The point is that they specialize in the theoretical side, not that they don't try to validate it. The difference is that their validation focuses on math rathe

The point is that they specialize in the theoretical side, not that they don't try to validate it. The difference is that their validation focuses on math rather than physical experimentation. Eg there's no way to verify Hawking radiation in person (because well, good luck getting near a black hole to do so). But it's still supported by existing models of physics, thus it is science and not mere speculation. Another recent example would be that the idea of time crystals was a theoretical physics result, backed by existing physics. That backing made it more than just speculation, leading to the investment of resources that eventually led to them actually being created. Of course probably the most famous example of a theoretical physicst would be Einstein. Lots of stuff typically goes through theoretical physicists before experimentalists determine how to test the idea. For example, all the particle accelerators, synchrotrons etc are initially designed by theoretical physicists via simulations etc to meet certain goals before putting in the billions of dollars it costs to actually translate those designs into something that can be built and used.