Has anyone noticed these signs posted on the streets and sidewalks of various US cities? I first noticed them in the summer of 1993 while vacationing in NYC, Philadelphia, Baltimore, and Washington D.C. I was reminded of them today after looking at some photos I took of them. At the time, I figured they were some kind of public paranoia, or prank. The ones I saw simply said "Resurrect Dead Planet Jupiter", and were made of plastic seemingly baked onto the street. Today I did a web search to see if I could find any information about their origins. The complete phrase seems to be "Toynbee Ideas in Kubrick's [or Movie] 2001 Resurrect Dead on Planet Jupiter", and the signs have become more elaborate. Now they are appearing as mosaics pressed into concrete. Even though these signs have spread to most major US cities, no one has any idea of their origin and no one will claim responsibility. I'm curious if anyone else here has seen them. Here is a good website about them.