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 Does Helium Get Underground In The First Place? (Synopsis) - “I have this one little saying, when things get too heavy just call me helium, the lightest known gas to man.” –Jimi Hendrix The second lightest and second...
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