A few months back, I attended a breast cancer meeting in Portugal. I started my last morning in Lisbon at 7:00 a.m. I knew from past experience that it always took more time to pack than I expected, particularly when I had been away from home for several days. There is something about being in a room I do not know, with socks and pants and shirts and keys and books randomly distributed on every previously empty table top, windowsill, and bathroom sink. I have left clothes and computer cords in many hotels over the years. So I spent a half hour packing the night before.
The flight to Newark was your usual United Airlines extravaganza. Halfway across the Atlantic the flight crew discovered that the ground crew in Lisbon had not serviced the toilets. Bad news, obviously, with no drink service for the last few hours and lots of nervous fidgeting by old folks. But the end result was that the plane got moved to the front of the line at Newark, so we landed 20 minutes early. No dark cloud without a silver lining.
I got off the plane, cleared customs, and headed for my flight to San Francisco. At Newark, the three terminals are connected by a light rail called Airtrain. I got on at Terminal B, headed for Terminal C. It wasn't a good time to ride Airtrain. It moved at a slow crawl. I could easily have outpaced it had there been a parallel walking path. And then, to make matters worse, the train went past the station stop, overshooting by about 30 feet. We sat there for a half hour, though in the mind it seemed far longer. When you want to get home after a long trip, time slows to a crawl as such inconveniences accumulate.
I got off the train, went through airport security, and walked to Gate 133 in Terminal C, arriving in the middle of boarding. After I sat, the pilot came on the intercom. There was some bad weather between New Jersey and California, but the crew had been working diligently on how to sneak around the thunderclouds, and he was certain we would arrive on time if not a bit early. A few minutes later, the doors were closed, and the plane readied for takeoff. It was at this point that one of the cabin crew noted, in the words of the pilot, and I kid thee not, that the plane had a defective life raft doohickey.
He assured us that it would only take 10 minutes to get this fixed. It was a trivial maintenance issue, not a major flaw. Now when an airline employee tells you that there will be only a 10-minute delay you know that they are being economical with the truth, to use Mark Twain's apt formulation. The next thing we heard was a flight attendant 's voice—I guess the pilot was too busy being embarrassed to share bad news—informing us that the flight was expected to land 40 minutes late.
Now, the above might be mistaken for another rant about the misery-inducing qualities of modern air travel: toilets that don't work because some employee couldn't be bothered to do his job, run-down airport facilities confirming the general perception of American civic decomposition, airline pilots bragging about how smart they are shortly before the flight gods punish that hubris with a "mechanical," and the courageous passing off of the delivery of bad news to a more junior employee. And, well, yes, those are all true. But that wasn't really my point.
My point was that all of these involved time, and my perception of time. When I travel, my overall sense of well-being largely revolves around when I unlock my front door, and that event is the summation of many small events. Because I fly a fair amount, I have missed flights, spent nights in awful airport hotels, hotels that I arrived at hours after my flight was supposed to have taken off, sat on tarmacs for hours all over the world, sat waiting for the gantry to roll down to the jet while local ground crews enjoyed late-night snacks, and stood for an hour in a long, winding taxi line. These all involved time, and my perception of it.
What is time? This turns out to be surprisingly difficult to define in any other than the most trivial of turns. The best physics is able to tell us is something like "time is what clocks measure." Yet time is the center of modern physics. Newton thought of time as a universal, what is now called Newtonian time. A standard 18th century meme was that of a clockwork universe, and God was the master clockmaker.
And then along came Einstein, who shattered Newtonian time. Time was a matter of your frame of reference. The faster you travel, the slower time moves. Einstein's time created the famous twin paradox, wherein one twin goes on a spaceship traveling close to the speed of light while the other stays here on Mother Earth. When the young space traveler returns, he finds a gray-hair sibling, even though only months have passed for the galactic traveler.
And while we haven't sent any astronauts away anywhere near the speed of light, time dilation is a real phenomenon, experimentally proven again and again, and practical for everyday life. The GPS and time clock measures my iPhone performs so effortlessly require adjustments for the time dilation caused by the satellites transmitting signals. They move fast enough around the earth, and so regularly, that if we did not make the adjustments our phone clocks would be off and Google Maps would tell me to turn left at the wrong street corner.
Most of the population is blissfully unaware of the physical reality of time dilation, or its effects on their lives. No doubt many would reject the very possibility of such effects as being either irreligious or a violation of plain old common sense, rather like some reject the Big Bang theory or the theory of evolution. But facts are stubborn things, and the universe is run by Einstein's playbook, not Newton's.
When I say "most of the population is blissfully unaware," I am not just talking about non-physics majors. There are populations of patients who experience their own personal time dilation, with altered perception of time, and while these alterations aren't associated with traveling near the speed of light, they are still eminently fascinating.
Take, for instance, the delightfully named but quite rare Alice in Wonderland Syndrome (AIWS). In AIWS, patients experience the sensation of visual distortions of body size (smaller), distance of external objects (farther away), auditory distortions (louder) and, finally, the sense that the passage of time is altered. To the AIWS patient, people may speak more quickly and things happen faster. Or, in some cases, that things move incredibly slowly. These alterations confer an altered sense of velocity (which, of course = distance/time) as well. AIWS has a very Einsteinian feel to it, if not an Einsteinian explanation.
AIWS patients have episodic attacks of time distortion. In one reported case in the neurologic literature, average reaction times increased during AIWS attacks, then returned to normal afterwards. There has been many a lecture or faculty meeting I've sat through where I wished I had the "time speeding up" version of the syndrome. Alas, I appear afflicted with "time slowing to a crawl" AIWS.
The "time slowing down" sensation is common in times of stress. I was driving home on an icy road a few years ago when my car spun out and headed for a tree. Time, or my perception of it, slowed. I saw the car approaching the tree at an agonizingly slow pace. I seemed to perceive every little branch and pine needle. Then the car hit the tree, my glasses flew off my face, and time sped up again.
It all happened in a few seconds, of course, but it seemed to go on a long time. That "time slowing down" experience was studied a few years ago by David Eagleman, now a Stanford neuroscientist, in a genuinely cool experiment conducted at an amusement park. Volunteers were raised 150 feet into the air and then dropped into a net, so-called SCAD jumping. It is a terrifying experience, apparently, and the perception that time slows down is a common one.
But does the SCAD jumper really see things in slow motion? In Eagleman's experiment, the jumpers wore perceptual chronometers, which flash numbers so briefly that one cannot perceive them under normal circumstances. If things really slowed down for the SCAD jumper, he should be able to read the numbers. Alas, this is not the case. The numbers are still a blur. Eagleman suggests that what has changed is not perception of time, but rather memory processing.
How do cancer patients perceive time? A 2011 Dutch study compared healthy cancer survivors with advanced cancer patients. Unsurprisingly, the healthy focus on the future, and the ill on the present. Somewhat to my surprise, patients with advanced disease experience the speed of time as being far slower than do healthy survivors. It is a frightening thought: being caught in a personal, inexorable horror where time slows to a crawl.
The neurologic basis of time perception has only been studied in recent years. Sofia Soares and her colleagues at the wonderfully named Champalimaud Centre for the Unknown in Lisbon, Portugal, have shown that manipulating midbrain dopamine neurons alters behavioral sensitivity to time. Transient activation or inhibition of dopamine neurons, in turn, slows down or speeds up time estimation. Does the cancer patient's experience of time have something to do with this phenomenon?
Ever since H.G. Wells, time travel has been a standard science fiction trope. The second law of thermodynamics seems a reasonable bar to traveling backwards in time: entropy is a beast. And even if you could, the paradoxes might get you: prevent your grandmother and grandfather from meeting, and you don't exist; if you don't exist, you can't prevent them from meeting, so you exist after all.
But I still can dream. Maybe I'd stay a day longer in Lisbon, have some fun in that lovely city, and avoid an awful flight. But then I'd be subject to the Airline Paradox: avoid one miserable air travel experience, and the universe artfully conspires to create an equally awful one. It seems an unalterable universal law, first discovered (perhaps) by Einstein while awaiting a flight from Berlin to Paris. Spooky action at a distance, or something similar.