No gravitational force pulls at the satellite, since it does not fall back to Earth. 9 times less than on Earth, since it is 9 earth radii above the surface and the force goes down with the distance from the surface 5. When a planet is closer to the sun its speed is higher than when it is farther away. In this case, the Angular Momentum is larger than when far away smaller than when far away the same as when far away The answer depends on the size of the planet. From the angular size of the galaxy in the sky From the number of stars in the galaxy From the velocity and the distance of the stars in the galaxy about their common center From the brightness of the galaxy 7.
Radio telescopes are much larger than optical telescopes.
They have to be large to compete with the radio stations on Earth. Because the wavelength of radio waves is much longer than that of visible light, the radio dishes have to be larger to allow a good angular resolution. Radio signals from celestial objects are much weaker than their emission in the visible wavelength regime. Thus the dishes have to be larger. Radio signals are strongly blocked by the Earth's atmosphere.