To try and make a point back on the original thread, I honestly believe that we need to pursue space travel and exploration for one simple, selfish reason. At some point in time, we as humankind on Earth will go extinct. You can speculate about the reason behind it - several options are even presented in this thread:
- China decides to take over the world and we have to fight them with nukes (both land and potentially space-based)
- Big asteroid smacks into our planet
- Our current modes of energy use eventually make our planet uninhabitable
But the one consistent thought is that Earth is a single point of failure. Once it goes, humankind does too. Now I realize that the timing of this may be on a geologic scale or that life may rise again (depending on your views on that whole debate) but honestly I seriously believe that humans should be investing in their perservation on a long-term basis. Yes, we can also invest in alternative fuels, affordable healthcare, feeding the starving people (many more of those that ones that are worried about space travel) but none of that gets us out of our current one-planet situation.
I recognize that we as humans with our massive brains and complex societies have an ability to react to and possibly even control these cataclismic events that threaten our existence. I also believe that we as humans are sometimes a little full of ourselves or don't know as much as we think. We should be hedging our bets that this arrogance doesn't cook our collective butts. Let's use that arrogance to our advantage by saying "Yep - the solar system, much less our galaxy, is a huge place and we have no idea how to explore it right now. So let's see what we can come up with." I'd be happy if we spent 1% of our annual defense budget in the USA on space. Notice I didn't say NASA - we have to use those funds wisely and their track record of late doesn't look "wise" to me.
Feel free to label me dilusional or idealistic or anything else that pokes holes in my argument. We can accomplish truly great things as humans once our society decides the costs are worth it. History has proven that sentiment, particularly in the areas of science and engineering when it comes to perceived threats outside our borders (the Manhattan Project comes to mind). You want to see our space program kick into high gear? Let some astronomer spot an asteroid the size of Texas that will smack us in a year. Too bad we're only scanning something like 3% of the sky right now. Or if you really want some action, let some alien race show up in orbit. Even if they are totally peaceful, we can count on our warmongers to start directing SERIOUS funds into space-based research.