"According to the more conservative cosmologists, an alien superpower – maybe a collective of Kardashev Type Three galaxy-spanning civilizations – is running a timing channel attack on the computational ultrastructure of space-time itself, trying to break through to whatever's underneath." in Accelerando
I believe they tried an experiment that was similar to that at the start of Schild’s Ladder — and for their troubles they were rewarded with a vacuum decay expanding through space at about 0.5c.
