This is an important day for Ronald L. Mallett, a retired professor of theoretical physics at the University of Connecticut who is trying to invent a machine that will allow him to travel back in time to reunite with his dead father. Of course, this is an important day for many of us. Today, after all, is Oct. 21, 2015, the date on which Marty McFly and Emmett Lathrop “Doc” Brown, Ph.D., emerged from a time machine of their own into a future world of hoverboards, flying cars and people wearing two ties at once for some reason.
For many of us, this is an opportunity to take stock of the "Back to the Future" franchise’s various predictions and think about the ways in which they have -- or, in most cases, haven’t -- come true.
Yes, there are hoverboards. No, people don’t have fax machines in their bathrooms. And with the Cubs down 3-0 in their pennant series against the Mets, it looks like it will be at least another year before they win their first World Series since Theodore Roosevelt was president.
But how about time travel itself? Mallett, who considers "Back to the Future" one of his favorite films, acknowledges that the idea of getting into a souped-up DeLorean and zooming into the future is the sort of fantasy that remains relegated to the imaginations of movie producers. But he insists that time travel could, in fact, become a reality, though perhaps on a very limited scale. Whether or not he succeeds, the author of Time Traveler: A Scientist's Personal Mission to Make Time Travel a Reality may one day follow “Doc” to Hollywood fame; Spike Lee has reportedly bought the rights to his life story.
Not surprisingly, many of Mallett’s peers do not share his belief that we are anywhere close to building a machine that allows us to travel through time. As Sean Carroll, a theoretical physicist at Caltech, put it in an email to The Huffington Post, “Unfortunately, 'building a time machine' here on Earth is not realistic.”
“To the best of our current understanding, we simply can't build time machines at all,” Carroll continued. “But one thing is clear: if we could build a time machine, it would require an enormously strong gravitational field, similar to that you would experience right next to a black hole. Nothing we can imagine making in a laboratory comes anywhere close.
Still, Mallett is determined to pursue his dream.
Below, he shares his thoughts on the realities of time travel, his favorite time-travel films, and his reception among his fellow physicists. The interview has been condensed and edited for clarity.
"Back to the Future Part II" came out in 1989. How close do you think we now are to being able to travel through time, and do you think this is something that people will ever be able to do?
It's important to realize that the real science of time travel is based on Einstein's theories of relativity. In a nutshell, Einstein's special theory of relativity, published in 1905, states that time slows down for moving clocks. In other words, the faster a clock moves the more time slows down. Your heart is a clock, so this would mean that your heart rate will slow down the faster that you move. So if you were able to travel fast enough, you would not age at the same rate as everyone else, and this would allow you to arrive in the future younger than everyone else. In other words, this is time travel to the future. This form of time travel has actually been achieved on a limited scale using fast-moving planes and high-speed subatomic particles.
An experiment was done at the U.S. Naval Observatory in 1971 using two atomic clocks. One of clocks was kept at rest at the Naval Observatory and the other clock was flown around the world at the speed of sound. When the two clocks were compared at the end of the flight, it was found that the clock that had been on the passenger jet had actually slowed down compared to the clock at rest. This means that the plane and passengers had flown fractions of a second to the future. The effect depends on speed. For rockets traveling close to the speed of light, the effect would be more dramatic. An astronaut traveling close to the speed of light returns to earth only a few years older and finds they have arrived decades into the Earth's future.
Einstein's general theory of relativity, published in 1915, says that time can be altered by gravity. In particular, Einstein showed that the stronger gravity is, the more time slows down. This has actually been observed. Clocks at the surface of the earth where gravity is strong run slower than clocks at high altitude aboard satellites where gravity is weak. This effect of gravity on time has practical consequences for the GPS units in our cars.
How did you get interested in time travel?
My interest in time travel began with a personal tragedy. I was the oldest of four children and grew up in the Bronx. My father, Boyd Mallett, was a television repairman. For me the sun rose and set on him. He was the center of my life. He spent a lot of time with me giving me scientific gifts like a gyroscope and a crystal radio set. My father looked like a healthy man but he had a very weak heart. He died of a massive heart attack at 33 years old. I was 10 years old and his death devastated my world. I was very depressed. Fortunately, I loved to read, and about a year after he died, when I was 11, I came across a Classics Illustrated edition of H.G. Wells' famous classic, The Time Machine. The quote at the very beginning of the story changed everything for me. It said, "Scientific people know very well that time is just a kind of space and we can move forward and backward in time just as we can in space." It was at that moment that I decided that I would have to figure out how to build a time machine so that I could see my father again and perhaps save his life.
Has your understanding of the science changed over the years?
After my father died, the family was very poor and I used to go to the Salvation Army for paperback books, which only cost 5 cents. On one of my visits, when I was 12, I came across a popular level book entitled The Universe and Dr. Einstein by Lincoln Barnett. The book implied that Einstein said that time is not fixed, time could be altered. That made me realize that there was real science behind the possibility of time travel. That's when I also began to realize that I would have to understand Einstein's work in order to understand how to build a time machine.
I've read that you consider the lecture where you announced your interest in time travel as akin to coming "out of the closet." How did your colleagues react when they learned of your interest?
It's important to point out that my work is squarely based on Einstein's general theory of relativity. In Einstein's theory, light as well as matter can create gravity. My breakthrough was to realize that if gravity can alter time, and light can create gravity, then light can alter time. This leads to the possibility of a time machine based on laser light. This breakthrough was published in 2000 in a professional physics journal. My first presentation at a professional physics conference occurred in 2002, at a meeting of the International Association for Relativistic Dynamics. I felt confident but nervous about presenting my work. However, one of of the most respected physicists in attendance was Bryce DeWitt, the director of the Center for Relativity at the University of Texas at Austin, who made a very complementary remark at the end of my talk. His remark is still one of the high points of my professional career. DeWitt said, “I don't know if you'll see your father again but he would have been proud of you."
Do you think attitudes have changed at all since then?
The attitude of the scientific community towards time travel to future and past has changed dramatically. In part, I believe this is due to the fact that the present generation of physicists have grown up with shows such as "Star Trek" and are more open to the possibility of time travel. There is, for example, the work of physicists such as Kip Thorne at Caltech, who has discussed the possibility of time travel to the past using wormholes, and Richard Gott at Princeton University, who has indicated how time travel to the past could occur using cosmic strings.
What's your response to critics like Carroll?
My work is based on Einstein's general theory of relativity, which allows for the possibility of time travel. However, the practical realization of a time machine is a technological one, which will require creative engineering innovation. It is sometimes forgotten that there was serious doubt that the enormous energy release implied by Einstein's famous equation E=mc² could be practically realized until the discovery of nuclear chain reactions.
I like to point out a quote that I had at the preface of my book Time Traveler that was made at the beginning of the 20th century by influential physicist Simon Newcomb, who was a professor at Johns Hopkins University. Newcomb stated, "Flight by machines heavier than air is impractical, if not utterly impossible." Newcomb made the statement in 1902. A year later, Orville and Wilbur Wright took to the skies.
How are you planning on spending this historic week?
During the "Back to the Future" week I'm going to look at some of my favorite time-travel movies which I have on DVD. Among them is the 1960 movie "The Time Machine" that starred the late Rod Taylor. In my opinion, this is the best and most accurate depiction of H.G. Wells' novel. I love that movie. I will also watch the "Back to the Future" series. Incidentally, the first movie in the series has a special meaning for me because Marty McFly goes back to 1955, which is the year my father died. By the way, it's also the year that Einstein died.
CORRECTION: An earlier version of this story incorrectly stated that "Back to the Future" came out in 1989. In fact, "Back to the Future II" came out in 1989.