**Herong's Notes on Physics** - Version 3.21, by Dr. Herong Yang

Introduction of Spacetime

This chapter provides an introduction of spacetime. Topics include definition of spacetime; world line of an object in a spacetime frame; light cone of an event in a spacetime frame.

Conclusion:

- Spacetime is a mathematical model that uses a frame of reference including both space and time with a 4-dimension coordinate system.
- A world line is the path of an object left in a spacetime frame of reference.
- A light cone is a 4-dimensional surface in a spacetime frame where all events on the surface can be connected to a central event by light.

Table of Contents

Introducion of Frame of Reference

Introduction of Special Relativity

Time Dilation in Special Relativity

Length Contraction in Special Relativity

The Relativity of Simultaneity