It turns out that time travel to the past is actually relatively easy. All you have to do is make the universe spin.
The famous mathematician Kurt Gödel was a friend and neighbor of Albert Einstein at Princeton. He became incredibly curious about Einstein’s general theory of relativity, which was and continues to be our modern formulation of the gravitational force.
This theory connects the presence of matter and energy to the bending and warping of space and time, and then connects that bending and warping to the behavior of matter and energy.
Gödel was curious if relativity could allow time travel into the past. Einstein’s theory claimed to be a final framework for the nature of space and time, and as far as we know, time travel into the past is forbidden. So Gödel thought that general relativity should automatically forbid it.
And Gödel discovered that, in fact, general relativity is perfectly fine with time travel into the past. The trick is to set the universe in motion.
Gödel constructed a relatively simple and artificial model universe to prove his point. This universe revolves and contains only one ingredient. That ingredient is a negative cosmological constant that resists the centrifugal force of rotation to keep the universe static.
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Gödel discovered that if you follow a certain path in this rotating universe, you can reach your own past. You would have to travel incredibly far, billions of light years, to do it, but it can be done.
As you travel, you will be caught up in the rotation of the universe. This is not only a rotation of things in the cosmos, but of both space and time itself. Essentially, the rotation of the universe would alter your potential forward paths so strongly that those paths loop back around to where you started.
You would set out on your journey and never travel faster than the speed of light and find yourself back where you started but in your own past.
The possibility of time travel creates paradoxes and violates our understanding of causality. Fortunately, all observations indicate that the universe is not rotating, so we are protected from Gödel’s problem of backward time travel.
But it remains a mystery to this day why General Relativity agrees with this seemingly impossible phenomenon. Gödel used the example of the spinning universe to argue that General Relativity is incomplete and may be right.
This article was originally published by Universe Today. Read the original article.