Lightcone is a daily RSS feed that tells you which stars the light-cone — the ever-spreading cone of light streaming away from any event — your birth has reached. Every day, the feed tells you how far your influence has spread in the universe.
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. [Wikipedia]
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… My light cone contains 37 stars. Chi-1 Orionis will be reached in in 9 days.