Tag Archives: time travel

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

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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

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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

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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