Why does the moon seem to follow you, when you’re in a car? The simple answer is … because the moon is so relatively distant, compared to the objects around you on Earth.
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 – when we’re moving along in a car – our brains automatically compare the distant moon and stars to that cluttered foreground sweeping past. Meanwhile, 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 you.
Or think of it in terms of the angle between you and the moon. The distance between you and the moon is about a quarter million miles. Any distance you travel by car on Earth is very small in comparison. So – when you’re moving in a car – from whichever angle we view the moon, it seems to remain in the same place … following you!
This phenomenon, by the way, is responsible for many of the UFO sightings around the world.
Bottom line: When you’re in a car, the moon seems to follow you, because the moon is so distant relative to earthly objects.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.