A Tipler cylinder, also called a Tipler time machine, is a hypothetical object (usually conceived of as being composed of neutron star matter) theorized to be a potential mode of time travel—an approach that is conceivably functional within humanity's current understanding of physics, specifically the theory of general relativity, although later results have shown that a Tipler cylinder could only allow time travel if its length were infinite (see the discussion of Hawking's theorem below). A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type The word theory has many distinct meanings in different fields of Knowledge, depending on their methodologies and the context of discussion. This article details time travel itself For other uses see Time Traveler. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916
Frank J. Tipler showed in 1974 that in a spacetime containing a massive, infinitely long cylinder which was spinning along its longitudinal axis, the cylinder should create a frame-dragging effect. Frank Jennings Tipler III (born February 1, 1947 in Andalusia Alabama Prof Year 1974 ( MCMLXXIV) was a Common year starting on Tuesday (link will display full calendar of the 1974 Gregorian calendar. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS A cylinder is one of the most basic curvilinear geometric shapes the Surface formed by the points at a fixed distance from a given Straight line, the axis In Mathematics and its applications a coordinate system is a system for assigning an n - Tuple of Numbers or scalars to each point Albert Einstein 's theory of General relativity predicts that rotating bodies drag Spacetime around themselves in a phenomenon referred to as frame-dragging This frame-dragging effect warps spacetime in such a way that the light cones of objects in the cylinder's proximity become tilted, so that part of the light cone then points backwards along the time axis on a space time diagram. Albert Einstein 's theory of General relativity predicts that rotating bodies drag Spacetime around themselves in a phenomenon referred to as frame-dragging In Special relativity, a light cone (or null cone) is the pattern describing the temporal evolution of a flash of Light in Minkowski spacetime Therefore a spacecraft accelerating sufficiently in the appropriate direction can travel backwards through time along a closed timelike curve or CTC. A spacecraft is a Vehicle or machine designed for Spaceflight. In a Lorentzian manifold, a closed timelike curve (CTC is a Worldline of a material particle in Spacetime that is "closed" returning to its 
CTC's are associated, in Lorentzian manifolds which are interpreted physically as spacetimes, with the possibility of causal anomalies such as going back in time and potentially shooting your own grandfather, although paradoxes might be avoided using some constraint such as the Novikov self-consistency principle. In Differential geometry, a pseudo-Riemannian manifold (also called a semi-Riemannian manifold) is a generalization of a Riemannian manifold. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS This article refers to the Time travel paradox In novels based on the television series Doctor Who, "Grandfather Paradox" is the semi-mythical The Novikov self-consistency principle, also known as the Novikov self-consistency conjecture, is a Principle developed by Dr They have an unnerving habit of appearing in some of the most important exact solutions in general relativity, including the Kerr vacuum (which models a rotating black hole) and the van Stockum dust (which models a cylindrically symmetrical configuration of rotating pressureless fluid or dust). In General relativity, the Kerr metric (or Kerr vacuum) describes the geometry of Spacetime around a rotating massive body In General relativity, the van Stockum dust is an exact solution of the Einstein field equation in which the gravitational field is generated by dust rotating In General relativity, a dust solution is an exact solution of the Einstein field equation in which the gravitational field is produced entirely by the
Some physicists argue that since Tipler cylinders allow closed timelike curves they violate Roger Penrose's cosmic censorship hypothesis, as naked singularities would be visible. A physicist is a Scientist who studies or practices Physics. Physicists study a wide range of physical phenomena in many branches of physics spanning Sir Roger Penrose, PhD, OM, FRS (born 8 August 1931) is an English Mathematical physicist and Emeritus The weak and the strong Cosmic Censorship Hypotheses are two mathematical conjectures about the structure of singularities arising in General relativity. In General relativity, a naked singularity is a Gravitational singularity without an Event horizon. Others argue that since causality is not built into Einstein's field equation, these regions may actually be able to exist (see also Godel's universe). Causality describes the relationship between Causes and Effects is fundamental to all natural Science, especially Physics, and has a basis in The Einstein field equations ( EFE) or Einstein's equations are a set of ten equations in Einstein 's theory of General relativity in which the The Gödel metric is an exact solution of the Einstein field equations in which the Stress-energy tensor contains two terms the first representing the
A limitation of the Tipler cylinder is that it is only possible to travel to times (and places) in which the cylinder already exists. Thus, one could not travel backwards further than the date that the cylinder was activated.
A more fundamental objection to the practicality of building a Tipler cylinder was discovered by Stephen Hawking, who proved a theorem showing that according to general relativity it is impossible to build a time machine in any finite region that satisfies the weak energy condition, meaning that the region contains no exotic matter with negative energy. In relativistic classical field theories of Gravitation, particularly General relativity, an energy condition is one of various alternative conditions Exotic matter is a hypothetical concept of Particle physics. It covers any material which violates one or more classical conditions or is not made of known baryonic particles The Tipler cylinder, on the other hand, does not involve any negative energy. Tipler's original solution involved a cylinder of infinite length, which is easier to analyze mathematically, and although Tipler suggested that a finite cylinder might produce closed timelike curves if the rotation rate were fast enough, he did not prove this. But Hawking points out that because of his theorem, "it can't be done with positive energy density everywhere! I can prove that to build a finite time machine, you need negative energy. " This result comes from Hawking's 1992 paper on the chronology protection conjecture, where he examines "the case that the causality violations appear in a finite region of spacetime without curvature singularities" and proves that "[t]here will be a Cauchy horizon that is compactly generated and that in general contains one or more closed null geodesics which will be incomplete. The chronology protection conjecture is a Conjecture by the Physicist Professor Stephen Hawking that the Laws of physics are such as to prevent In Physics, a Cauchy horizon is a Light-like boundary of the domain of validity of a Cauchy problem (a particular Boundary value problem of the One can define geometrical quantities that measure the Lorentz boost and area increase on going round these closed null geodesics. If the causality violation developed from a noncompact initial surface, the averaged weak energy condition must be violated on the Cauchy horizon. "