GOING INTO SPACE IS GOING HOME.
The whole life of humanity on Earth could be described as a dress rehearsal for space, and the reviews so far aren't good. Humanity is seriously kidding itself if it thinks it's going to spend the rest of eternity sitting around on Earth, wallowing in its own byproducts, playing office and watching porn. The whole history of human life is constant development. No part of human existence has ever been "stable" in that sense. Everything changes, all the time, and the most obvious change currently is that we're running out of planet.
Put simply, Ma Nature has pulled the old "solve or die" trick on H. Sapiens again. Much the same deal as "Learn to walk on two legs", and "Guess what the opposed thumb is for". It's either solve the problem of space travel, or the human race goes to extinction without its supper.
Let's face it, there are a few hints: Any number of people, but only so many resources. Food and water take up a lot of space. We use materials like there's no limit. Our economics have trashed most of the planet and beggared two thirds of the world's population. Life expectancy in some areas is going down, for the first time in recorded history since the Plague. There are global epidemics and a loss of the physical certainties of even the last 40 years.
Requests to clean up our room haven't been taken too seriously, either. Pollution and waste are the most expensive, difficult and toxic problems we have. Then there's Global Warming, which, incidentally, is quite obvious if you don't waste time trying to make facts not be facts. (Strange argument: if the Global Warming scenarios are wrong, there's no problem. If they're right, pretending they don't exist will crash the whole human species like a train wreck. You wear a seat belt because of what might happen)
If Ma Nature is trying to make a point, maybe we should pay attention, instead of pretending omniscience. We are now creating the environment, and a truly lousy, sleazy, dirty, paranoid, place it is. We use enormous amounts of space on Earth for food and industrial production, infrastructure, and just keeping the wheels turning. We dump waste literally as if there was no tomorrow, and it wasn't toxic. We then, brilliantly, cram the population into the bits we aren't using for other purposes. Then we add more people, and wonder why everyone's getting stressed out of their minds.
Fact is that Earth cannot handle its problems the way it's been done. We need more room for so many people to live, and that means some of our existing land use has to go elsewhere. Space is the only option. You could put things underground, but that isn't such a great move when you consider there's only so much underground, too, and you'd have to dig up half the world to make a dent in the issues. You can build upwards, to a point, but how do you achieve a 50 storey rice paddy/wheat field? Or a few hundred thousand of them?
The physical problems with being Earthbound are so numerous I'll just have to say it's not something remotely feasible, with the present population or anything like it. The likely human problems are much worse. Being Earthbound means stagnation, and utter dependency on a single home world. There are plenty of examples of stagnant cultures on Earth, the dried up remains of what used to be living cultures. A species which thrives on stimuli can't really be expected to grow up in a scrap yard of things from times when life was interesting.
Even astronomy's against it. The Sun has now burned up 70% of its hydrogen. At some point it will start burning helium, at which point all bets about viability of life on Earth are off. It won't wait until the last atom of hydrogen is gone, either. There will be a threshold at which helium begins to burn, and the radiation will therefore change, because it's a different fusion process, generating different radiation forms. This doesn't necessarily mean billions of years, either. G class stars have their peculiarities, and our Sun is one of the better behaved stars in the class, by a very long way. That doesn't mean it will stay that way. Homo Sap, however sedentary, will have to move.
So much for the basics. Now some real problems:
1. Payloads and speeds for rockets are absurd, in economic terms. Economics will be the real driving force behind space exploration, industry, and colonization. A cost effective, safe, reliable, form of space travel is required.
2. Physics has been so obstructive about the idea of faster than light speeds that it would take a book to describe it. Ignoring those who don't know how to use calculators, and persist in adding factors which aren't even vaguely relevant as integers, the whole discipline is behind the eight ball. Even if it's impossible, solve it. There is not, and never has been, a choice. By the way, "E is to F", folks. Try a Mandelbrot and see what happens.
3. The logistics of space travel will make the 20th century look like Spartan asceticism was the Baroque period. Everything will have to be provided from scratch. Until there's a trustworthy method of getting extraterrestrial resources, there's no point in guessing.
4. Our present form of Government By Tribal Tantrums will have to grow up. We can't afford the luxury of dragging our stupidity around with us.
5. We need law in space, not politics. Something like International Maritime Law would do, something with a clear existing legal basis which is well understood. If we try legislation by knee jerk in space, it'll be a real mess.
6. We need to do some real thinking for once about where this species thinks its going, and what it thinks it's doing. One of the reasons for the current Earthly Paradise is that nobody bothers to think in terms of the best interests of the species, and it's been a disaster.
7. Let's try, for once, not cluttering up the future with past mistakes. That would be novel, and very much out of character, but on the positive side we could make bets on what's going to go wrong. Healthy incomes are traditionally made from humanity's mistakes, so why not just try to beat the system occasionally? Somebody's bound to get something right, sometime.
8. We can, in theory, stick a lot of our nasty materials production out in space, if we can do it economically. That would mean that to clean up the inevitable horrors, we'd only have to use the equivalent of a vacuum cleaner, not permanently shut down an area the size of France. Chernobyl was only one accident, and one basic kind of accident. Given the state of new technology, what would happen if we had a compound incident, involving some of the really toxic materials? It makes sense to get these things off planet.
9. The statistical certainty of space events affecting Earth, in the form of asteroids or comets, isn't even arguable. We need defences against these things. Have a look at the other planets. Most of them show signs of impacts that would scramble Earth like an egg.
10. Resources in mega-multiples of those available on Earth are already known within the Solar System. Are we just going to sit here forever not using them? Do we have any idea which of them might be vital due to some new technology or need? It's like having a gold mountain next door, and being too bloody lazy to get out of bed.
There's something slightly obscene about the thought that anyone can live in an entire universe, and not want to go have a look at it. I don't claim to understand this mentality, but I do claim to distrust it intensely. Earth was made from space materials, and therefore so was the human race. Humanity's only been around for a couple of million years, and far less, in its present form. The colonization of Earth by human beings was a pretty demanding task, and if a bit easier and within walking distance, it's still the first planet we colonized.
Earth itself is in its mid-late middle age. It definitely won't be around forever. We can't just hang around waiting for God to drop in with a few travel brochures. If the human race is to continue to exist, by definition, most of its existence will be somewhere other than Earth. From space we came, and to space we go. Space is home.
Let's put it this way: never mind the impossibilities. There'll be a queue of volunteers clear around the Earth, several times, when a decent kind of spaceship is available. Space travel would be one of the few human ambitions where there's no selling required. Hit c, then hit the accelerator. Let the universe get out of the way. And good luck to you, whoever you are. We'll be home soon enough.