Skip to ContentGo to accessibility page
OpenStax Logo
Physics

Introduction

PhysicsIntroduction
Figure 10.1 Special relativity explains why travel to other star systems, such as these in the Orion Nebula, is unlikely using our current level of technology. (s58y, Flickr)

Chapter Outline

Introduction

Teacher Support

Teacher Support

Start a discussion that taps into the longing of humans to explore worlds beyond our planet. Is this basic human nature? Perhaps it is; humans have now been almost everywhere there is to go on this planet. Ask students why we have not traveled to other star systems yet. Is it just a matter waiting a few years for technological advances, or is there a more daunting problem? If no one knows, tell them it all has to do with achievable speeds, and use this as a lead-in to Einstein’s postulate related to the speed of light.

Have you ever dreamed of traveling to other planets in faraway star systems? The trip might seem possible by traveling fast enough, but you will read in this chapter why it is not. In 1905, Albert Einstein developed the theory of special relativity. Einstein developed the theory to help explain inconsistencies between the equations describing electromagnetism and Newtonian mechanics, and to explain why the ether did not exist. This theory explains the limit on an object’s speed among other implications.

Relativity is the study of how different observers moving with respect to one another measure the same events. Galileo and Newton developed the first correct version of classical relativity. Einstein developed the modern theory of relativity. Modern relativity is divided into two parts. Special relativity deals with observers moving at constant velocity. General relativity deals with observers moving at constant acceleration. Einstein’s theories of relativity made revolutionary predictions. Most importantly, his predictions have been verified by experiments.

In this chapter, you learn how experiments and puzzling contradictions in existing theories led to the development of the theory of special relativity. You will also learn the simple postulates on which the theory was based; a postulate is a statement that is assumed to be true for the purposes of reasoning in a scientific or mathematic argument.

Teacher Support

Teacher Support

Before students begin this chapter, it is useful to review the following concepts:

  • Using significant figures in calculations—Demonstrate how to use the proper number of significant figures when adding and multiplying.
  • Using scientific notation in calculations—Demonstrate how to use the proper scientific notation and operations in scientific notation (e.g., addition/subtraction, multiplication/division).
  • Converting units—Demonstrate how to convert from km/h to m/s.
  • Calculating average—Demonstrate how to average two numbers by dividing their sum by 2.
  • Reviewing the difference between mass and weight.
  • Commonly used terms—Explain that constant means unchanging. Constant speed refers to speed that is not changing. Explain that initial means starting. Initial time is the time at which the action of a problem begins. Explain that an object that is not moving is often described in physics as being at rest.

To reinforce this description, and to open the door for a discussion of frame of reference, take an object, place it in front of the class, and ask someone to describe its motion. Students will likely respond that the object is at rest. Explain that this correct, but it is not the only correct answer. Help students to understand that the object is sitting still but also moving at a high rate of speed as the earth rotates, orbits the sun, etc. It all depends on how you define the frame of reference.

Initiate a discussion aimed at making relativity theory less intimidating. Dispel the misconception that “Only three people in the world understand Einstein’s theories.” Stories like this come about because Einstein’s second relativity theory, called general relativity, was more difficult to understand. In this chapter, we will only learn about special relativity.

PreviousNext
Order a print copy
Citation/Attribution
Reuse and redistribution of this content in digital or print format:
  • This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's prior written permission.
  • This book uses the Creative Commons Attribution License, which means that you can reuse and modify the material only for noncommercial purposes, must attribute Texas Education Agency (TEA), and must distribute any derivative works under the same license. The original material is available at: https://www.texasgateway.org/book/tea-physics . Changes were made to the original material, including updates to art, structure, and other content updates.
  • Any commercial printing of this textbook, including using a local or custom printer, must be approved by OpenStax, and proper citation provided.
  • OpenStax-copyrighted images, activities, assessments, and similar components of this book are subject to the same licensing – CC-BY-NC-SA. They can be used for noncommercial purposes with attribution. Commercial use requires permission.
  • Permission requests: Anyone who intends to incorporate this content (including text, images, and other components) into large language models, use it in AI offerings, use it commercially (including in print), and/or has questions about another use case is welcome to complete our reuse request form.
Attribution information
  • If you are redistributing all or part of this book in a noncommercial print format, then you must include on every physical page the following attribution:

    Access for free at https://openstax.org/books/physics/pages/1-introduction

  • If you are redistributing all or part of this book in a noncommercial digital format, then for every page that includes OpenStax content, you must license the derivative work under the same CC-BY-NC-SA license as the original, and include on every digital page view the following attribution:

    Access for free at https://openstax.org/books/physics/pages/1-introduction

Citation information

The information below includes the information needed to generate citations in most major styles (APA, MLA, etc.); you must reformat and organize the information as needed to fit the requirements of the style. Use the information below to generate a citation. We recommend using a citation tool such as this one.

© Jul 8, 2026 Texas Education Agency (TEA). The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo, and Rice University name, and Rice University logo trademarks, or wordmarks are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.