In regards to the topic, let me say that I DO agree with reapersaurus' comment, after a fashion. It's flat wrong to say we know NOTHING about certain events and concepts, because we have documentation for many, many things.
However, in a larger sense, we really don't know many, many things. Ever seen the phrase,
"the more I know, the more I know, that I know nothing?"
Many times in the past, mankind as asserted that he has reached a pinnacle of knowledge or a plateau at least on a subject, only to have the rug pulled from under himself. Witness dynastic information on Ancient Egypt, true figures for Nazi Holocaust info, for that matter how many people killed under Stalin's regime - no one knows for certain because paper trails can be nonexistent or hidden (and in some cases falsified). Witness mankind's CERTAINTY in Newtonian physics at the turn of the 20th century, only to have advances from 1900-1950 render it useless, and Einstein redefines it to take not only Newtonian observations but relativistic observations into account.
I saw a fascinating special on the Soviet R7 rocket engine, and a bunch of American scientists baffled that the Soviets had Rocket Tech in the 50's and 60's that we STILL don't have a parallel for - because we bought it from them when we realized how good it was.
We know a LOT - but in one respect, the wider we probe, and the better our microscopes get, and the more evidence is uncovered, we find more theories to revise, more info to assimilate, and more questions than answers. So in an overall sense, we know far less than we think we do, as a people.