An exhibition for a star observatory. We gave the visitors access to the Quasar High Security Computer System. The moment they log in, a few cases are presented. Aliens spotted!, Life on Mars!, etc. Tabloid style.
The visitors get to investigate the case. When they do, a hacker breaks into the system and raises questions by showing how principles in astronomy work. Included is the hacker explaining the speed of light. And that in theory it is possible to look into the past of planet Earth, when standing on another planet. The user gets to choose a planet and through a telescope he can see light from our past . And what is light? You might even see Elvis alive!