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.

One of the computer models for a four degree temperature rise would give rise to a 10 degree temperature rise in Africa. And bear in mind also that in the depth of an ice age the mean temperature drop compared to the present was five degrees.

It's better to read first rate science fiction than second rate science-it's a lot more fun, and no more likely to be wrong.

Crucial to science education is hands-on involvement: showing, not just telling; real experiments and field trips and not just "virtual reality".

To ensure continuing prosperity in the global economy, nothing is more important than the development and application of knowledge and skills.

God invented space so that not everything had to happen in Princeton.

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