I dig this quote. 

“The Earth is the cradle of humanity, but one cannot live in a cradle forever.”

—Konstantin Tsiolkovsky

Well said:

The problems that will keep us from going to the stars can be loosely grouped into categories: physical, biological, ecological, sociological, and psychological. One could add economical, but economic problems are trivial compared to the rest, as economics is amenable to adjustment on demand. Reality is not so tractable.

Physically, the main issue is that the stars are too far away.

This problem has been finessed in many science fiction stories by the introduction of some kind of faster-than-light travel, but really this is not going to happen. It’s a convenience employed to get us out into a great story space, a magic carpet that gives us the galaxy. I like that story space very much, but any realistic plan for getting to the stars will require slower-than-light travel, probably quite a bit slower. The usual speed mentioned in these discussions, as keeping a balance between the fastest one can imagine accelerating a spaceship while still being able to decelerate it later, is one tenth of light-speed.

The closest stars are four light years away, although now we know that this Centauri group has no planets we can terraform. Among other nearby stars, Tau Ceti, twelve light-years away, is now known to have planets in its habitable zone; they are too massive for human inhabitation (five or six g), but they might be orbited by habitable moons. Traveling at one-tenth light-speed, a voyage there would take 120 years plus the time needed for acceleration and deceleration, so that people speak of approximately two hundred years transit time.

Thus a crossing to even the closest stars will require a multiple generation effort, and the spaceship will need to be a kind of ark, carrying all the other animals and plants the humans will carry with them to their new world. This suggests a very large and complicated machine, which would have to function in the interstellar medium for two centuries or more, with no possibility of resupply, and limited possibilities for repair. The spaceship would also have to contain within it a closed biological life support system, in which all the flows of energy and matter would have to recycle as close to perfectly as possible, minimizing catches or clogs of any kind.

Here is where the biological and ecological problems come to the fore, but sticking for now to purely physical problems, the starship would be exposed to far more radiation than we are on Earth, where the atmosphere and magnetosphere protect us to an extent. Effects of that extra radiation are not fully known, but they won’t be good. Cladding would help, but would add to the weight of the ship; the fuel carried for deceleration might serve as cladding en route, but that fuel will get burned as the starship slows down, increasing the starfarers’ exposure, already higher than it would have been on Earth.

Lastly, in terms of purely physical problems, if the starship runs into anything substantial (like a couple of kilograms) while moving at a tenth of light speed, the impact could be catastrophic.

These physical problems, especially those concerning propulsion and deceleration, are the ones that have received the most consideration by the starship discussion and advocacy community. As engineering problems they can can be given at least hypothetical engineering solutions, using equations from physics that we know to be true. Thus they are, in effect, the easiest problems that starships will face, being relatively straightforward. But they aren’t that easy.

Biological problems are harder for humans to solve than physical problems, because biology concerns life, which is extraordinarly complex, and includes emergent properties and other poorly understood behaviors. Ultimately biology is still physics, but it constitutes a more complex set of physical problems, and includes areas we can’t explain.

If I had a dime for every time somebody uttered this:

"...but really this is not going to happen."

and then reality became quite tractable enough to prove that utterance wrong, then I'd have more money than Gates and Buffett combined...

Do people still use dimes?