— Martin J. Rees, libro Our Final Hour
Our Final Hour: A Scientist's Warning (2003) <!-- | date = 2003-03-18
Contesto: Once the threshold is crossed when there is a self-sustaining level of life in space, then life's long-range future will be secure irrespective of any of the risks on Earth (with the single exception of the catastrophic destruction of space itself). Will this happen before our technical civilisation disintegrates, leaving this as a might-have-been? Will the self-sustaining space communities be established before a catastrophe sets back the prospect of any such enterprise, perhaps foreclosing it for ever? We live at what could be a defining moment for the cosmos, not just for our Earth.