Tyrannosaurus rex, an animal to spark the imagination for all of us. What kind of an animal was it? What did it look like? How did it live? Now, scie… - David Attenborough

Its heart that in flight contracted a thousand times a minute, slows until its beat is virtually undetectable. Its body temperature falls dramatically, and its breathing seems to cease altogether. [...] It's hibernating; but for a hummingbird, winter comes 365 times a year.

In moments of great grief, that's where you look and immerse yourself. You realise you are not immortal, you are not a god, you are part of the natural world and you come to accept that.

Immensely powerful though we are today, it's equally clear that we're going to be even more powerful tomorrow. And what's more there will be greater compulsion upon us to use our power as the number of human beings on Earth increases still further. Clearly we could devastate the world. […] As far as we know, the Earth is the only place in the universe where there is life. Its continued survival now rests in our hands.