It turns out that time travel into the past is quite simple. All you have to do is cause the cosmos to spin.
Albert Einstein’s buddy and neighbour at Princeton was the eminent mathematician Kurt Gödel. He got fascinated by Einstein’s general theory of relativity, which was and still is our current formulation of gravitational force. That theory relates the existence of matter and energy to the bending and warping of space and time, and subsequently to the behaviour of matter and energy.
Gödel was intrigued by the possibility of time travel via relativity. Einstein’s theory professed to be the final foundation for the structure of space and time, therefore time travel into the past is now prohibited. As a result, Gödel reasoned that general relativity would automatically rule it out. And Gödel found that general relativity is just good with backward time travel. The key is to get the cosmos moving.
To demonstrate his thesis, Gödel created a rather basic and artificial model world. This cosmos revolves and has just one element. This component is a negative cosmological constant that opposes the rotation’s centrifugal force in order to keep the cosmos steady.
Gödel discovered that if you choose a certain route in this revolving world, you may wind yourself in your own past. It would need a journey of billions of light years to accomplish, yet it is possible. You would get entangled in the spinning of the cosmos as you travelled. That isn’t simply a rotation of the things in the universe, but also of space and time. In essence, the rotation of the cosmos would change your possible future pathways so drastically that they would circle back around to where you began.
You would begin out on your adventure and never go faster than the speed of light, ending up back where you began, but in your own history.
Backwards time travel raises paradoxes and challenges our understanding of causation. Fortunately, all observations show that the cosmos is not spinning, therefore we are not subject to Gödel’s issue of reverse time travel. But it is still unclear why general relativity accepts this apparently inconceivable event. Gödel used the revolving world to demonstrate that general relativity is imperfect, and he may still be correct.
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