Is there a historical example of a theory that physicists all over the world pursued and developed in a concerted and organized research for more than 20 years without results, but then turned out to be correct? I get frequently as an answer the heliocentric vs. geocentric model, it took thousand of years. But I don't think this is a good example since at those times there was nothing such as a concerted global and organized effort and academic as research centers as we have nowadays. Science as we know it was still not born. Some others tell me about gravitational waves. But this does not fit with the above question. Gravitational waves are not a 'theory' but a prediction of a theory that was already confirmed. Some other again cite the standard model of particle physics. I don't think this is correct, it is a theory that grew throughout the decades, but it turned out to be correct 'piecewise' very soon until it took form as we know it today.