Board Thread:Warhammer 40k General Discussion/@comment-25618639-20150220210346/@comment-6078851-20150303150623

the tau know about warpspace, as is mentioned in canon material, although they know very little. what they know nothing about is that warpspace is also chaos - "given their limited exposure to the warp, the tau found it difficult to comprehend the hallucinogenic effects it had on other races and the terrible threat it could represent to psykers. such talents were a mystery to the tau as they had no psychic abilities whatsoever, their minds barely even registering in the warp at all."

i don't know when humans first discovered the effect of warpspace travel being quicker than realspace travel, but i think it's safe to assume that they would have used the 'short dips' method: they would be experimenting with an unknown medium, and even if they had navigators by then (again, no idea when the navigator gene first appeared but they would've had no astronomican and as they were making their initial forays into warpspace they wouldn't have developed warp-beacons yet) there would be extensive experimentation in the 'shallows' of warpspace - you don't attempt to circumnavigate the globe without extensive learning in shallow coastal waters :)

the tau have no navigators, but because they aren't travelling far (relatively speaking in galactic terms) they spend very little time in warpspace which "protected them from many of the inherent dangers of warp travel."

the quotes are from the previous tau codex but again i can't confirm if they're still canon since i have yet to read their current codex and things get changed, but i'm away to read about the nicassar right now :)