[Jack Simth]

Just a thought....

Learning A by research can make it effectively (but not truely) impossible to learn B by research - it is a matter of A saying certain things required for B are impossible when they may not be; this would cause anyone wanting to research B to be laughed out of the Scientific Community, and not recieve any of the necessary funding for finding B. The only way B gets opened back up is if it is concretely demonstrated to the SC that the portion of A which said B was impossible is wrong (e.g. someone bLasting them in their faces with technology B, or getting a sample of B from a captured ship, or finding a sample of B in some ruins, or ...).

Another way this could happen would be a matter of point - if you have method A of making holograms which, at present, is much more effective in every way than method C, then nobody is going research method C once A is discovered. However, if some of the principals used in C later lead to B, but A does not have these principals, then A being discovered may prevent B from being subsequently discovered. Again, it becomes effectively (but not truely - theoretically the powers-that-be could order research in C, eventually leading to B - but how likely is that?) impossible to learn B once A is discovered, barring picking the principals up from somewhere else.