Human beings are at the dawn of a new age. Either we will become a true spacefaring people, or we will be trapped on a overcrowded, strife-ridden planet with ever-dwindling resources.
There are many reasons to go into space.
Space is big
In an era of peak oil, peak food, peak water, we are increasingly faced with the realization that our world can no longer supply the raw materials and ecosystem services necessary to permit further population growth and prevent irreparable damage to the biosphere. If human populations and economies are to have any hope of avoiding a permanent crash in the future, we must start the space era now. The resources of our own solar system are vast. The energy from the Sun hitting our small planet everyday is roughly 10,000 times our current energy needs. The raw materials locked up in asteroids and comets could support economic growth for millennia to come.
Space is green
In addition to the obvious green benefits of space solar power and off-world extraction of natural resources, space provides a safe place for heavy industry. The byproducts of our civilization are quickly making our planet uninhabitable. Despite the overwhelming evidence that we are changing the very climate we need to survive, we seem unwilling or incapable of making necessary changes to our economic model if it even remotely threatens a loss of economic prosperity. Consequently, pollution of our atmosphere, oceans, groundwater is a fact of life in our industrial societies. The problem is especially severe in countries which are racing to raise their citizens out of poverty. Due to the vastness of space, however, space-based industry could safely provide economic prosperity for people on Earth, and beyond, without poisoning the environment we live in.
Space ensures our survival
As long as we remain solely on Earth, humanity is in constant danger of being snuffed out of existence. Whether it be by asteroid, or nuclear war, or global pandemic, the sum achievements and knowledge of our species could be erased in the blink of an eye. The colonization of space is an insurance policy against catastrophe. What a terrible waste it would be if our civilization was extinguished just at the moment when we were about to reach for the stars.
Space inspires us
Ever since the first humans left Africa, we have been wanderers and explorers. Exploration is the root of many of our myths and legends, and explorers have been our heros throughout history. The act of venturing out into the unknown, either for science or fortune, has always enthralled us and inspired new generations to search even further afield. In a very real sense, we have lost our identity as explorers here on Earth. There is no more frontier on Earth. Reaching for space can reinvigorate us as a species.
Space is freedom
People have sought out new lands to escape war, tyranny or oppression throughout history. As was written in the Declaration of Independence, we are all granted the inalienable rights of Life, Liberty and the Pursuit of Happiness. It becomes more and more difficult to uphold these rights on Earth as societies scramble and compete for dwindling resources. Space, with its vastness and vast resources offers a lasting chance to secure these inalienable rights for future generations.