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?
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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.

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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.

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Can Time Travel Be Used as a Weapon?

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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.

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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.