Moving clocks run slow.
The time measured by a watch that you carry with you ticks away at a constant rate whether you can see that you are moving or not.
(You can never change the rate at which time passes as measured by a watch that moves with you, but of course time may seem to drag or rush by in your perception.)
When you see a clock in motion it runs slow relative to your clock.
Image of an arm, you control the speed of travel (read out on the horizontal axis) an arm points to the rate of time passing. The arm moves along the arc of a circle.
Trading speed through space for speed through time
Explorations perhaps on this page
Frequent Flyer Seconds, enter your frequent flyer miles the calculator shows you the number of nanosecond that you are now younger since you have travelled.
Prove it! Experiments
Flying clocks in jet aircraft and in space
Particle Physics, moving muons.
The twin paradox
Do the math
Trading speed through space for speed through time, the math
How a light clock works. (Ron)
Scientific Explorations with Paul Doherty
31 May 2005