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What if you could travel through time just like you navigate space? The journey starts here


In the joyful, cult classic TV show, Doctor Who, a two-thousand-year-old Time Lord from the planet Gallifrey traverses space and time in a craft called the TARDIS. While the TARDIS (for Time And Relative Dimension in Space) looks like an old-style British police box on the outside, its vast interior is a technological marvel that has, seemingly, marshalled the laws of physics to visit such places and times as 1814 London, the Jurassic period, and future cities on distant worlds.

But will we ever be able to travel back and forth in time like the Doctor? Could we build a chariot capable of transporting us around the universe—not just in three dimensions, but four?

When I was young, I stayed over at my neighbors’ one night in Stoughton, Massachusetts.  Between the tick and the tock of their grandfather clock, I laid awake thinking about the perverse nature of time. Although Mr. O’Donnell is gone, his wife Barbara, now 98, still greets me when I visit. We watch our loved ones age and die, and we assume an external entity called “time” is responsible for the crime. But I have come to realize that time belongs to us, the observer rather than the observed. From that realization, I developed a theory of time built on quantum physics, traditionally used to describe the subatomic realm. By adding life to the equation, my theory, which I call biocentrism, taps quantum mechanics to explain how we influence reality and might, one day, even build machines to travel through time.

In classical science, humans place all things in time on a continuum. The universe is nearly 14 billion years old, the Earth around four to five billion years old, and we ourselves 20 or 45 or 90 years. Time in a mechanistic universe is a clock that ticks independently of us. Not so, says my theory of biocentrism. Life determines the laws of physics, rather than the other way around. As physicist Stephen Hawking pointed out, “There’s no way to remove the observer—us—from our perceptions of the world.” The world we perceive, in other words, is determined by us. Hawking also thinks the universe has many possible histories and possible futures. “In classical physics,” he says, “the past is assumed to exist as a definite series of events, but according to quantum physics, the past, like the future, is indefinite and exists only as a spectrum of possibilities.”

If the past and future are indefinite, and if we, the observers, determine which of many possible futures become real, then—so goes the argument—we definitely cannot travel into “the past” or “the future,” because there would be no one past and no one future. Paradoxically, specific events that “happened” in the past may not be determined until sometime in the future—and may even depend on actions you have yet to take.

Bizarre? Maybe. But consider an amazing experiment published in the journal Science. In 2007, French physicist Jean-François Roch and colleagues demonstrated that particles of light could retroactively change something that had already happened in the past. Light is made up of tiny packets of energy called photons, and depending on how you look at them, those photons can either behave like indivisible particles or like waves (which can split and recombine, like ripples going around rocks in a brook). In the experiment, Roch shot photons, one by one, at a beam splitter that splits the wave. However, if the photon acts like a particle, it cannot be split and must go one way or the other. Thus, the photons had to either behave as particles or as waves when they hit the beam splitter. Later, after the photons traveled nearly 50 meters past this fork in the road, the experimenter could choose to switch a second beam splitter on or off, again rendering the photon either a particle or a wave. It turns out that what happened at the second fork determined what the particle actually did at the first fork—in the past. In short, the experimenter chose a past by making a decision in the future.

Traditionally, physicists have believed that such results apply only to subatomic particles. In the “two-worlds” view, one set of physical laws applies to small objects like electrons, and another to the rest of the universe, including stars, planets, sofas, end tables, and us.


But what if the laws of quantum mechanics are universal and hold for larger objects, too? For decades, researchers have pondered this possibility, conceiving experiments to see if quantum concepts extend to the everyday realm. In 2011, an international team of scientists from Oxford University, the National University of Singapore, and the National Research Council of Canada, studied objects that definitely were not subatomic, not even microscopic. They focused on a pair of three-millimeter-wide diamond crystals—about the size of the diamonds in a nice pair of earrings. To understand the experiment, consider the light in your room. Common sense tells us that the light is either on or off, but not both at once. Yet, quantum mechanics allows bizarre states in which the lights have been turned neither on nor off. Instead, they exist in a “superposition” of the two states—that is, both on and off.

When a system containing two or more objects is put into quantum superposition, you get the phenomenon of entanglement. The quantum state is shared among the various objects—usually a pair of particles. The particles are linked in such a way that measurement of one of them instantaneously influences the state of the other, even when the particles are separated by great distances. Einstein described the effect as “spooky action at a distance.”

Experiments confirm that such entangled states exist at microscopic scales, at the size of atoms or elementary particles. For example, if an entangled photon is found to spin clockwise on its axis, then the other particle will be found to spin counterclockwise. You always get a perfect correlation no matter how many times you measure them. Spooky or not, entanglement undoubtedly exists in the quantum realm. But if the laws of quantum mechanics are universal, then we should also observe entangled states in the macroscopic objects surrounding us.

To test this, the scientists induced vibrations in one of the diamonds, creating a phonon—a unit of vibrational energy. Because of the design of the experiment, there was no way of knowing whether the phonon had been made to vibrate in the left-hand diamond or the right-hand diamond. The researchers used laser pulses to detect the phonon, and the pulses showed that the phonon came from both diamonds, rather than one or the other. The diamonds were entangled, sharing one phonon between the two of them, even though they were separated by a distance of about 15 centimeters—definitely a measurement in the macro world.

Another study showing that the laws of quantum physics can apply to macro-world systems was conducted in 2013 by Sandra Eibenberger of the University of Vienna and colleagues. The Vienna team investigated the concept of quantum superposition—the idea that if we do not know what the state of an object is, it is actually in all possible states simultaneously, as long as we don’t look to check. But instead of looking at subatomic particles, they tested a gargantuan compound, C284.H190.F320.N4.S12, which is composed of about 5,000 protons, 5,000 neutrons, and 5,000 electrons. When they watched these giant molecules pass through slits in a barrier, the molecules behaved like little bullets and went through one slit or another; but if they did not watch, the molecules behaved in wavelike fashion, and went through more than one slit at the same time. In other words, they acted like subatomic particles, even though they were thousands of times larger. For the next step, researchers have proposed testing the quantum nature of living organisms like viruses.

An experiment published in Science this June focused on the ability of quantum effects to span large distances. In the study, scientists pulsed a laser through a crystal aboard a Chinese satellite orbiting about 300 miles above the earth. The process generated pairs of entangled photons, which were subsequently separated and sent to two cities in China about 750 miles apart. When researchers measured the photons, they were still mysteriously connected. Multiple tests on the ground found that the photons had opposite polarizations far more often than would be expected by chance, confirming that “spooky action at a distance” takes place even on large scales.


Today, no scientist doubts the connectedness between bits of light or matter. True to the concept of entanglement, such particles are so intimately linked that there appears to be no space between them—and not even time can influence the deep connection.

For years physicists have known that Einstein’s equations, and even those of quantum theory, are “time-symmetrical”—time plays absolutely no role. There is no forward movement of time. This caused many scientists to question whether time even exists. Indeed, Einstein’s theories of relativity suggest that not only is there no single, special present, but that all moments are equally real.

Einstein illustrated the relative nature of the perception of time through one of his famous thought experiments. Imagine you are sitting in the middle of a train while your friend is standing on the embankment outside the train, watching it go roaring by. If lightning strikes on both ends of the train just as the train’s midpoint is passing, your friend would see both bolts of lightning strike at the same time because the lightning strikes are the same distance from the observer. Your friend would correctly say they happened simultaneously—an accurate statement of one’s perception of time. From your perspective, sitting in the middle of the moving train, you will see the lightning from the front of the train first because the lightning in the rear has a slightly greater distance to travel to catch up. Since the light arrives at different times, you might conclude the lightning strikes were not simultaneous, and that the one in front actually happened first—also an accurate statement of one’s perception of time. Neither your observation nor your friend’s is “right”—there is no objective viewpoint, just two different perceptions.

From this and other thought experiments, Einstein concluded that time moves differently for someone moving than for someone at rest, and that time only exists relative to each observer.


My theory of biocentrism takes this a step further by suggesting that the observer doesn’t just perceive time, but literally creates it. Time is not something out there in the world. You cannot put it in a bottle like milk. Space and time are not objects. Look at anything—say, this text. Everything you see and experience right now is a whirl of information occurring in your mind. Time is simply the summation of what we observe in space—much like the frames of a film—occurring inside the mind.

With Dmitriy Podolsky, a theoretical physicist at Harvard University, I have been developing some of these ideas further. We start with the observation that, in the real world, coffee cools and cars break down. Yet to the bafflement of scientists, the fundamental laws of physics—when reduced to equations—work just as well for events going either forward or backward in time.

If the laws of physics operate without regard to time, then why do we experience reality with the arrow of time strictly directed from the past to the future? (See Travel on Time’s Arrow, page 104.) Our paper, published in 2016 in Annalen der Physik, the same journal that published Einstein’s theories of special and general relativity, explains how the arrow of time (and time itself) emerges directly from the observer, that is, us. Our paper argues that time does not exist “out there,” ticking away from past to future, but rather is an emergent property that depends on the observer’s ability to preserve information about experienced events. In the world of biocentrism, a “brainless” observer does not experience time.

We are currently expanding this into a larger, overarching vision and paper that will provide a complete theoretical framework for biocentrism. Our work suggests many alternate histories and futures, each representing an actual universe, or sphere of physical reality. Each universe can be thought of as “bubbles of vacuum”, or spaces devoid of matter, which grow and are modified as an observer makes measurements. Every observer has their own, unique arrow of time. According to our calculations, when observers exchange information with each other, this readjusts the vacuum structure consensus.

Even though we create time ourselves, most people take for granted how our minds put everything together. We understand dreams as a mental construct, but when it comes to the life we live, the perception of time and space feels absolutely real, and traps us in the universe we think we know.

According to my theory, these mental constructs are based on algorithms, or complex mathematical relationships, whose physical logic is contained in the neurocircuitry of the brain. These algorithms are not only the key to consciousness, but also explain why time and space—indeed the properties of matter itself—are relative to the observer. The structure of the universe provides the best support for this biocentrist viewpoint. It has a long list of traits that make it appear as if everything—from atoms to stars—was tailor-made just for us. For instance, if the Big Bang was just one part in a million more powerful, the cosmos would have blown outward too fast to allow stars and worlds to form. Result: No us. If the strong nuclear force, which holds together the particles inside the nucleus of atoms, were decreased two percent, plain-vanilla hydrogen would be the only kind of atom in the universe. If the gravitational force were decreased by a hair, stars (including the Sun) would not ignite. These are just three of over 200 parameters so exact that it strains credulity to propose that they are random. Tweak any of them and you never existed. These fundamental constants of the universe all seem to be carefully chosen, often with great precision, to allow for existence of life and consciousness. Why? To me, the answer is simple: The laws and conditions of the universe allow for the observer because the observer generates them.

At present, we live and die in the world of here and now. But this could change once science has a full understanding of the algorithms we employ to construct the reality of time and space. Although time does not exist per se, travel into past and future universes is likely possible. Sometime in the future, we might be able to use our knowledge of these algorithms to create information systems and technology to generate consciousness-based reality. If we changed the algorithms—so that instead of time being linear, it was three-dimensional, like space—consciousness would be able to move through the multiverse. To achieve this, a machine would have to input enough information about both the traveler and her potential trajectories, defined as bubbles of vacuum (vacua). It would then calculate a new vacua in accordance with the laws of quantum mechanics, providing an entrée to another reality or place in time.

With a deep enough understanding and the right technology, we might be able to walk through time just like we walk through space. Travelers could render new universes simply by defining new vacua that contain them. Imagine traveling back to the Hadean Eon, when the Earth collided with the planet Theia to form the Moon—then following the appearance of life forward in time through the Cambrian and Jurassic periods to humans—and then to the evolution of a post-human future, with beings based on completely different information systems like the Vorlons in Babylon 5. After creeping along for 4 billion years, life will finally escape from its corporeal cage, and be free to flit around the multiverse at will, like the Time Lords in Doctor Who.


“Whoa!” you may say, “You can’t do that! Time travel is impossible because of the inevitable paradoxes it creates.” Consider the classic grandfather paradox: a person travels back in time and kills their own grandfather before the conception of their mother or father. Thus the traveler would never have been born, and would not have been able to travel to the past to kill their grandfather.

There are many other equivalent paradoxes and inconsistences that emerge through changing the past, such as going back in time and killing oneself as a baby, or the famous “Hitler paradox” in which killing Adolf Hitler erases your own reason for going back in time to kill him. Furthermore, killing Hitler would have monumental consequences for everyone in the world, especially for those who were born after World War II and the Holocaust. If you killed Hitler then none of his actions would have trickled down through history, including the millions of people who had died but would have now lived, people who met and had children would never have known each other, and the atomic bomb and all sorts of other technology might not have been invented. The entire course of history would have been unrecognizably different.

The problem is exemplified in one episode of Doctor Who called “Let’s Kill Hitler.” The TARDIS crash lands in Nazi Germany just as a humanoid robot is about to kill Hitler. The Doctor and his companion save Hitler while the assassins—intergalactic police who terminate evil beings—focus on yet another human target they have chased through time. Similar paradoxes also form the plot lines of the Terminator and Back to the Future movies, where visiting the past constantly threatens to rearrange the future from which the travelers came.

Despite ingenious attempts to get around these blockades, timeline inconsistencies are indeed problematic for classical time travel. But all of these paradoxes disappear if the rules of quantum mechanics apply to the macroworld, with no single past and multiple possible futures. If you traveled back in time, you would simply create an alternative timeline, or parallel universe, according to the multiverse point of view. Whether you are flipping a switch like the scientists conducting the 2007 Science experiment, or turning the dial of a time machine, it would still be you inside the experience. There are no paradoxes because any event you alter in the past will generate an alternate universe in keeping with the known laws of quantum mechanics. No matter which universe you inhabited, you would still be you.

Time travel is easier to conceive going toward the future rather than the past. Traveling forward in time is relatively straightforward in classical physics. We know from Einstein’s theory of special relativity that time passes at different rates depending on how fast objects are moving. This “time dilation” becomes awesome as you near the speed of light. For instance, at about 580 million miles per hour, a clock would run half as fast as when at rest. If you want to travel ahead in time quickly, you just need to travel near light speed for a while, and then turn around and come back.

Although this would be theoretically possible with the right equipment, there are a few “minor” snags. For instance, Einstein showed that nothing that weighs anything can quite attain the speed of light, because its mass would grow until (at just below light-speed) even a feather would outweigh a galaxy. And the amount of force needed to accelerate such a huge mass further would be impossible to obtain—it would exceed all the energy in the universe. Indeed, at the speed of light, a zooming mustard seed would outweigh the entire cosmos. You could try to achieve such speeds using a centrifuge, just spinning round and round, but that would be fatal. In fact, the speed required would be so great that ordinary matter would not be strong enough to construct the centrifuge in the first place.

Time travel into the future can also theoretically be achieved using gravity. Einstein’s theory of general relativity tells us that clocks tick slower in strong gravitational fields. A clock on Earth (like at Mission Control in Houston) ticks a tiny bit slower than a clock on the Moon. In fact, there are places in the universe where only a single second of events pass while a million years’ worth of activities simultaneously elapses here on Earth. Unfortunately, serious time travel using gravitational time dilation would require something extreme (and likely, deadly), like orbiting close to a black hole at tremendous velocities, or traveling in a machine with a spherical shell that weighs a million times more than the Earth. Standing on a neutron star—even if you could build a starship to get there—would flatten you like the huge boulders that fall on Wile E. Coyote in The Road Runner Show.

Of course, scientists have proposed other ways of traveling in time, but in most of those theories, there is no way a traveler can go back to a time before the time machine itself was built. It would require traveling faster than the speed of light—and that is not possible without using exotic theoretical materials that have not been found in nature, at least not yet. Thus, it has become increasingly clear that trying to build a time machine in a universe governed by classical laws of physics is like trying to force a square peg into a round hole. It is hard, if not impossible, to do, even if you have a large four-dimensional hammer.

Fortunately, the findings of quantum theory suggest that reality also works in other ways. If my theory of biocentrism is proven correct, it would complete this shift in worldview, building on quantum physics by adding life to the equation. Accepting space and time as forms of animal understanding (that is, as biological), rather than as external physical objects, may open a completely new vista for time travel.

I remember attending my 35th high school reunion with Vicki, one of my oldest friends from my time growing up in Stoughton. When I arrived at her house to pick her up, memories of Vicki’s long-dead mother flashed across my mind. Vicki’s mom had been a kind, self-effacing woman, her legs in braces because of polio. How proud she would have been for the lawyer and the doctor Vicki and I had become. It is sad she didn’t live to see the future, but if biocentric time travel is possible, Vicki and I might yet visit her mom through an alternate branch of the multiverse—and she’ll get to see it all unfold.

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