>Unfortunately this time, we've used up the irreplaceable (even on geologic time scales) coal and other fossil fuel deposits, so we would be out of the running,

>Unfortunately this time, we've used up the irreplaceable (even on geologic time scales) coal and other fossil fuel deposits, so we would be out of the running, forever, as a multi-planet species. I would take this further. In the past we've been able to kick problems down the road. Many of the problems we now face are actively manifesting and delaying response to them is not going to help, it will just make them worse, faster, now. So long standing problems that have been mostly ignored, can no longer be ignored. We'll either step up and actually fix them, or much will be destroyed. We no longer have a choice to wait. So look at those issues where it is obvious that a response can not be delayed. Those are the areas where either solutions will shape the future, or the destruction that accompanies ignoring them will manifest and shape the future. Some examples might be: obesity, climate crisis, pollution, insect decline, animal decline, decline in the variety of species, ocean acidification, financialization, misuse of commons, invasive pests, superbugs, the current pandemic, and decline in the quality of food. I'm sure you can think of more. Then extrapolate to the futures where we fix a few specific problems, we fix all the problems, we fix most of the problems, we fix none of the problems. Then you'll have a range of likely futures. That tells you how to work towards specific futures or by tracking current trends to predict which futures are most likely. This ignores new innovations of course because you can't easily predict them long term (though short term some things like technology advances are somewhat predictable.) So there will always be wild cards. Another large factor is what people think because what people think is what creates shared reality. This is like trying to predict fads, it mostly can't be done. So it represents another source of wild cards. #MeToo is an example of such a shift. There are some trends here though; there seems to have been a historical trend for populations to become more liberal over time. It doesn't happen fast but it seems to be true everywhere. Fifty years ago China embracing capitalism was unimaginable. People admitting they were gay publicly was not happening. So assuming a slow trend towards liberalism may be predictive. For example, marriage may decline and who you have sex with versus who you share your living quarters with may diverge over the next 100 years. Another example is if you assume the internet still connects most people in the world in 100 years (and even more people gain internet access with time) then that will likely have a homogenizing effect, blending cultures and reducing xenophobia.