Is it possible to time travel to the future or the past using a black hole?


black hole , which is thought to be formed when a huge celestial body collapses, is a celestial body whose mass is so large that space-time is distorted and even light cannot escape. Sam Baron, a philosopher of science at the Catholic University of Australia, explains whether time travel to the past and future is possible using such a black hole.

Are black holes time machines? Yes, but there's a catch

A black hole is a very massive celestial body that is formed when a huge star collapses. Like celestial bodies such as the earth and the sun, black holes also have gravity, and it is said that the greater the mass of the celestial body, the stronger the gravity. A black hole's gravity is so strong that not even light can escape, and when viewed from the outside, a black hole appears pitch black.

The theory of general relativity , published by the theoretical physicist Albert Einstein , states that the larger the object, the more the space around it stretches and bends, and is thought to form a valley-like shape in space. I'm here. Therefore, when another object approaches, it is said that the object will fall into the valley of space.

When you get close to a huge celestial body like a black hole, matter falls toward that celestial body. The side of the formed valley becomes steeper as it approaches the celestial body, and the point where it becomes steep enough that even light cannot escape is called the ``

event horizon ''.

As space is stretched by a black hole, it is believed that time is also stretched, with clocks near a massive object running slower than clocks farther from the object. A clock near a black hole moves much more slowly than a clock on Earth, and one year near a black hole is equivalent to 80 years on Earth.

Therefore, if you want to see the future of the earth, it is thought that time travel to the future is possible by flying near the black hole and then returning to the earth.

On the other hand, it is theoretically possible to travel to the past using a black hole, which is thought to be able to greatly bend time and rewind time. Travel has some obstacles. The first is that we can only go back to the past after the black hole was formed. ``If black holes were formed after the extinction of dinosaurs, it would be impossible to go back to the time when dinosaurs lived,'' Baron said.

Second, if you want to time travel to the past, you have to go beyond the event horizon. In order to escape from a black hole in a certain era in the past, it is necessary to go outside the event horizon, and it is required to move faster than light.

The third is that all substances, such as humans and spacecraft, become 'spaghetti '. Beyond the event horizon, the object is stretched flat like a spaghetti noodle, and eventually the string of atoms spirals and falls into the black hole.

``It's fun to think about the time-distorting properties of black holes, but for the time being, time travel to the past must be kept in the realm of fantasy,'' Barron said.

in Science, Posted by log1r_ut