Holograms
I'm old enough to remember when holograms first appeared commercially. I remember being amazed and trying to look behind to see if it wasn't just a 3-dimensional object masquerading as a 2-dimensional object (masquerading as a 3-dimensional object). It must have looked like when you show a chimp a mirror and it tries to reach behind it to touch its reflection. (I guess the same would happen to a human if it saw a mirror for the first time as an adult.) I did one year of physics at university before switching to maths. In general I didn't like the practical sessions because they were always at the end of the day, and very long and tiring. However, on one occasion we got to make our own holograms, and that really did impress me. IIRC mine was of a 2 pence piece. What I found really interesting, was finding out how they worked. I don't think we were taught this as such - it was up to us whether we wanted to go off and find out for ourselves. Anyway,