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#Did Einstein say - if you can - t explain it simply you don - t understand it well enough? Skeptics Stack Exchange

Did Einstein say if you can t explain it simply you don t understand it well enough ?

The short answer is: probably no he didn't say this quote. There is no citation supporting this claim.

Another unsourced variants:

You do not really understand something unless you can explain it to your grandmother.

If you can't explain something to a six-year-old, you really don't understand it yourself.

To de Broglie, Einstein revealed an instinctive reason for his inability to accept the purely statistical interpretation of wave mechanics. It was a reason which linked him with Rutherford, who used to state that "it should be possible to explain the laws of physics to a barmaid ." Einstein, having a final discussion with de Broglie on the platform of the Gare du Nord in Paris, whence they had traveled from Brussels to attend the Fresnel centenary celebrations, said "that all physical theories, their mathematical expressions apart ought to lend themselves to so simple a description 'that even a child could understand them.' "