Venus in culture the night sky, and follows a synodic cycle by which it seems to disappear for several says due to its proximity to the sun, then re-appear on the opposite side of the sun and on the other horizon. Depending on the point in its cycle, Venus may appear before sunrise in the morning, or after sunset in the evening, but it never appears to reach the apex of the sky. Therefore, many cultures have recognized it with two names, even if their astronomers realized that it was really one object. In old English, the planet was known as "morgensteorra" (morning
Sunrise is 34 arcminutes, though this amount varies based on atmospheric conditions. Also, unlike most other solar measurements, sunrise occurs when the Sun's "upper limb", rather than its center, appears to cross the horizon. The apparent radius of the Sun at the horizon is 16 arcminutes. These two angles combine to define sunrise to occur when the Sun's center is 50 arcminutes below the horizon, or 90.83° from the zenith. The timing of sunrise varies throughout the year and is also affected by the viewer's longitude and latitude, altitude, and time zone. These changes are driven by the axial tilt of