February 12, 2002 To the Editor: A Feb. 9 letter writer seems upset that I regard Michael Frayn's play "Copenhagen" as fiction. But though it is a gripping drama, it is still a work of fiction. That is why it got a Tony, not a medal of science. And now that we at last have Niels Bohr's own, striking account of the events with which the play tries to struggle, Mr. Frayn's version of Werner Heisenberg is more fictitious than ever - for example, when he says on stage, "I wasn't trying to build a bomb." GERALD HOLTON Cambridge, Mass., Feb. 9, 2002 The writer is emeritus professor of physics and history of science at Harvard University. Copyright 2002 The New York Times Company