Suppose you’re in a car, and you’re looking out the window. You see lots of motion in the landscape as you pass trees, buildings, and signs. Let’s say you’re driving by a house. First you see it in front of the car, then to the side of the car – then it’s behind you. That’s how your visual system knows that you’re moving by the house.
But the moon and stars are very distant. When we’re gazing at them from a moving car, we don’t have the ordinary clues in our environment to tell our visual system what’s going on. We don’t see the angle on the moon or stars change – we don’t see them from the front, then the side, then the back. Also, we compare the distant moon and stars to that cluttered foreground passing by.
Because the moon and stars are so far away, they seem to stay in one spot – and it can seem as if these objects in space are moving right along with us. This phenomenon, by the way, is responsible for many of the “UFO sightings” around the world.
Thank you for answering this so clearly! I often wondered about this as a child and its taken 50 years to get a good answer.
Why does that cause “UFO sightings”?
It causes UFO sightings because the same thing happens for less-obviou and/or seasonally visible astronomical bodies and people tend to think that “it’s following me” means something is a UFO. For example, the planet Venus is commonly mistaken for a UFO because it does the same thing as the moon and it’s one of the brightest astronomical bodies.