I had the good fortune to meet Stephen Hawking for the first time in 1982. This was to be the beginning of a long and vibrant scientific interaction and friendship.  I was fresh out of graduate school and Stephen could still speak in a growly voice. It took me a few days to understand what he was saying but I managed to do it. And there was a lot to say!  Stephen twirled around my Princeton apartment with son Timothy on the footrest of his wheelchair. Probably dangerous but they both had a blast.  This was a harbinger of the Stephen who loved to dance and go clubbing that I got to know later.  He never lost his sense of fun or humor to the very end.

What distinguished Stephen from the rest of our pack when I first met him, and ever since, was not his insane brilliance or his consummate knowledge of every last detail of Einstein’s theory of general relativity. It was his passion in the search for the truth. This helped keep him alive and in good spirits through unimaginable and unrelenting physical challenges. Einstein once said “Of all the communities available to us, there is not one I would want to devote myself to except for the society of the true seekers, which has very few living members at any one time.” Einstein would have counted Stephen as a member.

Stephen’s greatest work was his 1974 discovery that quantum black holes are not empty as Einstein thought, but store an enormous number of gigabytes, for which he gave a precise and famous formula. His argument is so simple and elegant that few have ever doubted it. Indeed, finding and describing the elusive quantum chips that store these gigabytes has become a holy grail of modern physics.  The absence of any obvious quantum chips is often referred to as the `black hole information paradox’. It now appears likely that we will have to rethink the whole structure of the universe around us to answer Stephen’s question.

In the last four decades Stephen pursued many blind alleys in attempts to resolve this paradox.  Unlike many, Stephen will vigorously pursue a blind alley and then, free of scientific pride, let go of it when it appears not to lead anywhere.  As a scientist it doesn’t matter how many blind alleys you go up. What matters is how many through roads you discover, of which Stephen discovered plenty. At one point, Stephen concluded that, since there are no obvious quantum chips in sight, black holes destroy rather than store information. This view, which eventually revealed itself as a blind alley, he graciously abandoned in a 1997 bet -  a complete reversal of a 32-year-old belief. He had no fear of being wrong and changing his mind, and importantly he knew when it was time to do so.

I began an intense and ongoing collaboration with him during a retreat at Great Brampton House in 2015. He, Malcolm Perry and I discovered a subtle but potentially far-reaching idea about where the quantum chips might be hidden. With characteristic and unmitigated enthusiasm, Stephen announced to the world that the three of us had solved the paradox. Maybe we did, but we have certainly not yet dotted all the i’s and crossed all the t’s, and there is plenty of room for everything to fall apart before that long job is finished.

That is how it is in science. What has transpired over the last few years is a wonderful and inspiring collaboration, with regular meetings all over the world, two published papers and a third—Stephen’s last—still in the works. It has been a highlight of my life to work with Stephen. His love for physics is never out of sight. Even in his last bedridden hours, he was eager for the latest detailed updates, and a never-ending source of pithy comments which cut to the heart of the matter. When his doctors let him type, talk, or meet with us for a few minutes, it was always about the latest physics issues.

Stephen had an incredible joie de vivre. From strange mountaintop trains in Wales to meeting with the Pope in the Vatican to sketchy bars in Brussels to places I can’t mention, we were always having fun in between our sessions of avid calculations. One might think that the wheelchair and surrounding battalion of (wonderful) nurses would put a damper on the fun. This was never the case. I will miss the fun almost as much as the physics. But it is hard to say where one began and the other ended.

Stephen’s contribution to science will be remembered forever.

I expect that much sooner, in the coming decades, his famous black hole information paradox will be definitively solved, by us or someone else. Along with it will come a whole new view of the universe as radical as the ones ushered in by quantum mechanics or relativity. I can’t bear the thought that he won’t be here to hear about it. 

Stephen touched and inspired many people around the world, perhaps especially the lucky few of us who got to know him well. He was a truly a great man. We are all the lesser for his loss.