Marie Curie

Greer Garson

Prof. Pierre Curie

Walter Pidgeon

Eugene Curie

Henry Travers

David Le Gros

Robert Walker

Professor Jean Perot

Albert Bassermann

Irene at Age Five

Margaret O'Brien

Reporter

Van Johnson

Lord Kelvin

C. Aubrey Smith

Madame Eugene Curie

May Whitty

Madame Eugene Curie

Dame May Whitty

President of University

Victor Francen

Dr. Becquerel

Reginald Owen

Madame Perot

Elsa Bassermann

Mme. Perot

Elsa Basserman

Narration Spoken By (voice)

James Hilton

Professor Roget (uncredited)

Lumsden Hare

Tall Woman (uncredited)

Mariska Aldrich

Board Member (uncredited)

Charles Trowbridge

Man at Accident (uncredited)

Tony Carson

Board Member (uncredited)

Edward Fielding

Swedish Queen (uncredited)

Ruth Cherrington

Board Member (uncredited)

James Kirkwood

Board Member (uncredited)

Nestor Eristoff

Lecturer (voice) (uncredited)

Ray Collins

Professor (uncredited)

Guy D'Ennery

President of Businessman's Board (uncredited)

Moroni Olsen

Cart Driver (uncredited)

George Davis

Dr. Bladh (uncredited)

Alan Napier

Madame Michaud (uncredited)

Almira Sessions

Professor (uncredited)

Harold De Becker

Assistant Tailor (uncredited)

Franz Dorfler

Nurse

Dorothy Gilmore

Eve at 18 Months (uncredited)

Gigi Perreau

Woman at Accident (uncredited)

Justine Duney

Man at Accident (uncredited)

Tay Dunn

Cart Driver (uncredited)

William Edmunds

King Oscar (uncredited)

Wyndham Standing

Man at Accident (uncredited)

Al Ferguson

Prof. Constant (voice) (uncredited)

Howard Freeman

Proud Papa

Michael Visaroff

Perot Granddaughter (uncredited)

Linda Lee Gates

Singing Professor (uncredited)

George Meader

Perot Granddaughter (uncredited)

Marie Louise Gates

Lucille (uncredited)

Lisa Golm

Seamstress (uncredited)

Ilka Grüning

Driver (uncredited)

Ray Teal

Wedding Guest (uncredited)

Noel Mills

Son (uncredited)

Teddy Infuhr

Woman at Accident (uncredited)

Isabel La Mal

Photographer (uncredited)

Leo Mostovoy

Master Michaud

Dickie Myers

Bit Part (uncredited)

Gene Lockhart

Monsieur Michaud (uncredited)

Francis Pierlot

Businessman (uncredited)

Miles Mander

Jewelry Salesman (uncredited)

Marek Windheim

Master Michaud (uncredited)

Dickie Meyers

Doctor (uncredited)

Eustace Wyatt

Woman at Accident (uncredited)

María Pagés

Isabelle Lamore

Businessman

Frederic Worlock

Woman at Accident (uncredited)

Nita Pike

Nurse (uncredited)

Dorothy Raye

Businessman (uncredited)

Arthur Shields