Can travel through time?

People want to fly to the future and return to the past? The answer is that physical principles are not forbidden, but technical barriers are insurmountable in the universe we live in.

The only way to travel to the future is to use the time effect to slow down on the very fast flying spacecraft of special relativity. If you leave the earth on a ship that accelerates continuously with gravitational acceleration (so that the body experiences a favorable acceleration force by the attraction of the Earth), after one year it can reach close to the speed of light. Continuing to accelerate, we can fly quickly to approximate light. Then the flight to the center of the Milky Way and then returned (a distance of 60,000 light years) took only 40 years, while on Earth, 600 centuries have passed. You will meet the future of humanity, with how many things change, if humanity still exists.

Although there is no physical rule that prevents such an interesting trip, technical difficulties are hard to overcome. For example, the energy required, even when converting the mass completely into energy according to the system E = mc ² , is greater than the mass of the planet.

The ability to travel back in time is even more difficult, although the laws of science also do not prohibit. The problem is creating the appropriate time machine.

The first possibility, introduced by Frank Tipler of the University of Maryland, in 1973, involved a naked bizarre that rotated very quickly (oddly, an infinite density, such as a black hole). At that time, the timeless structure is too strong for gravitational field to twist, causing one dimension to be replaced by time. The nearby cautious flying spacecraft may be fortunate to meet an orbit that the crew thinks is still traveling through space, but is through time. When leaving the singularity, the ship will appear at another time, like the time when the prehistoric people lived in the cave.

This ability is not as difficult as it seems: a cylinder 100 km long, 10 km wide, containing matter with the density of neutron stars (100 million tons / cm3), rotating two thousand rings a second is satisfactory. In the universe, some pulses are close to this standard.

The second time machine relates to a wormhole, the trans-space-time tunnel system, like a wormhole on your apple. According to general relativity, deep holes can connect a black hole in this space-time zone with a black hole or white hole in another space-time zone (as opposed to black holes that always attract matter and energy, white holes Big Bang is a white hole like that.

The concept of deep holes appears in physics in a humorous way. Number is astronomer Carl Sagan, author of the famous nuclear winter scenario, writing a fictional book about traveling through black holes to go from earth to hypothetical Vega star. Wanting the most accurate scientific arguments, Sagan calculated Kip Thorne, an attractive school expert at the California Institute of Technology.

At the end of 1985, Thorne realized that the wormhole could be opened when it contained a strange material with great tension to resist gravity in the black hole . Most suitable are cosmic strings, hypothetical matter in the form of smaller energy-stimulating atomic tubes that stretch across the universe. If it is true, and it is inserted into a deep hole, it is capable of keeping the wormhole always open to play a tunnel through space-time.

It was a very interesting conclusion to science, but Thorne was afraid of others laughing and arguing that he was crazy to study the possibility of traveling through time. Perhaps he did not know that the Tipler was unharmed when he studied the time machine, so he was very worried when the students announced their work, their careers would dissipate before starting. Careful and secretive research with Mike Morris and Ulvi Yurtsever, he gradually convinced himself that, indeed, Einstein's equations allow deep holes to connect time points together and thus play the role of a time machine. .

By 1988, three people published results in the famous journal Physical Review Letters . Still afraid of an unfavorable reaction, he asked the Institute leader not only to keep quiet but also to firmly forbid people to discuss the project.

The result is contrary to Thorne's worry. Both professionals and the public are very excited about the ability to travel through time, though only in theory. His career has grown markedly, with two students being offered many jobs. According to his example, many physicists publish in-depth research results with mass readers, a welcome side. The California Institute of Technology became the mecca of time travel.

Immediately appeared a series of works about traveling through space-time. While experts are biased towards the scientific and philosophical aspects, amateurs happily declare, that is how humanity travels towards the future or back to the past. But " grandfather paradox " can cool that excitement. Suppose you traveled back to the past and accidentally killed your grandfather when he was little, when he had not given birth to your father. Without a father, why is there a friend to travel back in time? There is also an opinion that you may not meet your grandfather, but that is just a sophistication (why not?).

That is why Hawking introduced " Predicting the protection of chronology ", in which the laws of physics prohibit a macro entity from traveling through time. To travel like that, you need to jump into the black hole, and immediately you are crushed into the basic particles, through the wormhole to erupt in a white hole in the other time-space. Only the basic particles used to create sexy long legs, not the model herself, experienced that amazing journey.