A train with skylights has the same rest length as a tunnel. The train goes through the tunnel at high speed. In the train’s frame, the tunnel is contracted to be shorter than the train. As the train passes through the tunnel two passengers, Wendy at the front and John at the rear, glance up at the same moment, and both of them see blue sky. In the tunnel’s frame, the train is contracted to be shorter than the tunnel. How can the two passengers look up and both see blue sky?

A train with skylights has the same rest length as a tunnel. The train goes through the tunnel at high speed. In the train’s frame, the tunnel is contracted to be shorter than the train. As the train passes through the tunnel two passengers, Wendy at the front and John at the rear, glance up at the same moment, and both of them see blue sky. In the tunnel’s frame, the train is contracted to be shorter than the tunnel. How can the two passengers look up and both see blue sky?