Investing in science and energy innovation is slowly swinging back into fashion in Silicon Valley. It seems like this is partly because of a backlash against the idea that Silicon Valley hasn’t been funding the world’s more difficult problems, and instead has been making easy money on things like social media apps. However, that doesn’t mean I think these more difficult investments will make investors the type of money that they’re used to.

While apps like Yo continue to get funded, so do, surprisingly, some early stage nuclear energy startups. Earlier this month it was nuclear startup Transatomic Power with funding from Founders Fund, and this week Tech Crunch reports that a nuclear startup called Helion Energy has raised $1.5 million from Y Combinator and Mithril Capital Management. Y Combinator, of course, is the accelerator program that has become synonymous with the quick-flip, social media apps of…