There seems to have been many sides to Albert Einstein. The German-born theoretical physicist who developed the theory of relativity, one of the pillars of modern physics, is best known for the equation E = mc2.

‘Relativity’
When: To June 18
Where: Northlight Theatre, 9501 Skokie Blvd., Skokie
Tickets: $30-$81
Info: northlight.org

But look deeper into his professional and personal life and Einstein becomes a complicated figure and not simply the fun-loving scientist depicted in that ubiquitous photograph where he’s sticking his tongue out at the camera. In recent years, numerous books about Einstein have delved not only into his scientific theories but also his tangled personal life.

One of these Walter Isaacson’s best-selling biography “Einstein, His Life and Universe,” is the basis for the engrossing 10-part “Genius,” now airing on the National Geographic Channel. Another Michele Zackheim’s “Einstein’s Daughter: The Search for Lieserl,” is the inspiration behind Mark St. Germain’s play, “Relativity,” which delves into the mystery of what became of Einstein’s only daughter.

St. Germain has long been interested in the idea of goodness and greatness and how the two play off each other. Can someone who is thought of as great and brilliant man also be a good man?

“It started out as an abstract thought,” St. Germain explains. “When I started reading about Einstein who was fascinating and brilliant, I started to see all of these inconsistencies in his character. He always came across so well in public and was so beloved but when you read statements from him like ‘Every relationship is a chain around my neck,’ it’s very unsettling.”

As St. Germain dug into his research, one fact grabbed his attention and wouldn’t let go: Einstein and his first wife Mileva Maric had a daughter, Lieserl whom he or his wife never mentioned. To this day there are no hard facts as to what happened to the child.

Mike Nussbaum and Katherine Keberlein star in “Relativity” at Northlight Theatre. | MICHAEL BROSILOW

“Relativity,” now at Northlight Theatre in a National New Play Network rolling world premiere, stars Chicago’s favorite 93-year-old actor Mike Nussbaum as Einstein, with Ann Whitney as his housekeeper and Katherine Keberlein as the reporter who comes around asking questions. Northlight artistic director BJ Jones directs.  St. Germain was impressed with Nussbaum’s performance in another of his play’s “Freud’s Last Session,” and wrote “Relativity” with the actor in mind.

“Mike was the first person I sent it to,” St. Germain recalls. “So it’s a real treat to finally have him in the play.” (The play, in an earlier form, has had several productions around the country, including one at TheaterWorks in Hartford, CT., starring Richard Dreyfuss as Einstein.)

“Mark has written a fascinating play, one that creates a lot of conflict,” says Nussbaum, who is letting his gray hair grow wild to mimic Einstein’s look. “I’ve done a lot of reading about Einstein, and in the play he is not the benign, loving, wise, witty character that we remember. The play reveals moments when his anger and his insistence on his work took primacy over everything.”

As St. Germain researched Einstein’s life, he realized the price the scientist paid in his personal life for his fierce concentration and dedication to his work. He also became convinced that Einstein did have a daughter and that she did live. He takes creative license to develop his own theory of her life in “Relativity.” (Zackheim believes Lieserl contracted scarlet fever and passed away.)

“Michele and I would have fun arguments about our theories,” St. Germain said. “There are all kinds of stories about what happened to Lieserl. Everything from being raised in a nunnery to living in California with no idea she was Einstein’s daughter.”

What convinced St. Germain that Lieserl may have lived, possibly brought up by another family, was a fact he found through his research.

“At one point in Einstein’s life a colleague reported a woman was making the rounds of London’s social circuit claiming to be his daughter,” St. Germain explains adding, “Now if she was dead, Einstein would have simply ignored it, but he hired a detective. So for me this was evidence that there’s a possibility she was alive.”

For the 93-year-old Nussbaum, an amazing 50 push-ups a day help keep him in shape and sharp on stage. He says he loves the challenge of a new audience every night.

“I sit in the wings before a show just to hear the hum of the audience. It reminds me of the potential excitement that crosses the stage from them to me and me to them. I love the excitement of live theater and the audience keeps me energized.”

St. Germain, who is currently at work on an adaptation of John Updike’s novel “Gertrude and Claudius,” a prequel to “Hamlet,” says he continues to find historical figures fascinating.

“There are so many great men who have this dark side. In order to achieve greatness, they block out parts of their personality. But then you have someone like Abraham Lincoln who always left the door open so his children could run in and see him during cabinet meetings. These personalities intrigue me. We think we know them but we really don’t.”

Mary Houlihan is a local freelance writer.