“Forty years will pass in the course of a few minutes,” Hong (Brian Lee Huynh) says toward the end of The Light Years, a magical new play by Hannah Bos and Paul Thureen that is currently running at Playwrights Horizons.  Hong immigrated to the United States to work for the engineer Hillary (Erik Lochtefeld), who has been commissioned by the actor and impresario Steele MacKaye (Rocco Sisto) to build an elaborate, lightbulb-bedecked moon for his play about Christopher Columbus, which will premiere at the four hundredth anniversary of the explorer’s arrival in the United States during the Chicago World’s Fair in 1893.

Four decades later, the home occupied by Hillary and his wife, Adeline (Aya Cash), will be rented by the jingle composer Lou (Ken Barnett) and his wife Ruth (also Ms. Cash), who bears a strong resemblance to Adeline.  Despite the presence of a new World’s Fair, Lou has trouble finding work and is forced to continually defer his son Charlie’s (Graydon Peter Yosowitz) wish to visit the fair and take the Skyride.  The Light Years shuffles back and forth between these two stories, thus Hong’s line about compacted time refers both to the play itself and our own tendency to live in memory.

The cast here is terrific: Mr. Lochtefeld, Mr. Barnett, and Ms. Cash carry their characters’ burdens with a wonderful subtlety, tonally matching a play that treats its swerves and surprises with uncommon understatement.  Steele MacKaye comes from a demonstrative school of acting, and Mr. Sisto gleefully obliges by imbuing nearly all his words and actions with the kind of bellowing gravitas that evokes Orson Welles at his histrionic best.  When he first meets Adeline, he booms with both melodrama and sincerity, “Your husband speaks of you daily, and I’ve told him many times he has rendered such an image of you in my mind’s eye that if I wasn’t so happily entangled within the ties of love myself … I should plot to steal you away from him.”  Never has the theft of a spouse appeared so cordial.

Still, it is the script by Ms. Bos and Mr. Thureen that makes The Light Years one the best new plays in quite some time.  The action beautifully evokes the period, the excitement and the trepidation about what the future will bring, and many moments onstage are accented by a “Silent Unfolding Announcer,” a scrolling apparatus invented by the real-life Steele MacKaye that offers the sort of intertitles that would soon be associated with silent film.  (The first commercial movie theater debuted at the fair.)  The two have clearly done their homework: fair highlights such as pancakes and the battle between Edison and Tesla also make cameos throughout the play.  But what struck me most was the delicate depiction of the passage of time, and the sense of haunting created by the back-and-forth between 1893 and 1933.  Hillary says proudly of his moon, “This is something that will be known forever.”  In fact, it will never be hung in the doomed Spectatorium Theater.  The Light Years reminds us that our own lives will be informed by a future of which we are unaware, and more often than not, these lives will be lived as cycles of melancholy and disappointment.  Still, there is a beauty to be found in that melancholy.

The Light Years runs through April 2nd at Playwrights Horizons.  416 W. 42nd Street  New York, NY.  1 hour 55 minutes.  No intermission.