People think that alien spaceships would be solid and made of metal and have lights all over them and move slowly through the sky because that is how we would build a spaceship if we were able to build one that big. But aliens, if they exist, would probably be very different from us. They might look like big slugs, or be flat like reflections. Or they might be bigger than planets. Or they might not have bodies at all. They might just be information, like in a computer. And their spaceships might look like clouds, or be made up of unconnected objects like dust or leaves.