The Great Filter is physics. I heard recently that if the earth was 3 times larger, the most advanced chemical rocket would not have the energy density to leav

The Great Filter is physics. I heard recently that if the earth was 3 times larger, the most advanced chemical rocket would not have the energy density to leave the atmosphere. Scientists now know that with out a Jupiter, the asteroid belt might not form in such a way to deliver 'water' and protect us from large comets roaming the galaxy. Even now it may not be possible to leave our solar system without a significantly different understanding of physics. Voyager is just no leaving our solar system, and it will take decades for it to actually leave the effect of our sun. Today if we launched a craft it probably would get just about as far as Voyager in just about the same amount of time, but maybe our power source could power a more efficient version for a decade longer, getting us just a bit further than voyager will, but still no where near Alpha Centauri. For us to explore the depths of space, it would need to be much easier and cheaper than it is today. For it to even be plausible a DIY Scientist as you suggest would need to create energy density so powerful, it would be hard to imagine a world where that sort of thing is not regulated. For us to study sub atomic physics, we have a structure that is 20 miles in length, this is not the research of... a DIY community. Today we argue about Iran getting enriched plutonium for nuclear research, when some think they want to build a bomb and others think they want to build a power plant. I really can't imagine a neighbor of mine being able to ... take that step without raising some alarms. Your mad scientist would have to be on a far off island/ comet/ moonbase with all of the resources and man power required without interference from others, but still have access to raw materials. I am just not sure we will find other worlds in humanity's lifetime. We may be able to colonize mars and a few other large bodies in our solar system, but leaving it is a different story.