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Home > Physics > Black holes and time travel

May 1, 2020,  |  1a. Time travel
In the article, I present theoretical considerations about time travel. A special theory of relativity published by Albert Einstein in 1905 explains that with increasing speed, time slows down and distance in the direction of motion decreases. Time dilation or time deceleration is an experimentally proven phenomenon. The faster a person moves, the slower his time flows. An experiment with a plane in which atomic clocks were stored proved that the time in the plane was different (slower) than the time on the ground clock. Let's look at another experiment with particles that accelerate at CERN to speeds approaching the speed of light. Accelerated particles have a half-life much longer than identical particles that are at rest - the time for particles that are in motion runs slower. Time travel is interesting already at the ratio of time in the rocket and on Earth 1:10. Even if you only spend 1 year in a rocket, it will take a full 10 years on Earth. When you return to Earth, all your peers will be 9 years older than you.

T₀: 1 year - Time in the Rocket
T: 10 years - Time on Earth

v: 298,290 km/s - Rocket speed
c: 299,792 km/s - Speed of light in vacuum
v/c: 0.995 - The ratio of the speed of the rocket to the speed of light in a vacuum

1b. Time travel to other planets
Length contraction or shortening of distance is a phenomenon that occurs when moving at a very high speed. Sailing spaceship technology is being developed that would be powered by an array of lasers from Earth. If we flew in a rocket to another planet at a speed of 0.995 c, the distance of the planet would be reduced 10 times. Thus, we would need 10 times less time to reach the planet.

L₀ - Real distance to another planet
L - 10 times shorter distance

2. Time travel with the help of a black hole
The general theory of relativity, presented by Albert Einstein in 1915, explains that the laws of physics in a standing rocket in a gravitational field are the same as in an accelerating rocket. Not only movement speed, but also gravity affects time. The higher the gravity, the slower the time goes. The atomic clock experiment was done on the hill and the ground - time on the hill went faster. Even for GPS, the watch goes faster due to weaker gravity. If we did not take this time dilation into account, erroneous GPS measurements would show up within a few minutes. Black holes have a huge gravity and therefore allow time travel. The speed of the rocket does not have to be as high as in the 1. case, time would be slowed by the gravity of the black hole. If we were in a rocket near a black hole, our time would run much slower than on Earth. If we returned to Earth, we would be much younger than our peers. The nearest black hole is too far away to be used for time travel. Therefore, it will be necessary to create a black hole much closer.