(WUTR/WFXV/WPNY) – Some 238,000 miles away is a bright sphere that illuminates our nights, the Moon. Though what causes it to change phases and does it actually tilt and wobble throughout the year?
Well, let’s start with the basics. The Moon is illuminated by the Sun which is what makes it so bright at night. It’s phases are an effect of it’s day and night side and how much of it we see throughout its orbit. The first phase is called the New Moon and that’s where the side we see is fully shaded. It rises and sets around the same time as the Sun so it’s up during the day.
First and Third Quarter Moon occur when the Moon is along the day-night line on the Earth so we only see one quarter of the Moon’s illuminated side. The most famous phase is the Full Moon which rises around sunset and sets around sunrise so it’s up all night.
Since the Moon is tidally locked with Earth, orbiting in a pattern known as synchronous rotation, people on Earth only ever see one side of the Moon! Though we see slightly different angles of that one side because of the shape and tilt of its orbit. This creates a wobbly appearance when watching the moon throughout its entire orbit, a phenomenon known as libration. It comes from the Latin word “Libra” which refers to the way a scale tips up and down on alternating sides.