This is the perfect desk toy to impress Colleagues and clients alike! Perpetual Motion Desktop Toy is perfect for your outer space themed office or room decor. It is also great for those enthusiastic about science or to demonstrate the laws of physics in science classrooms. A simple spin of the top of the base sets the galaxy in motion.A top seller in the space museum stores and a cool gift for the science physics enthusiast. Requires one 9V battery to operate. Battery not included.