Relativity of simultaneity: Concept in physics about whether two spatially separated events occur at the same time. It is not absolute and depends on the observer's reference frame.
Introduced by mathematician Henri Poincaré in 1900.
Became central in Albert Einstein's special theory of relativity.
Key Concepts
Observer's Reference Frame: Different frames may assign different times to the same events.
Example: Car crashes in London and New York may appear simultaneous on Earth but not for an observer in a moving airplane.
If events can be causally connected, the order is preserved across frames; if not, this order can vary.
Historical Context
Henrik Lorentz: Developed "local time" using a mathematical method.
Henri Poincaré: Emphasized the conventional nature of simultaneity and the constancy of light speed; introduced the concept of "local time" and its relation to Lorentz transformations.
Albert Einstein: Used light speed invariance and relativity principle to derive the complete Lorentz transformation.
Minkowski Space
Hermann Minkowski: Introduced the concept of world lines and Minkowski space, making simultaneity depend on hyperbolic orthogonality.
Thought Experiments
Einstein's Lightning Bolt Experiment: Demonstrates that observers in different frames perceive simultaneity differently.
Train-and-platform Experiment: Demonstrates how light reaches different points at different times depending on the observer's frame.
Spacetime Diagrams: Used to visualize and understand relativity of simultaneity.
Lorentz Transformation
Relates coordinates of one observer to another in uniform relative motion.
Shows how lines of simultaneity vary between different observers.
Equation: Given to show the time and space transformation between frames.
Accelerated Observers
Radar-time/Distance Definition: Used for accelerated observers to assign unique time and position to events.
Additional Concepts
Worldline: Representation of an object's path through spacetime.