Mindy Newell: The Grandfather Paradox Gives Me A Headache

Is time travel possible? Can history be changed?

Imagine you had a time machine and went back into the past. While there you meet and accidentally kill your grandfather before he got married and had kids, one of them your own parent. Then you automatically wipe out your own existence, right? But if you have never existed, then how do you go back in time and kill Grandpa?

This is called The Grandfather Paradox, and it is probably the most famous example of what is termed a temporal paradox. This scenario was first described by science fiction writer Rene Barjavel in his 1943 book, Le Voyager Imprudent – translated, The Imprudent Traveler. (I didn’t know that, either. I looked it up.)

The Grandfather Paradox is not exclusive to killing Gramps. The entire plotline of Back To Future depends on Marty, um, “pre”-uniting his parents after he inadvertently interfered with his father, George McFly, being the one nursed by his mom (thus kindling their romance) after dad fell out of the tree into the path of a passing car. Because George did not marry Lorraine Baines, Marty cannot exist, and we see this principle at work as his first-born brother and then second-born sister disappear from a family photograph, until, at the prom (and the penultimate scene), Marty starts to fade away as he plays guitar. But just in time, George (who has saved Lorraine from being mauled – raped? – by Biff Tannen, the town bully) dances with her – they kiss, and suddenly Marty springs back to life and his brother and sister reappear in the photograph.

Marty inadvertently changes history in other ways, because in his efforts to bring George and Lorraine together, he has given his father new confidence in himself. When Marty returns to 1985, he discovers that his sad sack family are now examples of the American success story. George is no longer a stumbling failure, but a successful science fiction writer. Lorraine is no longer a slovenly, overweight, complaining, straight-laced mom, and they are a happy, openly loving couple. His brother and sister are happy, too, and Marty discovers his parents have bought him his long-dreamed of truck.

Is time travel possible? Can history be changed?

Another example of the Grandfather Paradox is Star Trek’s “The City On The Edge Of Forever.” Written by Harlan Ellison, and winner of the 1968 Hugo award for Best Dramatic Presentation, City is the story of Jim Kirk and Edith Keeler, a social worker in Depression-era New York City.

It begins with the Enterprise investigating “disturbances in time” emanating from an unknown planet. Dr. Leonard “Bones” McCoy, sick and paranoid from an accidental overdose of cordrazine, transports down to the planet, and a landing party follows him, led by Kirk and Spock. While searching for Bones, the team discovers the Guardian of Forever, a self-aware portal into the time stream. Still delusional, Bones jumps into the portal. Uhura tells Kirk that she was talking to the Enterprise, and now, suddenly, there is nothing, not even static. The Guardian tells them that the past has changed and the Enterprise, indeed the entire Federation, no longer exists. The landing party is stranded and alone in a universe that is no longer theirs.

Kirk and Spock determine that McCoy somehow changed history, and they realize they must follow Bones and stop him from doing whatever it is he did that changed history.

The portal lands them, as I said, in a New York City circa 1933. Kirk and Spock meet Edith Keeler, who runs a soup kitchen for the down-and-out. While Spock puts together a rudimentary tricorder (“I am endeavoring, ma’am, to construct a mnemonic memory circuit using stone knives and bear skins.”), Jim and Edith fall in love. And meanwhile, unknown to both men, Bones is being nursed back to health in Edith’s soup kitchen.

Spock discovers that Edith is a focal point in time. His machine shows two possible futures for her. Either Edith, a determined pacifist, leads a movement that delays America’s entry into World War II, which allows the Nazis time to perfect the atom bomb and win the war, or she dies in 1933 in a car accident. Kirk realizes that Edith Keeler, the woman he loves, must die.

Jim and Edith are on their way to a movie – “A Clark Gable movie. Don’t you know? You know, Dr. McCoy said…” – Jim tells Edith to “stay right there” and runs back across the street to the mission, calling for Spock. Spock comes out, and so does Bones. Edith, curious and watching this reunion, starts to cross the street; her eyes on the three men, she doesn’t see the truck. Kirk instinctively moves, but Spock stops him, and instead of saving Edith, Kirk restrains McCoy from acting as well. Edith is killed. “Do you know what you just did?” Bones says in disbelief. Spock answers for Kirk. “He knows, Doctor. He knows.”

With Edith’s death, history is back on track, and the three men are returned to the Guardian’s planet. Uhura tells them that the Enterprise is there and awaiting instructions.

“Let’s get the hell out of here.”

Is time travel possible? Can history be changed?

The Novikov Self-Consistency Principle, theorized by Russian physicist Igor Dmitriyevich Novikov and American theoretical physicist Kip S. Thorne’s work on wormholes and other astronomical data – can the laws of physics actually permit space and time to be “multiply connected,” as Thorne put it, so that time travel through machines or via wormholes is actually possible? – both rely on the same hypothesis, i.e.,

there is no danger of temporal paradoxes because anything that a time traveler does in the past is (was?) an established and predetermined part of history.

In “Assignment: Earth,” a second season episode of Star Trek: TOS, Kirk and Spock discover that the Enterprise and its crew were actually part of the events of 1968 which led to the failed launch of a nuclear warhead platform into orbit by the United States. If they hadn’t travelled back in time, if they hadn’t interfered, then history (from the 23^rd century perspective) would have been changed. But history couldn’t be changed, according to the Novikov Self-Consistency Principle and Thorne’s hypothesis; the Enterprise’s presence was an established and predetermined historical fact.

Can history be changed? Is time travel possible?

In 1937, physicist Willen Jacob Van Strickum proposed an idea he called the “Closed Timelike Curve.” He theorized that if time is linear, you should be able to fold it in on itself, making time travel possible between any points touching each other.

This was the basis of Quantum Leap, although Dr. Sam Beckett, the time traveler in the series, used the term “string theory.”

From the episode “Future Boy”:

Moe: Time is like a piece of string. One end of the string is birth, the other is death. If you can put them together, then your life is a loop.

Al: Hey! Sam, that’s your theory!

Moe: If I can travel fast enough along the loop, I will eventually end up back at the beginning of my life.

Al: He – He’s got it!

Sam: Well, let me ask you what would happen if you would ball the string, right? And then each day of your life would touch another day. And then, you could travel from one place on the string to another, thus enabling you to move back and forth within your own lifetime. Maybe.

Moe: That’s it! That’s it! Then I could actually…

Sam: Quantum leap.

So, according to Quantum Leap, you can time travel, at least within your own lifetime.

But can history be changed?

In Quantum Leap, the only way that Sam Beckett could move on and try to find his way home was to “put right what once went wrong.” Which of course he did. So Sam was changing history.

Or was he simply creating alternate histories?

Alternate histories that led to whole new universes.

Parallel universes.

Parallel universes within the multiverse.

To Be Continued…

TUESDAY MORNING: Emily S. Whitten

TUESDAY AFTERNOON: Michael Davis