Even before Einstein suggested that time is relative and flexible, humanity was already thinking about time travel. Sci-fi heroes make such movements thanks to their superpowers, but more often they use a device known as a "time machine".

Physicists from the United States and Canada proposed their idea of ​​what a real machine could be for traveling between the past and the future from a mathematical point of view.

Curved space-time. © Interior Design | Shutterstock

“People think of time travel as fantastic, and we are no exception. But mathematically it is possible "

The division of space into three dimensions with time in a separate scientist calls it incorrect. Four dimensions, he said, must be represented simultaneously, when different directions are connected, as a space-time continuum. Based on Einstein's theory, the curvature of space-time is the orbits of the planets. In "flat" space-time, planets and stars would move in straight lines.

The time machine model uses the curvature of spacetime in the universe to bend time for passengers into a circle instead of a straight line. A kind of "bubble" or "box" of space-time geometry carries all space and time along a closed circular trajectory with a speed many times higher than the speed of light to obtain constant acceleration. In fact, it moves "forward" and then "backward" in time.

In some respects, this resembles bubble Alcubierre and hypothetical closed timelike curves (English closed timelike curve)... This is how the idea looks schematically.

The passenger inside the bubble / time machine - A. Outside observer - B. The arrow of time, which under normal conditions (at least for our Universe) always points forward, turning the past into the present, is represented by black arrows.

Both person A and person B will experience time in different ways, the researchers explain:

“The one inside the bubble A will see that the events of B periodically develop and then reverse. Observer B will see two versions of A in the same place, as some hands will rotate clockwise and others in reverse direction».

While it is possible to describe this type of time travel using a mathematical equation, Tippett doubts that anyone will ever build a workable machine.

“This is not possible yet, because we need materials, which we call exotic matter, to bend space-time in such an incredible way. But they may be discovered in the future. "

The time machine was named TARDIS (English Traversable Acausal Retrograde Domain in Spacetime) as in the British TV series Doctor Who. Research published in the journal Classical and Quantum Gravity.

Scientists have confirmed the reality of time travel

Professor of Physics and Mathematics at Columbia University and co-founder of the World Science Festival Brian Greene told what scientists know about time travel.

It is very important that you understand that there are two types of time travel, and they are radically different. Traveling to the future is definitely possible. We know how to do this because Einstein showed us the way over a hundred years ago. It's amazing how little people know about this. He showed that if you go out into space and fly at near light speed, then your clock will go slower. Thus, when you return, there will already be a distant future on Earth.

© andrey_l | Shutterstock

He also showed that if you hover near a sufficiently powerful source of gravity - neutron star or a black hole - and get close to the edge of this object at a safe distance, time for you will also slow down in relation to everything else. And then, when you return to Earth, you will again find yourself in the distant future.

There is no doubt about that. Any physicist who knows what this is about will agree with this. But another kind of time travel - travel into the past through a time machine - is already a topic of discussion, and most scientists consider it impossible.

The main concept of the time machine, which is usually given attention when discussing travel to the past, is associated with the so-called wormholes, or wormholes. Roughly speaking, it is a bridge from one place to another or a tunnel that offers you the shortest path to cross. Einstein discovered this phenomenon in 1935, but later realized that if you manipulate the holes in a wormhole - approach a black hole or move at high speed - then the time in the two holes in this tunnel will go with different speed so that you no longer just move from one place in space to another. If you walk through this tunnel, you will go from one point in time to another point in time. Following one path, you will go to the past, and the other - on the contrary, to the future.

But we do not know how real they are and whether you can get through them. So there are all kinds of uncertainties here. Most scientists believe that you will not be able to get through the wormhole into the past, but on the other hand, this is still possible.

The universe could be a hologram

The idea that the universe could be a giant hologram - a two-dimensional reality that only appears to be three-dimensional - has long been in the scientific community. Not so long ago, a team of Austrian researchers made mathematical calculations to prove that such a scenario is not as implausible as it seems. The calculation results were published in the journal Physical Review Letters.

© Technische Universität Wien

The hypothesis that our universe is a three-dimensional projection on a flat surface in outer space - goes back to the holographic principle. According to the concept outlined in the 1990s. physicists Gerard 't Hooft and Leonard Susskind, all the information you need to full description areas of space can be encoded in two dimensions.

To prove such a bold assumption, it is required that there is a phenomenon whose physics would be described and quantum theory field, and in the theory of quantum gravity of flat space, and the corresponding calculations were correct.

In a recent study, scientists calculated the natural rates of entropy of quantum entanglement - the entanglement between molecules (the process of particle binding and their effect on each other) in a quantum system - and found that the entropy entropy value was the same in flat space quantum gravity, and in two-dimensional quantum field theory.

This means that the holographic principle is applicable to our universe, which, therefore, could theoretically be a giant hologram. Which, of course, does not mean that it is it - it is just that now it has become more difficult to exclude such a state of affairs.

A system for computer modeling of the Universe has been developed

A group of British and Dutch astronomers have developed a system for computer modeling of the universe. Thanks to this, scientists will be able to study the development of galaxies and understand how the universe is expanding.

© Maria Starovoytova | Shutterstock.com

A system called EAGLE (Evolution and Assembly of GaLaxies and their Environments - Evolution and formation of galaxies and surrounding regions) is designed to create computer models of galaxies, the mass, size and age of which are similar to those observed in the real Universe. It is reported by "RIA News"... An article describing the results of the work of scientists will be published in January 2015 in the journal Monthly Notices of the Royal Astronomical Society.

Recall that recently NASA specialists released images of the merger of the galaxies NGC 2207 and IC 2163, obtained using the equipment of the American X-ray observatory "Chandra". Merging galaxies are located in the constellation Big Dog at a distance of 130 million light years from Earth. Over the past 15 years, they have recorded three supernova explosions.

In addition, the space scientific community is alarmed by the discovery of an unusual spiral galaxy containing huge streams elementary particles that rush outward at almost the speed of light.

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Theoretical physicist Ben Tippett of the University of British Columbia, along with University of Maryland astrophysicist David Zang, have created what they say is a working mathematical model of a "time machine" that uses the principle of curvature of the space-time of the universe. The research and findings of the scientists were published in the journal Classical and Quantum Gravity.

Scientists, based on the general theory of relativity, deduced a mathematical model that they called TARDIS or Traversable Acausal Retrograde Domain in Space-time. But do not rush to rejoice at the opportunity to visit your long-deceased grandmother in the past, scientists say. There is a problem that does not allow us to check the correctness of their mathematical model, but more on that later.

“People think of time travel as fiction. In fact, we think it's impossible just because we haven't actually tried to do it yet, ”says theoretical physicist and mathematician Ben Tippett.

"However, a time machine is possible, at least mathematically," adds the scientist.

The scientists' model is based on the idea of ​​the presence of the fourth dimension of the Universe, which is time. In turn, this allows us to assume the existence of a space-time continuum in which different directions of space and time are connected by the fabric of the Universe.

Einstein's theory of relativity links the gravitational effects of the universe to the curvature of spacetime, a phenomenon behind the elliptical orbits of planets and stars. In the presence of "flat" or non-curved space-time, the planets would move in a straight line. However, the theory of relativity says that the geometry of spacetime becomes curved in the presence of very massive objects, causing them to orbit the stars.

Tippett and Tsang believe that not only space can be curved in the universe. Time can also be curved under the influence of an object with a large mass. They cite the space around black holes as an example.

“The movement of time inside space-time can also be curved. Black holes are an example. The closer we get to them, the slower time begins to flow for us, ”says Tippett.

“My model of a time machine uses curved space-time to make time for passengers a circle rather than a straight line. And movement in this circle can send us back in time. "

To test the hypothesis, scientists propose to create something like a bubble that can carry everyone who is in it through time and space along a curved trajectory. If this bubble moves at a speed higher than the speed of light (according to scientists, this is also mathematically possible), then this will allow everyone who is in the bubble to move back in time.

The idea becomes clearer when you look at the scheme proposed by Tippet. It has two actors: one is inside the bubble / time machine (person A), the other is an external observer outside the bubble (person B).

The arrow of time, which under normal conditions (that is, in our Universe) always moves forward, in the presented scheme makes the past become the present (indicated by black arrows). According to the scientist, each of these people will feel the movement of time differently:

“Inside the bubble, object A will see B's events periodically change and then reverse. Outside the bubble, observer B will see that two versions of A are exiting from the same location: hour hand turns to the right and the other turns to the left. "

In other words, an outside observer will see two versions of objects inside a time machine: one version will evolve forward in time, the other backward.

Everything sounds, of course, very interesting, but Tippett and Zang say, we have not reached such a level of technology that this hypothesis could be tested in practice. We simply do not have materials suitable for the construction of such a time machine.

“Although from a mathematical point of view it might work, we cannot build such a machine to travel within space-time, since we do not have the necessary materials for this. And exotic materials are required here. They will allow space-time to bend. Unfortunately, science has not yet invented anything like that, ”says Tippett.

The idea of ​​Tippett and Zang echoes another idea of ​​a time machine, the so-called Alcubierre bubble, which should also use exotic materials to move in space and time. Only in this case we are not talking about circular motion in the space-time field, but about motion by compressing space in front of you and expanding it behind.

Physicists from the University of Queensland in Australia have set themselves the challenge
simulate a computer experiment that will prove the possibility of time travel at the quantum level, predicted back in 1991.

They managed to simulate the behavior of a single photon, which passes through a wormhole in space-time into the past and enters into interaction with itself.

Such a trajectory of a particle is called a closed time-like curve - the photon returns to the original space-time point, i.e. his world line becomes closed.

The researchers considered two scenarios. In the first of them, the particle passes through the mole, returning to its past, and interacts with itself. In the second scenario, the photon, forever enclosed in a closed timelike curve, interacts with another, ordinary particle.

According to scientists, their work will make an important contribution to the unification of two great physical theories, which until now had little in common: Einstein's general theory of relativity (GR) and quantum mechanics.

Einstein's theory describes the world of stars and galaxies, while quantum mechanics explores mainly the properties of elementary particles, atoms and molecules.

- Martin Ringbauer, University of Queensland

Einstein's general relativity admits the possibility of an object traveling backward in time, which falls into a closed timelike curve. However, such a possibility can cause a number of paradoxes: a time traveler can, for example, prevent his parents from meeting, and this will make it impossible for his own birth.

In 1991, it was first suggested that time travel in the quantum world could eliminate such paradoxes, since the properties of quantum particles are not precisely defined, according to the Heisenberg uncertainty principle.

In a computer experiment, Australian scientists were the first to study the behavior of quantum particles in such a scenario. At the same time, new interesting effects were revealed, the appearance of which is impossible in standard quantum mechanics.

For example, it turned out that it is possible to accurately distinguish different states quantum system, which is completely out of the question if you stay within the framework of quantum theory.

Sources:
http://iopscience.iop.org/article/10.1088/1361-6382/aa6549/meta;jsessionid=F0836BB9CB9CAE5578D9E6B7E07F4CF5.c1.iopscience.cld.iop.org

“People think of time travel as fantastic. We used to think that this is impossible, since we do not do it., - told Ben Tippett(Ben Tippett), theoretical physicist and mathematician at the University of British Columbia in Canada. - But mathematically it is possible. "

Tippett and his colleague David Tsang created a mathematical model called Traversable Acausal Retrograde Domain in Space-time (TARDIS).

Tippett and Tsang used Einstein's General Theory of Relativity as the basis for their model. The theory connects gravitational effects in the Universe with the deformation of space-time. It is this curvature that explains the displacement of the orbits of the planets, which are affected by the gravity of massive space objects.

Tippett and Tsang argue that not only can physical space be curved or twisted - time can also be curved when objects of large mass are near.

“The direction of time on the surface of space-time also shows distortion. It is known that the closer we are to the black hole, the slower time flows,- explains Tippett. - My model of a time machine uses curved space-time to enclose the time curve. "

The researchers described the time machine as a "bubble" in which a "box" with an observer moves in a circle in space-time. The speed of the box is several times faster than the speed of light, which allows it to return to the past.

“This bubble will be able to move in a circular path, first forward and then backward. Outside observers will be able to see how the "travelers" are developing in the opposite direction: they collect the eggshells and separate the cream from the coffee. "


Image: B. K. Tippett et. al. / sciencealert.com

The researchers described what observers would see inside and outside the bubble. The observer inside the bubble will first be able to observe the development of events in the "usual" direction, and then in the opposite direction. An observer outside the bubble will see two scenarios for the development of events inside the "machine" - both "forward" and "reverse".

"Although it is mathematically feasible, it is not yet possible to build a space-time machine.", - write the authors of the work. For this, in their opinion, "exotic matter" will be needed, which will allow the necessary curvature of space-time. Her man has yet to be discovered.

Theoretical physicist Ben Tippett of the University of British Columbia, along with University of Maryland astrophysicist David Zang, have created what they say is a working mathematical model of a "time machine" that uses the principle of curvature of the space-time of the universe. The research and findings of the scientists were published in the journal Classical and Quantum Gravity.

Scientists, based on the general theory of relativity, deduced a mathematical model that they called TARDIS or Traversable Acausal Retrograde Domain in Space-time. But do not rush to rejoice at the opportunity to visit your long-deceased grandmother in the past, scientists say. There is a problem that does not allow us to check the correctness of their mathematical model, but more on that later.

“People think of time travel as fiction. In fact, we think it's impossible just because we haven't actually tried to do it yet, ”says theoretical physicist and mathematician Ben Tippett.

"However, a time machine is possible, at least mathematically," adds the scientist.

The scientists' model is based on the idea of ​​the presence of the fourth dimension of the Universe, which is time. In turn, this allows us to assume the existence of a space-time continuum in which different directions of space and time are connected by the fabric of the Universe.

Einstein's theory of relativity links the gravitational effects of the universe to the curvature of spacetime, a phenomenon behind the elliptical orbits of planets and stars. In the presence of "flat" or non-curved space-time, the planets would move in a straight line. However, the theory of relativity says that the geometry of spacetime becomes curved in the presence of very massive objects, causing them to orbit the stars.

Tippett and Tsang believe that not only space can be curved in the universe. Time can also be curved under the influence of an object with a large mass. They cite the space around black holes as an example.

“The movement of time inside space-time can also be curved. Black holes are an example. The closer we get to them, the slower time begins to flow for us, ”says Tippett.

“My model of a time machine uses curved space-time to make time for passengers a circle rather than a straight line. And movement in this circle can send us back in time. "

To test the hypothesis, scientists propose to create something like a bubble that can carry everyone who is in it through time and space along a curved trajectory. If this bubble moves at a speed higher than the speed of light (according to scientists, this is also mathematically possible), then this will allow everyone who is in the bubble to move back in time.

The idea becomes clearer when you look at the scheme proposed by Tippet. It has two characters: one is inside the bubble / time machine (person A), the other is an external observer outside the bubble (person B).

The arrow of time, which under normal conditions (that is, in our Universe) always moves forward, in the presented scheme makes the past become the present (indicated by black arrows). According to the scientist, each of these people will feel the movement of time differently:

“Inside the bubble, object A will see B's events periodically change and then reverse. Outside the bubble, observer B will see that two versions of A are coming out of the same location: the hour hand is turning to the right and the other to the left. "

In other words, an outside observer will see two versions of objects inside a time machine: one version will evolve forward in time, the other backward.

Everything sounds, of course, very interesting, but Tippett and Zang say, we have not reached such a level of technology that this hypothesis could be tested in practice. We simply do not have materials suitable for the construction of such a time machine.

“Although from a mathematical point of view it might work, we cannot build such a machine to travel within space-time, since we do not have the necessary materials for this. And exotic materials are required here. They will allow space-time to bend. Unfortunately, science has not yet invented anything like that, ”says Tippett.

The idea of ​​Tippett and Zang echoes another idea of ​​a time machine, the so-called Alcubierre bubble, which should also use exotic materials to move in space and time. Only in this case we are not talking about circular motion in the space-time field, but about motion by compressing space in front of you and expanding it behind.