Before we invented civilization our ancestors lived mainly in the open out under the sky. Before we devised artificial lights and atmospheric pollution and modern forms of nocturnal entertainment we watched the stars. There were practical calendar reasons of course but there was more to it than that. Even today the most jaded city dweller can be unexpectedly moved upon encountering a clear night sky studded with thousands of twinkling stars. When it happens to me after all these years it still takes my breath away.

Science is based on experiment, on a willingness to challenge old dogma, on an openness to see the universe as it really is. Accordingly, science sometimes requires courage - at the very least the courage to question the conventional wisdom.

You're an interesting species, an interesting mix. You're capable of such beautiful dreams and such horrible nightmares. You feel so lost, so cut off, so alone, only you're not. See, in all our searching, the only thing we've found that makes the emptiness bearable is each other.

Books permit us to voyage through time, to tap the wisdom of our ancestors.

It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring.

'In his celebrated book, 'On Liberty', the English philosopher John Stuart Mill argued that silencing an opinion is "a peculiar evil." If the opinion is right, we are robbed of the "opportunity of exchanging error for truth"; and if it's wrong, we are deprived of a deeper understanding of the truth in its "collision with error." If we know only our own side of the argument, we hardly know even that: it becomes stale, soon learned by rote, untested, a pallid and lifeless truth.'

When permitted to listen to alternative opinions and engage in substantive debate, people have been known to change their minds. It can happen.