Well, I failed my first attempt (you were allowed 2). The reason the committee gave me for not passing was that my topic of choice was not a "significant improvement of basic science". This perplexed me. My committee was made up of members who were all 60+ years in age and had been the founding fathers of metallurgy. Collectively, they invented a completely new field called opto-electronics. When they gave me that response, I thought to myself, how the fuck do they expect me to improve basic science?!
It turns out the solution was much more nuanced. In the months that followed, my advisor would have thought experiments with me. He essentially helped me brainstorm problems that needed solving, but he always started our sessions with the question, "what is something that you always wanted to exist, but doesn't? What are you most curious about?" He then gave me the keys to his shop and told me to "tinker around". Take apart his vacuum tubes. Screw around with his argon laser and sputtering machine.
Innovation in the physical world comes from the same curious people that are inventing fun software programs. But we absolutely need to cultivate it, because that is what is dying. Put a workbench in every home, make it easier for people to take apart things they buy, encourage people to be creative without fear of punishment.