I posted this on Slashdot today

(Read here the very interesting discussion that took place.)

Earth is not a sustainable system. The Sun is getting brighter; in less than a billion years it will be too intense for Earth's oceans to continue to exist. Like Mars did in ages past, Earth is going to lose its water. On the other side of the balance, Earth's interior is cooling, geological activity is diminishing, and so volcanic replenishment of the atmosphere is slowly winding down. *These* are the long term environmental trends; at such time scales it is clear that no amount of "recycling for a better world" will make a difference.

It is also clear, at such time scales, that the entirety of life on Earth will go extinct if life does not branch out off the planet. That means launching equipment and people to build massive, robust infrastructure. Crops. Botanical gardens. Zoos.

Except that space is HARD. It's really expensive to get there and it is a high-vacuum radiation hell. It would take a long time and an expensive, sustained effort to construct off-planet habitats - a *tremendous* amount of effort and money before there is any payoff at all.

On the other hand, for example the asteroid 16 Psyche contains enough metal to construct a solid cylinder three miles in diameter stretching from here to the Moon. Or cover North America in a layer 900 feet thick. The resources available to an outer space civilization are great enough to insure that if outer space habitats do reach the point where they can expand and grow, the payoff would be big enough to sustain life past the death of the Sun.

We are half-way through the era of animals on Earth. There have been at least a half dozen mass extinctions since animals first started evolving a half-billion years ago; there will be more. The glaciers have grown and retreated dozens of times over the last two million years; they will return. Yellowstone is going to explode again. And again. And again. Time is not unlimited.

But we have time. Abundant fossil fuels, and the internet - we are right now living in the decades of maximum wealth. At some point, within a few decades, we will either run out of fuel or we will run out of the capacity to sink carbon emissions. When this happens, it will mean the end of a way of life. Maximum wealth *right now* means that *right now* is the best and possibly the only time to lift off. Life on Earth only gets one pass at the fossil fuel heritage; if the next extinction event brings us to a place where launching is not possible, life will have missed its chance.

I am a realist. I'm certain that outer space settlements will not solve our current growth vs. environment problems - the payoff will come way too late for that. None of our current issues will be solved, or even mitigated, by vigorous and immediate launches into the great expanse. Nonetheless, if DNA is to avoid extinction we need to start moving now as rapidly as we can. Nothing else matters.

The cocoon we call Earth is going to wither; whether or not she gives birth before she dies is entirely in the hands of human civilization. Our civilization, right now, we're the only chance. Sure, leaving Eden is a horrible burden. Suck it up. We have to go. Now.

Or, we can continue toasting marshmallows at the planet's one-time-only oil burning party.