Dark digits
In April this year, astronomers working on the Event Horizon Telescope captured the first direct images of a black hole and its “shadow” – the glowing ring of gas and dust trapped in a disc around them. Inspired by this revolutionary discovery, Physics World reader Michael Metcalf has created a variant of a traditional sudoku so that it begins with a central shadow surrounded by a bright region. Test your mettle over the holidays. We will share the solution next February.
Each number from 1 to 16 must appear once in each row, column and 4 × 4 box, as well as in each of the two diagonals (X-sudoku).
Michael Metcalf retired from CERN a long time ago and now lives in Berlin. His most recent book (with John Reid and Malcolm Cohen) is Modern Fortran Explained (2018 Oxford University Press), e-mail michaelmetcalf@compuserve.com