Time travel

hypothetical activity of traveling into the past or future

thumb|upright=1.3|A wormhole visualized as a two-dimensional surface. Route (a) is the shortest path through normal space between points 1 and 2; route (b) is a shorter path through a wormhole.

A tachyon () or tachyonic particle is a hypothetical particle that always travels faster than light. Physicists posit that faster-than-light particles cannot exist because they are inconsistent with the known laws of physics. If such particles did exist they perhaps could be used to send signals faster than light and into the past. According to the theory of relativity this would violate causality, leading to logical paradoxes such as the grandfather paradox. Tachyons would exhibit the unusual property of increasing in speed as their energy decreases, and would require infinite energy to slow

contradicting time travel of one’s biological parent’s death/separation

theoretical paradox resulting from time travel

hypothetical device capable of time travel

worldline (timelike curve) in a Lorentzian manifold that is closed (returns to its starting point)

principle developed to solve the problem of paradoxes in time travel

conjecture that the laws of physics prevent closed timelike curves

conceptual link between natural phenomena that temporally follow one another because one is the cause of the other

alleged reports of time traveling

a party for time travelers in the University of Cambridge hosted by Stephen Hawking