I'm personally sympathetic to "I'll need a research team and five years" missions. I think both university research and xkcd are great! But it's a critically di

I'm personally sympathetic to "I'll need a research team and five years" missions. I think both university research and xkcd are great! But it's a critically different from YC's definition that: Hard tech = "There is doubt that the technology can be built at all." Though many pieces of technology face huge doubts, what's key is often a team can get to a working prototype or partial release in way less than 5 years! (E.g. Dropbox.) YC is exactly the type of environment to refocus a 'research style' team exclusively on demonstrable progress. The problem with the xkcd definition (if attempted in a startup) is very few research teams can continue to fundraise for 5 years without a product or significant prototype. A partial solution to the "doubted" tech is often good enough to build a great company.