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

Second Prefixes and Other Units

This section introduces prefixes used on 'second' to represent decadic multiples or fractions of a second. It also covers other standard units to measure durations like minute, hour, day and year.

For the convenience of measuring a very long or very short duration, some prefixes have been defined on "seconds" to be decadic multiples or fractions of a second. Here are some commonly used meter prefixes and their abbreviated symbols:

Prefix Name Symbol Definition peta petasecond Ps 1 000 000 000 000 000 second tera terasecond Ts 1 000 000 000 000 second giga gigasecond Gs 1 000 000 000 second mega megasecond Ms 1 000 000 second kilo kilosecond ks 1 000 second second s 1 second milli millisecond ms 0.001 second nano nanosecond ns 0.000 000 001 second pico picosecond ps 0.000 000 000 001 second femto femtosecond fs 0.000 000 000 000 001 second

Beside "second", other standard units are also used to measure duration. For example:

- "minute" - "minute" is defined as 1 minute = 60 seconds.
- "hour" - "hour" is defined as 1 hour = 360 seconds, or 60 minutes.
- "day" - "day" is defined as 1 day = 86,400 seconds, or 24 hours.
- "year" - "year" is defined as 1 year = 31,557,600 seconds, or 365.25 days.

*Last update: 2014.*

Table of Contents

Introducion of Frame of Reference

►Second Prefixes and Other Units

Introduction of Special Relativity

Time Dilation in Special Relativity

Length Contraction in Special Relativity

The Relativity of Simultaneity