You're driving down the highway on a beautiful day as your child looks out the window. She asks, "Why is the sun following us?"
The sun, of course, doesn’t actually follow us. But it’s a neat trick of perception. When we drive, it looks like things on the side of the street pass by quickly. That nearby tree rushes into your vision. You suddenly see the side of the tree as you approach it, and then the front of the tree as you pass it. Then the tree is out of your sight.
Now you notice a house in the fields beyond the road. Like the tree, the house comes into your view, but it seems to move more slowly. You have time to watch the side of the house, and then the front, appear before you. And if you watch the mountains in the distance, it seems to take hours before they move out of your vision.
Our brain takes these visual details and turns them into information. When we’re moving, if an object appears and disappears rapidly, our brain tells us that that object is nearby. If an object takes time to move in and out of our sight, our brain says that, comparatively, that object is farther away.
But the sun is so far away that our brain doesn’t have the usual visual information. We can’t see the side or front of the sun, and we can’t see anything behind it, like the mountains behind the house. Without these visual cues or a sense of comparison, our brain can easily assume that the sun keeps pace with us exactly, wherever we go.
Sources and Further Reading
- Allain, R. Why does the Moon follow me?, Wired, September 27, 2010.
- Byrd, D. Why does the moon seem to follow me?, EarthSky.org, April 18, 2019.
You’re driving down the highway on a beautiful day as your child looks out the window. She asks, “Why is the sun following us?”
The sun, of course, doesn’t actually follow us. But it’s a neat trick of perception. When we drive, it looks like things on the side of the street pass by quickly. That nearby tree rushes into your vision. You suddenly see the side of the tree as you approach it, and then the front of the tree as you pass it. Then the tree is out of your sight.
Now you notice a house in the fields beyond the road. Like the tree, the house comes into your view, but it seems to move more slowly. You have time to watch the side of the house, and then the front, appear before you. And if you watch the mountains in the distance, it seems to take hours before they move out of your vision.
Our brain takes these visual details and turns them into information. When we’re moving, if an object appears and disappears rapidly, our brain tells us that that object is nearby. If an object takes time to move in and out of our sight, our brain says that, comparatively, that object is farther away.
But the sun is so far away that our brain doesn’t have the usual visual information. We can’t see the side or front of the sun, and we can’t see anything behind it, like the mountains behind the house. Without these visual cues or a sense of comparison, our brain can easily assume that the sun keeps pace with us exactly, wherever we go.
