And what if Picard's backward-moving tachyon pulse had prevented life from forming -- then what? Would your universe (at whatever time you're in) fade away like the photo of Marty McFly's sister? I think the TNG finale puts us in the awkward position of imagining that all times are happening "now"... which means what, exactly? Is one second ago happening now, too? (BTTF had the same issue.)