Tipler Cylinder

           TIPLER CYLINDER TIME TRAVEL 

    A Tipler Cylinder also called as Tipler time machine, the tipler cylinder is a cylinder of dense matter and infinite length.The tipler cylinder specialty is travel into the past, not the future,is a hypothetical object theorized to be a potential mode of time travel. Tipler cylinder could only allow time travel if its length were infinite or with the existence of negative energy.

      Willem Jacob van Stockum found Tipler cylinder solution to Einstein's equations of general relativity in1924. Later on in Kornel Lanczos found similar Tipler cylinder solution in 1936. Then in 1974, Frank Tipler's analysis the above solution of uncovered that a massive cylinder of infinite length spinning at high speed around its long axis could enable time travel. The tipler cylinder is not a practical time matchin, since it needs to be infinitely long. 

   An objection to the practicality of building a Tipler cylinder was discovered by Stephen Hawking, who posited a conjecture showing that according to general relativity it is impossible to build a time matchine in any finite region that satisfies the weak energy condition meaning that the region contains no exotic matter with negative energy. 

    On the other hand, Tipler does not involve any negative energy. Its original solution involved a cylinder with finite length. Which is easier to analyze mathematically and although Tipler suggested that a finite cylinder might produce close timelike curve if the rotation rate were fast enough, he did not prove this. 

     According to Hawking "It can be done with positive energy density everywhere! I can prove that to build a finite time matchine, you need negative energy". In the paper, he examines, "the case that he causality violations appear in a finite region of spacetime without curvature singularities" and proves that there will be Cauchy horizon that is compactly generated and that in general contains one or more closed null geodesics which will be incomplete.