It turns out that time travel to the past is relatively easy. All you have to do is make the universe turn.
The famous mathematician Kurt Gödel was a friend and neighbor of Albert Einstein in Princeton. He became incredibly curious about Einstein’s general theory of relativity, which was and still is our modern formulation of the force of gravity.
This theory links the presence of matter and energy to the bending and warping of space and time, and then links this bending and warping to the preservation of matter and energy.
Gödel was curious if relativity allowed for time travel into the past. Einstein’s theory purportedly provided the ultimate framework for the nature of time and space, and as far as we know, time travel into the past is forbidden. So Gödel decided that general relativity should automatically disallow 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 of the universe to prove his point. This universe rotates and contains only one component. This component is a negative cosmological constant that resists the force of centrifugal rotation to keep the universe static.
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Gödel discovered that if you follow a certain path in this revolving universe, you can end up in your own past. You’d have to travel incredibly far to do that, billions of light years, but it’s possible.
During the journey you would be caught up in the rotation of the universe. It is not just the rotation of things in the cosmos, but of both space itself and time. In fact, the rotation of the universe would change your potential paths forward so much that those paths would loop back to where you started.
You would go on your journey and you would never travel faster than the speed of light, and you would find yourself back where you started, but in your own past.
The ability to travel back in time creates paradoxes and violates our understanding of causality. Fortunately, all observations show that the universe does not rotate, so we are protected from Gödel’s problem of traveling backwards in time.
But to this day, it remains a mystery why general relativity is okay with this seemingly impossible phenomenon. Gödel used the example of the rotating universe to argue that general relativity is incomplete and may yet be right.
This article was originally published by Universe Today. Read the original article.