changed in 2016 (Synopsis) - “We are not the same persons this year as last; nor are those we love. It is a happy chance if we, changing, continue to love a changed person.” -W. Somers...
10 hours ago