I've heard a number of people mention that they think the space program is over-budget, more or less worthless, and a big waste of tax dollars. I can sort of understand that, but this is why that's wrong:
First: NASA's budget. The Entire National Aeronautics and Space Administration received only 0.44% of Congressional spending in 2010. To put this in perspective;
One $, out of: $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$, which is spent on other things. NASA does not even recieve 1% of Congressional spending, not even one out of a hundred dollars, but a bit less than one out of every two hundred dollars.
What does the space program do?
1)First, it inspires the general public. It gives the country something noble to hope for, and look forward to. Something where all the people of the Nation, or even all the people of the world, are all united in one endeavor, in one cause: The expansion, growth, development and progress of the Human Race. The exploration of the world beyond our little speck in the cosmos. It's literally taking steps forward, as a civilization and as a species.
2) It gives a cause, a challenge, and a goal for the Nation, or even the world to work towards. To look to. A civilization, just like an individual, thrives on challenge and withers without it.
In the words of Robert Zubrin, head of the Mars Society:
"Mars is the bracing positive challenge that our society needs. Nations, like people, thrive on challenge and decay without it. The challenge of a humans-to Mars program would also be an invitation to adventure to every youth in the country, sending out the powerful clarion call: "Learn your science and you can become part of pioneering a new world." There will be over 100 million kids in our nation's schools over the next ten years. If a Mars program were to inspire just an extra one percent of them to scientific educations, the net result would be 1 million more scientists, engineers, inventors, medical researchers, and doctors, making technological innovations that create new industries, finding new medical cures, strengthening national defense, and generally increasing national income to an extent that utterly dwarfs the expenditures of the Mars program.
This point is so critical that it is worthy of further emphasis. The wealth and the strength of a nation are based first and foremost on its intellectual capital. In this respect, the Apollo program produced a terrific return, as it doubled the number of our science graduates, at every levelhigh school, college, Ph.D. This paid off massively when those twelve-year-old little boy scientists of the 1960s became the forty-year-old technological entrepreneurs of the 1990s and launched the computer revolution. A humans-to-Mars program today would repay even greater dividends, because in this day and age the science and engineering professions are also open to women in a way that was simply not the case during the 1960s. Thus an Apollo-like challenge today would not only inspire into being legions of little boy scientists, but little girl scientists as well, whose ensuing research and inventions would benefit the nation, and humanity at large, for decades to come." - Robert Zubrin
I believe that sums up the first two reasons.
3) Right now our civilization is vulnerable. Human civilization has collapsed before, there was the fall of the Mayans, the withering of the Egyptians, and the Collapse of the Roman Empire, which involved the burning of the Library of Alexandria, and with it, mankind was set back in our progress as a species by thousands of years, opening the middle ages, a time of monarchy, inquisition, war, poverty and execution.
There are many things that can wipe out our species, especially in this new age of technology where we now yield weapons of mass destruction.
A terrorist, for whatever different reasons, could either steal or develop a super virus, something as transmutable as the flu and as deadly as AIDS would quickly bring an end to human civilization.
A supervirus could naturally occur, as did the Black Plague in the middle ages, which killed roughly half the world's population. Recently there was a large scare in the U.S. about avian flu and bird flu, neither of these were very serious, a lucky break for us.
A rogue nation could launch nuclear weapons, and through a chain of alliances start a nuclear armageddon. This is something that was taken very seriously, and came very close to happening just within the last century.
Should the ICBM become obsolete, Mutually Assured Destruction would end, and allow for World Wars to resume once more, bringing perhaps as much, if not more, death and destruction to mankind as any nuclear wars, as any historian that's studied WWII and WWI will know, if World Wars continue, uncontrolled by Mutually Assured Destruction that ICBM's and Nuclear Arms bring, human civilization would become unrecognizable as it is today.
An Asteroid could be detected on course to collide with Earth. If anything's discovered less than 10 years in advance, then space missions would be powerless to stop it. Current ICBM missiles cannot escape Earth's gravity to attack an incoming celestial body. Should a space missile be armed with nuclear warheads, it would be capable of carrying enough to deflect or destroy a large enough asteroid. It's known that we don't know of every such object, and should something come from the outer solar system, as every comet and many asteroids do, we would have no warning at all (these objects are on orbits that can take an excess of 2,000 years to complete, so it would take roughly as long to detect every one of them).
Asteroids are actually perhaps the most predictable threat that we face. Other astronomical events include an unusually large Coronal Mass Ejection, which could effectively black out major portions of the world's power grids. Such has already happened in Toronto, causing a city-wide blackout for days. A large enough one could even damage, or destroy the Ozone layer that protects Earth from UV radiation.
Also the Earth's poles could swap, they have done this thousands of times in Earth's history, and it's in the process of happening now. During that swapping time, the solar radiation protection offered by Earth's magnetic fields would be drastically weakened, exposing the entire world population to very high doses of radiation.
Now, aside from all the catastrophic events, is the greatest threat of all: Political unrest. This is what has caused human civilization to fail in the past, as the Roman and Mayan empires did. This is the greatest threat mankind faces; namely, itself.
I am not fear mongering, I do not expect to see any of these on a civilization-destroying scale happen in my lifetime. However, I don't doubt they will happen eventually, and if we're not prepared than our species and civilization will be set back thousands of years, as were the Romans, only doomed to repeate the cycle once more, and our species forever be stuck at a level similar to what it's at today, never growing to reach it's full potential.
If our species is to survive, it must expand, and for two reasons:
#1: We have to exist in more than one place. The reason a virus or a war or political collapse could destroy human civilization is because we're all so intricately connected. The market is international, world-wide. Beijing is only an airplane flight away from New York or London. ICBM's can reach around and hit anywhere on Earth. Any virus can take a short airplane ride and travel around the world.
#2: We need to overcome our dependancy on the lucious, pampered environment we experience on Earth. A colony elsewhere in the solar system would not be dependant on many of the things that could fail here on Earth. Should a life support subsystem fail, engineers can repair it. Should one of Earth's systems fail (magnetic field, ozone layer, etc.) there is no repair possible.
And finally, the ultimate goal, interstellar travel and colonization, would be the ultimate for our survival and continuation as a civilization and a species.
These goals are lofty, ambitious, and far beyond our ability today (that is, a significant colony on Mars. A small scientific station on Mars is very much possible with current technology, albiet somewhat expensive: 55 Billion. NASA's budget over the course of 4 years. A long 10-year program and a budget increase could make it possible.). But how are we ever to reach those points in our technology, and progression as a species, if we don't work at it today? Experience, technology, technical skills and know-how do not come from sitting and waiting. They come from experience, actually doing something.
We need our space program to be our pioneers. To blaze the trail ahead, lead the path, warn and teach us how it's done, how to survive, and ultimately, how to progress, grow, and survive as the human race.