There are many hypotheses in physics of almost comparable brillance and elegance that have been rejected because they did not survive such a confrontation with experiment. In my view, the human condition would be greatly improved if such confrontations and willingness to reject hypotheses were a regular part of our social, political, economic, religious and cultural lives.

I’m struck again by the irony that spaceflight-conceived in the cauldron of nationalist rivalries and hatreds-brings with it a stunning transnational vision. You spend even a little time contemplating the Earth from orbit and the most deeply engrained nationalisms begin to erode. They seem the squabbles of mites on a plum.

The Earth is a place. It is by no means the only place. It is not even a typical place.

Cleverly designed experiments are the key.

We are, in the most profound sense, children of the Cosmos.

We are rare and precious because we are alive, because we can think as well as we can. We are privileged to influence and perhaps control our future. I believe we have an obligation to fight for life on Earth - not just for ourselves, but for all those, humans and others, who came before us, and to whom we are beholden, and for all those who, if we are wise enough, will come after.

The usual rejoinder to someone who says 'They laughed at Columbus, they laughed at Galileo' is to say 'But they also laughed at Bozo the Clown'.