Ifis close to 1 becausethe Newtonian mechanics fits observations well, with the goodness of fit improving asdecreases.

The following table shows howdiverges from 1 asincreases. Divergence becomes noticeable as increases above 0.2.

0.001 |
1.0000005 |

0.01 |
1.00005 |

0.1 |
1.005 |

0.2 |
1.021 |

0.3 |
1.48 |

0.4 |
1.091 |

0.5 |
1.155 |

0.9 |
2.29 |

0.99 |
11.26 |

0.999 |
22.37 |

Depending on the accuracy required smaller values ofmay be acceptable, but values ofabove 0.2 are generally unacceptable.

Speeds at which Newtonian mechanics is a good approximation are cal non relativistic speeds and speeds at which Newtonian mechanics is not a good approximation are called relativistic speeds.