Use the slider to set the relative speed between a pole and the barn. Click the buttons to see the barn perspective and the pole perspective regarding whether or not the pole fits in the barn. When you choose the speed sufficiently large, notice the barn doors which open/close simultaneously in the barn’s frame, but asynchronously in the pole’s frame. Notice as well the flashes of light that occur on each end of the pole. You can see how from the pole’s perspective these flashes are simultaneous while from the barn’s perspective they are not.