What do scientists think about creating a time machine? Is it scientifically possible, or is it just the imagination of science fiction writers and dreamers?
Lev Safonkin, a reporter of the Chudesa i Vklyucheniya magazine, talks about this with a famous Russian astrophysicist, a leading researcher at the Institute of Theoretical and Experimental Physics and the State Astronomical Institute named after Sternberg Doctor of Physical and Mathematical Sciences S. I. Blinnikov
Sergey Ivanovich, astronomy, obviously, constantly deals with travel to the past, since light in space travels at a speed of no more than 300,000 km per second. Does this mean that all observations of astronomers do not refer to the present moment, but to the past tense?
- Quite right. The universe has a limit on the speed of light in a vacuum, and therefore, any instrument for observing the space around us is automatically a time machine. We are so used to it that we hardly pay attention to it. I do not mean specialists, who always realize that the more distant objects they observe, the more distant time this applies, but, so to speak, wide public circles. Modern telescopes already look into regions of the Universe that are billions of light years distant from us. This means that we see, say, quasars not in the form in which they are now, but as they were billions of years ago.
- Is a telescope a kind of time machine capable of looking into the past for, say, a billion years already today?
- Yes, we do, but we do not know anything about how these quasars look today. We can only build mathematical models and try to represent their evolution to the present moment.
- Will we never know what they are now?
- Theoretically, we could find out if, on a certain time machine, such as the one we all know from the movie "Ivan Vasilyevich Changes His Profession", we were quickly transported a billion years ahead. Then, if the Earth and civilization still existed, we could observe these quasars through a telescope and return to our time. In this case, we would have information about the current state of these quasars.
- And there is no other way?
- It is possible and in another way. If the time machine on Earth cannot be built, then a spaceship will serve instead. Under certain conditions, it will take us to the future, and as far as we like. This explains the so-called twin paradox, which follows from the equations of Einstein's special theory of relativity. Namely, if our hypothetical starship can accelerate almost to the speed of light, then, for example, by sending one twin twin on it, we will see that, having flown in space for a year (according to the ship's clock) at near-light speed, the twin astronaut will hardly age and will return to the Earth cheerful and healthy. But his brother on Earth can get old very much, depending on how much his twin astronaut approaches the speed of light. In the year that has passed on board the starshipa twin on Earth can even live to the end of his biological life. Moreover, centuries, millennia, or even millions and billions of years can pass on Earth, because time in a starship flying at near-light speed is terribly slowing down.
- Oh well! People will be able to get into the future due to the near-light speed. But what will it give them if it is impossible to return?
- You can find a thousand reasons why this way of traveling to the future was justified. Here is a typical example: a person is sick with cancer and is sentenced to death by doctors in a year. Modern medicine is powerless. What to do? The most logical thing is that if this person is ready for anything, send him into the future, say, for five hundred years. If civilization does not destroy itself, then oncology is likely to be already curable. It is possible, for safety reasons, to send such a patient into the future sequentially several times, say, with an interval of a hundred years, until he gets into an era when they will cope with oncology no worse than with appendicitis. In payment for hospitality and treatment, such a time traveler could share with people of the future invaluable information about the past, antiques, etc. It would be great to dream up about this topic.
- Is it possible not to fly anywhere and still get into any future, even the most distant? I do not mean traveling back in time, because the problem is even more difficult.
- This question is also not easy. We will proceed from the fact that now on Earth there is no time machine, as such. Neither as a purely natural phenomenon, nor as an artificial structure or mechanism, stuffed with equipment, nor as a physical law. The exception is particle accelerators - synchrophasotrons, where elementary particles, accelerating to near-light speeds, acquire a huge mass and extend their life thousands of times. Cosmic rays, falling on the Earth, also travel to the future because of their near-light speed. But let's not dwell on the microworld, because we are talking about the ordinary earthly world, to which near-light speeds are contraindicated.
It turns out that in order to travel to the future, you will have to leave Mother Earth. But in order not to wander through space, but as if from one point to see the entire future of the Universe, all its times and epochs, it would be possible to direct the ship to a massive black hole. It would be a wonderful experiment. Suppose that the ship's engines are so powerful and tireless that a black hole cannot immediately absorb it.
It will hover at some kind of libration point (from the Latin libratio - swing, oscillation) and since light will be absorbed by the black hole all the time, it will be able to provide astronauts with ideal conditions for accelerated observation of the evolution of the Universe. Time in the ship will go the same as always, but relative to it, in the Universe, it will accelerate terribly. This is a feature of a black hole. Its monstrous mass, compressed in a small volume, not only bends space, but also slows down time. Being in a ship above a black hole, astronauts during the period of one human life will be able to see at an accelerated rate everything that will happen to the Universe over billions of years. They may even live to see the end of the world predicted by some cosmologists.
But will not be able to return to their era and their time?
- Even if they break away from the black hole and return to Earth, the same thousands, millions or billions of years will also pass there, and the path to their original epoch will never be found.
Is there really no physical laws that would allow us to move freely back and forth in time? Or do they exist, but we do not know about them?
- Nothing can be stated absolutely and categorically, but personally I do not believe in it, as it leads to a lot of problems with the principle of causality. At the same time, it cannot be unconditionally asserted that it is possible to travel in time only to the future, and the return journey is impossible. If we do not see this path yet, do not know about it, this does not mean that it does not exist.
For example, corresponding member. RAS Igor Dmitrievich Novikov several years ago, he seriously discussed specific projects of this kind based on the so-called "wormholes" of space-time (they are also called wormholes). There are other projects as well.
“So you don’t deny that there is some way out for time travelers?”
- Travel to the distant future does not contradict any known laws of nature. The obstacles here are of a purely technical or energetic nature.
But I hope for the power of the human mind. However, when traveling to the future, people will always wonder if travel to the past is possible. It is very difficult to argue on this topic, but remember, until recently it was believed that it was impossible to prove the presence of planets even in the stars closest to us by means of astronomy. But scientific and technical progress and the development of astronomy led to the fact that at the end of the last century astronomers began to discover exoplanets one after another. In our time, their number has passed over a hundred and continues to grow rapidly. Recently, candidates for the title of the tenth planet of the solar system have been discovered beyond the orbit of Pluto: Kwavar, Sedna and the third, not yet named planetoid. In this distant zone, there may be other giant objects that can only be guessed at. The Americans are going to use space probes and telescopes they put into space to discover a whole belt of small volcano planets between the orbit of Mercury and the Sun. And here is the latest example of progress in astronomy: with the Hubble Space Telescope, scientists recently discovered the presence of carbon and oxygen in the atmosphere of one exoplanet. But this planet is 140 light years distant from us!
A decade ago, the whole world would have considered such a discovery a miracle. Who then could have studied exoplanets in such detail? So the theoretical restrictions and prohibitions on various time machines that already exist in the Universe and, possibly, will be built for their own purposes by man, may not be so insurmountable, as it seems to us now, at our level of development of science and technology.