No traffic lights in the early solar system

A Professor Minton has some new ideas to explain the puzzle that, when, two billion years ago, the sun was only 70% as bright as it is now, the earth did not become a frozen ball of ice. The answer is clever and involves the mechanics of solar system formation. It does involve another collision of two bodies as creating a night sky feature. Since recently it was theorized the moon was made of two different bodies that collided, it certainly makes for a busy scenario in the early solar system.