Servicing the Hubble Space Telescope
     
My friend admitted to me that although he had never before told anyone on the ground, he, too, had experienced the same frightening phenomenon. Feet securely in place on the robotic arm, he was being conveyed to the far end of the telescope, well out of the confines of the payload bay. So far, so good, he said. But in order to begin his repair work, he had to extricate himself from the stabilizing footloops and cross over to the telescope. Feet now free and reaching across the two-foot gap to the end of the telescope, he unexpectedly and overwhelmingly felt the sensation of falling off the edge of the world!