Want to "tesser" across the universe? Instantaneous travel between planets and stars is not as easy as it looks in Madeleine L'Engle's 1962 book "A Wrinkle in Time," whose film adaptation opens in U.S. theaters today (March 9). Physicists, however, say tessering might be possible — as long as it follows physics rules first laid down by Albert Einstein a century ago. [Is Time Travel Possible?]
In the plot of "Wrinkle," children Meg, Charles Wallace and Calvin (with the help of the powerful beings Mrs. Whatsit, Mrs. Who and Mrs. Which) tesser to different planets, in search of somebody very important to the kids. A famous illustration and description from the book explains tessering by showing an ant marching along a thread; that is intended to represent an ant traveling between two points as it normally does.
However, if the thread is folded, according to the book, the ant has to travel a much smaller distance, and the time it takes for the ant to travel is reduced. Extrapolating that idea to how humans move through space, "tessering" is a form of traveling — of wrinkling space and time — to get to faraway locations in a very short time. [Super-Fast Space Travel Propulsion Ideas (Images)]
The book uses a fifth-dimensional device called a "tesseract" to whisk people from place to place. But — here's where it gets confusing — a tesseract in real life has a very different meaning. "It's a four-dimensional field — that's it. It's what a cube looks like in four dimensions," said Eric W. Davis, the chief science officer of the research foundation EarthTech International's Institute for Advanced Studies at Austin, in an interview with Space.com.
Davis acknowledged that imagining a three-dimensional cube in four dimensions is difficult. (It gets worse: String theory suggests our universe might have 10 or more dimensions, but that's another story.) But fast travel across time and space is similarly tough for physicists to imagine. Interstellar craft are a common plot device in science-fiction franchises ranging from "Star Wars" to "Star Trek" to "Interstellar." That's science fiction, however.
How you would travel that quickly in real life is still a puzzle to physicists, but L'Engle's book has influenced some researchers. Patrick Johnson, an assistant physics professor at Georgetown University, first read the book — a signed copy from the author originally given to his father, as it turned out — when he was a preteen. "The thing that stuck with me was the tesseract. That was something I thought about throughout my life, ever since. I have not been able to tesser, but it's been a thought that has been present in my mind," he told Space.com.
Tesseracts and wormholes
Some of today's physicists do see a link between the fictional "tessering" and real-life theories about fast travel across the universe. "'A Wrinkle in Time' was one of my favorite books when I was a kid," Stephen Hsu, a physicist and vice-president for research and graduate studies at Michigan State University, told Space.com in an email. He said that from the description L'Engle gave, tessering "seems similar to transiting a wormhole."
A wormhole is a theoretical link between two spots. It's supposed to provide a way to get around the normal limitations to the speed of travel. The famous equation E=mc2, first proposed by Albert Einstein under the theory of relativity, deals with the relationship between energy and mass, and comes with strict stipulations. For instance, nothing can travel faster than light, because the object's mass would become infinite.
Wormholes might use black holes to work. Black holes are singularities caused by the collapse of massive stars. They warp space and time around them, causing weird time-dilation effects for anybody who gets too close. Under the right circumstances, perhaps we could morph the black holes into time travel devices. That would, however, take a lot of work: The physics says it would require a supreme amount of energy to keep a wormhole open, which is both an engineering and a physics problem.
"It's not something that [SpaceX founder] Elon Musk is going to release in a week. He has made great advancements in space travel, but if that [wormhole travel] happens during his lifetime, I will be genuinely surprised," said Johnson, who wrote "The Physics of Star Wars: The Science Behind a Galaxy Far, Far Away" (Adams Media, 2017).
Johnson pointed out that our understanding of wormholes could change as even more-exotic objects are discovered in the universe. He said that, for all he knows, tomorrow LIGO — the massive gravitational wave detector, which receives signals from huge events such as black holes merging — may find a better source for fast travel.
"It would be like a black hole, but way more controllable, and that would be the best way to create wormholes," Johnson said. "There could be things we don't know about yet that could be the best way to do" fast travel.
Across the universe
It's unclear if black holes would be the best raw material for a wormhole. One problem is that wormholes need to be threaded with negative mass, and this is "not a thing in our universe," Paul Sutter, an astrophysicist at The Ohio State University, told Space.com. Even if we were to use another device — such as an infinitely long cylinder rotating very fast, which is theoretically a good wormhole candidate — "that's kind of hard to find in our universe," he added.
"Either no such device exists, or we don't understand how to use it, or we haven't found the right device yet," Sutter said of using wormholes for traveling. Even if we could build and hold open a wormhole, new paradoxes pop into play, he added. In theory, one could accelerate one end of the wormhole to the speed of light, while keeping the other end still, Sutter said; in doing so, one could go through the wormhole and end up in the past due to the rules of general relativity. In other words, the wormhole would provide a form of time travel.
But time travel brings more problems, such as the famous "grandfather paradox," which asks what would happen to the person who killed his or her grandfather during a time-travel event. Would the time-traveler die, because he or she had never been born, or would some alternate scenario happen?
"That opens up a whole gigantic causality can of worms," said Sutter. "Then, you can influence events after they have happened, which does not appear to be allowed in our universe."
The mathematics of general relativity are also limited when it comes to time travel, particularly for someone picking a place to travel to. Sutter said it's easiest to construct a time machine if you remain at the same location while traveling in time. To open it up to another location "becomes very tricky, and the mathematics are not clear," he added.
While L'Engle's tessering is hard to explain in physics terms, Johnson — who read a signed copy decades ago — said he still finds her explanations a marvel. "Now that I'm a physicist looking back, her book was published in the early 1960s. At that point, we were still figuring out Einstein's theory of relativity," Johnson said. But L'Engle tried to incorporate it into her fiction nonetheless: "Not even all scientists were in agreement that it was a true, accurate theory. So, for her to come up with this book was amazing."