Science Common Sense

1552 - What is the difference between diurnal motion and annual motion in observing stars from Earth?

Imagine you're on Earth and looking at the stars.

Diurnal motion: This is the movement of stars that you see throughout one night, like 24 hours. The stars in the sky appear to move from east to west because the Earth is rotating (spinning around once) on its side. Think of it like a giant merry-go-round, where the stars are fixed to the sky and we on Earth are spinning around. So, you see the same stars rising and setting at the same time every night.

Annual motion: This is the movement of stars that you see throughout one year. As the Earth orbits (goes around) the Sun, different stars become visible in the night sky, while others disappear. Think of it like a big Ferris wheel, where the Earth is moving around the Sun in a big circle. So, you see different stars in the summer, winter, spring, or fall because the Earth has moved around the Sun to a new position.

In short, diurnal motion shows you the same stars every night moving across the sky due to the Earth's rotation. Annual motion shows you different stars throughout the year due to the Earth's orbit around the Sun.