Particle first confirmed in 1955 at Berkeley crossword clue
17 Across · WSJ Crossword, September 10, 2026 · 10 letters
Explanation
The answer to “Particle first confirmed in 1955 at Berkeley” is ANTIPROTON. It appears as 17 Across in the Wall Street Journal crossword of September 10, 2026, a Thursday puzzle titled “What Are You Waiting For?” by Mike Shenk, and it fills 10 squares running left to right from row 3, column 1 of the 15×15 grid.
The clue is a straightforward definition, so the answer is a direct synonym or a factual match for the words as written. The entry begins with A and ends with N, and contains 4 vowels and 6 consonants. If you are working from the crossings, two or three confirmed letters from the Down entries should be enough to lock it in. Thursday puzzles lean harder on misdirection, so expect the rest of this grid to be pitched at the same level.
Past appearances
ANTIPROTON has not appeared as an answer in any other WSJ puzzle in our index, which runs from May 2026 onward. It will be listed here the next time it turns up.