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First Evidence of Supernovae Found In Ice Cores
KentuckyFC writes "Supernovae in our part of the Milky Way ought to have a significant impact on the atmosphere. In particular, the intense gamma-ray burst would ionize oxygen and nitrogen in the mid to upper atmosphere, increasing the levels of nitrogen oxide there by an order of magnitude or so. Now a team of Japanese researchers has found the first evidence of a supernova's impact on the atmosphere in an ice core taken from Dome Fuji in Antarctica. The team examined ice that was laid down in the 11th century and found three nitrogen oxide spikes, two of which correspond to well known supernovae: one event in 1006 AD and another in 1054 AD, which was the birth of the Crab Nebula (abstract). Both were widely reported by Chinese and Arabic astronomers at the time. The third spike is unexplained, but the team suggests it may have been caused by a supernova visible only from the southern hemisphere or one that was obscured by interstellar dust."
There's no "fixed" time reference for the universe, so it seems perfectly reasonable to use the one on Earth where all the readers live.
Well, while the special relativity may claim that all inertial reference frames are equal, the general relativity—especially the Big Bang theory—suggests that there *is* one inertial reference frame that is more equal than others: the rest frame of the cosmic microwave background radiation, which could be termed the "inertial reference frame for the universe".
Having said that, yes, we should give the dates for when the events were observed on Earth. The universe may not revolve around earth (earth is not even at the inertial reference frame of the universe), but it sure gets confusing if we start dating events by when they actually happen, since then, in order not to get utterly confused, one must know how far this Crab Nebula (or any other intra-galaxy or deep-space objects) is.