When the earth is moving, the earth perceives the Sun to be in one of these degrees, and that becomes One Sky.
See, the stars are constant, but the earth is moving. When the earth moves around the sun, the earth is perceived to have moved, and it sees the Sun to be in different position. That is called Aries. When the Earth moves again, it finds itself in Capricorn. When the Earth moves further, it finds itself in Virgo. So, that is what seventh sky, eighth sky, etc., is.