Check in at Lincoln Center Theater's Vivian Beaumont Theatre Tuesday through Saturday and you'll get singing and dancing, courtesy of the hit musical Contact. But buy a ticket on Sunday or Monday, and the world of the mind takes over; Alan Alda will star as Nobel Prize-winning professor of physics Richard Feynman in Peter Parnell's QED, beginning performance Oct. 21. Official opening is Nov. 18, for a limited run through Dec. 17. (The original first preview of Sept. 30 and opening night of Oct. 22 was pushed back at the Sept. 11 terrorist attacks.)

QED was once called Tuva or Bust! and is based on the book that goes by the latter title, written by Feynman and Ralph Leighton. It traces the two men's friendship from the first discovery of a mutual passion for drumming to Feynman's many wild tales of safe cracking at Los Alamos, sharing gambling tips with Nick the Greek, joking with Einstein and finding the frozen "O Rings," the cause of the Challenger disaster.

Kellie Overbey plays Feynman's student. The show played the Mark Taper Forum in spring 2001.

Alda last appeared on Broadway in Yasmina Reza's Art. Other Broadway credits include the original The Apple Tree and Neil Simon's Jake's Women. He was nominated for a Tony Award for both roles. Overbey has starred on Broadway in Buried Child and Present Laughter and Off-Broadway in Betty's Summer Vacation (as Betty) and The Hologram Theory.

QED has a set by Ralph Funicello, costumes by Marianna Elliott, lighting by D, Martyn Bookwalter and sound by Jon Gottlieb. Tickets are $55 and $35. Call Tele-Charge at (212) 239-6200.

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Other physicists who have recently graced the New York Stage include those in Broadway's Tony-winning Copenhagen and Off-Broadway's The Wax.