I would definetly have to go with "brain surgery". Rocket-science, at least in it's basic form, isn't exactly... well, brain surgery, lol. It's more or less basic chemistry and physics. The human race, in one capacity or another, has been successfully playing around with "rocket science" for centuries. Not that we haven't also been playing around with brain surgery for centuries, but... I guess the key difference would have to be that whole "successfully" thing.