About the motivations of the Space Option
The theory of the asteroid extinction of the big Sauria is suggestive, but I think the Nature didn't need to incomodate an asteroid to write the world "THE END" to the dinosaurs history: it is enough to imagine how they were big, the enormous quantity of wood and grasses they eat (think about the methane emissions and the consequent green-house effect). It is enough to think about their number to imagine their end: they were animals too big to reach the critical number that allows the jump from this planet to the stars. About us, we can only hope to have the suitable size (mice and insects are waiting their turn to try). Of course the asteroid impact is a real danger, but what I want to point out is that it is not the only one. In Italy, as you probably heard by the media, we have a continuous eartquake, since 26 september, everyday the earth is moving. Thousands of people are entering the winter in the roulottes and containers, seeing their houses (the saved money of a whole life) reduced to a hill of ruins. The problem is always the same, since the neolitic revolution: how will we defend ourselves against the Nature's attacks, because the Nature holds thousands of weapons to kill us and even to eliminate our Species. There is a more general consideration to be done: only if we get our freedom from the Nature's cycles of this planet, we can hope to avoid the extinction. This is maybe less noble that our duty to take the life in the Universe, but it is directly linked to our survival instinct as Species, and it can't be forgotten, among the motivations. We all know what it happens when a fruct is ripe: the fruct rots, and the seeds drop on the earth, some of them, the most lucky, will maybe germinate in a new plant. This is the way of "mother" Nature: a cruel way, a murder of innocents. With the neolitical revolution we started another path: to make germinate all the seeds, to grow up and give enough space to all our children. And to win the challenge we need the help of all our children (6 billions people): when the ideal human starship will sail to explore and colonize the Solar System nobody is to be left down, because the next Galileo Galilei could birth in Indonesia, and because everybody has the right to the future (i.e. to the genetical continuation), and many earth-resources analysis agree saying that the resources of this planet will not be enough for more then 10 billions people (and some analysis says that we are already prressing on the bars of the cage). Even the people who will phisically remain on Earth, even those who will never put a foot on an airplane, they must be part of the World Space Program! And they will tell to their children: We are going to the stars!
The goals of a World Space Program before 2100
The realization of an artificial self-maintaining ecosystem out of Earth is the most important and the first problem to be solved. On this challenge we will play the game of our survival, and it is probably the most difficult task. I could probably agree, if we will submit a common document, to stress this point as the priority 0 of a WSP. But, about the time scheduling, in this case I should prefer to be more optimistic, indicating a shorter time for the solution of this problem. Also I think we must considere some other goals. I always have in my mind that, at the beginning of our Century, nobody could even imagine that man really had gone to the Moon and had sent automated machines out of the Solar Systems. May we hope that this problem can be solved in the first half of the new Century? If yes we could design a wider scenario before 2100: human consolidated installations in the most strategical points of the Solar System, with large human communities living there, and a New Economy, based on the Space Resources. But, as much important of the outside effects of a WSP, are the effects of such a Program on Earth: how will be the Earth populations involved in the WSP? Will it be only a matter of the Science with upper case "S" and of few privileged Companies, or will it be a formidable chance to help developing the underpriviliged? Will the WSP trace options to act also on the other Frontiers of our world? For instance, Thierry Gaudin spoke about the cities on the sea (also the Millennial Project deals with this). But we must be aware that our only real richness is our working power: the WSP can be a formidable impulse to the development in general terms, to take a word of organization to all the under-used intelligences of the world.