Graphed positions of clocks, rods, and light pulses correspond to velocity ([i]β=v/c[/i]) on the vertical axis against position [i]x[/i] (in units of light-seconds, c·s) on the horizontal axis.[br][br]Change [i]tobs[/i] to adjust observer's current time, or to animate the objects as time advances.[br][br]Use buttons to introduce new clocks, rods, and light flashes; to mark (x,t) events; and to change the observer's frame of reference.[br][b]Move the green "+" marker to specify coordinates for buttons to act on.[/b][br]Events can be given a description by hand in the Spreadsheet at right.[br][br]Clocks are always synchronized within a given reference frame, and all reference frames share the same x=0 coordinate at time t=0.[br]A "Blinking clock" emits flashes of light every second [i]of its own time[/i], on the second, starting at 0.0 seconds.[br]All rods have rest length 1 c·s in the [i]x[/i] direction.[br]Flashes of light travel left [i]and[/i] right at speed c as viewed from any reference frame.[br]Spreadsheet records position and velocity of objects as viewed by current observer, and coordinates of events as measured in observer's frame.[br][br]When selected, the marker or a slider can be precisely controlled using arrow keys; Ctrl-arrow (or Cmd-arrow) takes larger steps, and Shift-arrow takes finer steps.[br]The Input Bar at the bottom can be used to enter precise observer's time or velocity (β) values, using notation t_{obs}=0.854 or vobs=sqrt(3/4).[br][br]Shift-drag the background to pan the view; Shift-mousewheel to zoom. Shift-drag on x or y axis to stretch it (provided it's not covered by another line).

Graphed positions of clocks, rods, and light pulses correspond to velocity ([i]β=v/c[/i]) on the vertical axis against position [i]x[/i] (in units of light-seconds, c·s) on the horizontal axis.[br][br]Change [i]tobs[/i] to adjust observer's current time, or to animate the objects as time advances.[br][br]Use buttons to introduce new clocks, rods, and light flashes; to mark (x,t) events; and to change the observer's frame of reference.[br][b]Move the green "+" marker to specify coordinates for buttons to act on.[/b][br]Events can be given a description by hand in the Spreadsheet at right.[br][br]Clocks are always synchronized within a given reference frame, and all reference frames share the same x=0 coordinate at time t=0.[br]A "Blinking clock" emits flashes of light every second [i]of its own time[/i], on the second, starting at 0.0 seconds.[br]All rods have rest length 1 c·s in the [i]x[/i] direction.[br]Flashes of light travel left [i]and[/i] right at speed c as viewed from any reference frame.[br]Spreadsheet records position and velocity of objects as viewed by current observer, and coordinates of events as measured in observer's frame.[br][br]When selected, the marker or a slider can be precisely controlled using arrow keys; Ctrl-arrow (or Cmd-arrow) takes larger steps, and Shift-arrow takes finer steps.[br]The Input Bar at the bottom can be used to enter precise observer's time or velocity (β) values, using notation t_{obs}=0.854 or vobs=sqrt(3/4).[br][br]Shift-drag the background to pan the view; Shift-mousewheel to zoom. Shift-drag on x or y axis to stretch it (provided it's not covered by another line).

Graphed positions of clocks, rods, and light pulses correspond to velocity ([i]β=v/c[/i]) on the vertical axis against position [i]x[/i] (in units of light-seconds, c·s) on the horizontal axis.[br][br]Change [i]tobs[/i] to adjust observer's current time, or to animate the objects as time advances.[br][br]Use buttons to introduce new clocks, rods, and light flashes; to mark (x,t) events; and to change the observer's frame of reference.[br][b]Move the green "+" marker to specify coordinates for buttons to act on.[/b][br]Events can be given a description by hand in the Spreadsheet at right.[br][br]Clocks are always synchronized within a given reference frame, and all reference frames share the same x=0 coordinate at time t=0.[br]A "Blinking clock" emits flashes of light every second [i]of its own time[/i], on the second, starting at 0.0 seconds.[br]All rods have rest length 1 c·s in the [i]x[/i] direction.[br]Flashes of light travel left [i]and[/i] right at speed c as viewed from any reference frame.[br]Spreadsheet records position and velocity of objects as viewed by current observer, and coordinates of events as measured in observer's frame.[br][br]When selected, the marker or a slider can be precisely controlled using arrow keys; Ctrl-arrow (or Cmd-arrow) takes larger steps, and Shift-arrow takes finer steps.[br]The Input Bar at the bottom can be used to enter precise observer's time or velocity (β) values, using notation t_{obs}=0.854 or vobs=sqrt(3/4).[br][br]Shift-drag the background to pan the view; Shift-mousewheel to zoom. Shift-drag on x or y axis to stretch it (provided it's not covered by another line).

Graphed positions of clocks, rods, and light pulses correspond to velocity ([i]β=v/c[/i]) on the vertical axis against position [i]x[/i] (in units of light-seconds, c·s) on the horizontal axis.[br][br]Change [i]tobs[/i] to adjust observer's current time, or to animate the objects as time advances.[br][br]Use buttons to introduce new clocks, rods, and light flashes; to mark (x,t) events; and to change the observer's frame of reference.[br][b]Move the green "+" marker to specify coordinates for buttons to act on.[/b][br]Events can be given a description by hand in the Spreadsheet at right.[br][br]Clocks are always synchronized within a given reference frame, and all reference frames share the same x=0 coordinate at time t=0.[br]A "Blinking clock" emits flashes of light every second [i]of its own time[/i], on the second, starting at 0.0 seconds.[br]All rods have rest length 1 c·s in the [i]x[/i] direction.[br]Flashes of light travel left [i]and[/i] right at speed c as viewed from any reference frame.[br]Spreadsheet records position and velocity of objects as viewed by current observer, and coordinates of events as measured in observer's frame.[br][br]When selected, the marker or a slider can be precisely controlled using arrow keys; Ctrl-arrow (or Cmd-arrow) takes larger steps, and Shift-arrow takes finer steps.[br]The Input Bar at the bottom can be used to enter precise observer's time or velocity (β) values, using notation t_{obs}=0.854 or vobs=sqrt(3/4).[br][br]Shift-drag the background to pan the view; Shift-mousewheel to zoom. Shift-drag on x or y axis to stretch it (provided it's not covered by another line).