Nobel physicist Richard Feynman wrote hundreds of inspiring letters, often to strangers. Below, his daughter Michelle Feynman introduces an edited selection - published here for the first time

Guardian

As I grew older, I saw only what my father didn't know. He would ask me questions whose answers I found painfully obvious, such as, "Hey, where do we keep the spoons around here?" I discovered the truth in my teens: my father had interesting, profound ideas, and was highly engaging to listen to.

Here, more objectively, are the basic facts of his life. Richard Phillips Feynman was born in New York City in 1918 and grew up in Far Rockaway, Queens. He attended the Massachusetts Institute of Technology as an undergraduate, and he received his PhD from Princeton University. In 1942 he married his high school sweetheart, Arline Greenbaum, despite the fact that she was ill with TB. That same year Richard was asked to join the Manhattan Project; he accepted and went on to become a group leader at Los Alamos, New Mexico. Arline died in 1945. After the war, he became a professor of theoretical physics at Cornell University, later joining the California Institute of Technology. A brief marriage in the early Fifties did not work out, but he married my mother, Gweneth Howarth, in 1960. My brother, Carl, was born in 1962, and I was adopted in 1968.

His most public achievement came in 1965, when he won the Nobel prize in physics, sharing it with Julian Schwinger and Shin'ichiro Tomonaga for their independent work in quantum electrodynamics. In 1986, he worked on the commission investigating the explosion of the Challenger space shuttle. He died in 1988 after a long battle with abdominal cancer.

He was an adventurer who made a hobby of cracking safes while working on the atomic bomb, who played bongo drums for a San Francisco ballet. Never condescending when he explained things, he had a knack for breaking problems down to a small, comprehensible scale. "OK, say the Earth is this apple," he would begin.

That he wrote so many letters, both to scientists and to other people, surprised me. A few of his friends were also surprised, as my father had a reputation in the physics community for not writing letters. Why had he spent so much time corresponding with the general public and not with his fellow scientists? I believe the answer has to do with my father's great love for teaching. In an article on education he wrote for Caltech's Engineering and Science he stated: "The problem is clear language. The desire is to have the idea clearly communicated to the other person." I think this statement in part explains why he was such an effective and prodigious communicator. Again, his own words, this time from a letter to a young student seeking his advice, explain it best: "You cannot develop a personality with physics alone, the rest of life must be worked in."

After reading through hundreds of letters, I found a compass for them in his notes for the brief speech he delivered at the Nobel banquet: "The work I have done has already been adequately rewarded and recognised. Imagination reaches out repeatedly trying to achieve some higher level of understanding, until suddenly I find myself momentarily alone before one new corner of nature's pattern of beauty, and true majesty revealed. That was my reward ... Then, having fashioned tools to make access easier to the new level, I see these tools used by other men straining their imaginations against further mysteries beyond. There are my votes of recognition.

"Then comes the prize, and the deluge of messages ... from friends, from relatives, from students, from former teachers, from scientific colleagues, from total strangers ... But, in each I saw the same two common elements. I saw joy; and I saw affection. The prize was a signal to permit them to express, and me to learn about, their feelings. Each joy, though a transient thrill, repeated in so many places amounts to a considerable sum of human happiness. And, each note of affection released thus one upon another has permitted me to realise a depth of love for my friends and acquaintances, which I had never felt so poignantly before. For this, I thank Alfred Nobel and the many who worked so hard to carry out his wishes ... For I understand at last — such things provide entrance to the heart. Used by a wise and peaceful people they can generate good feeling, even love, among men ... For that lesson, I thank you."

• To order Don't You Have Time to Think (rrp £20) for £18 with free UK p&p, call the Guardian book service on 0870 836 0875 or visit guardian.co.uk/bookshop

On the bomb

The world's first atomic bomb was detonated in the New Mexico desert on July 16, 1945.

To his mother, Lucille Feynman, August 9, 1945.

Dear Mom,

Now I am in Cincinnati, waiting for a plane out. There is lots in the newspaper about the atomic bomb now, so I know some things I can tell you about. I got in Sunday near noon (Albuquerque) and was met by an army car and taken to the site, arriving three o'clock. We were all scheduled to leave on buses at 5pm to go south, about 100 miles south of Albuquerque. It was scheduled for 4am Monday morning — weather permitting.

Interesting event en route: three busloads of anxious scientists stopped, waited at the side of the road while one especially anxious scientist (not me) got off and went into the bushes.

We eventually arrived at our vantage point on a ridge overlooking a great bowl of desert at the centre of which, 20 miles away, was our gadget. It was mounted on a hundred-foot steel tower but we knew where to look because of searchlights, which were shining on it and alternately on the clouds — the weather looked bad.

Dark glasses were distributed. I looked at my flashlight through them and could hardly see it. Then everyone sat down to eat and wait.

We had two radios — one to listen to reports from a plane in the air. In a few minutes of listening (around 5am) I heard them say "the shot will be at 5.30, it is now minus 30 minutes." Everyone set their watches and crowded around the radio. "Minus 10 minutes" — then "minus three minutes." People scattered over the hill so they wouldn't be in each other's way. They took out their dark glasses. Some even put on suntan oil.

A bunch of crazy optimists, I thought. I had helped to figure out how powerful the bomb should be. I knew how many things had to go just right to get a really big blast and I wanted a full solid experience if it did go — so I was going to look at it directly — no dark glasses for me. I did get behind the windshield of the weapons carrier which had the radio on it, just so the ultraviolet light, if any, wouldn't hurt my eyes. I heard a voice of the man at my right — "it ought to be in 15 seconds." I got behind my glass, stared at the spot. Would everything go right?

I was blinded by a terrific silver-white flash — I had to look away. Wherever I looked an enormous purple splotch appeared: it was just as bright when I closed my eyes. "That," said my scientific brain to my befuddled one, "is an after-image caused by looking at a bright light — it is not the bomb you are looking at." So I turned back to look at the bomb.

The sky was lit up with a bright yellow light — the earth appeared white. The yellow gradually became darker, turning gradually to orange. In the sky I saw white clouds from above the gadget caused by the sudden expansion following the blast wave — the expansion cools the air and fog clouds form — we had expected this. The orange got deeper, but where the gadget was, it was still bright, a bright orange, flaming ball-like mass. This started to rise, leaving a column of smoke behind, below looking much like the stem of a mushroom. The orange mass continued to rise, the orange to fade and flicker. A great ball of smoke and flame three miles across it was, like a great oil fire billowing and churning, now black smoke, now orange flame. Soon the orange died out and only churning smoke, but this was enveloped in a wonderful purple glow.

Another after-image I thought, but on closing my eyes it did disappear, and appeared on opening them again. Others said they saw it too, probably caused by ionised air produced in the great heat. Gradually this disappeared, the ball of smoke rising majestically slowly upward, leaving a trail of dust and smoke.

Then suddenly there was a sharp loud crack followed by resounding thunder. "What was that?" cried the man at my left, a war department representative. "That is the thing," I yelled back. He had forgotten that sound takes much longer than light to travel, and what we had seen so far was a silent picture — the soundtrack for which was one minute and 40 seconds late. I knew then that the bomb was a success — big as it appeared at 20 miles, I was still more impressed with the solid sound of the thunder echoing in the hills.

We jumped up and down, we screamed, we ran around slapping each other on the back, shaking hands, congratulating each other, guessing at the energy released — it had worked as well as anyone could have dared to expect. Everything was perfect but the aim — the next one would be aimed for Japan, not New Mexico. We finally got into the buses and started home. We asked one of the bus drivers on the way what his impression of the explosion was. "Well, I don't know — you see I never had an opportunity to see one of these things go off before."

Later pictures and observations showed that an area almost one mile in diameter was covered by a green glasslike glaze formed by melting the sand at the surface. The sand is brown, the glaze is bright green. It is a wonderful sight from the air.

Well, when we got back I had the fun of telling lots of people about it. The fellows working for me all gathered in the hall with open mouths, while I told them. They were all proud as hell of what they had done. Maybe we can end the war soon. It was too much to hope. We went back to work.

Some expeditions went out to the mountains and saw the sky light up so brightly and worried for a moment that we had miscalculated and all the experimenters six miles away were cooked. It was seen in three states — over 200 miles in all directions. The head of the Alamogordo air base had to put out a statement that they accidentally blew up an ammunition dump.

• A number of Feynman's letters were from correspondents asking him if he had any regrets over his work on the bomb.

To Malcolm Gibson, age 15, December 29, 1972

I did work on the atomic bomb. My major reason was concern that the Nazis would make it first and conquer the world.

To Mark Minguillon, April 23, 1976

I see nothing wrong with nuclear power except questions of the possibility of explosions, sabotage, stealing fuel to make bombs, leaking stored radioactive spent rods, etc. But all these are technical or engineering questions, about which we can do a great deal. So I think the risks can be controlled and that nuclear power, if economical, should be developed. Problems about the atomic bomb and the future are much more complicated. Well, I guess that means you win your debate — but that doesn't mean we know what's true. Just because Feynman says he is pro-nuclear power, isn't any argument at all worth paying attention to because I can tell you (for I know) that Feynman really doesn't know what he is talking about when he speaks of such things. He knows about other things (maybe). Don't pay attention to "authorities", think for yourself.

On science

A former student wrote to extend his congratulations on the Nobel. Feynman responded, asking what he was now doing. The response, "studying the Coherence theory with some application to the propagation of electromagnetic waves through turbulent atmosphere ... a humble and down-to-the-earth type of problem".

To Koichi Mano, February 3 1966

I was very happy to hear from you, and that you have such a position in the Research Laboratories. Unfortunately your letter made me unhappy for you seem to be truly sad. The worthwhile problems are the ones you can really solve or help solve, the ones you can really contribute something to. A problem is grand in science if it lies before us unsolved and we see some way for us to make a little headway into it. I would advise you to take even simpler, or as you say, humbler, problems until you find some you can really solve easily, no matter how trivial. You will get the pleasure of success, and of helping your fellow man, even if it is only to answer a question in the mind of a colleague less able than you. You must not take away from yourself these pleasures because you have some erroneous idea of what is worthwhile. No problem is too small or too trivial if we can really do something about it. You say you are a nameless man. You are not to your wife and to your child. You will not long remain so to your immediate colleagues if you can answer their simple questions when they come into your office.

You are not nameless to me. Do not remain nameless to yourself — it is too sad a way to be. Know your place in the world and evaluate yourself fairly, not in terms of the naive ideals of your own youth, nor in terms of what you erroneously imagine your teacher's ideals are.

To Tord Pramberg, January 4, 1967

The fact that I beat a drum has nothing to do with the fact that I do theoretical physics. Theoretical physics is a human endeavour, one of the higher developments of human beings — and this perpetual desire to prove that people who do it are human by showing that they do other things that a few other humans do (like playing bongo drums) is insulting to me. I am human enough to tell you to go to hell.

On the Nobel prize

To Sandra Drachester, date unknown

I was delighted too when I heard about the Nobel Prize, thinking as you did that my bongo playing was at last recognised. Imagine my chagrin when I realised that there had been some mistake — they cited some marks I made on paper some 15 years ago — and not one word about percussion technique. I know you share in my disappointment.

On religion

Author Tina Levitan wrote to Feynman requesting a biographical sketch for her book-in-progress, The Laureates: Jewish winners of the Nobel prize.

To Tina Levitan, February 7, 1967

In your letter you express the theory that people of Jewish origin have inherited their valuable hereditary elements from their people. It is quite certain that many things are inherited but it is evil and dangerous to maintain, in these days of little knowledge of these matters, that there is a true Jewish race or specific Jewish hereditary character ...

At almost 13 I dropped out of Sunday school just before confirmation because of differences in religious views but mainly because I suddenly saw that the picture of Jewish history that we were learning, of a marvellous and talented people surrounded by dull and evil strangers was far from the truth.The error of anti-Semitism is not that the Jews are not really bad after all, but that evil, stupidity and grossness is not a monopoly of the Jewish people but a universal characteristic of mankind in general. Most non-Jewish people in America today have understood that.The error of pro-Semitism is not that the Jewish people or Jewish heritage is not really good, but rather the error is that intelligence, good will, and kindness is not, thank God, a monopoly of the Jewish people but a universal characteristic of mankind in general.

Therefore, you see at 13 I was not only converted to other religious views but I also stopped believing that the Jewish people are in any way "the chosen people".

On science writing

Early in 1967, while both visiting the University of Chicago, James Watson gave Feynman a copy of the manuscript for the book that would later be published as The Double Helix. They had met when Watson visited Caltech to give lectures. This was Feynman's reaction.

To James Watson, February 10, 1967

Don't let anybody criticise that book who hasn't read it through to the end. Its apparent minor faults and petty gossipy incidents fall into place as deeply meaningful and vitally necessary to your work (the book — the literary work I mean) as one comes to the end. From the irregular trivia of ordinary life mixed with a bit of scientific doodling and failure, to the intense dramatic concentration as one closes in on the truth and the final elation (plus with gradually decreasing frequency, the sudden sharp pangs of doubt) — that is how science is done. I recognise my own experiences with discovery beautifully (and perhaps for the first time!) described as the book nears its close. There it is utterly accurate.

And the entire "novel" has a master plot and a deep unanswered human question at the end: is the sudden transformation of all the relevant scientific characters from petty people to great and selfless men because they see together a beautiful corner of nature unveiled and forget themselves in the presence of the wonder? Or is it because our writer suddenly sees all his characters in a new and generous light because he has achieved success and confidence in his work, and himself? Don't try to resolve it. Leave it that way. Publish with as little change as possible. The people who say "that is not how science is done" are wrong.

In the early parts you describe the impression by one nervous young man imputing motives (possibly entirely erroneous) on how the science is done by the men around him. But when you describe what went on in your head as the truth haltingly staggers upon you and passes on, finally fully recognised, you are describing how science is done. I know, for I have had the same beautiful and frightening experience.

On teaching

A high school teacher in Venezuela sought help on a student's question: when a man lowers a weight from overhead to the ground, the law of conservation on energy says the weight must do work on his muscles. But experience says this can't happen. "The issue became a debate," Garcia wrote, "taking us nowhere; my class lost its prestige."

To Armando Garcia J, December 11, 1985

There is no harm in doubt and scepticism, for it is through these that new discoveries are made. The doubts can, and therefore must, be tested and resolved by experiment. It is true that energy is a scalar quantity, like temperature, that has no direction. But measured from some arbitrary level it can be either plus or minus — surely the changes have a sign. In lifting a weight the weight's energy is increased (and the rest of the world's decreased) and in lowering it, the signs are reversed.

I judge from your letter that in Venezuela you are teased badly if you are a professor and say you don't know or are not sure. I am glad that I am not so teased because I am sure of nothing, and find myself having to say "I don't know" very often. After all, I was born not knowing and have only had a little time to change that here and there. It is fun to find things you thought you knew, and then to discover you didn't really understand it after all.

On loss

Arline Feynman died on June 16, 1945. The paper on which this letter was written is well worn, and it appears as though he reread it often.

To Arline Feynman, October 17, 1946

D'Arline,

I adore you, sweetheart ... 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 what I have done so much in the past. I want to tell you I 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 to stand there.

I'll bet that you are surprised that I don't even have a girlfriend 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 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.