Tag Archives: time travel

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The Top Five Unsolved Mysteries of Science

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There are numerous unsolved mysteries in science. In this post, I will delineate the top five that I consider the most profound.

  1. What caused the Big Bang? Cosmologist are in strong consensus that the Big Bang resulted in the evolution of the Universe, but there is no scientific consensus as to what caused the Big Bang. There are several theories, including one that I put forward in my book, Unraveling the Universe’s Mysteries. However, none of the current theories, including the one that I forward in my book, have garnered consensus in the scientific community. The origin of the Big Bang is arguably the greatest scientific mystery of all time, and it remains an area of considerable research.
  2. How did life start on Earth? There are two fundamental theories regarding the origin of life on Earth. The first theory, panspermia, holds that life exists throughout the Universe and is distributed by meteoroids, asteroids and planetoids. This theory is compelling, but it still leaves us with another profound question, “How did life originate in the Universe?” There are no widely accepted theories to address that question. The second theory, regarding how life started on Earth, is termed biopoesis. It holds that life forms from inorganic matter through natural processes. This theory is also compelling, but no experimental process has resulted in life forming from inorganic matter. By simple logic, one or even both of these theories is correct. Obviously, in the early Universe, life had to form from inorganic matter. It is also possible that life also started on Earth via the same process. It is also possible that once life formed in the Universe, it was spread by meteoroids, asteroids and planetoids.
  3. What is the nature of time? Some scientists, myself included, argue time is real. This stance suggests that time travel would also be possible. In my book, How to Time Travel, I devote considerable attention to the various philosophies of time and to experiments that suggest time is real. I also delineate experiments that prove time travel to the future is real, as well as experiments that prove reverse causality is real (i.e., literally, the effect precedes the cause). I also delineate experiments that prove that something in the future can alter the past. Some philosophers and scientists argue that time is a mental construct. It is not real. That humans invented time to measure change. If that is true, time travel would not be possible, except in your mind. However, scientific experiments, such as time dilation and reverse causality suggest otherwise. What do you think?
  4. What is the fundamental theory of physics? Modern physics rests on two pillars, The first pillar is Einstein’s theories of relativity. The second pillar is quantum mechanics. Although Einstein’s theories explain phenomena on the macro-scale (i.e., the typical scale we observe in our every day life), it fails to explain phenomena on the quantum level (i.e., the level of atoms and subatomic particles). To explain phenomena on the quantum level we must turn to quantum mechanics. This would be acceptable, except Einstein’s theories of relativity are incompatible with quantum mechanics. They do not come together to adequately explain gravity. Physicists have long sought the “theory of everything.” Some physicists, like world renown cosmologist Stephen Hawking, suggest that M-theory (i.e., the most comprehensive string theory) fits the bill. However, there is no consensus or proof that M-theory is even valid. Until the next Einstein comes along and solves the problem, we don’t have a fundamental theory (i.e., a single unifying theory) of physics.
  5. Does life exist on other planets or is the Earth unique? Almost every scientist agrees that given the vastness of the Universe and the numerous Earth-like planets that have been discovered, there must be life somewhere else in the Universe. Indeed, many believe, myself included, that advanced aliens, similar or more advanced than ourselves, must also exist. However, there has been no definitive publication that proves life exists elsewhere in the Universe. I will refrain from getting into UFOs, government conspiracies and similar material. I don’t refute such theories, but as a scientist I must base my conclusions on definitive evidence. To date, we have no definitive evidence (i.e., widely accepted by the scientific community) regarding life on other planets. However, mathematically, I think life on other planets is a certainty. What do you think?
A cosmic spiral clock with a bright center, blending space and time elements with a rainbow arc.

Is Time Travel to the Future Possible?

Categories, Physics, Time Travel, , , , ,

Since the future doesn’t exist, how would it be possible to travel into the future? This question has been debated by both philosophers and scientists. However, time travel to the future is the only experimental evidence we have of time travel. To understand this, we will need to understand Einstein’s theories of special and general relativity.

The science of time travel was launch in 1905,  when Einstein published his special theory of relativity in the prestigious Annalen der Physik (i.e., Annals of Physics), one of the oldest scientific journals (established in 1790). The paper that Einstein submitted regarding his special theory of relativity was titled “On the Electrodynamics of Moving Bodies.” By scientific standards, it was unconventional. It contained little in the way of mathematical formulations or scientific references. Instead, it was written in a conversational style using thought experiments. If you examine the historical context, Einstein had few colleagues in the scientific establishment to bounce ideas off. In fact, Einstein essentially cofounded, along with mathematician Conrad Habicht and close friend Maurice Solovine, a small discussion group, the Olympia Academy, which met on a routine basis at Solovine’s flat to discuss science and philosophy. It is also interesting to note that Einstein’s position as a patent examiner related to questions about transmission of electric signals and electrical-mechanical synchronization of time. Most historians credit Einstein’s early work as a patent examiner with laying the foundation for his thought experiments on the nature of light and the integration of space and time (i.e., spacetime).

Einstein’s special theory of relativity gave us numerous new important insights into reality, among them the famous mass equivalence formula (E = mc2) and the concept and formula for time dilation. Time dilation lays the foundation for forward time travel, so let’s understand it in more depth.

According to special relativity’s time dilation, as a clock moves close to the speed of light, time slows down relative to a clock at rest. The implication is that if you were able to travel in a spaceship that was capable of approaching the speed of light, a one-year round trip journey as measured by you on a clock within the spaceship would be equivalent to approximately ten or more years of Earth time, depending on your exact velocity. In effect, when you return to Earth, you will have traveled to Earth’s future. This is not science fiction. As I mentioned above, time dilation has been experimentally verified using particle accelerators. It is widely considered a science fact.

What scientific experimental evidence do we have that time dilation is real. Here are several experiments that validate time dilation caused when particles move close to the speed of light.

Velocity time dilation experimental evidence:

Rossi and Hall (1941) compared the population of cosmic-ray-produced muons at the top of a six-thousand-foot-high mountain to muons observed at sea level. A muon is a subatomic particle with a negative charge and about two hundred times more massive than an electron. Muons occur naturally when cosmic rays (energetic-charged subatomic particles, like protons, originating in outer space) interact with the atmosphere. Muons, at rest, disintegrate in about 2 x 10-6 seconds. The mountain chosen by Rossi and Hall was high. The muons should have mostly disintegrated before they reached the ground. Therefore, extremely few muons should have been detected at ground level, versus the top of the mountain. However, their experimental results indicated the muon sample at the base experienced only a moderate reduction. The muons were decaying approximately ten times slower than if they were at rest. They made use of Einstein’s time dilation effect to explain this discrepancy. They attributed the muon’s high speed, with its associated high kinetic energy, to be dilating time.

In 1963, Frisch and Smith once again confirmed the Rossi and Hall experiment, proving beyond doubt that extremely high kinetic energy prolongs a particle’s life.

With the advent of particle accelerators that are capable of moving particles at near light speed, the confirmation of time dilation has become routine. A particle accelerator is a scientific apparatus for accelerating subatomic particles to high velocities by using electric or electromagnetic fields. In 1977, J. Bailey and CERN (European Organization for Nuclear Research) colleagues accelerated muons to within 0.9994% of the speed of light and found their lifetime had been extended by 29.3 times their corresponding rest mass lifetime. (Reference: Bailey, J., et al., Nature 268, 301 [1977] on muon lifetimes and time dilation.) This experiment confirmed the “twin paradox,” whereby a twin makes a journey into space in a near-speed-of-light spaceship and returns home to find he has aged less than his identical twin who stayed on Earth. This means that clocks sent away at near the speed of light and returned near the speed of light to their initial position demonstrate retardation (record less time) with respect to a resting clock.

Time dilation can also occur as a result of gravity. Our understanding of this comes from Einstein’s theory of general relativity. What is the difference between the special and general theory of relativity? Einstein used the term “special” when describing his special theory of relativity because it only applied to inertial frames of reference, which are frames of reference moving at a constant velocity or at rest. It also did not incorporate the effects of gravity. Shortly after the publication of special relativity, Einstein began work to consider how he could integrate gravity and noninertial frames into the theory of relativity. The problem turned out to be monumental, even for Einstein. Starting in 1907, his initial thought experiment considered an observer in free fall. On the surface, this does not sound like it would be a difficult problem for Einstein, given his previous accomplishments. However, it required eight years of work, incorporating numerous false starts, before Einstein was ready to reveal his general theory of relativity.

In November 1915, Einstein presented his general theory of relativity to the Prussian Academy of Science in Berlin. The equations Einstein presented, now known as Einstein’s field equations, describe how matter influences the geometry of space and time. In effect, Einstein’s field equations predicted that matter or energy would cause spacetime to curve. This means that matter or energy has the ability to affect, even distort, space and time. One important aspect prediction of general relativity was that gravitational fields could cause time dilation. Here are some important experiments that prove this aspect of general relativity is correct.

Gravitational time dilation experimental evidence:

In 1959, Pound and Rebka measured a slight redshift in the frequency of light emitted close to the Earth’s surface (where Earth’s gravitational field is higher), versus the frequency of light emitted at a distance farther from the Earth’s surface. The results they measured were within 10% of those predicted by the gravitational time dilation of general relativity.

In 1964, Pound and Snider performed a similar experiment, and their measurements were within 1% predicted by general relativity.

In 1980, the team of Vessot, Levine, Mattison, Blomberg, Hoffman, Nystrom, Farrel, Decher, Eby, Baugher, Watts, Teuber, and Wills published “Test of Relativistic Gravitation with a Space-Borne Hydrogen Maser,” and increased the accuracy of measurement to about 0.01%. In 2010, Chou, Hume, Rosenband, and Wineland published “Optical Clocks and Relativity.” This experiment confirmed gravitational time dilation at a height difference of one meter using optical atomic clocks, which are considered the most accurate types of clocks.

The above discussion provides some insight into time dilation, or what some term time travel to the future. However, is it conclusive? Not to my mind! Although we have numerous experiments that demonstrate time dilation (i.e., forward time travel) involving subatomic particles is real, we have been unable to demonstrate significant human time dilation. By the word “significant,” I mean that it would be noticeable to the humans and other observers involved. To date, some humans, such as astronauts and cosmonauts, have experienced forward time travel (i.e., time dilation) in the order of approximately 1/50th of a second, which is not noticeable to our human senses. If it were in the order of seconds or minutes, then it would be noticeable. Scientifically speaking, there is no documented significant evidence of human time travel to the future.

To answer the subject question of this post, time travel to the future appears to have a valid scientific and experimental foundation. However, to date the experimental evidence does not include significant (noticeable)  human time travel to the future, which leaves the question still unanswered. My own view is that when we develop space craft capable of speeds approaching the speed of light with humans on board, time dilation (time travel to the future) will be conclusively proven.

A digital abstract representation of interconnected blue clock faces with intricate geometric patterns.

Is Time Travel to the Past Possible?

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For time travel to the past to be possible would require that the past have a physical reality, namely that it continue to exist. If it did not continue to exist, it would suggest time travel to the past is impossible.

Time travel to the past has it theoretical foundation in Einstein’s special relativity. in the way of background, in November 1915, Einstein presented his general theory of relativity to the Prussian Academy of Science in Berlin. The equations Einstein presented, now known as Einstein’s field equations, describe how matter influences the geometry of space and time. In effect, Einstein’s field equations predicted that matter or energy would cause spacetime to curve. This means that matter or energy has the ability to affect, even distort, space and time.

Many of the predictions of general relativity have been scientifically verified. Two of the most important predictions for our study of time travel are (1) gravitational time dilation and (2) closed timelike curves.

Gravitational time dilation predicts that a clock in a strong gravitational field will run slower than a clock in a weak gravitational field. Therefore, a clock on the surface of Jupiter, a massive gas planet three hundred times larger than the Earth, resulting in a significantly stronger gravitational field, will run much slower than a clock on the surface of the Earth. This phenomenon was first verified on Earth, with clocks at different altitudes from the Earth’s surface. Using atomic clocks, time dilation effects are detectable when the clocks differ in altitude by as little as one meter.

Gravitational time dilation also occurs in accelerating frames of reference (i.e., noninertial frames of reference). According to Einstein’s general theory of relativity, an accelerated frame of reference produces an “inertial force,” also termed a “pseudo force,” that results in the same effect as a gravitational force in an inertial frame of reference. The equivalence of the inertial force in a noninertial frame of reference (i.e., an accelerating frame of reference) to a gravitational force in an inertial frame of reference (i.e., a frame of reference moving at a constant velocity) is termed the equivalence principle. The equivalence principle refers to the equivalence of “inertial mass” and “gravitational mass.” Therefore, a blindfolded person in a rapidly ascending elevator would experience a force equivalent to an increase in gravity, as if standing on a planet more massive than Earth. The blindfolded person would not be able to determine if the force experienced is inertial or gravitational. This effect also holds true for time dilation. Time moves slower in a highly accelerated frame of reference in much the same way it would as if it were in a strong gravitational field. It is important to note, a frame of reference can accelerate in two fundamental ways. It can accelerate along a straight line, or it can accelerate by rotating.

Next, let us discuss closed timelike curves. What is a closed timelike curve? It is an exact solution to Einstein’s general relativity equations demonstrating a particle’s world line (i.e., the path the particle follows in four-dimensional spacetime) is “closed” (i.e., the particle returns to its starting point). Closed timelike curves theoretically suggest the possibility of backward time travel. The particle’s world line is describable by four coordinates at each point along the world line, and when it closes on itself, the four coordinates at the start equal the four coordinates at the end. The particle, conceptually, went back to its past (i.e., the starting point). You can think of this like a horse racetrack. As the horse runs around the track, the horse eventually crosses the finish line, the starting point. If we allow the horse racetrack to represent a world line, then when the horse crosses the finish line, the horse has returned to its past (i.e., the starting point). In the mathematics of general relativity, the starting four coordinates, including the fourth dimensional coordinate that includes a time component, equal the four coordinates at the finish line.

The first person to discover a solution to Einstein’s general relativity equations suggesting closed timelike curves (CTCs) was Austrian American logician, mathematician, and philosopher Kurt Gödel, in 1949. The solution was termed the Gödel metric. Since 1949, numerous other solutions containing CTCs have been found, such as the Tipler cylinder and traversable wormholes, both of which will be discussed in section 3. The numerous solutions to Einstein’s general relativity equations suggest that time travel to the past is theoretically possible. However, the entire scientific community is not in complete agreement on this last point.

The largest issue that physicists have with backward time travel is causality violations (cause and effect), where the effect precedes the cause. These violations of causality are termed “time travel paradoxes.” Some physicists suggest that time travel paradoxes inhibit backward time travel, while other physicists argue that time travel paradoxes can be reconciled, and backward time travel is possible. There is no scientific consensus regarding the reality or practicality of time travel to the past. Although, there are a number of experiments that suggest reverse causality is scientifically possible.

Let us consider a recent experiment that demonstrates reverse causality is not only possible, but a scientific fact. In 2009, physicist John Howell of the University of Rochester and his colleagues devised an experiment that involved passing a laser beam through a prism. The experiment also involved a mirror that moved in extremely small increments via its attachment to a motor. When the laser beam was turned on, part of the beam passed through the prism, and part of the beam bounced off the mirror. After the beam was reflected by the mirror, the Howell team used “weak measurements” (i.e., measurement where the measured system is weakly affected by the measurement device) to measure the angle of deflection. With these measurements, the team was able to determine how much the mirror had moved. This part of the experiment is normal, and in no way suggests reverse causality. However, the Howell team took it to the next level, and this changed history, literally. Here is what they did. They set up two gates to make the reflected mirror measurements. After passing the beam through the first gate, the experimenters always made a measurement. After passing it through the second gate, the experimenters measured the beam only a portion of the time. If they chose not to make the measurement at the second gate, the amplitude of the deflected angle initially measured at the first gate was extremely small. If they chose to make the measurement at the second gate, the deflected angle initially measured at the first gate was amplified by a factor of 100. Somehow, the future measurement influenced the amplitude of the initial measurement. Your first instinct may be to consider this an experimental fluke, but it is not. Physicists Onur Hosten and Paul Kwiat, University of Illinois at Urbana-Champaign, using a beam of polarized light, repeated the experiment. Their results indicated an even larger amplification factor, in the order of 10,000.

The above experiment strongly suggest that the future can influence the past. This implies, the past must continue exist and have a physical reality. If it no longer existed, how could the future influence the past. as the above experiments demonstrate.

This is an exciting time for science. Physical experiments suggest that the past may continue to physically exist. If that is true, then time travel to the past may be possible. The is an old saying in physics, “That which is not forbidden by physical law is compulsory.” The exact origin of the saying is not clearly known, but is often attributed to Murray Gell-Mann (born 15 September 1929), an American physicist who received the 1969 Nobel Prize in Physics for his work on the theory of elementary particles. To my mind, this saying suggests it is only a matter of time before we discover how to time travel to the past.

A surreal, glowing clock surrounded by swirling golden particles and abstract light patterns in a dark background.

Can Time Travel Be Used as a Weapon?

Categories, Physics, Technology, Threats to Humankind, Time Travel, , ,

Time travel will be the ultimate weapon. With it, any nation can write its own history, assure its dominance, and rule the world. However, having the ultimate weapon also carries the ultimate responsibility. How it is used will determine the fate of humankind. These are not just idle words. This world, our Earth, is doomed to end. Our sun will eventually die in about five billion years. Even if we travel to another Earth-like planet light-years away, humankind is doomed. The universe grows colder each second as the galaxies accelerate away from one another faster than the speed of light. The temperature in space, away from heat sources like our sun, is only about 3 degrees Kelvin (water freezes at 273 Kelvin) due to the remnant heat of the big bang, known as the cosmic microwave background. As the universe’s acceleration expands, eventually the cosmic microwave background will disperse, and the temperature of the universe will approach absolute zero (-273 degrees Kelvin). Our galaxy, and all those in our universe, will eventually succumb to the entropy apocalypse (i.e., “heat death”) in a universe that has become barren and cold. If there is any hope, it lies in the technologies of time travel. Will we need to use a traversable wormhole to travel to a new (parallel) universe? Will we need to use a matter-antimatter spacecraft to be able to traverse beyond this universe to another?

I believe the fate of humankind and the existence of the universe are more fragile than most of us think. If the secrets of time travel are acquired by more than one nation, then writing history will become a war between nations. The fabric of spacetime itself may become compromised, hastening doomsday. Would it be possible to rip the fabric of spacetime beyond a point that the arrow of time becomes so twisted that time itself is no longer viable? I do not write these words to spin a scary ghost story. To my mind, these are real dangers. Controlling nuclear weapons has proved difficult, but to date humankind has succeeded. Since Fat Man, the last atomic bomb of World War II, was detonated above the city of Nagasaki, there has been no nuclear weapon detonated in anger. It became obvious, as nations like the former Soviet Union acquired nuclear weapons, that a nuclear exchange would have no winners. The phrase “nuclear deterrence” became military doctrine. No nation dared use its nuclear weapons for fear of reprisal and total annihilation.

What about time travel? It is the ultimate weapon, and we do not know the consequences regarding its application. To most of humankind, time travel is not a weapon. It is thought of a just another scientific frontier. However, once we cross the time border, there may be no return, no do-over. The first human time travel event may be our last. We have no idea of the real consequences that may ensue.

Rarely does regulation keep pace with technology. The Internet is an example of technology that outpaced the legal system by years. It is still largely a gray area. If time travel is allowed to outpace regulation, we will have a situation akin to a lighted match in a room filled with gasoline. Just one wrong move and the world as we know it may be lost forever. Regulating time travel ahead of enabling time travel is essential. Time travel represents humankind’s most challenging technology, from every viewpoint imaginable.

What regulations are necessary? I have concluded they need to be simple, like the nuclear deterrence rule (about thirteen words), and not like the US tax code (five million words). When you think about it, the rule of nuclear deterrence is simple: “If you use nuclear weapons against us, we will retaliate, assuring mutual destruction.” That one simple rule has kept World War III from happening. Is there a similar simple rule for time travel?

I think there is one commonsense rule regarding time travel that would assure greater safety for all involved parties. I term the rule “preserve the world line.” Why this one simple rule?

Altering the world line (i.e., the path that all reality takes in four-dimensional spacetime) may lead to ruination. We have no idea what changes might result if the world line is disrupted, and the consequences could be serious, even disastrous.

The preserve the world line rule is akin to avoiding the “butterfly effect.” This phrase was popularized in the 2004 film The Butterfly Effect, with the now famous line: “It has been said that something as small as the flutter of a butterfly’s wing can ultimately cause a typhoon halfway around the world.” Although the line is from a fictional film, the science behind it is chaos theory, which asserts there is a sensitive dependence on the initial conditions of a system that could result in a significant change in the system’s future state. Edward Lorenz, American mathematician, meteorologist, and a pioneer of chaos theory, coined the phrase “butterfly effect.” For example, the average global temperature has risen about one degree Fahrenheit during the last one hundred years. This small one-degree change has caused the sea levels around the world to rise about one foot during the same period. Therefore, I believe, it is imperative not to make even a minor change to the past or future during time travel until we understand the implications.

Based on the above discussion, the implications of using time travel as a weapon are enormous. However, if time travel is used as a a weapon, we have no idea how this may impact the world line. If it is possible to adhere to the preserve the world line rule, traveling in time may become safe. Remember, our first nuclear weapons were small compared to today’s nuclear weapons. Even though they were comparatively small, the long-term effects included a 25% increase in the cancer rate of survivors during their lifetime. We had no idea that this side effect would result. Similarly, we have no idea what the long-term effects will be if we alter the world line. We already know from laboratory experiments that the arrow of time can be twisted. Things done in the future can alter the past. Obviously, altering the past may alter the future. We do not know much about it because we have not time traveled in any significant way. Until we do, preserving the world line makes complete sense.

Multiple overlapping clock faces with various times, creating a surreal and abstract time concept in blue tones.

Stephen Hawking’s Chronology Protection Conjecture’s Impact On Time Travel Science

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Most of the scientific community agrees that time travel is theoretically possible, based on Einstein’s special and general theories of relativity. However, world-famous cosmologist and physicist Stephen Hawking published a 1992 paper, “Chronology Protection Conjecture,” in which he stated the laws of physics do not allow the appearance of closed timelike curves (i.e., time travel to the past). Since its publication, the chronology protection conjecture has been significantly criticized. Most of the criticism centered on Dr. Hawking’s use of semiclassical gravity, versus using quantum gravity, to make his arguments. Dr. Hawking acknowledged, in 1998, that portions of the criticism are valid.

However, not to take sides on this issue, I feel compelled to point out that the two fundamental pillars of modern science, namely, general relativity and quantum mechanics, are incompatible. This placed Dr. Hawking in a difficult position regarding the use of gravity in writing the chronology protection conjecture. General relativity and quantum mechanics do not come together to provide a quantum gravity theory. This argues that we still do not have the whole picture, which makes it difficult to completely rule out Dr. Hawking’s chronology protection conjecture.

Currently, there is no widespread consensus on any theory that unifies general relativity with quantum mechanics. If such a theory existed, it would be the theory of everything (TOE) and would provide us with a quantum gravity theory. Highly regarded physicists, such as Stephen Hawking, believe M-theory (i.e., membrane theory), which is the most comprehensive string theory, is a candidate for the theory of everything. However, there is significant disagreement in the scientific community. Many physicists argue that M-theory is not experimentally verifiable, and on that basis is not a valid theory of science. However, to be fair to all sides, Einstein’s special theory of relativity, published in 1905, was also not experimentally verifiable for years. Today, most of the scientific community views the special theory of relativity as science fact, having withstood over one hundred years of scientific investigation. The scientific community, which didn’t really know what to make of the special theory of relativity in 1905, hails it now as the “gold standard” of theories, arguing that other theories must measure up to the same standards of rigorous investigation. I think science is better served by a more moderate position. In this regard, I agree with prominent physicist and author Michio Kaku, who stated in Nina L. Diamond’s Voices of Truth (2000), “The strength and weakness of physicists is that we believe in what we can measure. And if we can’t measure it, then we say it probably doesn’t exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. The Big Bang is an example. That’s one reason why they scoffed at higher dimensions for so many years. Now we realize that there’s no alternative.”

In essence, we need to keep an open mind, regardless of how bizarre a scientific theory may first appear. However, we need to balance our open-mindedness with experimental verification. This, to my mind, is how science advances.

A diagram showing a black rod in space with concentric circles and arrows, labeled with time (x) and space (y) axes.

Tipler cylinder time travel – Is It Possible?

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The Tipler cylinder is a cylinder of dense matter and infinite length. Historically, Dutch mathematician Willem Jacob van Stockum (1910–1944) found Tipler cylinder solutions to Einstein’s equations of general relativity in 1924. Hungarian mathematician/physicist Cornel Lanczos (1893–1974) found similar Tipler cylinder solutions in 1936. Unfortunately, neither Stockum nor Lanczos made any observations that their solutions implied closed timelike curves (i.e., time travel to the past).

In 1974, American mathematical physicist/cosmologist Frank Tipler’s analysis of the above solutions uncovered that a massive cylinder of infinite length spinning at high speed around its long axis could enable time travel. Essentially, if you walk around the cylinder in a spiral path in one direction, you can move back in time, and if you walk in the opposite direction, you can move forward in time. This solution to Einstein’s equations of general relativity is known as the Tipler cylinder. The Tipler cylinder is not a practical time machine, since it needs to be infinitely long. Tipler suggests that a finite cylinder may accomplish the same effect if its speed of rotation increases significantly. However, the practicality of building a Tipler cylinder was discredited by Stephen Hawking, who provided a mathematical proof that according to general relativity it is impossible to build a time machine in any finite region that contains no exotic matter with negative energy. The Tipler cylinder does not involve any negative energy. Tipler’s original solution involved a cylinder of infinite length, which is easier to analyze mathematically, and although Tipler suggested that a finite cylinder might produce closed timelike curves if the rotation rate were fast enough, Hawking’s proof appears to rule this out. According to  Hawking, “it can’t be done with positive energy density everywhere! I can prove that to build a finite time machine, you need negative energy.”

One caveat, Hawking’s proof appears in his 1992 paper on the “chronology protection conjecture,” which has come under serious criticism by numerous physicists. Their main objection to the Hawking’s conjecture is that he did not employ quantum gravity to make his case. On the other hand, Hawking and others have not been able to develop a widely accepted theory of quantum gravity. Hawking did just about the only thing he could do under the circumstances. He used Einstein’s formulation of gravity as found in the general theory of relativity. Another fact, Hawking’s proof regarding the Tipler cylinder is somewhat divorced from the main aspects of his paper and could be viewed to stand on its own. However, in science we are always judged by the weakest link in our theory. Thus, with a broad brush, the chronology protection conjecture has been discredited, and even Hawking has acknowledged some of its short comings.

Where does that leave us with a finite Tipler cylinder time machine? In limbo! There is no widely accepted proof that a finite Tipler cylinder spinning at any rate would be capable of time travel. There is also another problem. We lack any experimental evidence of a spinning Tipler cylinder influencing time.

Source: How to Time Travel (2013), Louis A. Del Monte

A black and white image of a clock face with a spiral effect distorting the numbers and hands.

Twisting the Arrow of Time

Categories, Time Travel, , , , ,

The flow of time, sometimes referred to as the “arrow of time,” is a source of debate, especially among physicists. Most physicists argue that time can only move in one direction based on “causality” (i.e., the relationship between cause and effect). The causality argument goes something like this: every event in the future is the result of some cause, another event, in the past. This appears to make perfect sense, and it squares with our everyday experience. However, experiments within the last several years appear to argue reverse causality is possible. Reverse causality means the future can and does influence the past. For example, in reverse causality, the outcome of an experiment is determined by something that occurs after the experiment is done. The future is somehow able to reach into the past and affect it. Are you skeptical? Skepticism is healthy, especially in science. Let us discuss this reverse causality experiment.

In 2009, physicist John Howell of the University of Rochester and his colleagues devised an experiment that involved passing a laser beam through a prism. The experiment also involved a mirror that moved in extremely small increments via its attachment to a motor. When the laser beam was turned on, part of the beam passed through the prism, and part of the beam bounced off the mirror. After the beam was reflected by the mirror, the Howell team used “weak measurements” (i.e., measurement where the measured system is weakly affected by the measurement device) to measure the angle of deflection. With these measurements, the team was able to determine how much the mirror had moved. This part of the experiment is normal, and in no way suggests reverse causality. However, the Howell team took it to the next level, and this changed history, literally. Here is what they did. They set up two gates to make the reflected mirror measurements. After passing the beam through the first gate, the experimenters always made a measurement. After passing it through the second gate, the experimenters measured the beam only a portion of the time. If they chose not to make the measurement at the second gate, the amplitude of the deflected angle initially measured at the first gate was extremely small. If they chose to make the measurement at the second gate, the deflected angle initially measured at the first gate was amplified by a factor of 100. Somehow, the future measurement influenced the amplitude of the initial measurement. Your first instinct may be to consider this an experimental fluke, but it is not. Physicists Onur Hosten and Paul Kwiat, University of Illinois at Urbana-Champaign, using a beam of polarized light, repeated the experiment. Their results indicated an even larger amplification factor, in the order of 10,000.

The above experimental results raise questions about the “arrow of time.” It appears that under certain circumstances, the arrow of time can point in either direction, and time can flow in either direction, forward or backward. This is a scientific result, and I am not going to speculate about religious connotations, free will, and the like. Obviously, there are numerous religious connotations possible and a plethora of associated questions.

Source: How to Time Travel (2013), Louis A. Del Monte

A silhouette of a person with a clock face behind them, symbolizing the concept of time and human existence.

The Greatest Engineering Challenge to Time Travel

Categories, Physics, Technology, Time Travel, , , ,

Without doubt, harnessing sufficient energy is  the largest obstacle to time travel. For example, time dilation (i.e., forward time travel) is only noticeable when mass approaches a significant fraction of the speed of light or sits in a strong gravitational field. To date, we have been able to accelerate subatomic particles to a point where time dilation becomes noticeable. We have also been able to observe time dilation of a highly accurate atomic clock on a jet plane as it flies over the airport, which contains another atomic clock. Using sensitive instruments, we can measure time dilation. We have also been able to measure time dilation due to differences in the Earth’s gravitational field. However, these differences are only evident using highly accurate atomic clocks. Our human senses are unable to detect a high mounted wall clock moving faster than our wristwatch, which gravitational time dilation predicts is occurring.

The fastest humankind has traveled is 25,000 miles per hour, using the Apollo 10 spacecraft. The speed of light in a vacuum is approximately 186,000 miles per second. This means that a spacecraft would have to go about 13,000 times faster than Apollo 10 for humans to experience noticeable time dilation, or a speed of about 90,000 miles per second, which is roughly half the speed of light. Today’s science has not learned to harness the amount of energy required to accelerate a spacecraft to a velocity of 90,000 miles per second.

Let us consider a simple example to illustrate the amount of energy required to achieve the above velocity. If we have a mass of 1000 kilograms (i.e., 2204 pounds), and we want to accelerate it to 10% the speed of light, the resulting kinetic energy would be about 1017 (i.e., a 1 with 17 zeros after it) joules, whether you calculate the kinetic energy using Newton’s classical formula or Einstein’s relativistic formula for kinetic energy. To put this in perspective, it is more than twice the amount of energy of the largest nuclear bomb ever detonated. It would take a modern nuclear power plant about ten years to output this amount of energy.

The above example gives us a conceptual framework to understand the amount of energy that would be required to accelerate a sizable mass, 1000 kilograms, or 2204 pounds, to just 10% the speed of light. If we wish to accelerate the mass, for example, a spacecraft, to a greater percentage, the energy increases exponentially. For example, to accelerate to 20% the speed of light would require four times the amount of energy.

Today’s engineering is unable to harness this level of energy. In the popular Star Trek television series and movies, the starship Enterprise is able to travel faster than the speed of light using a warp drive, by reacting matter with antimatter. Factually, there is almost no antimatter in the universe. This is one of the mysteries associated with the big bang science theory, which I discussed in my book, Unraveling the Universe’s Mysteries. In theory, during the big bang, matter and antimatter should exist in equal quantities. Our observation of the universe, using our best telescopes, detects almost no antimatter. However, Fermi National Accelerator Laboratory (Fermilab) in Illinois is able to produce about fifty billion antiprotons per hour. This, though, is a miniscule amount compared to the amount needed to power a starship. According to Dr. Lawrence Krauss, a physicist and author of The Physics of Star Trek, it would take one hundred thousand Fermilabs to power a single lightbulb. In essence, we are a long way from using matter-antimatter as a fuel. In addition, the Enterprise was able to warp space. This provided a means to skirt around Einstein’s well-established special theory of relativity, which asserts no mass can travel faster than the speed of light. There is no similar physical law that prohibits space from expanding faster than the speed of light. If we are able to manipulate space, similar to our discussion of the Alcubierre drive in the previous chapter, then scientifically the spacecraft could collapse space in front of it and expand space behind it. However, the Alcubierre drive requires negative energy. Today’s science is unable to create and harness negative energy in any significant way.

Therefore, topping our list of major scientific obstacles regarding time travel is generating huge amounts of energy, in either positive or negative form.

Source: How to Time Travel (2013), Louis A. Del Monte

M-theory

Are There Any Real Time Machines? Part 2/2 (Conclusion)

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Are there any real time machines?

In my opinion, we are in about the same place space travel was at the beginning of the twentieth century. At the beginning of the twentieth century, all we knew about space travel came from science fiction. We knew that birds could fly, and this observation provided hope that human air flight would eventually be possible. However, at this point we could only fly using balloons, which was a long way from controlled air flight. We knew about projectiles, such as cannonballs and simple rockets, and this provided hope that one day humankind would be able to travel into space. However, at the beginning of the twentieth century we were still three years away from building the first successful airplane. The first successful airplane did not come from a well-respected theory or formal scientific investigation. Most early attempts at air flight tended to focus on building powerful engines, or they attempted to imitate birds. The early attempts at air flight were dismal failures. The first successful heavier-than-air machine, the airplane, was invented in 1903 by two brothers, Orville and Wilbur Wright. They were not scientists, nor did they publish a scholarly paper in a scientific journal delineating their plans. Quite the contrary, the two brothers had a background in printing presses, bicycles, motors, and other machinery. Clearly, their background would not suggest they would invent the first airplane and lead humankind into space. However, their experience in machinery enabled them to build a small wind tunnel and collect the data necessary to sustain controlled air flight. From the beginning, the Wright brothers believed that the solution to controlled air flight lay hidden in pilot controls, rather than powerful engines. Based on their wind tunnel work, they invented what is now the standard method of all airplane controls, the three-axis control. They also invented efficient wing and propeller designs. It is likely that many in the scientific community in the beginning of the twentieth century would have considered aeronautics similar to the way the scientific community in the early part of the twenty-first century considers time travel—still something outside the fold of legitimate science. However, on December 17, 1903, at a small, remote airfield in Kitty Hawk, North Carolina, the two brothers made the first controlled, powered, and sustained heavier-than-air human flight. They invented the airplane. It was, of course, humankind’s first step into the heavens.

I believe the invention of the airplane is a good analogy to where we are regarding time travel. We have some examples, namely, time dilation data, and a theoretical basis that suggests time travel is potentially real. However, we have not reached the “Kitty Hawk” moment. If Dr. Mallett makes his time machine work, and that is a big “if,” numerous physicists will provide the theoretical foundation for its success, essentially erasing any errors that Dr. Mallett may have made in his calculations. He will walk as another great into the history of scientific achievement.

My point is a simple one. The line between scientific genius and scientific “crank” is a fine one. When Einstein initially introduced his special theory of relativity in 1905, he was either criticized or ignored. Few in the scientific community appreciated and understood Einstein’s special theory of relativity in 1905. It took about fifteen years for the scientific community to begin to accept it. Einstein was aware of the atmosphere that surrounded him. In 1919, he stated in the Times of London, “By an application of the theory of relativity to the taste of readers, today in Germany I am called a German man of science, and in England I am represented as a Swiss Jew. If I come to be represented as a bête noire, the descriptions will be reversed, and I shall become a Swiss Jew for the Germans and a German man of science for the English!”

Dr. Mallett is on record predicting a breakthrough in backward time travel within a decade. Only time and experimental evidence will prove if his prediction becomes reality. Even if the Mallett time machine works, it would still represent only a baby step. We would still be a long way from human time travel, but we would be one step closer.

Source: How to Time Travel (2013), Louis A. Del Monte

science of time & time dilation

Are There Any Real Time Machines? Part 1/2

Categories, Time Travel, Universe Mysteries, , ,

There are no existing time machines capable of sending humans forward or backward in time. The closest we have come to time travel is using particle accelerators to cause subatomic particles to experience time dilation (i.e., forward time travel). There is a significant amount of time dilation data available. Particle accelerators succeed in achieving time dilation by accelerating subatomic particles close to the speed of light. Unfortunately, though, backward time travel has no similar body of experimental data. The major problems with creating backward time travel appear to fall into three categories:

  1. Backward time travel appears to require negative energy, based on arguments made by American theoretical physicist Kip Thorne and British theoretical physicist/cosmologist Stephen Hawking. Many in the scientific community acknowledge that negative energy likely exists, and point to the Casimir effect, discussed previously, as an example in nature. However, today’s science is unable to harness negative energy in any meaningful way to make a time machine.
  2. Many in the scientific community, like physicists Dr. Olum and Dr. Everett, believe the amount of energy required to twist space sufficiently for spacetime manipulation and enable Dr. Mallett’s time machine to work is enormous. Conceptually, we may be talking about the amount of energy provided by a star, similar to our own sun. Harnessing this level of energy is far beyond today’s science. Science’s best efforts to study high-energy physics has to date been confined to particle accelerators, such as the Large Hadron Collider. There is no experimental evidence that Dr. Mallett has succeeded in manipulating spacetime.
  3. Many in the scientific community are concerned with causality violations, especially regarding backward time travel. However, as we learned in the section titled “Twisting the arrow of time,” there can also be causality violations regarding forward time travel. The causality violations are generally termed “time travel paradoxes,” which we will discuss in detail in the next chapter.

Having made the above points, I think it is important to point out that some physicists believe subatomic antimatter particles travel in the opposite direction in time (i.e., backward in time) versus their matter counterparts. For example, some physicists assert that positrons, the antimatter equivalent of electrons, travel backward in time, while electrons travel forward in time. In solid-state physics, if we consider a current flowing in a semiconductor, electrons in a semiconductor move as a current in one direction, while the “holes” (i.e., the position the electron occupied in the semiconductor, which becomes vacant when the electron moves as a current) move in the opposite direction. Physicists differ on whether the “holes” represent positrons (i.e., actual physical antimatter particles). I mention this for completeness. There is no scientific consensus that antimatter travels backward in time.

Where does this leave us? I think this question deserves a complete answer. Stay tuned for part 2.

Source: How to Time Travel (2013), Louis A. Del Monte