All the atoms we are made of are forged from hydrogen in stars that died and exploded before our solar system formed. So if you are romantic, you can say we are literally stardust. If you are less romantic, you can say we're the nuclear waste from fuel that makes stars shine.

Absence of evidence is not evidence of absence.

We should all oppose - as Darwin did - views manifestly in conflict with the evidence, such as creationism... But we shouldn't set up this debate as 'religion v science'; instead we should strive for peaceful coexistence with at least the less dogmatic strands of mainstream religions, which number many excellent scientists among their adherents.

The carbon dioxide concentration in the atmosphere is measured. It's uncontroversial. It's going up. We know that has a tendency to warm the atmosphere and we should be worried about that.

Devastation could arise insidiously, rather than suddenly, through unsustainable pressure on energy supplies, food, water and other natural resources. Indeed, these pressures are the prime 'threats without enemies' that confront us.

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. Will this happen before our technological civilization 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 forever? We live at what could be a defining moment for the cosmos.

The 'clean energy' challenge deserves a commitment akin to the Manhattan project or the Apollo moon landing.