It's a window into a future timeline. 70 years ago at the beginning of the Atomic Age, scientists from the Manhattan Project received a localized tachyon burst lensed through the first atomic bomb test. Above ground testing continued at bigger and bigger magnitudes as the visions given by the tachyon bursts became clearer. Above ground testing only formally stopped when all relevant data had been gathered. It showed a bleak future where mankind was locked in a struggle against the forces of darkness, our sole hope against the endless struggle a quiescent traveler. Utilizing an AI downloaded from a future Vex mind core, they created an interactive training simulation to help prepare humanity to fight in this future conflict. Not everything is quite *exactly* as was seen in the future. The Fallen are quasi allies against the darkness, the Vex are much more ruthless and harder to kill, and the Cabal actually destroyed Mars on contact with our solar system (after seeing what happened to Mercury). And of course, we don't kill Crota over and over again. But it's a training sim, not a historical record. Hopefully we'll be ready this time...