In2014,theInternationalSpaceStationhadtomovethreetimestoavoidlethalchunksofspacedebrisandthereisanincreasingproblemofsatellitesmysteriouslybreakingdown.Withfirst-handaccountsfromastronautsandexperts,Horizonrevealsthescaleoftheproblemofspacejunk.Ourplanetissurroundedbyhundredsofmillionsofpiecesofjunkmovingat17,000milesperhour.NowtheUSgovernmentisinvestingabilliondollarstotrackthem,andcompaniesaroundtheworldaredevelopingwaystoclearuptheirmess-fromrobotarmstonetsandharpoons.HorizoninvestigatesthesciencebehindthehitfilmGravityanddiscoverstherealityisfarmoreworryingthantheHollywoodfiction.