Question R14 Q7 - NSB Regional 2007

Which of the following was discovered in the 1600's about Venus that was strong evidence that the planets orbited the Sun:

W) Venus's cloud cover reverses its direction in the sky at certain times of the year

X) Venus has phases varying from crescent to full

Y) Venus has an axial motion opposite to that of the Earth

Z) Venus is the brightest planet in the sky only part of the year

Science Bowl Question