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Who really said it

Physics is like sex: sure, it may give some practical results, but that's not why we do it

Not Richard Feynman — no source has ever surfaced Unknown Unattributed · in print by 2000
Disputed Rights unconfirmed

The line is repeated everywhere as Feynman’s and rests on nothing. It appears in none of his books and in no biography of him, and the earliest printed use Wikiquote’s editors could find is a 2000 popular-science paperback by the ABC science broadcaster Robyn Williams — which introduces it immediately after a saying Einstein also never said. Two unsourced quips in one sentence is the signature of a quote that was assembled rather than recorded.

Last verified 10 Aug 2026 · how we verify · spot an error?

For presentations

Put it on a slide

Disputed credit — copy with the correction

“Physics is like sex: sure, it may give some practical results, but that's not why we do it” No source has ever been found for this line. It is in none of Feynman's books or biographies; the oldest printing anyone has located is Robyn Williams, Scary Monsters and Bright Ideas (2000), p. 44, which quotes it beside a saying Einstein never said. Traced by Quotle.info.

The slide-ready mistake: crediting this to Richard Feynman. Use the credit shown above instead.

Can you use it?

We couldn’t verify where this wording comes from, so there’s no rights status to give. Safe to present as an unverified or anonymous line — just don’t assert a specific author or source.

Image direction — grounded in this quote’s real context; paste into your image tool

In context

Evoking the themes of knowledge, work and purpose. Theme: "Physics is like sex: sure, it may give some practical results, but that's not why we do it". Atmospheric and restrained, cinematic directional light, a muted period-appropriate palette, fine grain and texture. Compose with generous empty space for the quote and a small credit line. No lettering in the image itself.

Minimalist

Minimalist editorial slide for the quote "Physics is like sex: sure, it may give some practical results, but that's not why we do it". Clean background, a single muted accent color, generous negative space, subtle paper or linen texture, no literal illustration — let the words carry it. Reserve clear space for a serif quote and a small credit line. No lettering in the image itself.

Provenance

Where the trail runs out

Credited to
Richard Feynman — no source located
Earliest printed use found
Scary Monsters and Bright Ideas (2000), p. 44
That book
Robyn Williams, ABC science broadcaster; Sydney: University of New South Wales Press, 2000
In Feynman’s own books
Not present

Einstein said, ‘You do not really understand something unless you can explain it to your grandmother’. Richard Feynman added, ‘Physics is like sex: sure, it may give some practical results, but that’s not why we do it’. Scary Monsters and Bright Ideas, 2000, p. 44

This is how the passage is transcribed in the disputed section of Feynman’s Wikiquote entry. We were not able to read page 44 ourselves — the Internet Archive’s copy of the book is lending-restricted — so the wording and page here are Wikiquote’s, reported as theirs rather than confirmed against the printed page.

Wikiquote — the disputed entry, with the 2000 citation

How we traced it

  • The disputed section of Feynman’s Wikiquote entry states plainly that the line ‘does not appear to be from any of his books or cited in a biography’, and that a Google Books search puts the oldest book citing ‘physics is like sex’ at Scary Monsters and Bright Ideas (2000) by the science broadcaster Robyn Williams the disputed entry ↗.
  • The company it keeps is the strongest signal against it. On that page the quip is introduced directly after ‘You do not really understand something unless you can explain it to your grandmother’, credited to Einstein — a saying Einstein is not documented as having said. Wikiquote’s own reasoning runs the same way: given the first is not genuine, the second is unlikely to be the reasoning ↗.
  • We also checked Quote Investigator, which has traced a large share of the fake Feynman and Einstein canon: it has no article on this line, so no specialist has pushed the trail back beyond the 2000 book or turned up a Feynman source. The nearest thing to a positive case appears on the Wikiquote talk page, where an editor recalls Leonard Susskind attributing a cruder version to Feynman in a lecture series — and says outright that they cannot place which lecture, so it cannot be sourced either the talk-page discussion ↗.
  • The book itself is real and datable: the Internet Archive holds Scary Monsters and Bright Ideas, University of New South Wales Press, 2000. It is lending-restricted, so we could not open page 44 to confirm the transcription above the edition record ↗.

No rights status is asserted here, because the wording has no identified author or first publication. Copyright terms run from a work and its date, and this line has neither — the earliest printed use anyone has found is a 2000 book quoting it as somebody else’s. Treat it as unsourced rather than as free to reuse.

Rights status is our research, not legal advice — and copyright varies by country and edition. For commercial or published use, confirm with the rightsholder. See terms.

Fact-check

Often misattributed

This is one of the most-shared physics quips on the internet, and one of the least documented. The case against it is not that someone else said it — it is that nobody can show anyone saying it.

Credited everywhere, sourced nowhere no source located

Wikiquote’s disputed section states the line ‘does not appear to be from any of his books or cited in a biography’. No lecture transcript, essay or interview has been produced for it the disputed entry ↗.

The oldest printing found, not the origin early user

Robyn Williams’s book quotes the line as Feynman’s rather than claiming it, so it marks where the paper trail currently begins, not where the sentence came from. Wikiquote reached it by a Google Books search, and no earlier printing has been produced since the citation ↗.

The other half of the same passage, also unsourced no source located

The sentence immediately before it on page 44 credits Einstein with ‘you do not really understand something unless you can explain it to your grandmother’, which is itself not documented in Einstein. A pairing of two undocumented quips is the shape of received wisdom, not of a record.

Nobody has produced a source. The line is absent from Feynman’s books, lectures and biographies, and the trail ends at a 2000 popular-science paperback that was already quoting it as his Wikiquote, disputed ↗.

Context

Why it sounds like him

The joke is well made. It defends curiosity against the demand that research justify itself by its applications, and it does so in the register Feynman actually used — deflating, slightly rude, on the side of pleasure. He genuinely did argue that the point of physics is the finding out; The Pleasure of Finding Things Out is a title he put his name to.

That is exactly why the attribution is hard to dislodge. The line is not out of character, it is too much in character — a quip built to sound like Feynman, attached to him at some point before 2000, and repeated ever since by people with no more evidence than the fact that it fits.

The case against it is not that someone else said it. It is that nobody can show anyone saying it.

What has and has not been checked

Not found: any Feynman book, lecture transcript, interview or biography containing the line.

Found: Scary Monsters and Bright Ideas (2000), p. 44, quoting it as his — the oldest printing Wikiquote’s editors located via Google Books.

Also unsourced: the Einstein ‘explain it to your grandmother’ line printed beside it on the same page.

No Quote Investigator article exists for this quip, so no specialist has traced it further back.

Not established: who wrote it, or when it was first attached to Feynman.

Explore

Filed under

More provenance-checked quotes on the same theme, each with its reuse status.

Knowledge Work Purpose

Go further

Dig deeper

Trusted places to keep pulling the thread — primary archives, fact-checks, and scholarship. We show how we used each one before you leave.

Richard Feynman — disputed and attributeden.wikiquote.org

The entry that debunks this line and names the 2000 book as the oldest citation found.
Talk:Richard Feynman — sourcing discussionen.wikiquote.org

Editors working through which Feynman one-liners have documents behind them; this one does not.
Scary Monsters and Bright Ideas (2000)archive.org

The edition record for the book at the end of the trail — UNSW Press, 2000, lending-restricted.
Robyn Williamsen.wikipedia.org

Who he is: British-Australian science broadcaster, host of The Science Show on ABC Radio National since 1975.
Richard Feynmanen.wikipedia.org

The physicist the line is pinned on, and the published work it is absent from.

Popularly credited author

Why it gets pinned on Feynman

Richard Feynman

1918–1988 · theoretical physicist

Richard Feynman (1918–1988) shared the 1965 Nobel Prize in Physics for quantum electrodynamics and cultivated a public character — bongo player, safecracker, teller of stories against himself — that made him the natural home for any joke a physicist might plausibly tell. He wrote a great deal, and much of it is funny. None of it contains this line.

For writers & researchers

Cite this

Earliest documented printing (per Wikiquote)

Williams, Robyn. Scary Monsters and Bright Ideas. Sydney: University of New South Wales Press, 2000, p. 44 — cited by Wikiquote as the oldest book found quoting the line, which it credits to Richard Feynman. No source in Feynman’s own books, lectures or biographies has been located.

This verification page

Quotle.info. “Who really said ‘Physics is like sex: sure, it may give some practical results, but that's not why we do it’?” Last verified 10 Aug 2026. https://quotle.info/who-said/physics-is-like-sex-sure-it-may-give-some-practical-results/

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