special relativity

Time versus Velocity

Relativity is a geometric effect.


The relationship between your time and spacecraft time is simple. All you need is Pythagorus's theorem.

The following are a list of points to be mindful of when studying the animation.

  • A time interval of 1 second in your frame is represented by the red line.
  • The blue line is the time interval passed on the spacecraft for 1 of your seconds.
  • Less than 0.1c the difference in the two times is very small.
  • Above 0.9c a small change in velocity results in a big variation in spacecraft time.
  • At 1.0c the time passed on the spacecraft is zero seconds for each of your seconds. Time has stopped on the spacecraft.
  • The curve is a section of a circle and so is symmetric about the red line in the diagram to the right.

animation controls

There are two text boxes

spacecraft elapsed time : enter a time interval less than, or equal, to 1.0. The graph will update to show the corresponding spacecraft velocity.

velocity : enter a spacecraft velocity as a fraction of c. The graph will update to show the elapsed time in the spacecraft.