What Is Distance?

This section introduces distance between two objects. The standard unit of distance is called 'meter', which is the length travelled by light in 1/299,792,458 of a second.

What Is Distance? Distance is a measurement that we use to describe how much space is there between two objects at a specific moment of time.

In order to measure distance, we have to define a standard unit. Currently (as of 1983), the standard unit to measure distance is called "meter" or "metre" defined by BIPM (Bureau International des Poids et Mesures) as: "the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second".

This definition sounds very precise. But it is based on two other factors:

Before using the speed of light to define the "meter", CGPM (conférence générale des Poids et Mesures) used to construct a metal bar that has a length equal to a "meter", see the picture below. The length of that metal bar is defined as a meter.

Space - Standard Meter Bar to Measure Distance (wps.prenhall.com)
Standard Meter Bar to Measure Distance

With the standard unit defined, we can create measuring tapes and rulers that marked with multiples of meters and fractions within a meter. These tapes and rulers can then be used to measure distances between two objects as shown in the picture below:

Space - Using Ruler to Measure Distance (fao.org)
Using Ruler to Measure Distance

Last update: 2014.

Table of Contents

 About This Book

Introduction of Space

 What Is Space?

What Is Distance?

 Meter Based on Earth's Meridian

 Meter Based on Seconds Pendulum

 Meter Prefixes and Other Units

 List of Various Distances and Lengths

 Introducion of Frame of Reference

 Introducion of Time

 Introduction of Speed

 Newton's Laws of Motion

 Introduction of Special Relativity

 Time Dilation in Special Relativity

 Length Contraction in Special Relativity

 The Relativity of Simultaneity

 Introduction of Spacetime

 Minkowski Spacetime and Diagrams

 References

 PDF Printing Version