Collective human actions are transforming, even ravaging, the biosphere - perhaps irreversibly - through global warming and loss of biodiversity.

All space projects push the frontiers of technology and are drivers of innovation.

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.

Scientists surely have a special responsibility. It is their ideas that form the basis of new technology. They should not be indifferent to the fruits of their ideas. They should forgo experiments that are risky or unethical.

I think all countries need to aim to cut the CO2 emissions per person, taking account of externalities like imports and exports.

Science is a part of culture. Indeed, it is the only truly global culture because protons and proteins are the same all over the world, and it's the one culture we can all share.

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.