There is no record of Einstein saying this — not in his essays, letters or interviews, and Einstein quotation collections flag it as misattributed. Known print appearances date from decades after his 1955 death, with no source attached.
Where the line actually comes from
Nobody has ever produced a source. Searches through Einstein's published essays, lectures, letters and recorded interviews have turned up nothing resembling the line, and authoritative compilations of his quotations mark it as not by him. The sentence simply appears in print already wearing his name, decades after he died.
Earlier variants of the joke circulated attached to other names before settling on Einstein — a familiar migration pattern. Funny lines drift toward the most quotable authority available, and on the modern internet Einstein is the default genius, the way Abraham Lincoln and Mark Twain were the default authorities of earlier eras.
Part of why the attribution sticks is that it is plausible. Einstein genuinely was funny — his documented wit was dry and self-deprecating — and the joke sounds like something he might have said between lectures. Plausibility is the strongest glue misattributions have; the fake quotes that survive are the ones the great man could plausibly have said.
What it originally meant
Judged purely as a joke, it is well-made. The setup borrows the language of cosmology — infinities, the universe — and the twist replaces physics with misanthropy, ending on the elegant shrug of “I'm not sure about the universe,” which smuggles doubt about the infinity of everything into the punchline.
It is a joke about proportion, really: the claim is that human foolishness out-scales even the stars. Nothing in it contradicts anything Einstein actually wrote, and his documented sense of humour was similarly dry. The problem is not the joke's quality — it is that its humour is borrowed from a man who never wrote it.
How it gets used today — and why that’s off
Its main modern job is insult laundering. Quoted in an argument, it calls your opponents stupid while renting the authority of the smartest man in history to do it. The speaker gets to feel like Einstein for free.
It also gets pasted into presentations and memes as a fact about humanity. The misattribution is not harmless there: quoting it to an audience that checks sources costs credibility, and repeating fake quotes trains everyone reading to trust quotation less.
An honest way to quote it
If you want the joke, tell it honestly: “There's an old quip that the universe and human stupidity are both infinite — and they're not sure about the universe.” Anonymous attribution keeps the punchline and loses the fraud.
If you want real, documented Einstein, there is plenty — “Imagination is more important than knowledge,” from a 1929 interview, is genuine and better sourced than the fake ever was. A real Einstein line outperforms a fake one the moment anyone checks.
People also ask
Did Einstein say “two things are infinite”?
There is no documented source. The line appears in print decades after his 1955 death, and Einstein quotation scholars classify it as misattributed.
Why is it attributed to Einstein?
Funny and clever lines drift toward the most quotable authority available. Einstein is the internet's default genius, so jokes that need a genius's name end up wearing his.
What did Einstein actually say that was funny?
His documented wit was dry and often self-deprecating. Genuinely sourced lines, such as “imagination is more important than knowledge” (1929), show the real man was quotable enough without the fakes.
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