"In general relativity, the future light cone is the boundary of the causal future of a point and the past light cone is the boundary of its causal past." From the moment of my birth, light [that I could have influenced] has been expanding around the Earth and light [which could influence me, from an increasing distance of origin] reaching it -- this ever-growing sphere of potential causality is my light cone. Today, this surface contains 29 stars, and is 4 months away from enveloping Pi-3 Orionis (Alpha Lyrae was passed 6 months ago). If you're using the brown skin of Interconnected, there's an automatically updating line in the flannel (see it) to count down to (and away from) new additions to my personal universe.
(Update. Whoops, my script has been showing the wrong number of stars. Fixed now -- 29, not 27 as earlier. By which I mean to say, there's a shell 5 light hours thick in which I'm wrong, expanding at the speed of light, and the wavefront of accuracy will never overtake it. Ah well.)