Table of Contents
What Is Time Dilation?
From Einstein's special relativity: time passes more slowly for moving objects. At 90% light speed, time runs at only 43.6% the stationary rate. This is real and experimentally confirmed - muons from cosmic rays live 10x longer due to their 99.5% c velocity. GPS satellites correct for relativistic time dilation to maintain accuracy.
The Lorentz factor gamma = 1/sqrt(1-v^2/c^2) quantifies the effect. At everyday speeds, gamma is essentially 1. At 87% c, gamma = 2 (time runs half as fast). Effects become dramatic only at substantial fractions of light speed.
Formula
Lorentz Factor
| Speed (%c) | γ | 1 year becomes |
|---|---|---|
| 50% | 1.15 | 1.15 yr |
| 90% | 2.29 | 2.29 yr |
| 99% | 7.09 | 7.09 yr |
| 99.9% | 22.4 | 22.4 yr |
FAQ
Is it real or apparent?
Absolutely real. Atomic clocks on jets show measurably less elapsed time. GPS would drift 11 km/day without relativistic corrections. The Hafele-Keating experiment (1971) confirmed both special and general relativistic time dilation.