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A tachyonic antitelephone is a hypothetical device in theoretical physics that could be used to send signals into one's own past. Albert Einstein in 1907 [1] [2] presented a thought experiment of how faster-than-light signals can lead to a paradox of causality, which was described by Einstein and Arnold Sommerfeld in 1910 as a means "to telegraph into the past". [3]
After a sleepless night, he finally worked out a response which, ironically, depended on Einstein's general relativity. [6]: 348–349 Consider the illustration of Einstein's light box: [12]: 446–448 1. After emitting a photon, the loss of weight causes the box to rise in the gravitational field. 2.
Causality is the relationship between causes and effects. [1] [2] While causality is also a topic studied from the perspectives of philosophy and physics, it is operationalized so that causes of an event must be in the past light cone of the event and ultimately reducible to fundamental interactions.
A plot of geodesics between two points in a 180-point causal set made by sprinkling into 1+1 dimensions A link in a causal set is a pair of elements x , y ∈ C {\displaystyle x,y\in C} such that x ≺ y {\displaystyle x\prec y} but with no z ∈ C {\displaystyle z\in C} such that x ≺ z ≺ y {\displaystyle x\prec z\prec y} .
Retrocausality, or backwards causation, is a concept of cause and effect in which an effect precedes its cause in time and so a later event affects an earlier one. [1] [2] In quantum physics, the distinction between cause and effect is not made at the most fundamental level and so time-symmetric systems can be viewed as causal or retrocausal.
1. First postulate (principle of relativity) The laws of physics take the same form in all inertial frames of reference.. 2. Second postulate (invariance of c) . As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body.
Albert Einstein, physicist, 1879-1955, Graphic: Heikenwaelder Hugo,1999. Special relativity is a theory of the structure of spacetime. It was introduced in Einstein's 1905 paper "On the Electrodynamics of Moving Bodies" (for the contributions of many other physicists and mathematicians, see History of special relativity).
In physics, the special theory of relativity, or special relativity for short, is a scientific theory of the relationship between space and time.In Albert Einstein's 1905 paper, On the Electrodynamics of Moving Bodies, the theory is presented as being based on just two postulates: [p 1] [1] [2]