Why we are unlikely to ever leave the solar system.

I had the same conclusion initially and called it the horizont of space reachability principle. There is a limit to the travel distance defined by the energy consumption. Reducing the energy consumption to the minimum would allow to extend this horizont limit. Pushing this reasonning to its limit I noticed that we have plenty of examples on earth of live forms able to extend this limit to infinity by mean of seeds or spores form. In such form the organism is totally passive and consumes no energy. It has a trigger which induces reactivation of life and development that may be activated by external energy and appropriate condition.

So it is possible for a life form, human or extraterrestrial, to build such a civilization seed which contains enough energy reserve and machinery to sustain life activity restoration and live form rebirth. Throw such civilization seed vessel like a bullet toward a distant solar system so that the energy of the target can be used to trigger start of development and we have our space travel capacity.

This is not how we'd naturally imagine interstellar travel, but the important point is that this proves that it is possible without relying on exotic or hazardous hypothesis. We should also keep in mind that there is still the possibility to tap into the dark matter as source of energy. While this is still very uncertain, it should be known and well accepted By now that interstellar travel and space colonization is possible.

I would like to add to this that if human life is a result of a natural process, there is a very high likelyhood that we are not alone in the univers and that other entities are likely to have started colonization already a long time ago. As we can see from earth civilization history a key factor to perserve its liberty and life autodetermination is the mastering of science and technology, intelligence and defense capacity. While there is still a need to protect ourselves from oher humans, in which we spend and waste a lot of ressource, the clock is ticking, and other civilizations may be developping much faster and efficiently than humans. It is no hard to see what it all implies.

That is what plenty of earth life forms are already doing. The civilization seed could be conceived to minimize the hazard of the environment.

Who's making the specific predictions here?

I would be very surprised if the Gobi Desert, and Antarctica, and any other inhospitable place you care to name, was not colonized and exploited in the distant future. Right now we aren't doing that because we don't need to, but we could.

As for space colonization, there's enough of a romantic interest in it that I wouldn't think that the fact that it doesn't make economic sense would necessarily be a deal killer. There's also the possibility that some group would want to escape Earth at any expense. It didn't make a lot of economic sense for the Puritans to go to America, but they wanted out of the mother country.

In the 20th century we went from thinking that heavier-than-air flight was impossible to it being a major economic activity and the dominant form of medium-distance travel. We went from conventional explosives to nuclear explosives. We landed people on the Moon. We went from dying of dental caries to antibiotics and (very limited) genetic therapies.

In one short century we published more books and amassed more knowledge than all centuries past. Together. And we built the tools to search it and process it into meaning.

Traveling to another star is a formidable problem and doing it Newton style is not impractical. But if the past century teaches us something, we are a species prone to invent magic wands.

Besides that, we all know how futile is to try to predict the future. We can only see and express it in our own terms. The future is as alien to us as Twitter would be to my grandmother (who would be turning a century if she were alive).