Interactive
American Association of Physics Teachers

Com Padre Digital Library: Open Source Physics: Simultaneity Spacetime Diagram

For Students 9th - 10th
Manipulate variables in order to observe the effects of relative motion on events such as an explosion and the time at which its light signal reaches a destination.
Interactive
American Association of Physics Teachers

Com Padre Digital Library: Open Source Physics: Minkowski Diagram Model

For Teachers 9th - 10th
Simulation examining simultaneity and causality in special relativity by manipulating the space and time coordinates of one or two events.
Website
Stanford University

Stanford University: Conventionality of Simultaneity

For Students 9th - 10th
This site from Stanford University is on the topic of simultaneity in relativity.
Interactive
American Association of Physics Teachers

Com Padre Digital Library: Open Source Physics: Ejs Simultaneity Model

For Students 9th - 10th
A model for examining the simultaneity of two events where the relative velocity and the wave source, either light or sound, can be manipulated.
Interactive
American Association of Physics Teachers

Com Padre Digital Library: Open Source Physics: Simultaneous Events Program

For Teachers 9th - 10th
Simulation showing how relative motion affects event order in special relativity. Manipulate the relative speed of two simultaneous events and observe the results.