# Count On

## Explorer

#### From Mega to Micro

- Millimetre, milligram, millilitre;
- megabyte, megatonne and megabucks;
- microsecond and femtosecond,
- a billion, a trillion.

What do they all mean?

*Mega to Micro* is all about those prefixes that appear in everyday news items as well as in technical reports. Also, we have included examples for distances.

The table deals with powers of 10 which also measures the number of digits in a number - the higher the power, the longer the number.

Power | Size | Name | Prefix | Symbol | Metres example |

10^{18} | 1,000,000,000,000,000,000 | one quintillion | exa | E | Light takes 100 years to travel this distance, to the star Arcturus |

10^{15} | 1,000,000,000,000,000 | one quadrillion | peta | P | Distance to the "cloud" of comets 10 times as far away as the outermost planet, Pluto |

10^{12} | 1,000,000,000,000 | one trillion | tera | T | Distance to planet Jupiter |

10^{9} | 1,000,000,000 | one billion | giga | G | The diameter of the Moon's orbit |

10^{6} | 1,000,000 | one million | mega | M | Half-way across the USA |

10^{3} | 1,000 | one thousand | kilo | k | A kilometre: a 15 minute walk |

10^{2} | 100 | one hundred | hecto | h | The height of a giant sequoia tree and the Statue of Liberty |

10^{1} | 10 | ten | deca | The height of a house | |

10^{0} | 1 | one | The length of an adult arm | ||

10^{-1} | 0.1 | one tenth | deci | d | The length of your hand |

10^{-2} | 0.01 | one hundredth | centi | c | The width of a finger |

10^{-3} | 0.001 | one thousandth | milli | m | The width of a pin |

10^{-6} | 0.000 001 | one millionth | micro | u | The size of a living cell |

10^{-9} | 0.000 000 001 | one billionth | nano | n | The size of a water molecule |

10^{-12} | 0.000 000 000 001 | one trillionth | pico | p | Only atoms are at this scale |

10^{-15} | 0.000 000 000 000 001 | one quadrillionth | femto | f | The size of a proton |

10^{-18} | 0.000 000 000 000 000 001 | one quintillionth | atto | a | ? We know of nothing this small! |