[michael_nielsen]

Feynman said the first thing seriously in a superb in-depth interview with the historian Charles Weiner. The second is a facetious quote from someone else (Murray Gell-Mann, who seemed rather irritated with the question, as I recall).

As far as I can tell, most theoretical physicists: (a) can do a surprising amount in their head, especially when deeply familiar with a problem; and (b) have their ability greatly expanded when working on paper or with some other external aid (whiteboard etc).

Source: worked as a theoretical physicist for ~13 years. On a few occasions I solved publishable problems in my head, though usually after a lot of immersion in conversation and on paper first, just getting familiar with the problem, but (superficially) making little progress. More often, though, serious work involved a lot of exploration using external aids. I haven't done a poll of other theoretical physicists, but based on informal conversations wouldn't be surprised if many have a similar experience, with considerable variation.

Update: the Gell-Mann comment is here: https://www.nytimes.com/1992/09/20/magazine/part-showman-all... My interpretation is that he's being facetious, but with a grain of truth - a habit research students sometimes need to break is when they rely too much on methods as a crutch. Sometimes, no method will work, you just need to think really hard and try lots of things.

[anon_123g987]

Thanks for the correction! I also think that both "in the head" and "on paper" work is necessary, of course, and I also think that Feynman did both, like everyone else. But we know that he often presented himself in the way the Gell-Mann quote describes him; he purposefully cultivated his image as a genius who can solve complicated problems in his head in seconds (if I recall correctly, he "pre-solved" problems, waited until the problems came up in a conversation and came up with the memorized solution after five seconds of "thinking").

[hilbert42]

Thanks for that link, the fuller Gell-Mann quote was good to note but that article by Gleick is so much more.

Gleick provides us with a vivid portrait of Feynman's character and his descriptions of what Feynman's contemporaries thought of him not only round out that portrait but also reveal parts of their characters. And he masterly weaves all that into the then - and still current - physics zeitgeist.

I'd not seen that article previously but I've Gleick's book Genius so much of it was familiar to me, but having not read it in years his NYT article was a wonderful short refresher.

Gleick's an excellent science writer, I'd highly recommended that those reading and or commenting here read the article.

[gaze]

Steve Girvin says that to solve a problem you need to know the answer before writing anything down.