[填空题]
A science-fiction talrp u9vj;/u6x we describes an ; zo8om 5c3fh:rtzo8ya6 efa ,artificial "planet" in the form of a band completely encircling a sun (Fig. 5-40). The inhabitants live on thez8zhy:etoff8 6,5o oca r3;a m inside surface (where it is always noon). Imagine that this sun is exactly like our own, that the distance to the band is the same as the Earth-Sun distance (to make the climate temperate), and that the ring rotates quickly enough to produce an apparent gravity of g as on Earth. What will be the period of revolution, this planet's year, in Earth days?
