Carbon dioxide is unusual because it doesn't go through the usual three phases of matter, from solid to liquid to gas, but it goes straight from solid to gas. The volume of the gas is much greater than the volume of the solid. When a solid turns into a gas, we say it sublimes. The process is sublimation.

I don't believe in regretting - one should try to move on. My mum was good at that. She was deeply in love with my father, and he died when I was nine. She remarried, and her second husband died, too. I saw the grieving process she went through. My mother had this way of moving on. It was a fine trait.

The trouble with climate change is it's an extraordinarily diverse and complex issue, but for example if the BBC would let me make some of the programmes I'd like to make on climate change, I bet you there would be a change of emphasis.

Surgeons always underestimate the pain and disability involved in what they do to people.

Although religion might be useful in developing a solid moral framework - and enforcing it - we can quite easily develop moral intuitions without relying on religion.

The disturbed individual who believes himself to be Christ, or to receive messages from God, is something of a cliche in our society. Ever since Sigmund Freud, many people have associated religiosity with neurosis and mental illness.

You can't be judgmental about babies. They are all have different needs. I was left with an enduring hatred of cheese because it was forced down me when I was young.