How best to handle a "Big Reveal"

OK, I have been stuck on how to approach something for my Jashen Space setting, the default setting for StarCluster 4. There is something which the player characters in the game should not know, and the GM should. How do I handle this? I hate "Big Reveals", and I don't think this is something earthshaking enough to be a "Big Reveal". It's not a gotcha thing. The people in Jeshen Space may not be affected at all by this. If you told them, it would be more of a "Oh, huh! That's interesting!" reaction rather than "OMG! EVERYTHNG WE KNOW IS WRONG!!!?!" reaction. Thing is, if they *did* know about this, they would collectively be approaching something important in a completely different way.

So, how do I handle this? There is no separate Players and GMs Guides. Do I put this off behind spoiler alerts? Do I put it in a separate product? Do I just throw in vague clues and hope the GMs can figure it all out? I hate interfering between a GM and players! GMs should be able to handle things like this in whatever way they wish.

This all goes back to the Levels thing - RPGs being created at three different levels, Designer, Group, and Individual. I like to stay on my Designer level when I am creating games, because I dislike it when a designer starts mucking about on my Group level when I am a GM. What do you think, my friends?