A few years ago there was a story about the Large Hadron Collider where a possible tachyon was supposedly observed. It was later shown it didn't occur yet the incident made me think. If a large experiment using extreme amounts of energy trying to duplicate some processes or events of the 'distant' past , would the intense amount of energy in this 'early' Universe experiment create a situation where the speed of light was different?? If a particle was observed emanating from this experiment and it seemed superluminal could this be due to a different speed of light measurement due to this phenomenon.
Unfortunately, this result was later found to be caused by faulty electronics, according to the CERN press release.