Time Warped Travelers
Lists with This Book. This book is not yet featured on Listopia. May 04, Ruty B rated it really liked it Shelves: Tommy is a twentyish time traveler who after seeing a photo of a beautiful girl, transports himself to Time Warped Travelers is a book with humor, suspense, love and great characters, a fast and engaging reading. A hilarious and adventurous boy, Tommy is one of the funniest characters I ever read about.
Imagine a twentyish boy living almost a century before his time, he surely will do and say things that would look out of place. Every time he makes a mistake, says something from his time or Tommy is a twentyish time traveler who after seeing a photo of a beautiful girl, transports himself to Every time he makes a mistake, says something from his time or uses his knowledge from the future, you can expect to laugh and a lot.
In he meets Elizabeth, a. Have to say that Foke like Coke but with something especial sounds really interesting and seeing them acting like crazy after drinking it was great. One thing that you have to take on account is that this is an adults book so it has some sex scenes in it, which are well written nothing to erotic placed at the right time.
Another high point is the explanation of why he can time travel, there is never a scientific or complicated explanation. For me this is great because is not a sci-fi book not in extreme at least , he woke up someday with this possibility and he just does it. Simple, believable and entertaining. Cutting-edge physics may not be able to answer those questions yet, but it does offer up some tantalizing possibilities. Roman take readers on a clear, concise tour of our current understanding of the nature of time and space—and whether or not we might be able to bend them to our will.
Using no math beyond high school algebra, the authors lay out an approachable explanation of Einstein's special relativity, then move through the fundamental differences between traveling forward and backward in time and the surprising theoretical connection between going back in time and traveling faster than the speed of light. They survey a variety of possible time machines and warp drives, including wormholes and warp bubbles, and, in a dizzyingly creative chapter, imagine the paradoxes that could plague a world where time travel was possible—killing your own grandfather is only one of them!
Written with a light touch and an irrepressible love of the fun of sci-fi scenarios—but firmly rooted in the most up-to-date science, Time Travel and Warp Drives will be a delightful discovery for any science buff or armchair chrononaut.
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To see video demonstrations of key concepts from the book, please visit this website: Unfortunately, most are frothy concoctions that leave the serious reader unsatisfied. This is all the more reason to celebrate the arrival of Time Travel and Warp Drives— a deeply informed, richly detailed yet immensely readable account of science at the frontiers, by two physicists who know the territory. For well over a decade Allen Everett and Thomas Roman have been charting the strange realms of negative energy, twisted spacetime, temporal paradoxes, and travel between universes.
This book stands out in its depth and range. Written by two who have done the calculations, followed the field, and thought about what it all means, it leads the reader through the byzantine labyrinths of current theory. I found it enlightening and fun to read. If you have time for one book in this field, let it be this one. With Time Travel and Warp Drives , Everett and Roman have written an illuminating exploration of the physics of time travel.
What sets this book apart, however, is that the authors do not rely on analogies or metaphors. They actually explain the underlying science in a clear and accessible way. According to current theories on the nature of wormholes, construction of a traversable wormhole would require the existence of a substance with negative energy, often referred to as " exotic matter ". More technically, the wormhole spacetime requires a distribution of energy that violates various energy conditions , such as the null energy condition along with the weak, strong, and dominant energy conditions.
However, it is known that quantum effects can lead to small measurable violations of the null energy condition, : In , Matt Visser argued that the two mouths of a wormhole with such an induced clock difference could not be brought together without inducing quantum field and gravitational effects that would either make the wormhole collapse or the two mouths repel each other. However, in a paper, Visser hypothesized that a complex " Roman ring " named after Tom Roman configuration of an N number of wormholes arranged in a symmetric polygon could still act as a time machine, although he concludes that this is more likely a flaw in classical quantum gravity theory rather than proof that causality violation is possible.
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Another approach involves a dense spinning cylinder usually referred to as a Tipler cylinder , a GR solution discovered by Willem Jacob van Stockum  in and Kornel Lanczos  in , but not recognized as allowing closed timelike curves : If a cylinder is infinitely long and spins fast enough about its long axis, then a spaceship flying around the cylinder on a spiral path could travel back in time or forward, depending on the direction of its spiral. However, the density and speed required is so great that ordinary matter is not strong enough to construct it.
A similar device might be built from a cosmic string , but none are known to exist, and it does not seem to be possible to create a new cosmic string. Physicist Ronald Mallett is attempting to recreate the conditions of a rotating black hole with ring lasers, in order to bend spacetime and allow for time travel.tolsen.com.ua/images/472/7470-soltera-y-sin.php
Time Warped Travelers by Robert Westfall
A more fundamental objection to time travel schemes based on rotating cylinders or cosmic strings has been put forward by Stephen Hawking, who proved a theorem showing that according to general relativity it is impossible to build a time machine of a special type a "time machine with the compactly generated Cauchy horizon" in a region where the weak energy condition is satisfied, meaning that the region contains no matter with negative energy density exotic matter.
Solutions such as Tipler's assume cylinders of infinite length, which are easier to analyze mathematically, and although Tipler suggested that a finite cylinder might produce closed timelike curves if the rotation rate were fast enough, : But Hawking points out that because of his theorem, "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 can define geometrical quantities that measure the Lorentz boost and area increase on going round these closed null geodesics. If the causality violation developed from a noncompact initial surface, the averaged weak energy condition must be violated on the Cauchy horizon.
When a signal is sent from one location and received at another location, then as long as the signal is moving at the speed of light or slower, the mathematics of simultaneity in the theory of relativity show that all reference frames agree that the transmission-event happened before the reception-event. When the signal travels faster than light, it is received before it is sent, in all reference frames.
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This hypothetical scenario is sometimes referred to as a tachyonic antitelephone. Quantum-mechanical phenomena such as quantum teleportation , the EPR paradox , or quantum entanglement might appear to create a mechanism that allows for faster-than-light FTL communication or time travel, and in fact some interpretations of quantum mechanics such as the Bohm interpretation presume that some information is being exchanged between particles instantaneously in order to maintain correlations between particles.
Nevertheless, the fact that causality is preserved in quantum mechanics is a rigorous result in modern quantum field theories , and therefore modern theories do not allow for time travel or FTL communication. In any specific instance where FTL has been claimed, more detailed analysis has proven that to get a signal, some form of classical communication must also be used. A variation of Everett's many-worlds interpretation MWI of quantum mechanics provides a resolution to the grandfather paradox that involves the time traveler arriving in a different universe than the one they came from; it's been argued that since the traveler arrives in a different universe's history and not their own history, this is not "genuine" time travel.
This concept is most often used in science-fiction, but some physicists such as David Deutsch have suggested that a time traveler should end up in a different history than the one he started from. Everett also argues that even if Deutsch's approach is correct, it would imply that any macroscopic object composed of multiple particles would be split apart when traveling back in time through a wormhole, with different particles emerging in different worlds.
Certain experiments carried out give the impression of reversed causality , but fail to show it under closer examination. The delayed choice quantum eraser experiment performed by Marlan Scully involves pairs of entangled photons that are divided into "signal photons" and "idler photons", with the signal photons emerging from one of two locations and their position later measured as in the double-slit experiment.
Depending on how the idler photon is measured, the experimenter can either learn which of the two locations the signal photon emerged from or "erase" that information. Even though the signal photons can be measured before the choice has been made about the idler photons, the choice seems to retroactively determine whether or not an interference pattern is observed when one correlates measurements of idler photons to the corresponding signal photons.
However, since interference can only be observed after the idler photons are measured and they are correlated with the signal photons, there is no way for experimenters to tell what choice will be made in advance just by looking at the signal photons, only by gathering classical information from the entire system; thus causality is preserved. The experiment of Lijun Wang might also show causality violation since it made it possible to send packages of waves through a bulb of caesium gas in such a way that the package appeared to exit the bulb 62 nanoseconds before its entry, but a wave package is not a single well-defined object but rather a sum of multiple waves of different frequencies see Fourier analysis , and the package can appear to move faster than light or even backward in time even if none of the pure waves in the sum do so.
This effect cannot be used to send any matter, energy, or information faster than light,  so this experiment is understood not to violate causality either. Nimtz told New Scientist magazine: Aephraim Steinberg, a quantum optics expert at the University of Toronto , Canada, uses the analogy of a train traveling from Chicago to New York, but dropping off train cars at each station along the way, so that the center of the train moves forward at each stop; in this way, the speed of the center of the train exceeds the speed of any of the individual cars. Shengwang Du claims in a peer-reviewed journal to have observed single photons' precursors , saying that they travel no faster than c in a vacuum.
His experiment involved slow light as well as passing light through a vacuum. He generated two single photons , passing one through rubidium atoms that had been cooled with a laser thus slowing the light and passing one through a vacuum. Both times, apparently, the precursors preceded the photons' main bodies, and the precursor traveled at c in a vacuum. According to Du, this implies that there is no possibility of light traveling faster than c and, thus, no possibility of violating causality.
The absence of time travelers from the future is a variation of the Fermi paradox. As the absence of extraterrestrial visitors does not prove they do not exist, so the absence of time travelers fails to prove time travel is physically impossible; it might be that time travel is physically possible but is never developed or is cautiously used. Carl Sagan once suggested the possibility that time travelers could be here but are disguising their existence or are not recognized as time travelers.
Stephen Hawking stated that this would explain why the world has not already been overrun by "tourists from the future.
Time Warped Travelers
Several experiments have been carried out to try to entice future humans, who might invent time travel technology, to come back and demonstrate it to people of the present time. Events such as Perth's Destination Day or MIT 's Time Traveler Convention heavily publicized permanent "advertisements" of a meeting time and place for future time travelers to meet. Some versions of the many-worlds interpretation can be used to suggest that future humans have traveled back in time, but have traveled back to the meeting time and place in a parallel universe.
There is a great deal of observable evidence for time dilation in special relativity  and gravitational time dilation in general relativity,    for example in the famous and easy-to-replicate observation of atmospheric muon decay. Time dilation is a direct consequence of the invariance of the speed of light.
This can be achieved by traveling at relativistic speeds or through the effects of gravity. For two identical clocks moving relative to each other without accelerating, each clock measures the other to be ticking slower. This is possible due to the relativity of simultaneity. However, the symmetry is broken if one clock accelerates, allowing for less proper time to pass for one clock than the other.
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The twin paradox describes this: General relativity treats the effects of acceleration and the effects of gravity as equivalent , and shows that time dilation also occurs in gravity wells , with a clock deeper in the well ticking more slowly; this effect is taken into account when calibrating the clocks on the satellites of the Global Positioning System , and it could lead to significant differences in rates of aging for observers at different distances from a large gravity well such as a black hole.
A time machine that utilizes this principle might be, for instance, a spherical shell with a diameter of 5 meters and the mass of Jupiter. A person at its center will travel forward in time at a rate four times that of distant observers. Squeezing the mass of a large planet into such a small structure is not expected to be within humanity's technological capabilities in the near future.
A Scientific Guide to Shortcuts through Time and Space
Philosophers have discussed the nature of time since at least the time of ancient Greece ; for example, Parmenides presented the view that time is an illusion. Centuries later, Isaac Newton supported the idea of absolute time , while his contemporary Gottfried Wilhelm Leibniz maintained that time is only a relation between events and it cannot be expressed independently. The latter approach eventually gave rise to the spacetime of relativity.
Many philosophers have argued that relativity implies eternalism , the idea that the past and future exist in a real sense, not only as changes that occurred or will occur to the present. Presentism is a school of philosophy that holds that the future and the past exist only as changes that occurred or will occur to the present, and they have no real existence of their own. In this view, time travel is impossible because there is no future or past to travel to.
Presentism in classical spacetime deems that only the present exists; this is not reconcilable with special relativity, shown in the following example: Alice and Bob are simultaneous observers of event O. Therefore, Alice and Bob disagree about what exists in the present, which contradicts classical presentism. A common objection to the idea of traveling back in time is put forth in the grandfather paradox or the argument of auto-infanticide.
Some philosophers answer the paradoxes by arguing that it might be the case that backward time travel could be possible but that it would be impossible to actually change the past in any way,  an idea similar to the proposed Novikov self-consistency principle in physics.
According to the philosophical theory of compossibility , what can happen, for example in the context of time travel, must be weighed against the context of everything relating to the situation. If the past is a certain way, it's not possible for it to be any other way.