If a satellite explodes in orbit, debris traveling at 1000 mph would initially continue moving due to inertia, but gravity would eventually slow it down. The debris could enter an unstable orbit around Earth, leading to re-entry into the atmosphere or being ejected into a solar orbit. The negligible drag from gas and particles means gravity is the primary force acting against the debris. Compared to the Earth's orbital speed around the Sun, 1000 mph is relatively slow, indicating that the debris would maintain its momentum for a significant distance. Ultimately, the debris would continue moving until it encounters another celestial body.