In June 1945, the 27-year-old physicist Richard Feynman lost his wife, Arline Feynman, to tuberculosis. Only 25 years old, she was Richard's high-school sweetheart. And yet she was much more. As Lawrence Krauss writes in 2012 biography on Feynman:

Richard and Arline were soul mates. They were not clones of each other, but symbiotic opposites - each completed the other. Arline admired Richard's obvious scientific brilliance, and Richard clearly adored the fact that she loved and understood things he could barely appreciate at the time. But what they shared, most of all, was a love of life and a spirit of adventure.

During their years together, Richard and Arline exchanged frequent letters, many now collected in the volume, Perfectly Reasonable Deviations from the Beaten Track. But none is more poignant than the one written to Arline sixteen months after her death. Still despairing, still lost, Feynman wrote a cathartic letter that was sealed and never opened until his own death in 1988. Deeply touching, it reads as follows:

October 17, 1946

D’Arline,

I adore you, sweetheart.

I know how much you like to hear that — but I don't only write it because you like it — I write it because it makes me warm all over inside to write it to you.

It is such a terribly long time since I last wrote to you — almost two years but I know you'll excuse me because you understand how I am, stubborn and realistic; and I thought there was no sense to writing.

But now I know my darling wife that it is right to do what I have delayed in doing, and that I have done so much in the past. I want to tell you I love you. I want to love you. I always will love you.

I find it hard to understand in my mind what it means to love you after you are dead — but I still want to comfort and take care of you — and I want you to love me and care for me. I want to have problems to discuss with you — I want to do little projects with you. I never thought until just now that we can do that. What should we do. We started to learn to make clothes together — or learn Chinese — or getting a movie projector. Can't I do something now? No. I am alone without you and you were the "idea-woman" and general instigator of all our wild adventures.

When you were sick you worried because you could not give me something that you wanted to and thought I needed. You needn’t have worried. Just as I told you then there was no real need because I loved you in so many ways so much. And now it is clearly even more true — you can give me nothing now yet I love you so that you stand in my way of loving anyone else — but I want you to stand there. You, dead, are so much better than anyone else alive.

I know you will assure me that I am foolish and that you want me to have full happiness and don't want to be in my way. I'll bet you are surprised that I don't even have a girlfriend (except you, sweetheart) after two years. But you can't help it, darling, nor can I — I don't understand it, for I have met many girls and very nice ones and I don't want to remain alone — but in two or three meetings they all seem ashes. You only are left to me. You are real.

My darling wife, I do adore you.

I love my wife. My wife is dead.

Rich.

PS Please excuse my not mailing this — but I don't know your new address.