Ten long trips around the sun since I last saw that smile, but only joy and thankfulness that on a tiny world in the vastness, for a couple of moments in the immensity of time, we were one.

And what greater might do we possess as human beings than our capacity to question and to learn?

It takes a fearless, unflinching love and deep humility to accept the universe as it is. The most effective way he knew to accomplish that, the most powerful tool at his disposal, was the scientific method, which over time winnows out deception. It can't give you absolute truth because science is a permanent revolution, always subject to revision, but it can give you successive approximations of reality.

The aspirations of democracy are based on the notion of an informed citizenry, capable of making wise decisions. The choices we are asked to make become increasingly complex. They require the longer-term thinking and greater tolerance for ambiguity that science fosters. The new economy is predicated on a continuous pipeline of scientific and technological innovation. It can not exist without workers and consumers who are mathematically and scientifically literate.

In the way that scepticism is sometimes applied to issues of public concern, there is a tendency to belittle, to condescend, to ignore the fact that, deluded or not, supporters of superstition and pseudoscience are human beings with real feelings, who, like the sceptics, are trying to figure out how the world works and what our role in it might be. Their motives are in many cases consonant with science. If their culture has not given them all the tools they need to pursue this great quest, let us temper our criticism with kindness. None of us comes fully equipped.