There is still no generally accepted theory of time or even a description that would suit everyone. Nevertheless, scientists have invented many time machines - after all, no physical law forbids this. Will we ever be able to manipulate this strange category of the universe.
Arrow of time
We do not perceive time with any of the senses, but we know about it intuitively and even know how, within certain limits, to predict what will happen soon. In our view, time passes, runs, flows. We are talking about the present moment, past and future. Two different events can be linked as cause and effect: one gives rise to the other. Never the other way around. This is the essence of the principle of causality, or irreversibility of time.
Nobel laureate Academician Vitaly Ginzburg included irreversibility (arrow of time) in the list of three great problems of physics.
In classical mechanics, irreversibility is due to the fact that bodies consist of many atoms, molecules, tending to a chaotic state (entropy increases). The simplest example is cream in tea. They can be stirred, but they cannot be collected back into exactly the same drop, although the molecules of the substance and their number seem to remain the same.
Another thing is the quantum world, where objects are elementary particles, fields. There the arrow of time does not exist, the processes are reversible, but only as long as we do not try to measure them, observe them. Particles are in all possible states at the same time (physicists prefer to talk about the wave function). But at the moment of measurement with our devices, they "choose" one of the states (or we choose).
Legal questions arise: is time an objective phenomenon that exists independently of consciousness, like a lake, a house, the sun? Or is it a property of consciousness, and without us it does not exist?
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“Time is the worst thing you can ask a modern physicist. The complete discord is that each of the sciences sees time only from one, its side. Therefore, we have to talk about geometric, thermodynamic, quantum-mechanical time. Even understanding why different definitions of time have something to do with each other is a problem,”says Sergei Baranov, Doctor of Physics and Mathematics, Leading Researcher at the Laboratory of Interaction of Radiation with Matter at FIAN.
The twins and the clock paradox
In the Soviet era, stories about temporary anomalies, where people, ships, and airliners fell, were popular among fans of sensations. On the Web, you will find eyewitness accounts of "time-traveling" inside a strong tornado.
According to Sergei Baranov, if you exclude deliberate deception, "time anomalies" are explained by errors of perception, breakdowns of electronics under the influence of atmospheric phenomena or industrial factors.
“Drivers passing near military radars notice GPS system failures, but this is unlikely to be related to teleportation,” the scientist gives an example.
Physicists encounter real paradoxes of time in experiments, but they are all explainable. For example, in the special theory of relativity, the "twin paradox" is known: one of the twin brothers exploring space on a fast rocket, upon returning, discovers that the twin remaining on Earth has grown older. No mysticism. It's just that in four-dimensional space-time for a moving body, time flows more slowly.
Time dilation is fixed on accelerators during decay of unstable particles. The atomic clock on board orbiting satellites, on the contrary, runs ahead a few microseconds in a day. Here gravity plays a role, which, increasing with height, slightly stretches the energy levels of electrons and nuclei.
The twins paradox. Left: One twin rocketing into space, the other - remains on Earth. Right: more time has passed for the brother who remained on Earth than for the space traveler / Illustration by RIA Novosti / Alina Polyanina.
Wormholes as a teleport
The theory of relativity predicts the existence of black holes in the Universe - objects with a huge mass that distort space. To an outside observer, it seems that ahead is the end of the world, beyond which there is nothing. This is called the event horizon. Time slows down behind it, inside the black hole any matter is torn apart by tidal forces. You can only fall into a black hole. There is no turning back.
In this sense, the "wormhole" (or "wormhole") offers more opportunities. The two entrances are connected by a short tunnel. They can be located in distant parts of our universe or be in different universes. As the physicist Michio Kaku states in The Physics of the Impossible, wormholes allow you to travel through time and space.
The problem is that wormholes are unstable and collapse under the influence of gravity. Cosmologist Igor Novikov from the Astronomical Center of the Lebedev Physical Institute believes: if the "wormhole" is filled with exotic matter with negative energy density (create antigravity), it will become passable.
“Exotic substance is a quantum state of matter, known only in theory. We do not know if there are large quantities of such a substance, whether it can be obtained artificially. There are no laws prohibiting its existence, including in nature,”the cosmologist specifies.
Modern scientific concepts assume that in the centers of galaxies, including our Milky Way, the place of black holes is occupied by "wormholes". Future projects, such as Russia's Millimetron, a space station at the Lagrange point, which, together with ground-based radio telescopes, forms a giant interferometer capable of distinguishing objects at a relatively small distance from each other, will help to understand this. Its launch is scheduled for 2023.
“The main difference between a 'wormhole' and a black hole is that the inputs have a magnetic monopole field. In addition, matter can flow out of a wormhole, but only flow into a black hole. You can look into the "wormhole" like into a corridor. If it leads to another universe, you can see what is happening there,”Novikov explains.
A wormhole that connects the two universes with an arrow of time (from the article by I. D. Novikov, 2018) / Illustration by RIA Novosti / Alina Polyanina.
Time Machine
According to the conventional theory of gravity, wormholes should be very small, with a Planck neck radius of the order of 10-33 centimeters. But the wormhole can be enlarged. For this, an additional parameter should be introduced into the theory, believes Arkady Popov, senior researcher at the Institute of Physics at Kazan Federal University.
“There is another option for increasing the radius. It is necessary to take into account the temperature of the vacuum of quantized fields - an exotic substance that creates a "wormhole" in space-time. We are calculating this now,”says the scientist.
According to him, teleportation through wormholes is not prohibited.
“It may turn out that the path through it is much shorter than through the outer space. Then the observers from the side will consider that you have moved very quickly - teleported,”Popov adds.
They also tried to create a time machine with the help of the "wormhole". For example, one end can be brought into the region of a black hole, and the other - far away, where time flows in a different way. But then all kinds of violations of the theory arise.
“This means that time machines are most likely prohibited, which, by the way, Stephen Hawking said,” the physicist recalls.
Tatiana Pichugina