Take a picture with one person 6 feet from the camera and one person 12 feet from the camera. The closer person will look twice as big (assuming they're actually the same size).
Now walk away 1000 feet and take another picture. The person 1006 feet away will look (almost) the same size as the person 1012 feet away. That would be true even if you used the same lens for both shots (assuming you could otherwise make that work).