Some of the NIKE ABM radars used Luneburg lenses made from bits of copper wire precisely embedded into blocks of styrofoam. This was a meta-material from the 1

Some of the NIKE ABM radars used Luneburg lenses made from bits of copper wire precisely embedded into blocks of styrofoam. This was a meta-material from the 1950s, but it did not have the negative index of refraction as far as I can tell. https://hackaday.com/2013/04/30/retrotechtacular-history-of-the-u-s-antiballistic-missile-systems/ https://hackaday.com/2013/04/30/retrotechtacular-history-of-... https://srmsc.org/pdf/004438p0.pdf https://srmsc.org/pdf/004438p0.pdf